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When Charles Darwin wrote his classic Origin of Species in 1859, "humans" were mentioned only once, in passing: "light will be thrown on the origin of man and his history". But the implications of the theory of evolution for the place of humans in nature were earth-shattering, and nobody missed them. In 1871, Darwin took the step of specifically applying his theory to humans, in his book The Descent of Man, in which he made what was at the time a bold prediction: "In each great region of the world the living mammals are closely related to the extinct species of the same region. It is therefore probably that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; and as these two species are now man’s nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere." Half a century later, discoveries in South Africa proved Darwin to be correct.

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Sterkfontein cave entrance, at the Cradle of Humankind World Heritage Site in South Africa.

Fossil hominids had already been found before Darwin published his books, but were not recognized as ancient human ancestors. In 1851, quarry workers in Germany found thighbones, ribs, some arm bones, and part of a skull in a limestone cave in the Neander Valley, which had unusually thick bones and a heavy brow ridge. They were explained as the remains of a diseased human, perhaps a Cossack deserter from the time of Napoleon.

Darwin's postulate of an African origin for humans was not accepted by everyone, however. The German biologist Ernst Haeckel concluded that orangutans were closer to humans than chimps or gorillas were, and therefore the earliest human ancestors should be found in Asia. Haeckel postulated a transitional "missing link", an "ape-man" halfway between orangutans and humans that he called Pithecanthropus alalus ("ape-man without speech").

One person influenced by Haeckel's speculations was Eugene Dubois, a Dutch doctor who joined the army and got himself posted to Java in the Dutch East Indies so he could look for early human fossils. In an incredible stroke of fortune, he succeeded, and discovered a thighbone and part of a skull in 1891. The skull indicated that this creature had a brain size larger than any ape, but smaller than a modern human; the thigh bone showed that it walked bipedally on two legs. In honor of Haeckel's hypothesis, Dubois named it Pithecanthropus erectus ("the upright ape-man"). The press referred to it as "Java Man". Today it is known as Homo erectus. In the 1920's, a number of similar fossils were found at the Zhoukoudian cave in China. "Peking Man" was grouped into the same species as Java Man. Asia, it appeared, was the cradle of humanity after all.

Then in 1908 a spectacular find was made in a gravel pit at Piltdown, England. "Piltdown Man" had a modern-looking skull with a large brain, but a primitive-looking jaw with apelike teeth. The discovery did not fit into the pattern that was already emerging with Java Man and Peking Man, which both had modern-looking skeletons with small brain sizes. A handful of scientists (mostly American) argued that the Piltdown fossil didn't make any sense, and concluded that the skull and jaw must be from two separate species and did not actually belong together. The Europeans, on the other hand, embraced Piltdown enthusiastically, because it told them what they already wanted to hear--humans were distinguished very early by a large brain, and these big-brained early humans were (white) Europeans. No one at the time suspected the real truth--Piltdown was a deliberate fake, made from a modern human skull and an orangutan jaw with the teeth filed down (this would not be discovered until the 1950's, when new dating methods proved that the find was a fake.). Throughout the 1910's and 1920's, paleoanthropology was dominated by European scientists, and they pushed Java Man and Peking Man to the side, and pushed Piltdown Man to the forefront. The first humans were European, and they had risen to prominence because of their superior intellects.

The first challenge to this story came in 1924, from South Africa. Raymond Dart, an Australian doctor working in London, went to Johannesburg and became the head of the anatomy department at the University of Witwatersrand. When he asked his students to bring in interesting bones for study, Josephine Salmons (his only female student) brought him a fossilized baboon skull which had been dug up at the Northern Lime Company's limestone mine at Taung. Dart contacted the mine and asked that any other fossils that might be found in the future be sent to him. That summer, Dart received two large boxes from Taung, and in one he found the fossil skull of a young primate, and the fossil endocast of the brain cavity. Having no lab equipment available to him, Dart set about removing the hard breccia rock from the fossils using his wife's steel knitting needles.

He revealed the skull of a very young primate, still with its milk teeth, that had humanlike teeth and not the large canines of an ape, a flat humanlike face rather than the projecting muzzle of an ape, and which, judging from the location of the hole at the bottom where the spine entered, belonged to an upright-walking bipedal creature. As an anatomist, Dart also recognized immediately that the brain endocast showed an unmistakably human pattern, despite its relatively small size. Dart, believing the "Taung Child" to be an evolutionary intermediate between apes and humans, nevertheless gave it the conservative scientific name Australopithecus africanus, "the southern ape from Africa".

