In a famous manifesto, the geneticist Theodosius Dobzhansky (1900-1975) claimed in 1973 that “nothing in biology makes sense except in the light of evolution.” One could also wonder if anything in anthropology makes sense except in the light of evolution. Indeed, there is a part of anthropology that does not deal with evolutionary issues. This is true for most of cultural anthropology, especially on the fringe of the sociology domain. It is even true for some aspects of physical anthropology. Medical anthropology deals with the health status of different populations in relation to different geographical and sociocultural environments. Forensic anthropology focuses mostly on identification of body remains, as well as of living subjects. It should be also underlined that anthropology was born and developed as a science in a preevolutionist period. Although the word anthropologos was used in antiquity, it is not before the Renaissance that it was used in a context involving goals of knowledge. Until the Classical Age, it was mostly centered on the “knowledge of one’s self.” However, dissertations on the moral nature of humans developed in parallel to studies of character and anatomical descriptions. From the middle of the 16th century, surgeons such as André Vesale (1514-1564) put emphasis on the anatomical determination of the human body. The word anthropologia appears for the first time in its anatomical meaning in a German book by Magnus Hundt (1449-1519), published in 1501, Anthropologium, de hominis dignitate, natura et proporietatibus. In the 17th century, anthropology, the science of the study of humans, was divided between anatomy, addressing the body structure, and psychology, which speaks about the soul. In the 18th century, the first anthropological syntheses were developed, including the Treaty of Man by Georges-Louis de Buffon (1707-1788) and The Anthropology or General Science of Man published in 1788 by Alexandre Cesar Chavannes (1731-1800). Under the influence of the 18th-century naturalists such as Carl Linnaeus (1707-1778) and Buffon, anthropology became the natural history of humans. It was defined as such in 1795 by Johann Friedrich Blumenbach (1752-1840). The middle of the 19th century is marked by the creation of anthropological institutions, faculty chairs, and scientific societies in France, England. Germany, and the United States.
Revolutionary Perspectives on Anthropology
Anthropology was already established as an official science when three major events revolutionized perspectives on the place of humans in nature. In 1856, fossil remains of an extinct form of humans were discovered in the site of Feldhofer (Neandertal, Germany). Discoveries of fossil humans had already occurred in 1830 in Belgium (Engis) and in 1848 in Gibraltar (Forbe’s Quarry). However, although these specimens were later identified as genuine fossil hominids, the finding of Neandertal was the first recognized as such. It is not before the latter part of the 19th century that the concept of Neandertals as a distinct and extinct form of humans was universally accepted. Second, in 1859, Charles Darwin (18091882) published his master work, On the Origin of Species by Means of Natural Selection. The notion of evolutionary change in living species predated Darwin, and the French scientist Jean-Baptiste Lamarck (1744-1829) can be considered the father of the evolution concept in its biological meaning. However, Lamarck failed to propose a valid mechanism to explain the mechanism of evolutionary processes. The primary contribution of Darwin was the identification of natural selection as a major force driving evolutionary changes. The third event of major importance also occurred in 1859. English archaeologists and geologists including Hugh Falconer (1808-1865), Joseph Prestwich (1812-1896), and Sir John Evans (1823-1908) accepted the association of human-made Paleolithic flint implements with extinct fauna in geological ancient deposits that had been described by Jacques Boucher de Perthes (1788-1868) in northern France. Although a large portion of anthropological studies still remained out of the evolutionary perspective, beginning with this period, prehistoric archaeology and human paleontology became important topics of research for cultural and physical anthropologists. Because of the complexity of the roots of anthropology, this science is the crossing point of several distinct fields of knowledge and is multidisciplinary in nature. Evolutionary anthropology can be defined more as a perspective than as a science. It is the synthesis of the various fields of anthropological studies addressing the behavioral and biological nature of humans and their mechanisms of emergence through time.
