Biological Anthropology Definition
Biological anthropology is concerned with the origin, evolution and diversity of humankind. The field was called physical anthropology until the late twentieth century, reflecting the field’s primary concern with cataloging anatomical differences among human and primate groups. Biological anthropology is one of the four subfields of anthropology, together with archaeology, linguistic anthropology, and social/cultural anthropology. Under the name of biological anthropology, it is an ever-broadening field that encompasses the study of: human biological variation; evolutionary theory; human origins and evolution; early human migration; human ecology; the evolution of human behavior; paleoanthropology; anatomy; locomotion; osteology (the study of skeletal material); dental anthropology; forensics; medical anthropology, including the patterns and history of disease; primatology (the study of non-human primates); growth, development and nutrition; and other related fields.
Anthropology is the scientific study of humankind (Birx, 2006a). It strives for a comprehensive understanding of and proper appreciation for our species within the earth’s history. As such, anthropology is grounded in the empirical facts of the special sciences and the logical argumentation of critical thought. Furthermore, scientific evidence is supplemented with rational speculation, especially when facts are lacking. Ongoing advances in science and technology continuously add new information to the growing discipline of anthropology, thereby strengthening some concepts and hypotheses, while modifying or dismissing others.
Besides incorporating the scientific method, anthropologists view the natural history of humankind within an evolutionary framework (Fortey, 1998; Hublin, 2006; Mayr, 2001). Our species is seen as a product of organic evolution in general, and primate history in particular. The human species is related to apes, monkeys, and prosimians. Both fossils and genes substantiate the biological and historical unity of primates in terms of the factual theory of organic evolution (Coyne, 2009; Ridley, 2004).
Biological anthropologists (Kennedy, 2009) use the comparative method in order to understand and appreciate the evolutionary relationships among primate fossils, as well as living species. They compare and contrast fossil skeletons (especially jaws and teeth), DNA molecules, and morphologies (both anatomy and physiology), as well as psychological and behavioral patterns. A convergence of facts and concepts clearly shows that the human animal is closely related to the four great apes, or pongids (orangutan, gorilla, chimpanzee, and bonobo).
This anthropological quest is both intradisciplinary and interdisciplinary. Specialists in the discipline work together to achieve a comprehensive and coherent view of our human species; for example, biological anthropologists work closely with prehistoric archaeologists at a fossil hominid site, while sociocultural anthropologists work closely with anthropological linguists in studying other societies with different cultures (particularly nonliterate peoples with a “primitive” technology). One goal is to derive meaningful concepts and generalizations from the vast range of empirical evidence (Fuentes, 2007).
More and more, as naturalists and humanists, anthropologists are multidisciplinary in their approach. They strive to be relevant in the modern world. Consequently, one speaks of applied anthropology (e.g., forensic anthropology and biomedical anthropology). Anthropological knowledge adds to human enlightenment, particularly in terms of increasing tolerance for human biological and sociocultural differences. In the discipline of anthropology, teaching and research go hand in hand; that is, biological anthropologists aim for a clearer view of humankind that concerns its evolutionary past, present convergence on the earth, and future possibilities (perhaps its migration beyond our planet and even outside this solar system).
Biological anthropologists focus on the organic evidence of primates (e.g., their fossils, skeletons, teeth, genetic makeup, and physical characteristics, as well as psychological and social behavior patterns). They present this evidence in a comprehensive and intelligible manner, while searching for meaningful concepts and generalizations about primate evolution in general, and our species in particular.
The German naturalist Johann Friedrich Blumenbach (1752–1840) is considered to be the father of biological anthropology (previously known as physical anthropology) because he focused on studying the human variations in those biological characteristics that manifest themselves within a population and among populations. Although the academic discipline of anthropology did not yet exist, his pioneering research paved the way for the later, intensive studies of our species and the other primates—from comparative paleoanthropology to comparative genetics.
Charles Darwin (1809–1882) was a major influence on the emergence of biological anthropology. As presented in his two major works, On the Origin of Species (1859) and The Descent of Man (1871), his theory of evolution suggested that much light would be shed on the history of lifeforms and the nature of our own species (Darwin, 1859, 1871). The origin and development of humankind, as well as its evolutionary relationships to the other primates, now became the subject matter for scientific inquiry. No longer was our species viewed as being isolated from other lifeforms or organic history. As such, the discipline of anthropology dedicated itself to rigorously studying humankind in terms of science and reason (Bollt, 2009).
As biological anthropologists, early naturalists worked alone in their search for fossil hominid specimens. Usually, outside funding was not available and significant findings were often dismissed by the scientific community. However, as more evidence was discovered, the theory of human evolution was taken seriously. Since the middle of the 20th century, paleoanthropologists have stressed a multidisciplinary approach (both intradisciplinary and interdisciplinary) in their research (Wolpoff, 1999). As a result, at a fossil hominid site, a scientific team of international specialists may include chemists, geologists, paleobotanists, paleozoologists, prehistoric archaeologists, photographers, and artists. Specialists also work with paleoanthropologists in museums and laboratories. Some biological anthropologists specialize in primate-behavior studies or primategenetics research (including twin studies, as well as growth and development research). Today, thanks in part to anthropologists, there is a growing awareness of the critical relationship between our species and the natural environment, both inorganic and organic. Academic books (Angeloni, Parker, & Arenson, 2009; Haviland, Walrath, Prins, & McBridge, 2008; Park, 2010; Relethford, 2010; Stanford, Allen, & Antón, 2009), professional journals, museum exhibits, college and university courses, and educational programs in the mass media are making the scientific evidence in biological anthropology available to a widening audience of teachers and students, as well as the interested public. The presentation of facts, concepts, hypotheses, and perspectives is very helpful in discrediting racism and promoting evolution.
