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Average dimensions of the human back (anthropometry)

Average dimensions of the human back (anthropometry)


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I am wondering if anyone can point me to (a scientific source that provides) the estimates of the dimensions (length x width) of the human back?

I am specifically interested in the dimensions (length * width, or surface) of the lower back of the average adult, and in specific the region between the 7th thoracic and 4th lumbar vertebra - i.e., the region between T7 - L4 in the image below:

Ideally a distinction is made between males and females and perhaps kids as well. The area of research dealing with this matter is anthropometry.

Please mention the source to any information provided. I have access to some not-scientifically based sources (clothing companies for example). Although additional such sources are welcomed, scientifically-based answers are preferred.


This doesn't really answer the question and I only post it at the asker's request.

NASA has measured the dimensions of the back in 40 year old American males and 40 year old Japanese females in the year 2000 at 1G. Of course gravity matters to NASA…

From figure 3.3.1.3-1 (American male). All data in centimetres:

  • 921 Waist back
    • 5th percentile: 43.7
    • 50th percentile: 47.6
    • 95th percentile: 51.6
  • 506 Interscye
    • 5th percentile: 32.9
    • 50th percentile: 39.2
    • 95th percentile: 45.4

Anthropometry in Workspace Design

In this technological age we are surrounded by artifacts and environments which can greatly influence our personal and communal health, safety, effectiveness and well-being. For most of us the majority of our lives are spent in buildings and environments which have been designed and constructed to accommodate us. Without ignoring the impact of the domestic setting, the industrial workplace has the potential to be more hostile to us because of the nature of the very operation and processes being carried out. Within this context it is important that workspace - the area within which we are required to carry out our work - is designed to promote our health and well-being without detriment to our effectiveness.

Anthropometry has been defined as the science of measurement of body size (NASA, 1978). The application of anthropometry is an essential element in the process of designing the workspace to fit the worker. The physical size of a population can be determined by measuring body lengths, breadths and girths, and the data derived can be used to design workplaces, equipment and products which match people's dimensions. In this way the workspace (which includes the equipment, tools, furniture etc) can be fitted to the man or woman's physical dimensions and functional capabilities.


Anthropometry in Forensic Medicine and Forensic Science-'Forensic Anthropometry'

K Krishan. Anthropometry in Forensic Medicine and Forensic Science-'Forensic Anthropometry'. The Internet Journal of Forensic Science. 2006 Volume 2 Number 1.

Abstract

Anthropometry is a series of systematized measuring techniques that express quantitatively the dimensions of the human body and skeleton. Anthropometry is often viewed as a traditional and perhaps the basic tool of biological anthropology, but it has a long tradition of use in forensic sciences and it is finding increased use in medical sciences especially in the discipline of forensic medicine. It is highly objective and reliable in the hands of trained anthropometrists. The significance and importance of somatometry, cephalometry, craniometry and osteometry in the identification of human remains have been described and a new term of 'forensic anthropometry' is coined. Some of the recent studies which employ various techniques of anthropometry are discussed. The ultimate aim of using anthropometry in forensic medicine/science is to help the law enforcement agencies in achieving 'personal identity' in case of unknown human remains.

Introduction

All the human beings occupying this globe belong to the same species i.e. Homo sapiens . No two individuals are exactly alike in all their measurable traits, even genetically identical twins (monozygotic) differ in some respects. These traits tend to undergo change in varying degrees from birth to death, in health and disease, and since skeletal development is influenced by a number of factors producing differences in skeletal proportions between different geographical areas, it is desirable to have some means of giving quantitative expression to variations which such traits exhibit. Anthropometry constitutes that means, as it is the technique of expressing quantitatively the form of the human body. In other words, anthropometry means the measurement of human beings, whether living or dead or on skeletal material.

Although, there are numerous methods of measurement used in biological anthropology, but ‘anthropometry' is uniquely its contribution and peculiar to it. Other methods have been borrowed from anatomy, medicine, physiology, biochemistry, genetics and statistics 1.

Forensic medicine is an interdisciplinary science which in everyday practice applies all the knowledge that medical sciences, have accepted as reliable and scientifically solid facts or processes, and qualitative and quantitative definitions with the help of which accurate and reliable statements can be made 2. The use of anthropometry in the field of forensic science and medicine dates back to 1882 when Alphonse Bertillon, a French police expert invented a system of criminal identification based on anthropometric measurements. His system was based on three fundamental ideas- the fixed condition of the bone system from the age of twenty till death the extreme diversity of dimensions present in the skeleton of one individual compared to those in another the ease and relative precision with which certain dimensions of the bone structure of a living person can be measured using simply constructed calipers. This system of identification spread rapidly through much of the world but the system was not accepted much in view of some major drawbacks and discovery of other identification systems e.g. dactylography 3.

As anthropometry is an important part of biological/physical anthropology, hence the persons specializing in anthropometry are familiar with range of biological variability present in the human populations and its causes, and are well trained in comparative osteology, human osteology, craniometry, osteometry, racial morphology, skeletal anatomy and function. They are well aware of the knowledge of archaeological field techniques and methods which serve well in crime scene recoveries involving buried and surface remains 4. The term ‘forensic anthropometry' can be coined for this branch of applied physical anthropology, involving the use of methods/techniques of anthropometry in forensic/legal context. In other words, “forensic anthropometry is a scientific specialization emerged from the discipline of forensic anthropology dealing with identification of human remains with the help of metric techniques”.

Anthropometric characteristics have direct relationship with sex, shape and form of an individual and these factors are intimately linked with each other and are manifestation of the internal structure and tissue components which in turn, are influenced by environmental and genetic factors. Anthropometric data are believed to be objective and they allow the forensic examiner to go beyond subjective assessments such as ‘similar' or ‘different'. With measurement data, the examiner is able to quantify the degree of difference or similarity and state how much confidence can be placed in this interpretation 5.

The main aim of an anthropometrist employed in the forensic medicine/medico-legal department, working with unknown variables, is to describe the remains in such terms so that one can achieve the goal of estimating age at the time of death, sex, stock/race/ancestry/ethnicity, stature, body weight/body build, details of individualizing characteristics i.e. amputations, fractures, ankyloses, deformities and bone pathologies and to some extent the cause of death if reflected in the remains/bones. The objective is to enable the law enforcement agencies to achieve the ultimate goal of personal identification.

Krogman6 in his monumental publication (later on revised with Iscan7) “ The Human Skeleton in Forensic Medicine ” describes that the use of anthropometry may arise under several sets of circumstances i.e. Natural, intentional and accidental (war dead cases, air crash, road and train accidents, earth quake, flood, fire deliberately mutilation, disfigurement, pounding, gouging etc. of the dead body).

Forensic anthropometry incorporates most of the techniques originating with the analysis of human skeletal material from archaeological sites the two disciplines have been closely linked. A good forensic anthropologist must, by definition, be a good skeletal biologist8. He helps a forensic pathologist to reconstruct the biological nature of the individual at the time of postmortem examination, and sometimes giving clues and reconstructing the circumstances surrounding death. He is prepared for this by his training in describing the prehistoric skeletons from archaeological sites and usually by special experience in identifying unknown modern skeletons 9.

Anthropometry can be subdivided into Somatometry including Cephalometry and Osteometry including Craniometry.

Somatometry

It is the measurement of the living body and cadaver including head and face. Somatometry is considered as a major tool in the study of human biological variability including morphological variation. Studies of morphological variation, by their very nature have a comparative focus in which variation within and among populations is the central theme.

Somatometry is useful in the study of age estimation from different body segments in a given set of individuals. The sample selected should be described adequately for all key relevant factors. Although, the description will vary from study to study, it should include data of examination, birth date, age, sex, ethnic group, geographic location, socio-economic status etc. Age should be expressed in days up to the age of one month, thereafter, decimals of years should be used, employing, if necessary, tables for their computations 10. Attallah and Marshal11 described a method to estimate chronological age from different body segments in British boys and girls using somatometric techniques. They used seven body measurements to estimate the chronological age of a child and evaluated the accuracy of the estimation and discussed applicability of the method on both live individuals as well as on cadavers.