Human Evolutionary Processes
Looking at the anatomical changes of humans in a remote past, and at the changes in technical skills, is the most obvious way to approach human evolutionary processes. Indeed, paleoanthropology represents the core of evolutionary anthropology and is essentially the field that unites all the others. The term paleoanthropology is sometimes understood as a synonym of human paleontology; however, more often it encompasses paleontological and archaeological studies. In the course of their evolution, humans have combined biological and cultural adaptations while they geographically expanded. Even if technical responses to the challenges offered by the conquest of new geographic and ecological niches became preponderant, it is most important to consider the two aspects of human adaptation and their complex interactions. One defining aspect of human paleontology lies in the fact that the study of rare and precious specimens remains the core of the discipline. The fossil hominids give a very fragmentary and discontinuous picture of the past evolution of humans. Traditionally, they have been described and compared in order to provide a picture of the phylogenetic tree of our ancestors and direct relatives. One major problem in this process is related to the difficulty in accessing specimens. After discovery, they can remain unpublished for long periods, and later, they can be possibly under the care of curators more preoccupied by conservation than by scientific studies. Since the 1990s, new techniques, primarily from medical imaging (for example, CT scanning) have allowed development of new approaches for the study of these fossils. “Virtual paleoanthropology” is based on the utilization of 3-D images that allow virtual extraction and reconstruction, precise quantitative analyses of internal structures, and also mathematical analyses of the shape through 3-D morphometrics and the modelling of ontogenetic processes, biomechanical properties, and evolutionary changes themselves. Although the resolution of these 3-D images is still far from perfect, one can expect that in the future their use will reduce the need to access the specimens. Work on the original specimens will be restricted to specific issues such as the analysis of fine anatomical details, cut marks, microstructure, and chemical composition.
A new series of approaches have developed, inherited primarily from histology, geochemistry, and biochemistry. With the rise of non- (or less) destructive methods, this field is rapidly expanding. In parallel, it should be noted, there have been growing interests in biological issues, for example, diet or growth processes, that are not directly related to phylogentic issues. Microstructural studies have developed mostly in the field of dental anthropology. Several types of incremental mineralized structures, to date, represent the primary way to assess life history in extinct species. This emergence of microstructural analyses has been made possible by large technological advances in microscopy.
Chemical analyses of fossil specimens aimed to reconstruct paleobiological features are mostly concerned with extraction of organic molecules. The sequencing of small fragments of mitochondrial DNA extracted from fossil remains of humans and animals has opened a new area of paleobiological study. The analysis of stable isotopes, mostly carbon, oxygen, and nitrogen, represents another major field of research in paleoanthropology. Stable isotope rate is an essential source of information about the environment and the diet of individuals during their lifetimes. In the future, issues such as migration and seasonality will become accessible through these kinds of studies. These methods may also provide a better knowledge of the environmental conditions of humans in the continental environment.
Paleoanthropologists place a great deal of emphasis on the understanding of evolutionary processes. Important methodological progress was made in the 1970s with the rise of cladistic methods. However, specialists still investigate the significance of the features used in phylogenetic analysis. To what extent are they genetically determined, or depend on environmental conditions and behaviors? Are they homologous from one species to another? These are the questions that need resolution in order to gain better insight into phylogenetic relationships. Among the paleobiological issues, changes in growth and development processes along life history are increasingly seen as a powerful mechanism to explain evolutionary changes. A consistent effort is applied to the establishment of developmental trajectories in extant hominoids and extinct hominins. Other aspects of the biology of extinct species are also accessible through the progress of archaeological sciences. Proteins and lipids are extracted with increasing frequency from fossil bones and may give us access to physiological features that have been inaccessible to date. Paleodemographic questions related not only to life history and longevity but also to population size and their fluctuations through environmental changes are also of high interest.
Importance of Fieldwork
A very important aspect of paleoanthropological studies is related to fieldwork. The spectacular increase of fossil material in the last two or three decades, resulting in a much better understanding of human evolutionary history, is mainly the consequence of the development of field surveys and excavations. This is also where, often, human paleontologists and prehistoric archaeologists meet. Contrasting with the rarity of ancient human remains, artifacts are found in large numbers in areas where humans have lived in the past. The occurrence of stone artifacts is the most reliable parameter to assess the occupation of given geographical areas through geological time. However, the abundance of stone artifacts provides a biased picture of ancient behaviors and technologies.