The idea of evolution neither originated with the thoughts of Charles Darwin nor had its final formulation in his scientific writings; as such, one may speak of the evolution of evolution from an early concept in antiquity to its present status as a brute fact of the modern worldview (Birx, 1984, 1991b).
During the pre-Socratic Age, several early philosophers as natural cosmologists anticipated the evolutionary framework in their rational speculations on the nature of things. Rejecting legends and myths, as well as personal opinions and religious beliefs, these critical thinkers emphasized deriving explanatory concepts by rigorously reflecting on their own experiences within nature and the use of reason. Although they were neither scientists nor evolutionists, their answers to general questions about this universe did establish a dynamic worldview that paved the way for further discoveries in the future development of the special sciences, from geology and paleontology to biology and anthropology.
Among the pre-Socratic thinkers, Thales claimed that life first appeared in water; for him, water is the fundamental substance of this cosmos. He argued that, over time, aquatic organisms changed and eventually there were lifeforms that could adapt to and survive on dry land. It is reassuring that Thales, as the first Western philosopher, had glimpsed the biological significance of change throughout planetary time. In his rational speculations, he had grasped both the fluidity of life and the unity of this universe.
Extending this vision, Thales’s student Anaximander held that, in the development of life-forms from water to land, lineage leading to the human animal had once passed through a fishlike stage of development. It is tempting to refer to this pre-Socratic thinker as the father of comparative morphology; one may imagine Anaximander comparing the innards of a dead fish with those of a human corpse, and consequently being very impressed with the similarities (rather than with the differences).
Reflecting on the flux of reality, the naturalist metaphysician Heraclitus argued that change is the quintessential characteristic of this universe. Looking for order in this dynamic world, he further claimed that all changes in nature are cyclical. As a result, for Heraclitus, there is the endless repetition of day and night, life and death, the four seasons of the year, and even the cosmos itself. For later naturalists to accept the evolutionary framework, it was necessary for them to take both time and change seriously.
Of particular importance was Xenophanes, who recognized both the organic and historical significance of fossils as the remains of once-living but often different organisms related to the living life-forms of today. The fossil record is crucial, in that it provides empirical evidence to substantiate the fact of organic evolution. Despite our present knowledge of genetic variations, it would be difficult to convince many people of the truth of organic evolution if no fossil evidence had ever been discovered. However, the more paleontologists search, the more fossils they find (including paleoanthropologists discovering fossil hominid specimens).
Lastly, Empedocles even offered an explanation (although a bizarre one) for the origin of organisms. He speculated that in the past, the surface of the earth had been covered by free-floating organs of different sizes and shapes; they haphazardly came together, forming organisms (some, of course, were monstrosities). Those organisms that could adapt to the environment survived and reproduced, while the monstrosities perished. What is implicit in this explanation are the basic ideas that constituted the evolutionary framework of both Charles Darwin and Alfred Russel Wallace: multiplicity, variation, adaptation, survival, and reproduction or extinction. Unfortunately, with irony, the proto-evolutionary ideas of these five pre-Socratic thinkers were squelched by the greatest thinker of ancient Greece—Aristotle.
Aristotle was the “father of biology,” including comparative studies in embryology, morphology, and taxonomy. His encyclopedic interests ranged from cosmology and meteorology to botany and zoology. Aristotle assumed that the human mind is capable of discerning a natural design within the mixed species on this planet. He referred to this terrestrial order as the great chain of being, or ladder of nature. For him, each species is eternally fixed in nature, each type of organism occupying a special place in the great chain of nature depending upon its degree of complexity and sensitivity or intelligence. This hierarchical ladder ranged from the simplest mineral at its bottom to the rational human at its apex. Since Aristotle dismissed both the creation and extinction of species, as well as the appearance of new ones, he was not an evolutionist (although he was interested in the development of individual organisms). Because many thinkers gave priority to the fixed Aristotelian worldview, a serious evolutionary framework did not emerge until the scientific writings of Charles Darwin and Alfred Russel Wallace over 2,000 years later.
Challenging the fixed Aristotelian worldview, the Roman philosopher and poet Lucretius presented a dynamic interpretation of both the earth’s history and the material universe. In his groundbreaking work On the Nature of Things, he argued that our planet itself has created plants and animals, and even outlined the sociocultural development of our own species from cave-inhabiting early creatures to the citizens of the Roman empire. Furthermore, Lucretius boldly held that life-forms (including intelligent beings) inhabit planets elsewhere in the cosmos. His ideas paved the way for a naturalistic study of humans within nature.
During the Italian Renaissance, the artist and visionary Leonardo da Vinci recognized the biological and historical significance of fossils as the remains of once-living but usually different species—in fact, he had found these fossils in the top rock strata of the Alps. Moreover, his dynamic view of the earth’s history in terms of geology argued that the age of our planet must be at least 200,000 years (an astonishing claim in the eyes of his contemporaries). Furthermore, Leonardo’s study of the human body foreshadowed serious comparative-anatomy research.
In 1735, Carolus Linnaeus fathered modern taxonomy. He recognized the close similarities among the human animal and the apes, monkeys, and lemurs. Consequently, he placed all of these forms in the primate order. Although he was not an evolutionist, Linnaeus discovered that species are capable of producing varieties of themselves (an example of microevolution).