Many authors have made use of somatometry extensively in the estimation of stature from different body segments. One of the foremost studies is by Bhatnagar et al12 on Punjabi males. In their study, in addition to stature, three anthropometric measurements were taken on left and right hands separately. Regression equations were calculated to estimate stature from these hand measurements. A similar kind of study was conducted by Abdel-Malek et al13 on Egyptian subjects. They took two somatometric measurements of the hands and successfully determined stature by computing multiple regression equations. Jason et al14 estimated stature from the length of cervical, thoracic, lumbar, thoraco-lumbar and cervico-thoraco-lumbar segments of the spine in white and black American autopsy sample. Regression formulae were calculated which help in estimation of stature from these segments. Krishan and Sharma15 conducted a study on the bilateral asymmetry and estimation of stature from arm length and its segments on a Punjabi population and computed regression equations and lines. Krishan and Vashisht16 also conducted a similar study on adult male Gujjars of North India. They took six measurements of limbs and computed bilateral asymmetry and calculated regression equations for estimation of stature and they recommended that in view of the marked bilateral asymmetry of the limbs, it is necessary that while estimating stature of a person from amputated limb or any of its segments, we must first identify the side (whether left or right), then apply the appropriate formula. Duyar and Pelin17 established relationship between tibial length and stature. They proposed a new method for height estimation. They made three different groups on the basis of short, medium and tall stature and computed regression equations between stature and these three different groups. Ozaslan et al18 conducted another study on the estimation of stature from body parts. They analyzed anthropometric relationship between stature and seven somatometric measurements of the lower limbs and computed regression coefficients and standard error of estimate used to calculate stature.

All the somatometric measurements (including measurements of the head and face) and standard procedures described by Olivier 19, Weiner and Lourie10, Lohman et al20, Hall et al21 can be used for estimating stature from different body segments.

Osteometry

It includes the measurements of the skeleton and its parts i.e. the measurements of the bones including skull. It is defined as a technique to take measurements on the skeletal material. Through this technique, a forensic scientist can study variation in bony skeleton of different populations of the world. The technique has been successfully used in the estimation of stature, age, sex and race in forensic and legal sciences. These four parameters i.e. age, sex, race and stature are considered as the “Big Fours” of forensic anthropology. Various studies have been conducted and are in progress in many parts of the world in this regard.

Estimation of stature

There are various ways to estimate stature from bones but the most easiest and the reliable method is by regression analysis 22, 23. In the past, scientists have used each and every bone of the human skeleton right from femur to metacarpals in estimation of stature. They all have reached a common conclusion that stature can be estimated with great accuracy even from the smallest bone, although, they have encountered a small error of estimate in their studies. Some authors have used fragments of the long bones i.e. upper or lower end etc. but most of the time, long bones have been used in the determination of stature because they relatively give better accuracy in prediction of stature.

The major difficulty in developing a stature estimation formula is the non-availability of skeletal series with known body height data 23. The Harmann-Todd, Terry collection and the Raymond Dart Pretoria skeletal collection24, 25 are the best collections in this regard.

Various studies conducted on the estimation of stature indicate that every part of the skeleton has been used for estimation. One of the foremost and famous studies on estimation of stature from long bones of American whites and blacks is by Trotter and Gleser26. Since then, scientists have carried out extensive work on the estimation of stature from a variety of bones throughout the world. Kate and Majumdar27 successfully estimated stature from lengths of femur and humerus by regression method and autometry in an Indian sample. Boldsen28 statistically evaluated the prediction of stature from length of the long bones in different European populations. Rother et al29 conducted a study on the estimation of stature from fragments of the femur and devised some regression formulae. Mysorekar et al30 also estimated stature on the basis of lower end of femur and upper end of radius. Badkur and Nath31 reconstructed stature by measuring 12 anthropometric parameters on ulna and multi-linear regression equations were computed. Simmons et al32 provided regression equations for the estimation of maximum femur length and stature from three well defined and easy to measure segments of the femur in a sample from Terry collection. Holland33 calculated strong linear regression equations for estimation of stature from measurements of condyles of tibia in a sample from Harmann-Todd collection. Introna et al34 correlated stature with several parameters of the skull and obtained multiple linear regressions for estimation of stature. The study sample consisted of 119 adult black and white males from the Terry collection. Meadows and Jantz35 developed regression equations from two samples of metacarpal specimens one of 212 individuals from the Terry collection and the other of 55 modern males and concluded that in spite of the differences noted, the Terry equation perform acceptably on modern individuals. Jantz et al36 presented results in the estimation of stature from tibia and critically commented upon the method of measurement of tibia by Trotter and Gleser26. Ousley37 commented that should we estimate biological or forensic stature? He recommended that forensic stature estimation is generally less precise than Trotter and Gleser stature estimation but is more accurate for modern forensic cases because a forensic stature is the only stature available for a missing person. Compobasso et al38 used scapular measurements for estimation of stature. They took seven anthropometric parameters of scapula and developed multiple and linear regression equations. Mall et al39 correlated humerus, ulna and radius lengths with stature and concluded that the linear regression analysis for quantifying the correlation between the bone lengths and the stature led to unsatisfactory results with large 95% confidence intervals for the coefficients of high standard error of estimate. Ross and Konigsberg40 devised new formulae for estimating stature in the Balkans. They compared the data obtained from 545 white males from World War II with East European sample of 177 males including the Bosnian and Croatian victims of war. Bidmos and Asala41 derived regression equations for estimation of stature from nine calcaneal measurements. The sample consisted of 116 complete skeletons (60 males and 56 females of South African blacks) from Raymond Dart collection. Hauser et al42 established the relationship between stature and greatest length of femur and computed correlation coefficients and regression equations to predict stature. Pelin et al43 evaluate the possibility of prediction of living stature from the coccygeal vertebral dimensions in adult male population of Turkey. They recommended the use of combined variables of the different coccygeal vertebral segments for accurate prediction of stature. Raxter et al44 revised Fully's technique for estimation of stature and tested the accuracy and applicability of his method and clarified measurement procedures. Sarajlic et al45 developed formulae from the lengths of femur, tibia and fibula for estimation of stature in Bosnian population. Krishan and Sharma46 gave linear and multiple regression equations for estimation of stature from dimensions of hands and feet in North Indian Rajputs. Krishan and Kumar47 calculated regression equations for estimation of stature from cephalo-facial dimensions in Koli adolescents of North India. They also suggested that future researchers should categorize their adolescent sample into various age groups for better reliability and practical utility of stature estimation.

Due to substantial diurnal variation in stature, one should avoid taking stature measurements at different times of the day48 . It means, while making standards or reference data of stature estimation, careful consideration should be given to the time of the day at which the measurements are to be recorded.

Determination of sex

Sex is considered as one of the easiest determinations from the skeletal material and one of the most reliable if essential parts of the skeleton are available in good condition7. The most often chosen bones for the determination of sex are the pelvis and the skull although the round heads of the ball joints also provide very reliable means of determining sex49, 50. Sex determination is also supposed to be reliable when the remains are from long bones and up to 95% accuracy can be achieved.

Anthropometry is being used more often in sexing the skeletal remains. Worldwide, various studies have been conducted on the determination of sex from variety of human bones i.e. skull, pelvis, long bones, scapula, clavicle, and the bones like metatarsals, metacarpals, phalanges, patella, vertebrae, ribs etc. The most popular statistical model in sex determination is recently developed discriminant function analysis which encouraged many forensic scientists to assess their anthropometric data accordingly 23.

Iscan et al51 used seven anthropometric parameters of tibia including tibial length, diameters and circumferences for determination of sex from 84 Japanese skeletons. They used multiple combinations of measurements to develop formulae for determination of sex and the average prediction accuracy ranged from 80% to 89%. They further conclude that the accuracy of prediction was higher in males (96%) than females (79%). Falsetti52 made assessment of sex from dimensions of metacarpal in three samples i.e. The Terry collection, sample from Royal Free Medical School, forensic collection of Maxwell Museum of Anthropology, University of New Mexico. He designed five measurements for the metacarpal and found different accuracy rates in different samples. Trancho et al53 made use of 132 femora of adult Spanish population for determination of sex by discriminant function analysis. They measured femur for five anthropometric variables and achieved between 84% to 97% accuracy when each variable was considered independently. 99% accuracy was obtained when two variables of the epiphysis were combined. Smith54 utilized metatarsals, proximal pedal phalanges and the first distal phalanx of the foot in determination of sex from The Terry and Huntington Collections of the Smithsonian Museum of the Natural History. The anthropometric measurements include lengths and medio-lateral and dorso-plantar widths of these foot bones. He recommended the use of combination models for correct assignment of sex as he achieved 87% accuracy with this model.

Asala55 used femur head to determine sex in South African whites and blacks from Raymond Dart collection. He took two variables i.e. vertical femoral head diameter and transverse femoral head diameter and concluded that these can be used successfully for sex determination in absence of complete bone. He further concluded that the sex from this bone must be calculated separately for each population. Mall et al39 measured various anthropometric dimensions of humerus, ulna and radius to determine sex by using discriminant analysis. They concluded that radius (94.93%) is the best bone for sex determination, followed by humerus (93.15%) and ulna (90.58%).