Dart's find was enormously significant, but it caused barely a ripple in Europe. Scientists in England and France rejected Dart's assertion that this was a human ancestor. They pointed out that young apes always look more like humans than adult apes do, and concluded that Dart (who, they smugly pointed out, was not a trained paleoanthropologist but a mere medical doctor and anatomist) had simply mistaken a young ape for a human. The Peking Man fossils were also beginning to be found at this time, and they seemed to be better candidates for human ancestors than Dart's apelike Australopithecus. Other reasons for rejecting Australopithecus went unsaid but were nevertheless perfectly clear--Dart was an Australian and was living and working in a cultural and intellectual backwater in South Africa, and his find did not support the preferred "big-brained Europeans" hypothesis.

Only one scientist openly supported Dart's conclusions. Robert Broom, of the Transvaal University in Pretoria, was best-known as an expert on the Permian mammal-like reptile fossils, but Dart's find interested him, and he became the most ardent defender of Australopithecus. At first, no one paid him much attention; Broom was already known as a gadfly--a spiritualist with an interest in the paranormal, he asserted that the process of evolution was directed by "spiritual forces", and once declared that "spirits" told him where to look for fossils.

Whether guided by spirits or not, Broom now had a remarkable string of luck. In 1935, he found some small fragments of humanlike bones at the Sterkfontein cave, about 30 miles northwest of Johannesburg. Further digging revealed some complete bones, which Broom concluded were the adult version of Dart's Australopithecus. In 1937, at a nearby cave called Kromdraai, Broom found bones that were similar to Australopithecus but thicker and more robust, with a heavy crest at the top of the skull, which he gave the name Paranthropus robustus ("the robust near-man"). These "robust australopithecines" formed a side branch to the main line of human evolution. They remain important, since they show that human evolution was not much different than most other organisms--our family tree is not an orderly ladder, steadily climbing from bottom to top, but is more like a bush, with lots of side branches and twigs, all of which, except us, went extinct.

After being delayed by World War II, Broom restarted his excavations, and in 1947, at Sterkfontein, found a nearly intact skull he named Plesianthropus transvaalensis ("near-man from Transvaal"), which was given the nickname "Mrs Ples". Today, Mrs Ples is grouped with Australopithecus africanus. In 1948, Broom found more hominid fossils at the nearby Swartkrans cave.

All of these discoveries (and the uncovering of the Piltdown hoax in 1953) at last convinced paleoanthropologists that the earliest hominids did indeed appear in Africa. Darwin (and Dart) had been correct. All of the earliest hominids lived in Africa (including the earliest members of our own species, Homo sapiens.) At our deepest roots, we are, all of us, Africans.

Since Broom's work, excavations have continued at Sterkfontein, Kromdraai, and Swartkrans. In addition, over 30 other caves and sites nearby have yielded fossil hominids and stone tools. (The hominids did not live in these caves--they had been killed and dragged inside by predators, or had fallen in through holes in the roof.) One important find was "Little Foot", a nearly complete skeleton found at Sterkfontein in 1997. Originally classed as Australopithecus africanus, "Little Foot" has now been placed in the separate species Australopithecus prometheus (which earned its name when the earliest traces of the controlled use of fire, about one million years old, were found nearby). Another significant find came in 2010, when two partial skeletons of the species Australopithecus sediba were discovered at Malapa, about ten miles away. About 40% of all known hominid fossils, from at least three different species, have been found in this area, dating back to around 3.5 million years old.

In 1999, the UN designated Sterkfontein, Swartkrans, Kromdraai and the surrounding 180 square mile area as the Cradle of Humankind World Heritage Site. Today, there is a museum at Maropeng which exhibits the fossils and stone tools that have been found here, and guided tours are conducted through Sterkfontein cave. Scientific excavations are also continuing throughout the site.

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Fossil hominid skulls on display. Cradle of Humankind Museum, Maropeng

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Stone tools found at Sterkfontein

Originally posted to SciTech on Thu Jan 16, 2014 at 01:06 PM PST.

Also republished by History for Kossacks.

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