Decades later, as a result of taking the implications of geology and paleontology seriously, Jean-Baptiste de Lamarck wrote the first serious book on organic evolution. In his Philosophy of Zoology (1809), he argued that species are mutable and have changed throughout organic history. Without a testable explanatory mechanism or sufficient empirical evidence, Lamarck was unable to convince other naturalists that life-forms had evolved throughout geological time. Ironically, however, Lamarck’s book appeared exactly 50 years before the publication of Charles Darwin’s On the Origin of Species (1859).
With its emphasis on science, reason, and a historical perspective that took both time and change seriously, the Age of Enlightenment established an intellectual atmosphere that allowed for the emergence of three important earth sciences: historical geology, comparative paleontology, and prehistoric archaeology. Ongoing advances in biology (especially embryology, morphology, and taxonomy) and extensive travels by curious naturalists (e.g., Haeckel, Humboldt, Huxley, and Lyell) provided overwhelming scientific evidence and convincing rational argumentation for the vast age of this planet, the evolution of life-forms, and the great antiquity of our own species. Clearly, rocks and fossils and artifacts did not support a strict and literal interpretation of the biblical story of creation as presented in the book of Genesis in the Holy Bible. It was now necessary for some ingenious naturalist to bring all of these facts and concepts together in a comprehensive and intelligible view of life on earth in terms of biological evolution. Unintentionally, this task fell to the young geobiologist Charles Darwin (Birx, 2009).
Three major events contributed to Darwin’s developing his scientific theory of organic evolution: his unique experiences as a naturalist aboard the HMS Beagle during its 5-year circumnavigation of the world in the Southern Hemisphere (1831–1836), his reading Charles Lyell’s three-volume work Principles of Geology (1830–1833), and his later fortuitous reading in 1837 of Thomas Robert Malthus’s An Essay on the Principle of Population (1798).
For Darwin, the convergence of evidence from geology, paleontology, and biology (as well as the implications of both biogeography and variations in organisms) argued for the pervasive mutability of species throughout immense periods of the earth’s history within a naturalist framework. Of particular significance, he offered natural selection as the primary mechanism to explain biological evolution. Darwin’s scientific facts and rational arguments for his evolution theory were first presented in On the Origin of Species (1859). However, at that time, the sensitive naturalist did not yet extend his theory of evolution to include the human animal.
In his The Descent of Man (1871), Darwin now seriously considered the evolutionary implications for understanding and appreciating the place of our own species within natural history. He argued that, biologically, the human animal is closest to the three great apes known to science at that time (orangutan, gorilla, and chimpanzee), with which it shares a common ancestral group whose fossils would be found in Africa. Furthermore, as had Huxley in England and Haeckel in Germany, Darwin even claimed that our species differs merely in degree, rather than in kind, from these three great apes. As such, his ideas were a major contribution to the emergence of biological anthropology. Even so, the resultant creation-evolution controversy still continued as an ongoing debate between biblical fundamentalists and scientific evolutionists. Today, the religious position is grounded in the alleged argument for intelligent design.
Although convinced of the veracity of his evolution theory, Darwin was still perplexed by four questions (among others): What is the true age of planet earth? Why is the fossil record so incomplete? How are organic variations inherited from generation to generation? Can slow biological evolution account for the emergence of the complex human eye? Throughout the following decades, ongoing advances in science and technology (especially in dating techniques and computers) would help to answer these four questions in favor of the evolution theory and a naturalist viewpoint.
The discipline of anthropology emerged during the middle of the 19th century. Greatly inspired by the writings of Charles Darwin, several naturalists were very interested in extending the evolutionary framework to include our own species. In general, early biological anthropologists were eager both to find fossil evidence to substantiate human evolution and to compare the morphology of living primates in order to demonstrate the remarkable similarities among lemurs, monkeys, apes, and the human animal. In particular, some biological anthropologists extended taxonomy to include a racial classification of human groups in terms of different physical characteristics. (Rigorous primate behavior studies and primate-genetics research would not appear until the middle of the 20th century.) Although conflicting interpretations of evolution were offered by naturalists, and even though anthropologists could not agree on the number of human races, there was no doubt that our species was both the product of organic evolution and closely related to the great apes, especially the chimpanzee.
During the succeeding decades, biological anthropologists would specialize in areas ranging from paleoanthropology and primatology to forensic anthropology and biomedical anthropology. The theory of evolution offers a comprehensive and intelligible framework in which both the physical characteristics of the human animal and its place within natural history made sense in terms of science and reason. Today, one may speak of the biological unity of Homo sapiens sapiens in terms of the DNA molecule.
Science of Genetics
As the father of biology, Aristotle was interested in the embryological and morphological development of organisms. He held that a female contributes the matter and a male contributes the form to an embryo, which then develops according to an innate, preestablished goal within the embryo itself (a movement from potentiality to actuality). However, Aristotle was not an evolutionist, since he held to the eternal fixity of all species within his assumed static hierarchy of planetary existence that ranged from simple minerals to complex animals. This worldview dominated Western thought until the persuasive scientific theory of evolutionist Charles Darwin.