Frutos56 measured maximum length and circumference of the mid shaft of the clavicle and height and width of the glenoid fossa of the scapula for sex determination in Gautemalan contemporary rural indigenous population. They made use of jackknife method (leave-one-out method) and it produced classification success rates ranging from 85.6% to 94.8%. An investigation by Bidmos and Dayal57 is based upon anthropometric study of 60 male and 60 female tali of South African white from Raymond Dart collection. They concluded that by using discriminant analysis, the level of average accuracy of sex classification was 80% to 82% for the univariate method, 85% to 88% for the stepwise method, and 81% to 86% for the direct method. Rissech et al58 analyzed four variables of the ischium by polynomial regression in order to determine sex during and after growth. They calculated growth curves for ischium length, horizontal diameter of ischium acetabular surface, vertical diameter of ischium acetabular surface and ischium acetabular index and concluded that the ischium length is the best variable for determination of sex in west European collections.

Frutos59 conducted a study based on 118 complete humeri from Guatemalan forensic sample. He studied six anthropometric dimensions and concluded that the classification accuracies for the univariate functions range from 76.8% to 95.5% and for stepwise function procedure was 98.2%. Kemkes-Grottenthaler60 evaluated the reliability of patella anthropometry in sex determination in a material from different archaeological samples. He achieved almost 84% accuracy in sex determination. Patil and Mody61 conducted a lateral cephalometric study on central Indian population to devise a model for determination of sex. They took ten measurements on the radiographic cephalograms of 150 normal healthy individuals and determined sex by discriminant function analysis. They concluded that the variables provided 99% reliability in sex determination. Patriquin et al62 designed nine measurements of pelvis and analyzed sex differences in South African white and black population. They made use of stepwise discriminant function analysis and presented anthropometric standards of the pelvis of South African white and blacks. They further concluded that the ischial length is the most sexually dimorphic dimension in whites (averaged accuracy 86%) and acetabulum diameter is the most diagnostic in blacks (averaged accuracy 84%). Purkait63 conducted a study on 280 femora from central India. She used the points of traction epiphysis on the upper end of the femur and the triangle was drawn on the posterior aspect of the femur using the apex of two traction epiphysis and the lateral most point on the articular margin of the head. Each length of the triangle was analyzed. She observed that all dimensions were greater in females. The accuracy rate ranged from as little as 63% for the distance between the point on the femoral head and the greater trochanter to 85% for the distance between the greater and lesser trochanters. Slaus and Tomicic64 used 180 tibiae from six medieval archaeological sites in Croatia in sex determination. They measured six anthropometric dimensions on tibia and showed that complete tibiae can be sexed with 92.2% accuracy. Rissech and Malgosa65 used coxal bones of 327 individuals taken from four documented skeletal series i.e. The St. Bride's Collection, London Esqueletons identificados , Coimbra The Lisbon Collection, Lisbon and UAB Collection, Barcelona in sex determination. The measurements include ilium width, ilium length, ilium index, horizontal diameter of the ilium acetabular area and vertical diameter of the ilium acetabular area and they concluded that the ilium width is the best variable fore sex determination.

Determination of Race

Determination of race is not so simple. In spite of several multivariate statistical studies of specific measurements of the skull and a few long bones, this is still one of the most problematic areas skeletal identification 66, 67. Race determination is further complicated by another major factor i.e. one may encounter intrinsic variability within each major genetic breeding population or endogamous group.

Practical implications and reliability in anthropometry

Precision in anthropometry is of utmost importance as it requires lot of practice. Reliability of the measurement should be established and the best order for recording the measurements selected for a particular study or a particular problem should be determined. The most common errors in anthropometry are positioning of the body or bones, reading measurements and recording. In other words, these errors are also termed as personal error and technical error of measurement respectively. In order to minimize these errors, standard procedures for recording these measurements should be used which are internationally recognized.


Anthropometric Measurements Usage in Medical Sciences

Morphometry is introduced as quantitative approach to seek information concerning variations and changes in the forms of organisms that described the relationship between the human body and disease. Scientists of all civilization, who existed until today, examined the human body using anthropometric methods. For these reasons, anthropometric data are used in many contexts to screen for or monitor disease. Anthropometry, a branch of morphometry, is the study of the size and shape of the components of biological forms and their variations in populations. Morphometrics can also be defined as the quantitative analysis of biological forms. The field has developed rapidly over the last two decades to the extent that we now distinguish between traditional morphometrics and the more recent geometric morphometrics. Advances in imaging technology have resulted in the protection of a greater amount of morphological information and have permitted the analysis of this information. The oldest and most commonly used of these methods is radiography. With developments in this area, CT and MRI have also been started to be used in screening of the internal organs. Morphometric measurements that are used in medicine, are widely used in the diagnosis and the follow-up and the treatment of the disease, today. In addition, in cosmetology use of these new measurements is increasing every day.

1. Introduction

Since ancient times, the human body has been measured for several reasons. During the ancient era, human body measurement was mostly practiced for the figurative arts. Eventually, the practice was adopted by the naturalist field and then by anthropologists to identify human basic morphological characteristics. The term anthropometria dates back to the 17th century in the naturalist field, when it first appeared in the short manual Anthropometria by Johann Sigismund Elsholtz [1–3]. The manual seems to be the earliest recorded material that investigated the human body for scientific and medical purposes. It introduced a quantitative approach to seek information concerning variations and changes in the forms of organisms that described the relationship between the human body and disease [4]. Elsholtz proposed that the use of anthropometry constituted a valuable measurement strategy for different fields such as medical practices, physiognomy, the arts, and ethics [3, 5]. In the second half of the century, a strong need for counting and measuring the human body arose, and the representation of the instruments used in clinical practices became vital for the medical field. The pulsilogium, which was invented by Sanctorius at the University of Padua, was one of the first instruments in the field and was used to evaluate the pulse rate. During the 18th century, the well-known French anatomist Jean-Joseph Sue, Swiss physiognomist Johann Kaspar Lavater, and German naturalist Johann Friedrich Blumenbach presented valuable research on different issues concerning measurement [6]. At the prompting of these academics, “the season of measurers” began, and practitioners started to believe in the practical application of numbers. Making use of mathematics, geometry, and statistics, anthropologists presented human investigation methodologies and became “anthropometers” [1, 2]. The anthropologists’ prior object of investigation was “the skull,” which they believed represented the most important part of the body. The anthropometrical method became more popular in several fields due to the research of Adolphe Quetelet in the 19th century [2]. During this period, the new conceptualization of human diversity advanced this practice for the creation and validation of racial typologies [1].

In the West, the use of measurements and the description of the human body emerged among the artists of classical civilizations however, more systematic body measurements and records gained importance due to the demands of early modern military organizations [2]. The measurement of the height of individuals, especially young men, became the basic procedure used to classify them as appropriate or not for military recruitment. Through the end of the 19th century, anthropometry became a new tool for clinical practices and taxonomy as public health measurements gained importance. In the 19th and 20th centuries, anthropometry manifested in the measurements of weight, circumference, stature, and skinfold thickness that were used to identify environmental influences that impacted child growth [4].

Because ancient anthropometric research was a relatively current concept, the related medical literature concerning nutrition and physical growth served as a valuable theoretical source. Hence, the biomedical literature of the World Health Organization (WHO) was regarded as one of the best sources that represented general health conditions within a society [3].

Because of its use as a measurement of physiological and developmental human growth, anthropometria appeared in several clinical practices that utilized instruments such as the manometer, sphygmograph, hemocytometer, hemoglobinometer, and spirometer [2]. The need for these measurements stemmed from the interaction between several intricately linked concepts, including nutrition and infection, psychosocial stress, food contaminants, hypoxia, and pollution [1]. Factors mostly linked to socioeconomic status and poverty indicated that body size was a signal for the quality of life. Thus, anthropometric practices could be used as a tool for social welfare, whereas factors such as culture, society, behavior, and the political economy played important but distal roles in the outcomes of growth and body size [1, 3, 5].

2. Historical Development of Anthropometry

Over the ages, all civilizations have been interested in the human body. Artists in particular have reflected the effects of this interest in their works.

In the ancient Egyptian, Greek, and Roman civilizations, famous artists used male figures in their artwork (i.e., pictures and statues) with the desire to represent issues such as beauty, virtue, independence, military power, and authority [6, 7].

In the ancient era, artists were interested in the depiction of body parts based on reciprocal proportions. Artists believed that the human body represented as “an ideal human figure” had specific proportions between its constituent parts. Throughout history, these proportions were considered to be canon. In practical use, any given part of the human body could be chosen for measurement and proportioned to the other parts due to the absence of standardized measurement units such as the meter, centimeter, or millimeter. Therefore, any given human body part could be described as a “unit of measurement” (module). These measurement units contained various modules such as the length of the feet, length of the hand, and height of the head [5, 8, 9].