The evidence for the “Stone Age” comes mostly from the fact that tools manufactured by flaking of hard stones are virtually indestructible and can accumulate in very large numbers over long periods of time. Most of the Pleistocene was actually, rather, a “Wood Age,” at least in some parts of the world. The study of archaeological sites with mixed artifacts, faunal remains, and sometimes structures such as fireplaces left by humans aim to separate human activities from natural processes. Most of the time, it is a somewhat naive view to assume that these accumulations represent “habitats.” In many cases, human occupation was discontinuous and other mammals such as carnivores may have played a major role in the accumulation and alteration of the faunal remains. The artifacts themselves could be displaced in a secondary accumulation. Finally, the whole site may have undergone significant geological modifications. Site formation and taphonomical studies are important issues in the interpretation of archaeological sites. The density and distribution of the human occupations in the landscape are related to environmental factors that one tries to discriminate. These data help us to understand the history of the peopling, past demographic fluctuations and the way ancient humans could exploit the environment. Zooarchaeology research aims to analyze the faunal remains in order to reconstruct hunting (or scavenging) strategies, carcass processing, and transportation and, in a broader context, how ancient hunter-gatherers interacted with the animal world. The stone and bone artifacts themselves are the objects of many studies. They were, in the past, considered as chronological markers, but today the technology leading to their production has become of greater interest and gives us some clues about the skills and cognitive abilities of ancient humans. The raw materials that have been used by ancient humans also inform us about the patterns of land occupation and possible long-distance exchanges between human groups. For the most recent periods of prehistory, the occurrence of symbolic manifestations such as body ornaments, geometric signs, paintings, engravings, and sculptures reveals the development of modern thinking. It can give some clues on the major changes in the social organization in humans and, likely also, in the development of modern language. For these late periods, it is possible to use the archaeological evidence to identify ancient ethnocultural entities.
Study of Nonhuman Primates
Because evolutionary anthropology is mainly concerned with the question, “What makes humans different?,” the study of nonhuman primates represents an important part of its scope. In this perspective, primate studies focus on biological and behavioral aspects. A large proportion of evolutionary studies have been dedicated to comparative anatomy and physiology. Attention has also been paid to differences in the process of growth and development among different species of monkeys and apes. Primate paleontology is an important field of research, as it brings light on the phylogenetic relationships of living and extinct species and also on the adaptive strategies of the different groups. However, with respect to phylogeny, molecular studies and genetics have as well made a very significant contribution in the last decade. Finally, social organization and behavior of living apes and monkeys is also an important field of research that aids in understanding the emergence of hominin societies.
Among the primates, the species that are the closest to our own are classified together with humans and their ancestors into the superfamily of hominoids. This is the reason that many studies put emphasis on the gibbons, the orangutans, and our even closer relatives, the African apes: gorillas, common chimpanzees, and bonobos. One major problem faced by evolutionary anthropology lies in the fact that, in the wild, these species are greatly endangered. Although they may survive only in zoos in the near future, there is still a lot to learn from them. This is especially true in the areas of development, genetics, and ethology (the science of animal behavior). Unfortunately, life in captivity will make many questions regarding these issues inaccessible. In the past, hominoids have been a much more successful group than they are today. The human species, which covers an entire planet, represents an exception. In fact, the number of species of hominoids has been reduced since the Miocene period. Other groups of primates (cercopithecoids), on the contrary, have undergone an expansion during the same period. Hominoids represent a group of middle- to large-bodied primates, primarily adapted to forested or semiforested environments. Analyzing the anatomy of the living and fossil species is of crucial interest to understand human origins. Indeed, hominins achieved a very unique adaptive model. They adapted to a new evological niche for hominoids, in particular the open environments of the middle and high latitudes. They adapted to an entirely new locomotor repertoire with the development of bipedalism. They accessed new diets with the developments of carnivory and hunting. Finally, they developed cultural and technical adaptations to a level unequalled in the primate world. In an evolutionary perspective, primatology is interested in analyzing these differences between humans and apes but also in the separate emergence of some features once considered unique to humans in the other hominoids. In terms of behavior, it is important to understand how the variety of social systems developed by apes responds to different adaptative strategies. This includes social organization and reproductive patterns that can be quite different from one species to another. The types of cognitive abilities that have been developed by these different species are under the scrutiny of primatologists. Sociocognitive processes, including communication, cooperation, social interactions, and learning, are also very important to analyze.