The monk Johann Gregor Mendel discovered the basic principles of inheritance as a result of his rigorous, long-term experiments with the common garden pea plant Pisum. A particulate theory of inheritance was presented in his monograph Experiments in Plant Hybridization (1866), in which he not only distinguished between dominant and recessive characteristics for the same trait, but also presented the principles of segregation and independent assortment. Unknown to himself and the scientific community, which did not understand or appreciate the far-reaching significance of his pioneering discoveries, Mendel had established an empirical foundation for the science of genetics.
In 1900, building upon Mendel’s findings, Hugo DeVries both discovered the phenomenon of incomplete dominance and presented his mutation theory. Within several decades, evolutionists realized that, taken together, genetic variation and natural selection form the explanatory foundation of organic evolution. Thus emerged neo-Darwinism, or the so-called synthetic theory of biological evolution, with its focus on dynamic populations or gene pools.
If naturalist Charles Darwin had given to biological anthropology the factual theory of organic evolution, then James Watson and Francis Crick (along with Maurice Wilkins and Rosalind Franklin) gave to it a genetic foundation by discovering a working model for the DNA molecule, the so-called code of life or language of heredity (Watson, 2003). Since 1953, this groundbreaking discovery has had awesome consequences for understanding and appreciating life-forms, from a bacterium to the human animal. The DNA molecule gives undeniable evidence for the historical continuity and chemical unity of all lifeforms on planet earth. In particular, it now clearly links our species with the four great apes or pongids: orangutan, gorilla, chimpanzee, and bonobo.
The DNA molecule has the structure of a double helix with six parts: a phosphate group, the sugar deoxyribose, and four bases (adenine, thymine, guanine, and cytosine). Changes to the sequence of bases, or nucleotides, in the genome may result in changes in the phenotype or biological expressions of an organism. Mutations may be major or minor, and of positive, neutral, or negative value for the organism in terms of its adaptation to and survival in a dynamic environment. Successful reproduction will pass on the altered hereditary information to the gene pool of the next generation. Therefore, one may hold that the members of a population represent differential reproduction. Over time, a species may produce a variety of itself, and this variety may eventually become a new species; further evolution may result in the emergence of higher taxonomic groups, such as new families, orders, or classes of organisms. Nevertheless, within the sweep of organic evolution, a very sobering fact is that the extinction of species is the rule rather than the exception.
The next step for naturalists and biological anthropologists was to extend the science of genetics to comprehend the evolution of populations (gene pools) in terms of both changes in gene frequencies and the appearances of mutations within dynamic environments, as well as natural and social selection (Hartl & Clark, 2006; Wells, 2002). Such studies shed significant light on biological variations in human populations, consequently challenging earlier anthropological views on race and racism (Mielke, Konigsberg, & Relethford, 2006).
In the early decades of the 20th century, anthropologists could not agree on either the number of alleged distinct races that comprise our human species or the criterion or criteria to be used in determining the assumed number of human races; the number of races ranged from 3 to over 200 (obviously, the methodology was faulty). Unfortunately, however, the concept of human race was extended by some anthropologists to justify racism, resulting in a racial hierarchy from inferior groups to superior groups (Birx, 2003; Wolpoff & Caspari, 1997). Nevertheless, as a result of understanding and appreciating human variations in terms of the DNA molecule and dynamic populations, modern biological anthropologists now speak of the genetic unity of Homo sapiens sapiens, with organic differences being scientifically meaningful only below the subspecies level of classification. Human differences in blood groups, skin pigmentations, and morphological types are significant only in terms of adaptive genetic variations from gene pool to gene pool. The biological anthropologist Ashley Montagu (1905–1999) was instrumental in discrediting race and racism, while advocating the evolutionary framework (Montagu, 1997). Today, it is stressed that humans manifest cultural differences that are far greater than their biological differences. Of particular interest are ongoing twin studies, which are hoped to shed more light on the influences that both biology and culture have on determining the physical and social differences among human beings.
The mapping of the human genome, in order to discover which gene or genes determine specific characteristics or traits, has made possible the genetic engineering of the DNA molecule (Ridley, 2000; Scherer, 2008). Of course, such research holds both awesome promises and foreboding perils for the future existence and evolution of our species. In particular, ongoing stem cell research may eliminate hereditary diseases and even improve the human organism. As with any new science, there is (at first) widespread apprehension and the possible abuse of such powers. Even so, one may argue that the long-range benefits of genetic engineering and stem cell research far outweigh any short-range problems, given common ethical guidelines and rational value judgments to prevent the misuse of scientific research and its application.
Today, one may even speak of emerging teleology. As the use of and advances in both nanotechnology and genetic engineering increase, our species will more and more be able to guide the once-random process of organic evolution, including directing human evolution for chosen goals on planet earth and elsewhere. If the human gene pool departs significantly from its present makeup, then one may anticipate (in the remote future) the emergence of a new species, Homo futurensis.
Biological anthropologists as paleoanthropologists compare and contrast fossil bones and teeth in order to discern whether a specimen is pongid-like or hominid-like, and where it most likely should be placed within the long and complex evolutionary history of hominoids (Anderson, 2005; Arsuga & Martínez, 2006; Birx, 1988; Cela-Conde & Ayala, 2007; Tattersall, 1993). Dental features, as well as the cranium and innominate bone, greatly help to determine how close an apelike specimen is to the emergence of our own species. Modern computers and improved dating techniques significantly aid paleoanthropologists in constructing viable models depicting human evolution in light of the growing fossil record, as well as genetic research information when it is available. Furthermore, fossil and genetic evidence sets limits to probable models for human evolution in particular, and primate evolution in general.
