MORE HOMININS

Still more African hominins

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Some terrestrial hominins moved into Africa just prior to the onset of the first glacial maximum or just after it. They did not quite seem to belong to the Homo clade.  But almost.

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Australopithecus sediba

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Australopithecus sedibafound their way into places where fruiting trees were abundant.  Their ancestors had needed to climb trees in order to find piles of bones, but in Africa they found trees that fruited throughout the year. Moreover, Australopithecus sediba seldom needed to venture cross-country.  Consequently, they evolved a twisted ankle which was not so good for walking cross-country but helped them to walk on branches while they wrapped their very flexible feet around the branches. Their hands, however, gave them away as close relatives of Homo habilis.

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Homo habilis

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These hominins were closely related to Australopithecus sediba, but they relied more on what they could salvage from animal carcasses.  Homo habilis still climbed trees on occasion, so as to escape from predators or to forage there, and they still had shorter legs and longer arms that some later hominins, including ourselves.  Like Australopithecus sediba, however, their hands were not well adapted to climbing trees.  Instead, they were better designed for gripping a rock firmly so as to strike it accurately during rock-chipping operations.  A firm grip was also needed for throwing rocks accurately, so as to deter predators or drive them away from carcasses.

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Although Homo habilis were generally able to defend themselves against medium-size carnivores, they were not good at stealing carcasses from them, so Homo habilis often had to make do with scraps of skin and bones that were not eaten by other carnivores.

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Some archaeologists have posited that Sediba were ancestral to Habilis, but it was the other way around.  The ancestors of Australopithecus sediba might have come earlier to Africa, while the climate there was wetter, and adapted to those conditions, whereas the ancestors of Homo habilis retained the characteristics of their ancestors.

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In any event, it might be more apt to give these closely related sister species a new genus name, such as Habilopithecus.

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Homo rudolfensis

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These sister species must have been closely related to yet another hominin, Homo rudolfensis, who had surprisingly large molar teeth, obviously needed for chewing vegetation, but only moderately sized jaw muscles and brain a case that was rather large, in comparison with contemporary hominins.

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This seemingly contradictory combination of features must mean that when they entered Africa, where they found an abundance of low-quality food, they gave up; hunting in favor of hand-processing and then chewing low-quality foods.  When the climate of Africa became even drier and the quality of the available vegetable foods even poorer, they became extinct.

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Homo rudolfensis probably does not belong in the Homo clade, either.  I would place them, also in a new clade, perhaps Habilopithecus.

Bone choppers

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The bones of freshly killed animals presented a special problem for Homo habilis, because the bones were not brittle, like those that their ancestors had found lying about in Eurasia.  And when Homo habilishit a fresh bone with a hammerstone it would splinter badly, and the tiny splinters in the marrow were not good for the stomach.  Homo habilis responded to this problem by inventing bone choppers.

The first bone choppers were probably invented accidentally when Homo habilisremoved chips from one edge of a rock.  As they did this, the edge would be whittled down until it was sharp.  Then, if this sharp edge was struck against a large bone so as to put a dent in it, the bone could then be broken at that point without splintering it badly.

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Later hominins who were more closely related to ourselves than Homo habilis, either copied the design or reinvented bone choppers, and then went on to invent hand axes, which were good for efficiently butchering very large beasts.