Throughout history there have been studies related to the “human body” branches of art (i.e., sculpture and painting) as well as studies related to anatomy in the field of medicine. In the three most well-known ancient civilizations, scholars evaluated the “human body” using the concepts of canon and modules [6, 10].

3. Anthropometric Measurements in Ancient Civilizations

3.1. Egyptian Civilization

The first known dissections with the aim of learning (III century BC) were performed by scholars in Egypt [7]. In the most ancient cannon, “length of feet” (LF) was used as the module. Human figures drawn on the walls of the pyramids by Egyptian artists were depicted with heights six times longer than the length of their feet however, when the artists noticed that the proportions did not reflect reality, they adjusted the height of taller human figures to a height equivalent to seven feet. According to our present arithmetic knowledge, they proportioned the horizontal lines based on height and the vertical lines based on the width of the human body [7, 9].

3.2. Ancient Greek Civilization

The most famous artist of this era was Polykleitos. Polykleitos evaluated the human body and wrote the first known artistic anatomy book. The renowned scholars used the “width of hand” (WH) as a module and described the proportions he used between various body parts and the width of hand as well as the inequalities. During the period of Greek civilization, for the first time multiple equalities were used in drawings of the human body between the longitudinal, oblique, and transversal dimensions [7].

3.3. Roman Civilization

Roman artists and scholars further developed studies of the “human body.” Moreover, some equalities were described after a human figure in the college position was placed in a square frame. Because notables of the era such as Leonardo da Vinci found that the human figure in the college position had an equal length and width, human paintings were often performed using a square frame [7, 9, 10]. Artists during the era of the Roman Empire continued these studies by merging art with anatomy and quietly exploiting mathematics [11].

3.4. Anthropometric Measurements during the Renaissance

Great artists of the renaissance (Leonardo da Vinci and Albrecht Dürer) created many works based on these rules and proportions. Works related to the human body were developed according to rules that were considered to represent classical anthropometrical measurement techniques [7].

(i) The renowned renaissance artist Leonardo da Vinci was interested in both art and sciences. He performed cadaver dissections and notated his measurements, notes, and drawings with the attention to detail of a scientific investigator. For the first time in history, he investigated the human face, head, neck, and other related parts in detail, mainly following the “Polykleitan theory.” He worked on a drawing belonging to Vitruvius, and after rigorous investigation of this work he demonstrated his success in this field. Indeed, the “Vitruvian man” became one of his most renowned works [7, 9].

(ii) Durer was a versatile artist and architect who worked in both the mathematics and anatomy fields. He was born in Germany and examined both the male and female figures from the perspective of science and art. However, in his era dissection was not allowed in Germany, so his work relied on the use of live models and examinations of the literature. He also has investigated the positions of the internal organs and depicted the projections of the spleen in his work. His most famous work titled “Adam and Eve” showed his incredibly rigorous calculations [7].

3.5. Anthropometric Works in the “20th” Century

After the 19th century, the concept of the “average” male figure was developed based on comprehensive measurements. In the early 20th century, the French doctor of medicine and painter-sculptor Paul Richer performed one of the most detailed and scientific studies of the postrenaissance era due to his use of anthropometric methods. He described the “average human figure” based on comprehensive measurements rather than the “ideal human figure.” He chose “height of head” as the module and depicted the front and the back view. Additionally, he explained human anatomy in the context of the medial and lateral views of the extremities [1, 5, 10].

Morphometrics, a branch of anthropometry, is the study of the size and shape of the components of biological forms and their variations in populations [11]. Morphometrics is a field concerned with studying variations and changes in forms (i.e., size and shape) of organisms morphometrics can also be defined as the quantitative analysis of biological forms. The field has developed rapidly over the last two decades to the extent that we now distinguish between traditional morphometrics and the more recent geometric morphometrics [4].

3.5.1. Traditional Morphometrics

In traditional morphometrics, it is not possible to recover the shape of the original form using the usual data matrices of distance measurements, even as an abstract representation. The overall form is neither archived nor used in the analysis. For example, a researcher may know that several measurements share a common landmark, but this information is not used in the multivariate analyses. As a result, the analyses cannot be expected to be as powerful as they could be if that information were taken into account [4, 11].

Traditional morphometrics consisted of applying multivariate statistical analyses to sets of traditional measurements between points with biological and anatomical meanings to define shapes called landmarks. These measurements usually represented the lengths and widths of structures and the distances between certain landmarks, which are described as the points of correspondence on each matching object between and within populations. Sometimes angles and ratios were used [11, 12].

When multivariate morphometrics was combined with both quantitative morphology and multivariate statistics, several difficulties still remained. As an example, many ways of size correction were proposed, but there were great debates about which method should be utilized [4, 11]. It was important due to little different results caused by different size correction methods. Second, homology of linear distances was difficult to be evaluated due to insufficiency of homologous points about defining many distances (maximum width, etc.). Thirdly, similar set of distance measures may be obtained from two different shapes because data did not include location of each distance measurement which were relative to the other distance measurements. Traditional morphometrics does not allow recovering shape of original form from usual data matrices even if it is an abstract representation. Archives and analyses did not include whole form. A researcher may know the common landmark shared by several measurements however, this knowledge has no role in multivariate analyses. As a result, analyses will not be powerful as the condition which information were used in [4, 11–13].

3.5.2. Geometric (Modern) Morphometrics

In the 1960s and 1970s, biometricians began applying multivariate statistical analyses to sets of traditional measurements. Geometric morphometric methods are more valid than traditional morphometric methods in protecting morphological information and permitting the analysis of this information. For morphometrics to fulfill its promise of fusing geometry with biology there must be equal emphasis on the two components. Morphometric techniques need to be designed and applied with biology in mind, and the quantitative results must be directly interpretable using biological methods [11, 13].

In geometric morphometrics, biological shape is defined via transformation of the original shape, which is selected as a reference shape. Thompson proposed the idea in 1942, and although the method was attractive and promising for the analysis of biological shapes, the method did not have an analytical procedure. With the advent of computers, applications for morphometric analysis based on Thompson’s idea became possible. Data are recorded to represent the geometry of the structure being studied [11]. These data are in the form of two-dimensional (2D) or three-dimensional (3D) coordinates of morphological landmark-points. The estimates of the parameter of the fitted function can then be used as variables in standard univariate and multivariate statistical analyses [12]. The coordinates are much more useful than traditional measurements, and the usual distance measurements can be computed from the coordinates [11, 12, 14]. Using landmark coordinates, concise encoding of all information in any subset of distances or angles between them is possible. Analysis and visualization which is on coordinate-based approaches are called complete retention of geometric information from data collection. Within geometric morphometrics, collecting information concerning the location of different points as landmarks addresses comparisons between organic forms. Considering points as homogenously distributed on the organism and have some biological meaning, a set of homologous points, landmarks provide information of biological life forms [11–13].

The fundamental advantages of geometric morphometrics over traditional approaches (i.e., multivariate morphometric techniques) include the development of powerful statistical methods based on models that are used to examine the shape variation of all configurations that correspond to morphologic landmark locations. Indeed, in many biological or biomedical studies, the most efficient way to analyze the forms of whole biological organs or organisms is by registering landmarks [4]. Many studies in medicine are related to the examination of the geometrical properties of an organ or organism. In these studies, statistical analysis consists of the quantitative or qualitative measurement of given values for example, recently a given organ or organism’s appearance or shape has been used as the input data for the development of imaging techniques [13]. Commonly, quantitative or qualitative data sets used for statistical analysis consist of measurement values. In recent times, following the development of imaging techniques an organ or organism’s appearance or shape began to be used as the input data [4]. In these studies, the statistical analysis consists of the quantitative or qualitative measurement of the given values.

For over 50 years, qualitative morphometric techniques have been used within limits to assess bone density. Grading systems for the spine and proximal femur were developed with the aim of characterizing the severity of bone loss. However, because the use of such systems could cause highly subjective interpretations, the inclusion of a series of reference radiographs is recommended. Quantitative morphometric techniques are repeatedly used for imaging of the spine or proximal femur with X-rays. However, some measurement parameters were required for these techniques to produce a quantitative assessment of the severity of bone loss [15–17].