For early biological anthropologists, the theory of evolution implied that our own species has an evolutionary past that links it to the fossil apes of about 7 to 5 million years ago. Thus, it is not surprising that some early naturalists wanted to discover the so-called “missing link” among those fossil hominoid specimens that are ancestral to both the living apes and the human animal of today. However, a debate emerged as to whether this evolutionary link would be found in Africa or in Asia. Inspired by the writings of Charles Darwin in England and Ernst Haeckel in Germany, the Dutch naturalist Eugene Dubois decided to leave Europe for Indonesia, where he was convinced that his research would unearth a fossil form midway between apes and humans. In the early 1890s, with incredible luck, Dubois actually did find a hominid specimen that he classified as Pithecanthropus erectus or erect ape-man (now relegated to the long Homo erectus stage of hominid evolution); it was found at the Trinil site on the island of Java. Skeletal features revealed that this fossil specimen was an early hominid dated from at least 500,000 years ago. Darwin would have been delighted with this discovery, but he himself had favored Africa as the cradle of human evolution, since the gorillas and chimpanzees (two of our closest evolutionary cousins) still inhabit this continent.
Eugene Dubois’s success inspired other naturalists to search for more fossil hominid evidence in Java. Subsequently, several decades later, G. H. R. von Koenigswald found an even earlier fossil hominid at the Djetis site, which he referred to as Pithecanthropus robustus (now also relegated to Homo erectus).
In 1924, anatomist Raymond A. Dart analyzed a fossil skull that had been fortuitously found at the Taung site in the Transvaal area of South Africa. He correctly determined that it was a hominid child over 1 million years old. It represented the australopithecine group of fossil hominids that existed for several million years. This discovery of Australopithecus africanus from Taung suggested that Darwin had been correct in maintaining that fossil apelike forms in Africa (not in Asia) had given rise to those hominids that are ancestral to our species. This incredible discovery inspired other naturalists to continue the search for fossil apes and fossil hominids in Africa. Even so, more evidence for human evolution was next found at the Zhoukoudian site near Beijing, China, due to the ongoing research of Davidson Black and Franz Weidenrich (including Pierre Teilhard de Chardin, among others). The specimens represented Sinanthropus pekinensis, a form of Homo erectus that lived about 350,000 years ago.
Later, with steadfast determination, the anthropologist Louis S. B. Leakey was convinced that the earliest fossil hominids would, in fact, be found in central East Africa. In 1959, after searching for 30 years, his second wife Mary found the cranium of Zinjanthropus boisei at Olduvai Gorge in Tanzania—a 1.75-million-year-old specimen. Although the cranium was that of the first fossil hominid ever found in central East Africa, it nevertheless represents a side branch that became extinct (as several other forms did) during the early evolution of hominid species.
In 1961, Louis S. B. Leakey himself found the skull of Homo habilis at Olduvai Gorge. This specimen was 1.9 million years old, and associated with the Oldowan pebble-tool culture. Homo habilis not only stood erect and walked upright with a bipedal gait, but also made simple stone implements. Unlike other hominid forms that became extinct, this bigger-brained and culture-making species gave rise to Homo erectus, the next phase of hominization. The astonishing success of the Leakey family, including both Richard E. F. Leakey (who also found a Homo habilis skull, but at Koobi Fora) and later Meave Leakey in Kenya, encouraged other biological anthropologists to search for hominid fossil specimens elsewhere in central East Africa (Morell, 1995).
During the 1970s and 1980s, three other major discoveries were made: the Lucy skeleton found by Donald C. Johanson and his team at the Hadar site in the Afar Triangle of Ethiopia (Johanson & Edey, 1981; Johanson & Shreeve, 1989; Johanson & Wong, 2009), the human Laetoli footprints found at a site in Tanzania by Mary Leakey and her team, and the Homo erectus skeleton found by Richard Leakey and his team on the western shore of Lake Turkana in Kenya. By the 1990s, there was no doubt that Africa had played the major role in the origin and early evolution of hominid species (Leakey & Lewin, 1992). More recent fossil specimens make it clear that many different hominid forms once occupied Africa during the past 4.5 million years. To date, the fossil australopithecine complex is represented by at least eight hominid species: aethiopicus, afarensis, africanus, anamensis, boisei, garhi, robustus, and sediba. No doubt, in the coming years, more incredible fossil hominid specimens will be discovered in both Africa and Asia.
One remaining puzzle in human evolution is the “sudden” extinction of the Neanderthal people and the remarkable success of their contemporaries, the Cro-Magnon people (Sauer & Deak, 2007; Tattersall & Schwartz, 2000). A probable explanation for the Neanderthal extinction is that they could not compete with the far more intelligent Cro-Magnon people, who most likely had a more complex language and certainly an advanced material culture (including stone and bone carvings, as well as exquisite cave murals). New findings and ongoing research may answer questions concerning the biosocial relationship between these two groups of early Homo sapiens. For now, one fact is certain: The Cro-Magnon people gave rise to the modern human being as Homo sapiens sapiens.
Actually, there is no common consensus among paleoanthropologists concerning the classification of fossil hominid specimens. Some paleoanthropologists argue that skeletal differences represent numerous species, and perhaps even distinct genera. Other paleoanthropologists place different skeletons into the same species, or maintain that they merely represent sexual dimorphism. Nevertheless, three generalizations seem true: (1) Hominid evolution has taken place over 4 million years; (2) fossil hominid specimens represent many species that became extinct; and (3) evidence shows that sustained bipedality preceded Paleolithic culture, which preceded the modern cranial capacity. No doubt, present models for and interpretations of hominid evolution will be modified in light of future discoveries.
