Suwa, Gen et al
Fossilized teeth of the earliest known human ancestor Ardipithecus ramidus were found in the Afar Depression of Ethiopia. Researchers recovered and analyzed 145 different teeth making up 62 cataloged specimens. Researchers looked at the Ar. ramidus teeth in comparison with the more primitive Ardipithecus kadabba and the more humanoid Australopithecus anamensis and Australopithecus afarensis. Specifically, the researchers spent time studying the variation, size, scaling and enamel thickness of the teeth to reveal possible implications regarding diet and behavior. The Suwa et al found that there was a low level of sexual dimorphism in the canines and premolars. In this sense Ar. ramidus has more in common with the later australopithecines than with chimpanzees and other apes. Presumably, the less dimorphism there is the more likely social equality between the sexes is. This may also indicate a sharing of the parental responsibilities between sexes. The upper canines are also more diamond shaped, which appears “less-threatening” than the honing apparatus of chimpanzees. This could also indicate a decreased amount of aggression between males.
The relative intermediate enamel thickness (between that of chimpanzees and the australopithecines) of Ar. ramidus appears to indicate a mixed diet with an emphasis on fruit. The study does not mention whether or not meat was an important part of the Ar. ramidus diet, but it does make a point of saying that the enamel is relatively thin when compared with humans and that it probably means less reliance on a frugivorous diet, but not total abandonment of ripe fruits. Enamel evidence also suggests that Ar. ramidus lived in a forested environment and not a savannah as was previously thought.
The importance of this case study is that it debunks the “killer ape” hypothesis developed by Raymond Dart and Robert Ardrey in the 1950s and 60s. It paints a picture of our oldest ancestors as cooperative creatures. It also undermines the possibility of understanding human nature through the study of chimpanzees and other apes that clearly diverge from the human line as far back as the Miocene. Chimps are clearly far more aggressive in their sexual relations as well as social hierarchies. The possibility that male and female “Ardis” shared the task of child rearing is also an important finding that relates to sexual relations. Finally, the tooth enamel of Ar. ramidus reveals that it may not have been hunting that made our ancestors unique. Rather, Ar. ramidus appears to still have been reliant of fruit.
Suwa, Gen et al2009 The Ardipithecus ramidus Skull and its Implications for Hominid Origins. Science 326: 68-68e7.
The discovery of an Ardipithecus ramidus skull was not easy. The skull was found in the Afar Depression in Ethiopia, but it was badly damaged and scattered over a wide area. Researchers used computers to digitally reconstruct the skull, revealing a nearly complete cranium. They found that Ardipithecus ramidus had a brain about the size of a bonobo’s or female chimpanzee’s. Although the skull may share its cranial capacity with the chimp, it does not share its overall structure. The brow-ridge is different from the chimpanzee’s and its lower face does not project forward like a chimpanzee’s. Although the cranial capacity of Ardipithecus ramidus was relatively small, it did have a steep bone on which the brain stem would rest suggesting the possibility of growth in the areas that in humans we relate to visual and spatial perception. When compared, the cranial structures of Ar. ramidus, australopithecines, and chimpanzees all appear to be unique. The chimpanzee’s facial structure is forwardly placed revealing a possible association with a greater degree of aggression.
The chewing apparatus of Ar. ramidus is consistent with that of an omnivore/frugivore that avoids hard and abrasive foods. Combined with a non-honing dentition this may indicate a greater reliance on vegetation, although it is pretty clear that meat was an important part of our Miocene ancestors’ diet.
In particular, what is of relevance to human nature is the fact that the skeletal make-up of the lower face diverges from that of the chimpanzee. In chimpanzees this forward projection indicates aggression. The absence of this projection in Ar. ramidus may indicate a more peaceable species. This has an impact on the human nature debate as Ar. ramidus appears to be very close to the human/chimp split and this discovery may explain what separates humans from chimps and bonobos, especially in regards to behavior.
All this evidence tells me we were headed in a good direction from the start and things could only get better, until the invention/intervention of the state. Tool use in the Australopithecines followed by art and symbolic culture in early Homo coupled with a gradual increase in brain size made life much more interesting. Creativity is probably the universal defining trait in humans that separates us from other animals, and that is why I believe another world is possible. But we must get back to living in harmony with nature (and with our nature) the way our ancestors did. The state has alienated us from nature.