The analysis of Ardipithecus ramidus has produced a plethora of new information about the lifestyle of early hominids. For example, scientists have noticed that the anatomy of Ardipithecus ramidus suggests that the last common ancestors of humans and African apes were not as similar to chimpanzees as most people have previously thought. In the paper, Ardipithecus ramidus and the Paleobiology of Early Hominids, White et al. state that "most aspects of the craniofacial structure of Sahelanthropus/Ardipithecus are probably close to the African ape and hominid ancestral state." We also know that Ardipithecus was most likely an omnivore. The dentition shows no strong signs of "ripe-fruit frugivory, folivory-herbivory, or feeding on hard objects...wear patterns suggest that its diet was not particularly abrasive but may have included some hard foods." This nutritional pattern can also indicate what type of locomotion was most commonly used, as some foods are more commonly eaten on the ground than in trees and vice versa.
The dietary pattern of Ardipithecus ramidus, which has been pieced together by the dentition, is indicative of a partially terrestrial and partially arboreal pattern. When looking at the pelvis of Ar. ramidus scientists can see that the ischial structure was similar to that of current African apes. This means that the shift from arboreal to bipedal locomotion was in process, but not yet realized. This theory is further proven by looking at the foot, as White et al. mention that it is a culmination of primitive characteristics and traits specialized to facilitate bipedality. The skull is also indicative of the locomotion, as the foramen magnum is more anteriorly positioned, which is often associated with bipedality.
Many other features of the skull also show that evolution was most likely more blurred than some people believe it to be. For example, the cranium has an upper facial projection that is similar to Sahelandthropus and other late hominins, but the projecting midface of the cranium is more ape-like than those mentioned later hominins. Some tend to believe that hominin evolution happened in stages, being very primitive and very close to apes, then becoming more human-like and "intelligent," finally becoming humans. Instead, each genus and species represents the "in-between stages" of human evolution. These hominins, and Ardipithecus ramidus specifically, are a culmination of primitive and evolved traits, referring to what some scientists refer to as the mosaic theory of evolution.
Suwa, G., et al. “The Ardipithecus Ramidus Skull and Its Implications for Hominid Origins.” Science, vol. 326, no. 5949, 2009, doi:10.1126/science.1175825.
White, T. D., et al. “Ardipithecus Ramidus and the Paleobiology of Early Hominids.” Science, vol. 326, no. 5949, 2009, doi:10.1126/science.1175802.
great! the skull is of course super impt and there is so much here to think about and analyze. You are right that a major takeaway is that they are suggesting the LCA isn't very chimp -like at all. If they are right that does change a lot of things. This lead to an interesting back-and-forth summarized in this paper: https://www.annualreviews.org/doi/abs/10.1146/annurev-anthro-092611-145815?journalCode=anthro
ReplyDeleteArid seems to have walked very oddly with her big toe abducted like that. def seems that they were spending time in the trees still. and her long arms are just strange!