In the footsteps of Aristotle and Linnaeus, modern taxonomists are interested in classifying living primates into groups that reflect both their similarities and evolutionary relationships. However, besides relying upon comparative studies in embryology and morphology, modern taxonomists also use computer technology and research information from comparative genetics. In general, primates are characterized by a large brain, great intelligence and memory, an emphasis on vision (rather than smell), grasping hands and remarkable motor-sensory coordination, and complex psychosocial behavior. These special features were slowly acquired over millions of years as adaptive characteristics to enhance survival—and therefore reproduction— in the trees. Only the human species spends its entire lifetime on the ground.
There is no common consensus among modern taxonomists concerning the classification of the primates. However, most biological anthropologists agree that six major groups comprise the living primates of today: prosimians, New World monkeys, Old World monkeys, lesser apes, great apes, and our own species (Campbell, Fuentes, Mackinnon, Panger, & Bearder, 2007; Rowe, 1996).
The earliest group of primates to emerge was the diversified, arboreal prosimians. Living representatives include the tree shrews, lorises, tarsiers, and lemurs. Although they once inhabited the trees in both hemispheres, all prosimians are now found only in Africa and Asia. The classification of tree shrews as primates is debatable, but this is to be expected since they represent an evolutionary link between the earlier ground-dwelling insectivores and the later tree-dwelling prosimians. Nevertheless, the tree shrews show an emphasis on vision and motor-sensory coordination, as well as grasping digits and a comparatively large brain.
Monkeys evolved out of the prosimians in both hemispheres. Thus, a distinction is made between the New World monkeys of the Western Hemisphere and the Old World monkeys of the Eastern Hemisphere.
New World monkeys are arboreal and divided into two groups: one group consists of the small marmosets and tamarins, while the other group includes the larger monkeys, such as the spider monkey and the howler monkey. Old World monkeys are very diversified, with some representatives spending considerable time on the ground, such as the baboons. Biological anthropologists are particularly interested in studying the behavior patterns of the terrestrial baboons, since these largest of the monkeys inhabit open woodlands and grassy savannahs when on the ground. Consequently, baboon behavior may shed light on the social behavior of our earliest ancestors, the protohominids, who became successful in adapting to life on the ground in terms of biological characteristics and behavior patterns. Other Old World monkeys include the mandrill, drill, gelada, colobus, and vervet of Africa; the langurs of India; and the macaques of Asia (e.g., the rhesus monkey). Larger, more intelligent, and far better adapted to arboreal habitats, the monkeys dominated the trees in both hemispheres and nearly brought the prosimians to extinction.
The apes are placed into two groups: the lesser apes or hylobates, and the great apes or pongids. They are larger and more intelligent than the monkeys. The hylobates include the gibbon and siamang. The pongids include the orangutan, gorilla, chimpanzee, and bonobo. Fossil and living apes are found only in the Eastern Hemisphere, where they evolved from some earlier Old World monkeys. Evolutionary relationships among the fossil and living primates are determined by genotypic and phenotypic similarities. However, interpretations of the evidence vary among paleoanthropologists and primatologists. One intriguing question remains: Which of the four pongids is closest to our own species? Many biological anthropologists maintain that the human animal is closest to the chimpanzee (Diamond, 1992) and bonobo. Yet, there are a few naturalists who argue that Homo sapiens is actually closest to the orangutan (Schwartz, 2005). Although fossil ape specimens are rare, future discoveries may shed more light on the evolution of early hominids from even earlier fossil pongids.
Since the writings of Huxley, Haeckel, and Darwin himself, evolutionary naturalists recognize the biological similarities among the primates: They all have large eyes, flexible digits, a complex brain, and great motor-sensory coordination. Over millions of years, primates adapted successfully to life in the trees. They not only adapted to their arboreal habitats in terms of physical characteristics, but also in terms of social behaviors (Fleagle, 1998; Jolly, 1985; Strier, 2007). Our own species is particularly similar to the four great apes: orangutan, gorilla, chimpanzee, and bonobo (McGrew, Marchant, &Toshisada, 1996). With the acceptance of evolution, it is not surprising that in the middle of the 20th century, some biological anthropologists began to study wild primates in their natural habitats. In general, the more complex the physical features of a primate species, the more complex is its behavior patterns. The prosimians exhibit simpler social structures than the monkeys, while the six apes (especially the four pongids) manifest the most complex behavior patterns outside our own species.
In the Eastern Hemisphere, prosimian behavior is reflected in the solitary tree shrews, pair-bonded adult lorises and tarsiers, and the lemurs of Madagascar that are monogamous or live in small social groups with female dominance. The ring-tailed lemurs (Lemur catta) communicate through sounds, smells, and body movements (e.g., social grooming). Their behavior patterns are social adaptations to life on the ground, enhancing survival and therefore reproduction.
New World monkeys are arboreal and live in small social groups. The red howler monkey (Alouatta seniculus) eats fruits and leaves, defends a home range, and communicates through loud howls. Also important is cebid behavior research on the spider monkey and woolly monkey of South America.
Among the Old World monkeys, of particular importance is the common baboon (Papio anubis) in Africa (Smuts, 1985; Strum, 1987). On the ground, a baboon troupe is headed by the dominant adult alpha male. Since these baboons are often terrestrial during the day, in the open woodlands and on the grassy savannahs, their social behavior may give biological anthropologists a glimpse into the group behavior of the early hominids, who adapted to and evolved in similar environments. However, there are some primatologists who speculate that early hominid behavior may have been closer to the social behavior of living chimpanzees and bonobos. Significant behavior research continues on the terrestrial langurs and macaques of Asia.