It is fascinating to consider the behavioral diversity that can exist between different populations of the same species of apes. One of the most important discoveries of the last decades has been the revelation of “ape cultures.” Different groups within the same species can develop “traditions.” This issue has been studied especially in common chimpanzees in which technical skills involving the use of tools such as hammers and anvils, but also “fishing sticks” to acquire insects, have been described. These technologies, as well as specific behaviors such as hunting strategies for a spectrum of prey, are transmitted between generations and vary from one group to another. Wherever possible, wild apes are studied by direct observation in the field, which implies long-term projects dedicated to the follow groups and individuals over long periods of time. In the course of these field projects, some biological aspects are also analyzed, and molecular geneticists analyze samples of feces and hair collected noninvasively to address questions concerning paternity, reproductive strategies, relatedness between and within social units and phylogeny.
Evolutionary anthropological genetics investigates the genetic history of primates in general and humans in particular. This field of evolutionary anthropology focuses on the processes directly affecting the evolution of the genome, such as mutation, recombination, natural selection, and genetic drift. Rebuilding the detailed history of different lineages in terms of demographic evolution and phylogenetic relationships is also of great interest in this discipline. With increasing frequency, studies are dedicated to living great apes, which provide a very important comparative model for the evolution of early hominids even if, in general, their demographic and genetic evolution differed in important ways from our own over the course of the last 2 million years. Molecular phylogeny has provided invaluable information on the origin, relationships, and times of divergence for the different species of hominoids, including humans. Another important aspect of genetic studies is dedicated to examining the ways in which the genome determines development and function of organisms. The comparison of the gene expression patterns in various tissues in primates has given us a greater understanding of many biological aspects of the human nature. The history of ancient populations, or even extinct species, can be approached by using genetic analyses. It is possible to extract, amplify, and sequence mitochondrial DNA fragments from fossils, such as Neandertals 40,000 years old. This genetic information helps us to establish the phylogenetic status and times of divergence of such an extinct species. It provides insights into the variation of the size of these ancient populations throughout their evolution. Fossil DNA is as well extracted from nonhuman mammals, which were the hunted game or the competitors of our ancestors and relatives. Such genetic material is extracted from bone remains but also from coprolites (fossil feces). It provides data for interesting comparisons, as animal material is much more abundant that are human fossils. A major challenge faced by paleogenetics results from the problem of contamination of ancient samples by modern human DNA, which is abundant in our present environment. Paradoxically, it is easier to identify genuine fossil DNA in extinct humans such as Neandertals than in more recent modern populations.
Population Genetics
Since the 1980s, population genetics has emerged as a major methodological framework in which to understand the origin, migration, and evolutionary history of the modern humans and their direct ancestors.
The analysis of genetic variation in living populations has been intensively explored in evolutionary anthropological research. This is particularly true for research examining variation in the mitochondrial DNA, transmitted from mother to offspring, and in the Y chromosome, exclusively transmitted from fathers to sons. Most of these studies establish a recent origin of modern humans (between 200,000 and 100, 000 BP), most likely in Africa. They suggest past bottlenecking of ancient populations and indicate a late dispersal of modern populations throughout Eurasia and Australia, and even more recently, throughout the Americas and the Pacific Islands. Genetic analysis provides not only a general tree for human populations but also some indications of the timing of colonization by modern humans. In the details, it can bring some light on interactions between groups, mating strategies, differences in mobility between genders, or the geographical origin of pioneer groups like those that colonized the Pacific. Population genetics often interacts with linguistics in order to elucidate the detailed history of human groups. Like genes, languages are transmitted from parents to their children. Words and grammatical structures also undergo “mutations,” which result in a diversification and divergence of numerous linguistic groups.