4. Radiological Development of Imaging Modalities

Throughout history, many studies have focused on the human body, especially with the aim of identifying anatomical, physiological, and pathological features of the internal organs. Among these studies, those related to imaging modalities of internal organs are especially very valuable [18, 19]. During his work with cathode ray tubes in 1895, German physicist Wilhelm Conrad Röntgen noticed radiating rays when high-voltage electric current passed through a Crookes tube Röntgen named them unknown rays (X-rays). On December 22, 1895, Röntgen obtained an image of his wife’s hand following 15 minutes of irradiation. These rays were identified as very high frequency electromagnetic waves with light bursts as florescence. X-rays can pass through soft tissues and partially penetrate into dense tissues such as bone. This process enabled internal views to be obtained as images from living organisms. Röntgen presented his invention to the Physical Medicine Society in Germany, and two weeks later he obtained images of his own upper and lower teeth using irradiation on black paper and a glass photography plaque wrapped with plastic. These images represented the first radiography images. The first medical X-ray radiography (Röentgen graphy) in history was also obtained during these experiments, and Röntgen officially announced his important discovery on December 28, 1895. Although potential radiation hazards due to the use of X-rays had been ignored, the dentist Frank Harrison reported skin peeling and hair loss in his patients due to the use of X-ray radiography [15, 16].

In Turkey, the usage of X-rays in the field of medicine was first performed by medical students Esat Feyzi and Osman Rifat. Both students detected bullets in wounded soldiers during the Ottoman-Greece battle using radiography [20–24]. One of the first studies concerning X-rays was performed by M. Hubert. In this study, Hubert evaluated the physiological and pathological values of kidneys collected from different species of animals. Rich et al. studied the X-ray sensitivity of human tumor cell. Both Rich et al. and Taoka and Shuloeva provided examples of roentgenological studies of pulmonary function [22, 23, 25].

5. Computerized Tomography (CT)

The first quantitative CT measurement was proposed by Johann Radon. In 1972, J. N. Hounsfield scanned a section using thin and weak X-rays and turned the result into an image after computer evaluation by reading the signals in the scintillation chamber. Using this technique, a cross-sectional image could be obtained from anywhere in the body. Investigations of the CT accessibility of tissues and body regions showed that CT is more successful in imaging bone tissue than soft tissues due to its working principles and design. This invention was an important development for the imaging of brain and malignant tumors [26, 27].

Quantitative computed tomography (CT) is used for quantifying bone mineral density (BMD) in the spine, proximal femur, forearm, and tibia as a three-dimensional nonprojectional technique. It has several advantages over other densitometric techniques, including the ability to separate the cortical and trabecular bone, the fact that degenerative changes in the spine cannot affect the volumes of interest (VOI), and the ability to determine 3D geometric parameters [26, 28].

6. Magnetic Resonance (MR) Imaging Technique

The identification of spin-based physic resonance by Wolfgang Pauli in 1920 initiated the first attempts to obtain images using the MR technique. Quantitative measurements in this field were first performed by physicists Bloch and Purcell. In their experiments, they demonstrated that atoms with one nucleon in their core were affected by the magnetic field and that the orbit of the atomic cores was changed in response to the magnetic field. For a long time, this finding was applied solely to the field of physics. Then, in 1970 Paul Lauterbur obtained a clear MR image. The first diagnosis using this modality was performed by Hawkes et al. in 1980. Currently, the ability to obtain fast and quality images of internal organs using the MR technique and the relatively low risk of side effects has led to its common use both internationally and nationally [26–30].

7. Current Utilization of Three-Dimensional Imaging

Currently, the direct calculation of the measurements of morphometric quantitative area shapes has been made possible by utilizing various programs after the common usage of MRG. Due to its imaging capacity on multiple planes, absence of ionizing radiation, and utilization for the diagnosis of mediastinum, this method has an important place in the field of medicine [29].

Mathematical analyses are used to identify the shape of an anatomic region in the human body. These evaluations are performed using optic measuring methods with 3D imaging modalities. These methods are especially important for quantitating data in the complex anatomical structures of the human body. The assessment of the validity and safety of these data has led to improvements in human health and quality of life [31].

The most commonly used imaging modality trio today includes the PET/CT modalities. In addition to imaging structures in the human body, these modalities can also detect exact tumor locations and biological properties that are essential for diagnoses in cancer patients [28, 30].

Anthropometric measurements are important for the evaluation of morbidities of individuals in society and thus meet the requirements of that society. For human health, the field of medicine requires constant development and renewal. Throughout history, anthropometric measurements were improved as details of human anatomy were discovered, until the field reached today’s standards. In recent years, the utilization of many new measurement devices for clinical use and primary studies has inevitably led to improvements in measurement parameters and techniques [6, 7].

In the eras of the Ancient Egyptian, Greek, and Roman civilizations, artists made detailed evaluations of the human body. Artists of the renaissance period created ideal ratios in their works using mathematical methods (i.e., canons and module measurement). The “golden ratio” that was used by Leonardo da Vinci in his drawings currently remains the norm for beauty. In this ratio, anthropometric data and ratios are used to compare the ratios of disproportions present on the face [7].

A tendency towards plastic surgeries has become widespread over the past several years. Interventions related with this field include corrections of congenital malformations as well as various optional modifications on individual’s bodies. Anthropometries of the human body and especially the face are used for the identification of these disproportions. Therefore, more standardized and purpose-oriented measurements in the field of plastic surgery are important for a more objective evaluation of human bodies [32].

8. Cosmetology

The use of imaging techniques in facial cosmetics is an undesirable feature caused by extrinsic photo damage and the intrinsic aging process [33]. A decrease in wrinkle severity has become a very important evaluation criterion in aesthetic dermatology for the assessment of the success of rejuvenating treatments. Many quantification methods have been developed to analyze wrinkles. The comparative evaluation of modern scales and 3D images can lead to a further understanding of facial wrinkles and may elucidate the connection between clinical assessment and appraisal using biophysical measuring methods. Luebberding et al. investigated facial wrinkles in a study designed to compare clinical ratings and 3D fringe projections [34]. Jiang et al. [35] used the SWIRL (Stephens wrinkle imaging raking light) method as an example. The use of this method represents a step towards better understanding of the actions and changes produced by prescription and cosmetic wrinkle treatment products and medical procedures [35]. Another branch of medicine using imaging techniques is breast cosmetics. However, the concept of breast size itself remains controversial. Breast volume and breast density must be distinguished, and the appropriate measurement, whether subjective reporting, cup size, mammographic assessment, or three-dimensional imaging, remains unclear [26]. Ultrasound and mammography are useful imaging techniques for the assessment of reconstructed breasts in symptomatic settings. Magnetic resonance imaging of the breast is another important diagnostic technique that is useful for breast cancer. Its performance is indicated in several situations, including staging of the disease and treatment planning [27]. MR imaging is the most accurate of the three preoperative imaging modalities in assessing the size and number of malignant lesions in the breast. The studies of Faermann et al. [29] were the first to assess the tumor-to-breast volume ratio measured by MRI and to correlate it to the type of surgery selected for the patient (i.e., breast conservation or mastectomy) [29]. To evaluate the comparative accuracy of magnetic resonance (MR) imaging relative to mammography and ultrasonography (US) for the assessment of the extent of breast tumors, Yımaz et al. reviewed the findings of Boetes et al. [28] and Fischer et al. [30] and suggested that the sensitivity and specificity of US and MRI exams for detecting local recurrence were higher than clinical examinations [7, 28, 30]. Furthermore, MRI plays an important role in treatment planning and is more objective in determining the response of tumoral lesions to systemic treatment. The use of 3D imaging and computerized measurements brings a new dimension into surgical planning. Indeed, studies showed that the portrait 3D platform create in cosmetology [35].

Today, many fields, including plastic surgery, depend on photo documentation as a crucial part of both clinical practice and medical education. The most recent advancement in breast plastic surgery is ideally suited for 3D technology. The portrait 3D breast imaging system provides a highly reproducible 3D tool for measuring breast volume and simulating breast augmentation [33].

9. Conclusion

The main reasons for the widespread use of statistical shape analysis in medicine include the fact that geometric morphometric methods are more valid than traditional morphometric methods. Advances in imaging technology have resulted in the protection of a greater amount of morphological information and have permitted the analysis of this information. There is hope that advances in both screening and diagnostic technology will ultimately have a positive impact on treatment. Furthermore, the use of these treatment modalities for cosmetic use has been rising.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

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Copyright

Copyright © 2015 Nevin Utkualp and Ilker Ercan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Personal Factors

Dennis A. Attwood , . Mary E. Danz-Reece , in Ergonomic Solutions for the Process Industries , 2004

2.3.2 Anthropometry: Body Size

Anthropometrists, measurers of the human body, have collected body size data for many years. For example, the measuring units of foot and hand have been derived from the dimensions of body parts. The term anthropometry is derived from two Greek words: antropo(s), or human, and metricos, or measurement. Anthropometry is used extensively by ergonomists to design tools, equipment, plants, manufacturing lines, clothes, shoes, and the like to ensure the proper fit to the person. Therefore, to achieve proper fit, it is important to have details on the dimensions of the appropriate body part. For example, the size of the hand is used to design the dimensions of controls such as switches and push-buttons, while details of arm reach are necessary to position controls at appropriate distances.

