Bones and Genes Apples and Oranges or Peas and Carrots

Some say that bones and genes, when studied in our evolutionary biology, are like apples and oranges—sort of the same but not really, so they should be considered separately and individually. Others believe that skeletal anatomy of fossils ("bones") and data from biomolecular analyses ("genes") go together like peas and carrots—fundamentally compatible and therefore to be considered in the same context. In our opinion the most convincing theories of human origins are the ones that integrate the paleontological and genetic approaches. After all, fossils and molecules must ultimately reflect the same thing—the evolutionary history of human adaptation.

In this age of the human genome, some critics of paleoanthropology maintain that so much paleontological data are lost and irretrievable that fossil-based hypotheses are overly prone to fanciful and untestable theories. Zealots of a molecular-only approach also claim that anatomy can provide only a rough idea of ancestral and descendant relationships. To paraphrase a quip by molecular anthropologist Vincent Sarich, they know that their molecules had ancestors while the paleontologists can only hope that their fossils had descendants.

Fossil-only theoreticians, on the other hand, seek refuge in an illusory security of "character states." These are ideal constructs erected for extinct species' anatomy that proponents believe avoid the inconvenient uncertainty of the probabilistic statements of population genetics. Convenient they may be, but the constructs tend to last only until the next new fossil is found. Very much like the ancient Ptolemaic astronomers, the fossil-only theoreticians must make up new rules every time a new discovery is made.

Are we not interested in the details of the evolutionary story that only fossil data sealed at a particular time and place in the past can tell us? And at the same time, is it not a fascinating undertaking to integrate this detail with the undeniable reality of our genetic blueprint, seen both at the species level and in all its local complexity and variability? Our best view of human evolution will be from an integration of all the good data that we can bring to bear on the questions, regardless of the doctrinal turf from which they derive.

Peking Man and Dragon Bone Hill played an important part in transforming paleoanthropology from an arcane paleontological discipline into a modern science that brought in evolutionary biology. The crucible was New York City in the 1940s, and the reaction involved three unlikely protagonists: veteran anatomist Franz Weidenreich, arrived from Beijing in 1941; leading geneticist Theodosius Dobzhansky, who came to Columbia University as professor of genetics from the California Institute of Technology in 1940; and a young physical anthropologist named Sherwood Washburn, still one year away from earning his doctorate at Harvard University when he joined the Columbia anthropology faculty in 1939. In 1937 Dobzhansky had published Genetics and the Origin ofSpecies, one of the foundations of the modern synthetic theory of natural selection and an anchor of modern evolutionary biology. In this work Dobzhansky used his and geneticist Thomas Hunt Morgan's experiments and observations on the fruit fly Drosophila to extrapolate to other species, including humans. He emphasized populations of organisms, not individual "types," in the study of evolutionary biology. Dobzhansky laid out an approach that integrated fossils and genes, and evolutionary biologists have been using it ever since. He wrote: "The problem of evolution may be approached in two different ways. First, the sequence of evolutionary events as they have actually taken place in the past history of various organisms may be traced. Second, the mechanisms that bring about evolutionary changes may be studied."29 Washburn sought Dobzhansky out early at Columbia, despite the fact that Washburn's former professor at Harvard, Ernest Hooton, was a typologist antagonistic to Dobzhansky's writings on human evolution. Dobzhansky first asked Washburn warily if he had been a Hooton student. Washburn replied, "I do not believe in types and think it is populations which should be compared." Dobzhansky smiled and heartily shook his hand.30

When Weidenreich arrived in New York City in 1941, Sherwood Washburn lost no time in getting to know him. He told Weidenreich about his anatomical experiments with rats, in which he investigated the formative effects of muscles on bone. Even though Weidenreich at first asked him, "But what have rats to do with anthropology?" 31 he quickly agreed with Washburn's comparative approach to teasing apart the underlying functional causes of the changes in skull form—changes that he had spent years describing for Homo erectus. Discussions with the up-and-coming Washburn may well have influenced Weidenreich's ongoing efforts to understand homi-nid cranial evolution through comparative studies of dogs, which he incorporated into his 1941 volume on the evolution of the human skull.32

Weidenreich and Dobzhansky became aware of each other as scientists on the important issue of race, a topic of overriding concern at the end of World War II as the world tried to make sense of the European Holocaust and horrendous ethnically based genocides worldwide. Weidenreich, who had suffered intense personal and family distress over the course of his lifetime because of ethnic persecution, opined that "physical anthropologists have gotten into a blind alley so far as the definition and the range of individual human races and their history are concerned."33 He showed that modern populations did not exhibit the preponderance of ideal anatomical traits that propagandists claimed for "pure races," and that mixing between populations had created a "hybrid or multihybrid" character to the human species. Dobzhansky agreed wholeheartedly with these findings and added that genetic determinants should be known for anatomical traits used to assess human evolutionary relationships.34 Weidenreich integrated genetics into his multiregional model and concluded, somewhat surprisingly, that "not only the living forms of mankind but also the past forms—at least those whose remains have been recovered—must be included in the same species."35 Yet he steadfastly refused until the end of his days to revise the taxonomy of the hominids that he had done so much to reveal to the scientific community. He cited long-established usage of the old terms, but perhaps he could just not bring himself to abandon the names for which so many of his old friends and colleagues had labored for so long. In frustration, fruit-fly expert Dobzhansky was forced to sink the Javan Pithecanthropus erectus and Chinese Sinanthropuspekinensis formally into the species Homo erectus in 1944. Paleontologist George Gaylord Simpson, another architect of the modern evolutionary synthesis, sneered in 1945 that "perhaps it would be better for the zoological taxonomists to set apart the family Hominidae and to exclude its nomenclature and classification from their studies."36

Sherwood Washburn left New York for the University of Chicago in 1947, the year before Franz Weidenreich died. He went on to revolution ize the study of human evolution in America by introducing the "new physical anthropology" in 1951-37 The central tenets of Washburn's vision were crystallized in New York during the war years of 1939 to 1946 when he integrated the synthetic theory and its genetics from Dobzhansky and then the anatomy of the hominid fossil record from Weidenreich. The Peking Man fossils, though lost, may be said to have played a fundamentally important role in the development of biological anthropology in the United States, far and above their importance in documenting a stage of human evolution. Washburn not only worked hard throughout the rest of his career to ensure that the family Hominidae stayed a part of the research agenda in evolutionary biology, but he also continued to be biological anthropology's most important theoretical link to Franz Weidenreich and the fossils from Longgushan.38


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