Language is indeed a unique feature of humans, and a great deal of effort is dedicated to the study of its structure and evolution. Although “communication” is common among other animal species, human language distinguishes itself by the complexity of sounds that the human vocal tract is capable of producing, as well as the control of sound production at a rapid time scale. It is also characterized by the complexity of its syntax, which facilitates the organization of concepts in a way that goes much further than the simple combination of vocal signals. The question of the origin of language is difficult and much debated. Anatomical features allowing the physical production of human languages, as well as the cerebral abilities necessary for its manifestation, may well have been selected independently and for other needs in the course of hominin evolution. Linguists are very much interested in establishing the common features of all human languages (“language universals”). Some have even tried to delineate some traits of an original language ancestral to all the others. Language universals may result primarily from the way the human mind is able to conceptualize ideas and articulate them into speech. Other aspects of linguistic studies are dedicated to the way languages can differ from each other and how they vary over the course of time. Understanding these processes allows the construction of language trees at different scales. Families of languages descending from a single ancestor have been established. Sometimes they present distribution that can be related to the spread, development, or movement of large human groups. Establishing the relationships between these families into larger units has proven to be a more difficult task. The fact that linguistic traits can be imposed or adopted from one group to another through complex historical processes greatly complicates comparisons of archaeological, genetic, and linguistic features in order to rebuild the history of different populations.
Developmental and Comparative Psychology
Developmental and comparative psychology is also crucial to the understanding of what makes humans different. This field of research investigates cognitive and social features of humans and compares them to those of other primates. These studies aim to establish the abilities that have been uniquely developed by humans. Studies on large apes are generally conducted through experiments exploring the abilities of the different species. The field also explores individual variation within groups. Several types of cognition are explored and are generally grouped into two areas referred to as social cognition and physical cognition. The first is relevant to how individuals are able to understand the actions and intentions of other individuals. Analyzing the learning and imitation processes is a main issue in the analysis of social cognition. Physical cognition is implemented by individuals in their interactions with their environment. Experimental psychology is also much interested in the development of human children. Humans contrast with other primates with an extended period of brain maturation occurring after birth while the individual is already interacting with his or her physical and social environment. The learning period is longer in humans than in any other species of primates. The acquisition of language is one of the most spectacular changes during this period. Psychologists are interested in how humans read and understand the minds of other people and develop social skills during the first year of life. Techniques of medical imaging have opened the possibility to connect the brain development with the acquisition of specific abilities. In older children, the development of social and physical cognition is also explored. The acquisition of language is, of course, a main focus of interest. Its learning processes are investigated in a clinical way, as well as cross-culturally.
Evolutionary psychology also analyzes human behavior in adults. The reproductive strategies, mating patterns, and parental investment in children have played a particularly important role in the past and present evolution of human groups. However, the field extends to many other behaviors, such as reciprocity and cooperation between individuals, or even violence and homicide. The determinism of these behaviors and/or of their transmission is often difficult to clarify, as they are also depending on cultural and economical conditions. Ultimately, cultural features in past and present societies can also be assessed in an evolutionary perspective.
The animal nature of humans has always been a matter of fascination, if not of anxiety, for us. For centuries, philosophers, writers, and scientists have tried to define the unique nature of humans and to separate them from the animal world. Evolutionary anthropology deals with the oldest origins of humans, among the primates, and utilizes our closest relatives as comparative models. It interprets the complex features of human behavior in the light of adaptation and faces the challenge of unweaving the complex interactions between biology and culture at work in the course of human evolution.
References:
- Barrett, L., Dunbar, R., & Lycett, J. (2002). Human evolutionary psychology. New York: Palgrave.
- Boesch, C. (2000). Behavioral diversity in chimpanzees and bonobos. Cambridge, UK: Cambridge University Press.
- Cavalli-Sforza, L. L. (2000). Genes, peoples and languages. Berkeley: University of California Press.
- Delson, E., Tattersall, I., van Couvering, J. A., & Brooks, A. S. (Eds.). (2000). Encyclopedia of human evolution and prehistory. New York: Garland.
- Klein, R. (1999). The human career: Human biological and cultural origins (2nd ed.). Chicago: University of Chicago Press.
- Spencer, F. (Ed.). (1997). History of physical anthropology (Vols. 1-2). New York: Garland.
- Tomasello, M. (2003). Constructing a language: A usage-based theory of language acquisition. Cambridge, MA: Harvard University Press.