Two primary categories of anthropometric data interest ergonomists:

Structural anthropometry, also referred to as static anthropometry or static dimensions. These are measurements with the body in a still or fixed position for example, stature or height, weight, head circumference.

Functional anthropometry, also referred to as dynamic anthropometry or dynamic dimensions. These are measured with the body engaged in various work postures, indicating the ranges of motion of individual body segments for example, arm reach.

It is important to point out that static anthropometry data are often measured on unclothed (nude) individuals, mainly to ensure consistent results. Therefore, corrections must be made to account for increases in body size due to clothing, such as a process operator working outside during an Alaskan winter and another during a Texas summer. In addition, allowances must be made for wearing safety shoes and hard hats, which could add about 10–12 cm (4–5 in.) to the stature that must be considered in the design.

2.3.2.1 Sources of Body Size Variability

The various genetic, biological, and physiological differences between humans influence the way they vary with respect to body dimensions in terms of height, weight, shape, and the like. This can be noticed if you observe people in a shopping mall. Therefore, we need to be very careful using anthropometric data if they are to be of value ( Pheasant, 1982a, 1982b ).

The common practice in ergonomics is to specify anthropometric data in terms of percentiles. A percentile refers to a percentage of the population with a body dimension up to a certain size or smaller. For example, if a 95th percentile height (stature) is 170 cm (66.9 in.), it indicates that 95% of the population have heights up to 170 cm. Or, 95% of the population have heights of 170 cm or less and 5% are taller than 170 cm. If, on the other hand, the 5th percentile stature is 150 cm (59 in.), it indicates that 5% of the population are shorter than 150 cm and 95% are taller.

When a particular design (i.e., placing a valve hand wheel at a given height) is expected to be used by many people, we need to consider the following variables in influencing body size and adjust the design accordingly:

Gender. Men are generally larger than women at most percentiles and body dimensions. The extent of the difference varies from one dimension to another. For example, hand dimensions of men are larger than women sizes—hand finger thickness of men is about 20% larger, while fingers are about 10% longer for men than for women ( Garrett, 1971 ). Women, in general, exceed men in five dimensions: chest depth, hip breadth and circumference, thigh circumference, and skin-fold thickness. O’Brien (1985) proposes a complete list of anthropometric differences between men and women.

Age. Body dimensions generally increase from birth to early twenties, remain constant to around age 40, and decline afterward into old age as part of the normal aging process. For example, stature or height reaches full growth at around age 20 for males and 17 for females ( Trotter and Gleser, 1951 Damon, Stoudt, and McFarland, 1971 Roche and Davila, 1972 Stoudt, 1981 ). Decline in stature is more pronounced in women than in men. Therefore, it is important to define the user population early in the design cycle.

Nationality and culture. Nationalities and cultures differ in body sizes. For instance, Asians tend to be somewhat shorter on average than Northern Americans, while certain cultures from southern Sudan (Africa) tend to be taller. Therefore, it is important for the designer to define and use the anthropometry data related to the user population nationality and culture. Table 2-1 (and Figure 2-5 ) presents an example of anthropometric values for three different nationalities: North American, Japanese, and Hong Kong.

Table 2-1 . Selected Anthropometry Data for Different Nationalities in Centimeters (cm) and Inches (in.)

North AmericansJapaneseHong Kong
95th% Man5th% Woman95th% Man5th% Woman95th% Man5th% Woman
Anthropometric Dimensions(cm)(in.)(cm)(in.)(cm)(in.)(cm)(in.)(cm)(in.)(cm)(in.)
A. Vertical grip/reach217.585.7177.870.0207.581.7168.066.1210.582.9168.566.3
B. Stature/head height184.472.6149.558.9175.068.9145.057.1177.569.9145.557.3
C. Shoulder height152.460.0121.147.7143.056.3107.542.3146.057.5118.046.5
D. Elbow height119.046.993.736.9110.543.589.535.2108.042.587.034.3
E. Eye height172.768.0138.254.4163.564.4135.053.1164.064.6133.052.4
F. Forward grip/reach88.334.864.025.275.029.557.022.477.030.358.022.8
G. Knuckle height80.531.764.325.380.531.765.025.681.532.165.025.6
H. Knee height59.223.345.217.853.020.942.016.554.021.341.016.1
I. Waist height110.543.586.434.089.535.270.027.692.036.271.528.1

Note: Add about 4 cm (1.5 in.) for shoes and 7.5–10 cm (3–4 in.) for hard hat.

Figure 2-5 . Anthropometry figure to guide Table 2-1 .

Occupation. Differences in body size dimensions among occupational groups is common and well documented. For example, manual workers, on the average, have larger body sizes than sedentary workers. Sanders (1977) found truck drivers to be taller and heavier than the general civilian population. This difference among occupations may be the result of

Physical activities imposed by the job (i.e., manual handling).

Imposed selection, such as individuals need to be a certain height to be accepted in a particular job.

Self-selection, such as individuals with a given height choose a particular job for practical or sociological reasons.

We must take great care of not using anthropometric data obtained from groups of one occupation, such as armed forces, to design the environment of another, such as office workers.

Historical trends. The average size of people has been increasing over the years. For instance, the average adult height in Western Europe and the United States increased about 1 cm (0.4 in.) per decade ( Sanders and McCormick, 1993 ). This is so, perhaps, because of better diet, medical care, hygiene, and living conditions. As designers, we need to consider present-day users as well as future generations to ensure proper systems design few decades down the road.

Body position. Posture affects body size. For example, restraints such as seat belts, affect data applicability of forward reach.

Clothing. As mentioned earlier, almost all anthropometric data are obtained from nude individuals. Therefore, the type (material) and amount of clothing add to body size and can also create restriction of movement such as affecting overhead and forward reach. Another example is the use of gloves where allowance must be made to accommodate different thicknesses of gloves.

2.3.2.2 Principles of Body Size Application

When determining the proper anthropometric data to be used in a design, the following must be observed: we need to carefully define the population or group we are designing for and ensure that the data are reasonably representative. For most purposes, a range of dimensions from the 5th to the 95th percentile is generally acceptable. The range can also increase, if possible, from the 2nd to the 98th percentile or even larger. The choice of design percentile is largely a matter of cost. Three general principles of body size application to specific design problems are accepted ( Chapter 6 covers these principles in detail):

Design for the average. The average value is taken as the 50th percentile, meaning 50% of the population is above and 50% below this value.

Design for the extreme. In designing for the extreme, the ergonomists constantly apply the following two principles:

Design fit or clearance dimensions for the largest individual.

Design reach dimensions for the smallest individual.

It is frequently the practice to use the 95th percentile male for the clearance or fit dimensions and the 5th percentile female for reach dimensions. Therefore, it is safe to say that a design that would accommodate individuals at one extreme would also accommodate virtually the entire population.

Design for the adjustable range. Designing for the adjustable range is generally the preferred method to accommodate individuals of varying sizes. This use of adjustability can be seen in car seats, office chairs, desk heights, bench heights in a maintenance shop, adjustable tables for manual materials handling jobs, and the like. However, this may not always be possible:

If we strictly use the range, then we must accommodate people from 3 feet tall to 9 feet tall and weighing from 23 kg (50 lb) to 227 kg (500 lb). This is why the 5th and 95th percentile values are traditionally advocated.

Adjustability may not have any practical value and the cost outweighs the benefit for example, an eye wash station in a plant or a bathroom toilet height.


The basic components of population change

At its most basic level, the components of population change are few indeed. A closed population (that is, one in which immigration and emigration do not occur) can change according to the following simple equation: the population (closed) at the end of an interval equals the population at the beginning of the interval, plus births during the interval, minus deaths during the interval. In other words, only addition by births and reduction by deaths can change a closed population.

Populations of nations, regions, continents, islands, or cities, however, are rarely closed in the same way. If the assumption of a closed population is relaxed, in- and out-migration can increase and decrease population size in the same way as do births and deaths thus, the population (open) at the end of an interval equals the population at the beginning of the interval, plus births during the interval, minus deaths, plus in-migrants, minus out-migrants. Hence the study of demographic change requires knowledge of fertility (births), mortality (deaths), and migration. These, in turn, affect not only population size and growth rates but also the composition of the population in terms of such attributes as sex, age, ethnic or racial composition, and geographic distribution.


Morphological Trends in Human Evolution

There are a number of trends in the evolution of the proto-hominins to modern Homo sapiens. These traits do not occur all at once, but over millions of years. In general, the trends include:

  • the forward movement of the foramen magnum
  • a reduction in the size of the canines
  • an increase in the size of the molars
  • disappearance of the diastema (gap between the incisors and canines)
  • an increase in cranial capacity
  • a decrease in prognathism (jutting forward of the bottom part of the face)
  • thinnng of the bone
  • rounding of the skull

Again, not all of these traits occur at the same time and there is variation among the various hominin species, but all of these morphological characteristics occur in the evolutionary line of Homo sapiens. More details will be given about these traits in the sections on the hominins.