The two lesser apes, or hylobates, are the gibbon (e.g., Hylobates lar) and the larger siamang (Symphalangus syndactylus). They are found only in the tropical rainforests of Southeast Asia, where they have adapted very successfully to life in the trees. Gibbon behavior varies from adult male/female pair bonding to small social groups. Gibbons actively defend a territory through loud sounds and aggressive displays, which warn off intruding groups.
It was to be expected that some primatologists would focus their research on studying the behavior of the great apes. Most important are past and ongoing close-range, long-term observations of the pongids in their natural environments.
Inspired by paleoanthropologist Louis S. B. Leakey, three female primatologists established the rigorous study of wild apes in their natural habitats: Biruté Galdikas, Dian Fossey, and Jane Goodall. Their steadfast and pioneering observations resulted in remarkable discoveries concerning the behavior patterns of the three pongids. These social findings supplemented the biological evidence that already supported the close evolutionary link between the great apes and our species.
In their natural habitats, wild orangutans (Pongo pygmaeus) live only on the islands of Borneo and Sumatra in Indonesia. Galdikas devoted her research to observing the orangutans on the island of Borneo (Galdikas, 1996, 2005). Her close-range, long-term observations of this pongid have added greatly to understanding and appreciating this great ape of Asia. She not only focused on their behavior patterns, but also prepared orphaned infants for their return to the tropical rainforests. In doing so, her devotion to studying and caring for orangutans has helped to ensure their survival, while also informing the world that this great ape needs to be protected from both human harm and the threat of extinction. Unfortunately, orangutans are now facing extinction due to the encroachment of human civilization, especially because it causes the deforestation of their environment and disrupts their behavior. Furthermore, adult orangutans are killed in order to capture their infants; subsequently, these young orangutans often die in captivity.
Adult orangutans are primarily loners, living in trees and surviving primarily on fruits and leaves. There is no complex social behavior. Nevertheless, orangutans are intelligent. Unfortunately, in captivity, where they are removed from an active life in the trees, orangutans are prone to boredom and obesity; placing them in natural settings therefore improves their health and extends their longevity. Fortunately, for biological anthropology, Galdikas continues her efforts to understand and appreciate this “red ape” of the primate world. Following in her footsteps, other primatologists will devote their efforts to studying this pongid in order to save this endangered great ape from vanishing completely.
The largest ape ever discovered is Gigantopithecus from fossil sites in China, India, and Vietnam. It existed from the Miocene epoch to about 500,000 years ago, but is now known only from its massive jaws and huge teeth (especially its premolars and molars). In part, the extinction of Gigantopithecus may have been due to the evolutionary success of a competitor, Homo erectus. Evidence suggests that, astonishingly, this fossil pongid might have stood over 9 feet tall and could have weighed at least 500 pounds. Future research may discover a skeleton of this astonishingly huge ape, which is related to the living orangutan through primate evolution.
The gorilla is the largest of the four great apes, and the two isolated subspecies are found living only in the forested areas of equatorial Africa. In the footsteps of zoologist George B. Schaller, Dian Fossey dedicated her research to studying the wild mountain gorilla (Gorilla gorilla beringei) on the slopes of the Virunga volcanoes in central East Africa (Fossey, 1983). Not content with merely observing them from the safety of trees, she was the first primatologist to actually make contact with this large pongid. Her efforts were rewarded with surprising findings that demolished the traditional view of the gorilla as a dangerous and ferocious ape. In fact, Fossey discovered that the gorilla is actually a shy, gentle, intelligent but introverted pongid.
Gorillas are very intelligent and live in small social groups, each dominated by an adult silverback male who determines when the group members will move, eat, or rest. There are also loner adult males. Gorillas eat fruits and leaves, and fear few predators (except human poachers with weapons). Unfortunately, the natural range and population of wild gorillas are diminishing due to the ongoing encroachment of human settlements.
For about 50 years, Jane Goodall has devoted her efforts to studying the wild chimpanzee or common chimpanzee (Pan troglodytes) at the Gombe Stream National Park near Lake Tanganyika in central Africa (Goodall, 1986, 2000). She has made significant discoveries about the social behavior of this very humanlike great ape. Chimpanzees are very intelligent, are both arboreal and terrestrial, systematically make and use simple tools, and are capable of learning and communicating through symbols. They exhibit both intriguing and disturbing behavior patterns. Chimpanzees are aggressive, promiscuous, live in loosely structured and constantly changing social groups, and are capable of killing both their own infants and adults.
Chimpanzees communicate through distinct sounds, body movements, facial expressions, and social grooming. One remarkable discovery is that they modify twigs in order to “fish” ants and termites from their mounds, adding these insects to their diet. Chimpanzees crack open nuts using rocks or branches, and also use a bone pick to extract bone marrow. They also hunt and kill monkeys, adding meat to their otherwise usual diet of fruits, nuts, seeds, and leaves. One particular activity is especially interesting: adult males will participate in a so-called “rain dance” during a thunderstorm.
