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 sediba found 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.

Australopithecus sediba and Homo habilis both had very human-;ole hands, but the two species used their hands differently​.  Even though Australopithecus sediba did not have long, ape-like hands that were suitable for supporting their weight while hanging from branches, they often did partially support their weight by holding onto branches.  The resulting strain on their finger bones caused the phalanges of the forefinger and two other fingers to become thickened by straine that was imposed on them.  They also evolved especially long and powerful thumbs to partially make up for their shorter hands, and they had re-evolve the slight curvature of the finger bones that is observed in the hands of the Australopithecines.

Homo habilia, had straighter fingers, and their fossilized hand bones show evidence of loading throughout their lifetimes that was very similar to that of modern humans, who seldom use their hands for climbing trees.

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 than 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, in order to put them in the same genus.

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Homo rudolfensis

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Another hominin, Homo rudolfensis, were similar to Homo habilis insofar that he had human-like hands and most likely used them for similar purposes, but they had veery large, rounded teeth, indicating that they relied more ion low3-quality foods in order to squeeze nutrients out of them.  Contradicting this was the fact that they lacked the huge jaw muscles that would enable them to chew on their food all day.

The key to this contradiction might be that their brain cases were larger than those of Homo habilis and much larger than those of the Paranthropines.  In other words, they had evolved new mental capabilities, similar to those of later members of the Homo clade. that enabled them to find and select foods that had a high nutrient content.  They probably used their human-like hands to do more hand processing of their food, so they didn't have to do so much chewing.

As the climate of Africa became increasingly dry, the foods that they needed became increasingly rare, and they became extinct, as did Homo habilis.

Homo rudolfensis probably do not belong in the Homo clade, either.

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.