Three other trends are important in the evolution of hominins: bipedalism, non-honing chewing complex, and encephalization of the brain. These are discussed in more detail next.

Bipedalism

For a long time, paleoanthropologists thought that large brains were the first hallmark of becoming human however, research in the 20th century showed that bipedalism, or upright walking, was the first morphological trait on the road to humanity. Human bipedalism differs from the bipedalism practiced by other primates in that it is habitual. In other words, it is the primary form of moving around. Other primates practice facultative bipedalism, which is a temporary form of bipedal locomotion, e.g., primates like chimpanzees may walk bipedally while they carry something in their hands. Few other animals are habitual bipeds, e.g., birds and kangaroos.

There are numerous anatomical changes that evolved to make hominins efficient bipedal locomotors. Here are some, but not all, of the major changes that occurred (eLucy 2007):

  • foramen magnum: the foramen magnum is the hole at the bottom of the skull, allowing for the spinal cord to pass through perpendicular to the ground
  • spinal cord: the s-shape of the spine lowers the center of gravity needed for efficient bipedal walking
  • lumbar vertebrae: hominins have five lumbar instead of four like gorillas, which are also larger than those of gorillas, allowing for more flexibility in the lower back which in turn allows the hips and trunk of the body to swing forward
  • pelvis: the pelvis became bowl-shaped to help support the upper body while walking, aid in balance, and provide for the necessary muscle attachment that allows for the forward swing of leg the hip joint is larger than other apes to help with stress absorption the ilium has a more lateral orientation that helps prevent the leg that is on the ground during walking from collapsing toward the swinging leg wider hips help with maintaining the center of gravity
  • femur: the larger femoral head along with the hip joint absorbs more stress while walking femur, along with the knee joint, is angled toward midline of hip to help with balance--the angle is called the bicondylar angle (this is sometimes called being "knock-kneed")
  • knee: the knee joint, or valgus knee, is closer to the midline of the hip to help with maintaining balance while walking upright
  • tibia: placement is almost directly parallel with center of gravity
  • feet: big toe, or hallux, is inline with other toes, which allows for more force when pushing off while walking the heel bone is robust, which helps with shock absorption and stability--it also allows the attachment of strong ligaments from the ankle to the foot that form a double arch, helping with shock absorption

The morphological changes associated with bipedalism take millions of years to evolve. They first appear with the proto-hominin Sahelanthropus tcahdensis, which is dated to 6.0-7.0 million years ago (mya), but are not fully in place until around 4.0 mya. These physical changes continue to refine until we see them as we do today in modern Homo sapiens (Jurmain et al. 2013).

You can explore all of the anatomical changes associated with bipedalism in more detail by visiting Step by Step: The Evolution of Bipedalism hosted by the Department of Anthropology at The University of Texas-Austin [optional].

Hypotheses on the evolution of bipedalism

Several hypotheses have been proposed over the last century or so to explain the evolution of hominins. As bipedalism is the first trait on the road to modern humans, these hypotheses focus on the emergence of habitual bipedalism. Many have been refuted as new data is discovered. The first hypothesis was the hunting hypothesis proposed by Charles Darwin. The hunting hypothesis claims that the key to human evolution was the shift from an arboreal life to a terrestrial one. He predicted that the earliest hominins would be found in Africa based on the similarities he saw between humans and African apes. He suggested that bipedalism gave the first hominins an advantage in that it freed up their hands to carry weapons used to hunt animals. Darwin also suggested that larger brains preceded bipedalism as intelligence was needed to make the tools. Now we know that habitual bipedalism predates large brains so Darwin's hypothesis is no longer considered an adequate explanation. With the discovery of new data, other hypotheses have been proposed including the patchy-forest and provisioning.

The patchy forest hypothesis suggests that the emerging mosaic environment that began emerging at the end of the Miocene made bipedalism advantageous. The phrase mosaic environment in this case refers to an environment that had patchy forest interspersed with grasslands that eventually became the African savannas that we know today. This caused food resources to become spread out over the landscape. For traveling long distances, bipedalism is more energy efficient than quadrupedalism. Traveling bipedally freed up hands for carrying provisions and the early hominins could have easily fed from both terrestrial and arboreal resources.

The provisioning hypothesis states that having hands free to carry food allowed males to provision females and offspring. Since much of the females energy went to child-rearing, the ability of a male to provision her and her offspring would have been an attractive quality. Those males who could walk more efficiently bipedally while carrying food would have been prime mate material, allowing both the male and female to reproduce successfully.

The truth of the matter is that the origins of bipedalism are still murky. Further research will hopefully help us come closer to a determination of why bipedalism, and hence our early ancestors, evolved. In the meantime, you can explore other hypotheses on the origins of bipedalism on the NOVA web site: http://www.pbs.org/wgbh/nova/evolution/origins-bipedalism.html [optional].

Non-honing Chewing Complex

Apes have a honing chewing complex, which is good for cutting and shredding food. Their upper canines are large, pointed (triangular shape), and projecting. These two teeth also have a sharp edge on the back. This edge is kept sharp because each time the jaws close, the upper canine rubs against, or hones, the sharp edge of the lower third premolar. This can happen because of the diastema present on the jaws that allows for the jaws to close completely. Without the honing action, the canines and premolars would not be able to efficiently shred leaves and fruit.

Over time, hominins lose this honing complex. The diastema disappears, the canine reduces in size, and the molars increase in size (Larsen 2014).

Encephalization of the Brain

Non-human primate brains are symmetrical as are the brains of early hominins. With the emergence of Homo we see the lateralization of the brain--it becomes asymmetrial (right brain, left brain). We know this from endocasts. Endocasts form when minerals replace brain matter inside the cranium during the fossilization process. These endocasts allow paleoanthropologists to study the cortical folds of the brain and compare it to modern humans. Based on endocasts, researchers determined that three areas of the brain began to change in Homo: the cerebellum, which handles learned motor activities, the limbic system, which processes motivation, emotion and social communication, and the cerebral cortex, which is responsible for sensory experiences. It is these changes that may have allowed the early members of our genus to develop cultural adaptations to environmental pressures.

Why did the brain change in early Homo?

The question that confronted paleoanthropologists was why the brain changed. Big brains have some disadvantages:

  • it take approximately 25-30% of a human's metabolic energy to run their brain
  • requires infants to be born prematurely, resulting in a longer period of infant dependency (the average infanat brin is about 1/3 the size of an adult brain)
  • longer infant dependency is an increased drain on maternal energy the mother must have proper nutrition not only for herself but for the nursing infant
  • it has been suggested that larger brains decrease the bipedal efficiency of females because they must have a wider pelvis and birth canal to give birth to a large brained infant

So, for large brains to become fixed in the Homo population, the advantages had to outweigh the disadvantages listed above.

One possible explanation incorporates the interaction of three different variables: group size, complex subsistence patterns, and the nutritional value of meat (Campbell and Loy 2000: 318). Let's address group size first. Research suggests that brain size and size of social groups correlates positively among living primates, implying that big brains helped individuals keep track of such things as dominance hierarchies, allies, etc. Second, a big brain allows for primates to keep track of large subsistence territories and allows for omnivores to develop strategies for collecting a wide-variety of foodstuffs. Third, eating meat is a relatively easy way to get the nutrition needed to run a big brain, which, as mentioned above, in modern humans takes about 1/3 of our daily metabolic energy. The argument for this, the social brain hypothesis, is laid out by Robin Dunbar in this [psych.colorado.edu/

tito/sp03/7536/Dunbar_1998.pdf article]. Dunbar also claims that it was changes in the neocortex, a 2-4mm thick top layer of the cerebral hemispheres, that were critical in the "homininzation" (development of cognitive abilities) of our ancestors. Please read this short article on the evolution of human cognitive abilities.


Acknowledgements

We gratefully acknowledge The Royal Society Professors Eric Barrington, Graham Burton and Ashley Moffett for inviting us to participate in the June 2014 Royal Society discussion meeting, ‘Human Evolution: Brain, Birthweight and the Immune System’ and other discussion meeting participants for thought-provoking and helpful comments. We also thank Matt Cartmill, Yoel Rak, Chris Ruff, Jack Stern, Steve Churchill, Michael Black and Wenda Trevathan for stimulating conversations about pelvic mechanics and selective pressures on pelvic shape. Finally, we are grateful to two anonymous reviewers for suggestions that improved the quality of this paper. L.G. and D.S. researched, wrote and edited this manuscript.