Since 1929, scientists have known about the chimpanzeelike bonobo (Pan paniscus) or the so-called pygmy chimpanzee. Nevertheless, only during the past two decades have a few biological anthropologists studied the wild bonobos in the forests of Zaire in central Africa (de Waal & Lanting, 1997). Although they frequently walk on their knuckles, bonobos are capable of walking upright for short distances; they are taller and thinner than the common chimpanzee. Bonobos eat fruits, plants, and monkeys. There is strong bonding among adult females, and social groups may even be dominated by them. The social behavior of this peaceful pongid is grounded in “make love, not war” (in sharp contrast to the sometimes vicious behavior of the common chimpanzee). Sexual activity is pervasive among bonobos, strengthening group interactions and diminishing social tensions. Like chimpanzees, bonobos share about 98% of their DNA with the human animal.
Several primatologists have focused their research on ape communication studies; for example, Francine Patterson has taught two lowland gorillas American Sign Language. However, her success and similar work by other biological anthropologists have come under sharp criticism by scientists who claim that the great apes are merely mimicking the behavior of their teachers. Even so, anthropological research has revealed that pongids have greater mental ability than is suggested by merely observing their social behavior in natural habitats.
Since the middle of the 20th century, the discipline of anthropology has striven to be relevant in terms of solving problems in the modern world. One area of applied anthropology is forensic anthropology (Birx, 2002; Komar & Buikstra, 2008), which has increased greatly in its popularity during the last 10 years. An outgrowth of biological anthropology, forensic anthropology focuses on the skeleton of our own species. As such, forensic anthropologists analyze and describe a human skeleton in order to determine the biological characteristics of a human corpse and, ideally, to make a positive identification of the deceased individual.
All human beings belong to the same genus, the same species, and the same subspecies: Homo sapiens sapiens. Consequently, each human individual is a biological variation on a common theme, that common theme being the genetic unity of humankind. Biological anthropologists specialize in understanding and appreciating our species in terms of primate evolution and human variation. The detailed study of a skeleton is crucial to forensic inquiry (Schwartz, 2007). The human skeleton has 206 bones, ranging from the large femur to the three small ear bones or ossicles (Birx, 1991a); the glaring similarity among the hominid and pongid skeletons, of both living and fossil species, is convincing evidence for human evolution and our common ancestry with the great apes. Osteological and dental remains help the forensic anthropologist determine the age, gender, height, weight, health, and ethnic background of an individual. Such studies may also reveal anomalies, mutations, and the results of past diseases and injuries. However, when present, other biological evidence may also determine the cause or manner of death, as well as help to identify suspects. Yet, in some cases, a positive identification is never achieved.
Furthermore, forensic anthropologists help to reconstruct a death scene. Forensic inquiry may determine that the death of an individual is due to murder, accident, suicide, or a natural cause; in some cases, the cause of death may remain unknown.
Forensic anthropologists use methods that have emerged in the history of biological anthropology and prehistoric archaeology (e.g., in the methods they use for the careful investigation of a death scene). Today, data banks of human bones and genetic fingerprints are now available for comparative studies, as well as the use of modern computers. Additional information comes from the DNA molecule, serology, entomology, toxicology, and ballistics (among other areas of specialty).
Forensic anthropologists may study such diverse subjects as Neanderthal fossil remains, the 5,200-year-old Iceman (named Ötiz) from the Alps, mummies from ancient Egypt (e.g., the remains of King Tut) and the Incas of Peru, and individuals from bogs, war grave sites, and recent catastrophes. Likewise, forensic scientists help to reconstruct both a death scene and the face of a human corpse. However, only human remains from the past 50 years have legal significance; in these cases, the forensic anthropologist may be an expert witness at a trial.
The discipline of biological anthropology continues to shed light on the origin, evolution, and diversity of our own species, as well as its relationship to other primates (both fossil and living forms). Each year, new discoveries in paleoanthropology add more empirical evidence that enhances our understanding of and appreciation for hominid evolution. No doubt, over the coming decades, other exciting findings will be made in both Africa and Asia. Ongoing discoveries of fossil specimens will likely help to explain the emergence of both bipedality and our modern cranial capacity. As such, the present model of hominid evolution will be modified in order to accommodate all the new facts and concepts. Likewise, more nonhominid fossil specimens will be found, shedding new light on the evolution of primates throughout the Cenozoic era.
Ongoing advances in genetics and psychology will clarify the biological, social, and evolutionary relationships among the primates. Findings from continued primate behavior studies, both in captivity and in the wild, will help to narrow the gap between the human animal and the great apes, especially in terms of language acquisition (Bickerton, 2010) and the making of stone implements. One urgent need is to protect the nonhuman primates from the threat of extinction. It is deeply regrettable that the four pongids (orangutan, gorilla, chimpanzee, and bonobo) are now vanishing animals primarily because of the encroachment of human civilization. It would be a tragedy if these wonderful species became extinct. Of course, there is a need to protect all the primates. It is also important that future biological anthropologists continue to research the relationship between humans and apes in terms of the origin and transmission of infectious diseases within ever-changing environments.
Human growth and development research, especially twin studies, will help clarify the dynamic relationship between biology and culture, discrediting unfounded racial classification systems and overcoming their resultant entrenched racism. And there is also a need to examine the influence of culture and the environment on the human gene pool and the biological variations that emerge from external changes in the natural world.
Of course, the ongoing teaching of both biological anthropology and the evolutionary framework is quintessential for the spread of rational thought and scientific evidence necessary for a proper interpretation of our human species within natural history. Consequently, research in biological anthropology needs to remain open to new facts, concepts, hypotheses, and perspectives.
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