Fossil Hominids, Human Evolution: Thomas Huxley & Eugene DuboisWhen Charles Darwin wrote the Origin of Species, he had to wonder about how humans came to be. Humans had hereditary variation in every generation, and some individuals had more children than others the key ingredients for natural selection. But he chose not to write about humans in his first book about evolution, in large part out of strategy. In 1857, two years before Darwin published the Origin of Species, Wallace asked him in a letter if he would discuss the origin of mankind in the book. Darwin replied, "I think I shall avoid the whole subject, as so surrounded with prejudices, though I fully admit that it is the highest and most interesting problem for the naturalist."
But Darwin also knew that he had no fossil record to use to develop a hypothesis about human evolution. Over the years, naturalists had uncovered a few stone tools lying alongside the fossils of extinct mammals. But even in the 1800s, these relics were considered to be only a few thousand years old, and to have been made by lost tribes of savages.
Even when the first part of a fossil human came to light in 1857, naturalists had a hard time recognizing it for what it truly was. German miners working at the Feldhofer Grotto in the Neander valley dug up a skullcap. It looked somewhat human, but it was remarkably thick and sported a massive brow ridge. Did it belong to an ancient individual from a human-like species now extinct? Or was Neanderthal man just an extreme member of Homo sapiens? One of the German naturalists who described the skull for the first time, Herman Schaaffhausen, was convinced of the latter. He ignored evidence that the skull had been found alongside extinct cave bears and mammoths, and claimed that it was some recent barbarian, perhaps a member of one of the wild tribes mentioned by Roman historians.
Shortly after Darwin published the Origin of Species, his great champion Thomas Huxley (right) considered the skull from the Neander valley. Huxley shared some of the Euro-centric notions of his time. Based on their skulls, it was thought that Europeans had the best-developed brains, compared to the Australian aborigines with skulls having relatively low profiles and thicker brows. This view led Huxley to consider Neanderthals as occupying a slightly lower position within Homo sapiens.
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Dubois came back to Europe in 1895 to champion his discovery. He met with some stiff opposition from skeptics. Some wondered whether the ape-like skull and the human-like femur came from the same skeleton. Others thought the skull was similar to Neanderthals. Dubois became embittered by the debate over his bones and hid the fossils from other scientists. But in time, as more fossils were uncovered in Asia, scientists came to recognize that Dubois had indeed found the first representative of the ancient species, Homo erectus.
The twentieth century brought a great many more fossils of humans and hominids. Today twenty hominid species have been identified, the oldest of which date back six million years. They point to an African origin, as Darwin had proposed. Hominid evolution was sometimes pictured as a single line of descent and a steady progression from primitive forms to more advanced forms. The fossils suggested otherwise. Instead, hominid evolution produced a dense thicket of branches, with several species co-existing at any given time except for the last 30,000 years or so. Added to this wealth of data is the knowledge gathered from comparisons of DNA from humans, apes, and even Neanderthals. While many questions remain to be answered about human evolution, scientists have a growing treasury of evidence at their disposal.
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Dubois image courtesy of the National Museum of Natural History: Naturalis, Leiden, The Netherlands; Homo erectus skull image courtesy of the National Museum of Natural History: Naturalis, Leiden, The Netherlands
Understanding Evolution © 2017 by The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California