Huyssteen, Interpreting the hominid fossils

The second epochal event for human evolutionary studies was the 1856 discovery of a fossil human at the Feldhofer Grotto in the Neander Valley, Germany. Most authorities of the day dismissed this find as the remains of a “barbarous” type of Homo sapiens. However, in 1864 the anatomist William King named the new form Homo neanderthalensis, thereby implying that there had been at least one ancient human extinction and speciation event. With further discoveries of the remains of extinct fossil humans, evolutionary concepts were more palatably applied to modern humans. The British geologist Charles Lyell (1797–1875), once a firm believer in God’s role, abandoned many of his theological notions and accepted Darwin’s theory of descent with modification after examining the remains of the Feldhofer Neanderthal.

At the turn of the twentieth century, the rediscovery of Mendelian genetics provided a basis for Darwin’s evolutionary mechanism. Nonetheless, some paleontologists continued the attempt to integrate Christian beliefs with the idea of evolution. One such was the French Jesuit Pierre Teilhard de Chardin (1881–1955). While in Jesuit training in England, Teilhard also trained in paleontology and archaeology, and became embroiled in the Piltdown controversy that was just erupting. In 1912, he was invited to the Piltdown site in Sussex, which had yielded fossil bones including those of a human, and flint tools. Upon arrival he found a tooth. Reconstruction of the fragmentary hominid pieces seemingly offered the perfect transitional candidate from apes to humans— perhaps too perfect.

In 1912, “Piltdown Man” was introduced to the world as Eoanthropus dawsoni. At that time, the large brain was considered to be the hallmark of humanity; and for forty years British anatomists would disregard many significant fossil human discoveries because of their prized and large-brained Piltdown fossil. Teilhard later continued his paleontological research at the “Peking Man” site of Zhoukoudian in China. The Chinese fossils helped Teilhard to reconcile his now expansive knowledge of the human fossil record with his Christian beliefs. In The Phenomenon of Man (1938–1940), Teilhard proposed a theory of human evolution in which humans were evolving towards a final spiritual unity, also known as Finalism. This notion elicited the disapproval of his Jesuit superiors.

Early in the 1950s, Piltdown was exposed as a hoax—the doctored remains of a human and orangutan—and Teilhard has even been fingered as the hoaxer, though he remains only one of the more unlikely suspects of many. By the late 1950s the human fossil record had greatly expanded, as had the plethora of names used to describe it. A tidying-up was in order, and this was gradually achieved under a gradualist and progressivist model of human evolution.

In the 1970s and 1980s, new systematic methods began to transform the understanding of the constantly expanding human fossil record. Further, molecular studies were providing new perspectives. In particular, the “molecular clock” shortened the ape-human divergence to as little as five to six million years ago (from maybe twelve to fourteen).

From around 1970 researchers uncovered bipedal but otherwise rather apelike hominids from sites in eastern Africa. These joined the Australopithecus fossils already known from southern Africa in the 2.5 to 1.5 million years ago range, and dated mostly from about 3.5 to 2.0 million years ago. Interpreted using an underlying gradualist model, these archaically- proportioned fossil hominids mostly reflected the search for an “earliest ancestor.”

The situation at the beginning of the twenty-first century

Over the following few decades, hundreds of fossil human discoveries offered fuel for systematic debates. The “single species hypothesis,” which stated that the human ecological niche was so wide that only one species of hominid could have existed at any one time, was rapidly invalidated by new finds, but still lingers in models of human origins that find deep roots in time for contemporary geographical groups of humankind. Evolutionary theory, as well as the rather sparse fossil record, imply in contrast that the species Homo sapiens must have had a single origin at one time and in one place, probably Africa. All of the human diversity familiar today has apparently appeared within the past 150 thousand years or so.

Despite minor differences of opinion, it is clear that the diversifying pattern of human evolution is similar to that of other mammalian taxa. Hominid phylogeny is a story of evolutionary experimentation, with multiple speciations and extinctions. The hominid family comprises at least five genera and eighteen known species, some of which shared territories in both time and space. At present, all geographical varieties of modern humans occupy the single surviving twig of what appears once to have been a densely branching bush.