Funding statement

We are supported by Radford University Department of Biology and College of Science and Technology and Duke University Department of Evolutionary Anthropology.


The Apportionment of Human Variation: Genetic Diversity Is Greater Within-Group Than Between-Groups

One problem with race-based classifications is they relied on an erroneous idea that people within a typological category were more similar to each other than they were to people in other groups. In other words, “race” concepts were predicated on the notion that individuals with particular characteristics would share more similar genes with each other within a particular “race” and share less with individuals of other “races” possessing different traits and genetic makeups. However, since around 50 years ago, scientific studies have shown that the majority of human genetic differences worldwide exist within groups (or “races”) individually rather than between groups.

Richard Lewontin (1929‒) is a biologist and evolutionary geneticist who authored a paper evaluating where the total genetic variation in humans lies. This article, titled “The Apportionment of Human Diversity” (Lewontin 1972), addressed the following question: On average, how genetically similar are two randomly chosen people from the same group when compared to two randomly chosen people from different groups? Lewontin studied this problem by using genetic data. He obtained data for a large number of different human populations worldwide using 17 genetic markers (including alleles that code for various important enzymes and proteins, such as blood-group proteins). The statistical analysis he ran used a measure of human genetic differences in and among populations known as the fixation index (FST). Technically, FST can be defined as the proportion of total genetic variance within a subpopulation relative to the total genetic variance from an entire population. Therefore, FST values range from 0 to 1 (or, sometimes you will see this stated as a percentage between 0% and 100%). The closer the FST value of a population (e.g., the world’s population) approaches 1, the higher the degree of genetic differentiation among subpopulations relative to the overall population. In his paper, Lewontin (1972) identified that most of human genetic differences (85.4%) were found within local subpopulations (e.g., the Germans or Easter Islanders), whereas 8.3% were found between populations within continental human groups, and 6.3% were attributable to traditional “race” groups (e.g., “Caucasian” or “Amerind”). These findings have been important for scientifically rejecting the existence of biological races (Long and Kittles 2008).

In 2002, another landmark article by Noah Rosenberg and colleagues (2002) explored worldwide human genetic variation using an even-greater genetic data set. They used 377 highly variable markers in the human genome and sampled from 1,056 individuals representative of 52 populations. The markers chosen for study were not ones that code for any expressed genes. Because these regions of the human genome were made of unexpressed genes, we may understand these markers as neutrally derived (as opposed to selectively derived) as they do not code for functional advantages or disadvantages. These neutral genetic markers likely reflect an intricate combination of regional founder effects and population histories. Analyses of these neutral markers allowed scientists to identify that a majority of global genetic variance (93%‒95%) can be accounted for by within-population differences at the 377 genetic loci, while only a small proportion of genetic variance (3%‒5%) can be attributed to differences among major groups (Rosenberg et al. 2002). Like Lewontin’s (1972) findings, this lends support to the theory that distinct biological races do not exist, even though misguided concepts of race may still have real social and political consequences.


Why Is the Human Vagina So Big?

We are obsessed with penis and testicle size. Yet, we can barely say &ldquovagina&rdquo and when we do we&rsquore usually talking about the vulva.

Everyone&rsquos come across some article somewhere on-line that is thrilled to share how big human penises really are, for primates, and to explain why they evolved to be so big. It&rsquos not really the length, but the girth. Alan Dixson is your go-to on this. He&rsquos conservative in his assessment of the literature on penis size and even he concedes that human penis &ldquocircumference is unusual when compared to the penes of other hominoids (apes)&rdquo (p. 65 in Sexual Selection and the Origins of Human Mating Systems).

A favorite explanation for the big phallus is female mate choice, that females selectively make babies with males who have larger and, presumably, more pleasurable semen delivery devices. This is backed up by studies. When life size projections of naked men are shown to female subjects, they say they find the ones with bigger ones to be more attractive. [This is exactly how mate choice works where I live, how about you?]

Other explanations include male competition. If you can deliver your package to the front yard but the other guy can deliver to the front door, his is more likely to be carried inside the house first. Or, if he can steal away what you just delivered, then, again, his package has yours beat. Thanks to his big penis he&rsquos more likely to pass on his winning penis genes than you are to pass on your loser penis genes. Loser.

All this is just terribly fun to write about and I&rsquom not even going nuts (gah) like they do. And they do. They really do. And all over the Internet they do: &ldquoEvolution of human penis&rdquo gets 53,000 hits just on scholar.google alone, and about 832,000 on Google.

But doesn&rsquot it make sense that for a penis to be somewhat useful it has to be somewhat correlated to vagina size?

I&rsquom talking about all penises in the universe and all vaginas too. Sure there&rsquos variation, but a penis can&rsquot be too wide. It helps to be long, probably, but it can&rsquot be too long.

So neither pleasure nor psychology need matter at all, just function associated with some sort of fit. Pleasure and psychology are never invoked to explain penis morphology in other animals. If anything, it&rsquos the cornucopia of horrifying, not pleasing, animal penises that begs for evolutionary explanations.

Examples of genital covariation in waterfowl. Stars are male parts, arrows show female parts. Figure from &ldquoCoevolution of Male and Female Genital Morphology in Waterfowl&rdquo DOI: 10.1371/journal.pone.0000418

Wouldn&rsquot you explain the size and shape of the key by the size and shape of the lock? So wouldn&rsquot it be a little more scientifically sound to hypothesize that the human penis is sized and shaped like that because it fits well into the human vagina?

Sure, it gets chicken-and-eggy or turtles-all-the-way-downy, but c&rsquomon. Isn&rsquot it a bit obvious that the privates that fit inside the other privates are probably correlated? You&rsquod think that even the people who have never had intercourse would default to this explanation for the evolution of the human penis.

But we&rsquore rarely, if ever, told that human penises are relatively girthy because human vaginas are. It&rsquos always about male competition or female preference.

Sure, we may be a little weird compared to our close relatives for not having a baculum (penis bone), and maybe that&rsquos the sort of thing you want to explain for whatever reason, but does human penis size and shape need a uniquely human story?

Assuming it&rsquos correlated to the vagina like it probably is in many other species,* then no it doesn&rsquot&hellip unless the size and shape of the human vagina has an exceptional story.

Does it? We wouldn&rsquot know. There are zero (look!) articles titled &ldquoWhy is the human vagina so big?&rdquo

Here we go. If we were going to answer it the same way we&rsquove long explained the human penis, and other animal penis shapes, then we&rsquove got a few ideas&hellip

Because walking upright made the vagina conspicuous and males thought a bigger vagina was better. Because big vaginas outcompete small ones at catching sperm. Because of male pleasure from coitus with a big vagina. Because of heat dissipation or thermoregulation. Because of a tradeoff with brain size.

And of course, we&rsquod need to demonstrate that the human vagina is in fact larger, relative to body size, than the vaginas of other primates. Regardless, a sound answer to the question of vagina size and shape focuses on childbirth, wouldn&rsquot you say? She&rsquos got to be big enough to push out a baby and, for humans, it&rsquos a great big baby.

Comparison of orangutan (Pongo), gorilla, chimpanzee (Pan), and humans. These are essentially departures from a primate-wide regression analysis. Figure from Dunsworth et al. 2012. PNAS 109(38): 15212-15216.

So if there&rsquos an exceptionally human story for the great big human penis, that exceptional story originates not in a woman&rsquos orgasms, not in her pornographic thoughts or her lustful eyes, but in her decidedly unsexy &ldquobirth canal.&rdquo

And I dug up a nice little note to explain this to us all written by Dr. Bowman, a gynecologist, back in 2008 for the Archives of Sexual Behavior which is magnificent. It starts out giving the only vagina-size-based, not to mention childbirth-based, explanation for human penises that I can find in the literature (which is thankfully cited by Dixson in his book mentioned above). But it still manages to bring the explanation beyond the vagina and onto another proud triumph: &ldquoIn sum, man&rsquos larger penis is a consequence of his larger brain.&rdquo

After you clean up the coffee you just spat onto your computer screen, you can read it all for yourself by clicking on the link up there (or emailing me for the pdf).

Guess who didn&rsquot read it? That study in PNAS, mentioned above, that showed women naked penises, got a high attractive score for the big ones, and thinks that&rsquos evidence for mate choice now, today, let alone back when (I&rsquom going to speculate that) women had a tiny bit less of it.

Point is, the literature rages on with the special explanations for the big penis with nary a big vagina in sight.

But you heard it here, at least.

Childbirth is why the human vagina is so big and, consequently, why the male penis is so big. It&rsquos pretty straightforward. Yet we&rsquore still left scratching our heads as to why the penis question endures.


Watch the video: Human Mind. Mind Dimension. Human Mind Psychology. Sadhguru on Mind (June 2022).


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