Behavioral reconstruction

Today I will be talking about the behavior of Ardipithecus ramidus, because this is a fossil and not a living animal, behavior will have to be assumed from physical characterizes of the fossil as well as environmental characterizes which I talked about in a pervious blog post. I will specifically be looking at the article: “Behavioral and phylogenetic implications of a narrow allometric study of Ardipithecus ramidus” and critically analyzing it.

The article compared the dimensions of the fossil bones of Ardi to different primates like chimpanzees, baboons, and humans. The authors of the study were hoping to find some correlation in the length on Ardi’s limbs and teeth dimensions to a living primate, which could give some insight into the behavior and lifestyle of Ardipithecus ramidus. They only compared Ardi to primates with weights close to 44.6-58.3kg, which is the estimated weight that Ardi would be if she were living today. One thing that I think would have made the study better is if the researcher had direct access to Ardi, instead they used the measurements given in the initial articles and analysis of the Ardipithecus ramidus fossil, some of which were estimated based on other lengths so they were not direct lengths.

In the discussion section of the article the authors concluded that “Body segment lengths of Ardipithecus showed greatest overlap with those of hominoids,” and not with the monkeys that they included in the study. This makes sense because Ardi is a hominin. All of the measurements were almost exactly in the middle of the chimpanzee and ape lengths and the human lengths. So far none of the findings surprised me because Ardipithecus ramidus is an intermediate hominin and possibly a stem hominin and could have bridged the gap between human’s last common ancestors with non-human apes. One thing that the study said that I do not agree with is that they concluded that Ardi was mostly a palmigrade walker and only practiced habitual bidealism. Multiple other studies about Ardipithecus ramidus’ pelvis have proven that Ardi was bipedal and but retained arboreal qualities. I think because the study only compared limb length is was limited in its analysis of the pelvis and that could be why they came to this conclusion.

Overall the forest environment in which Ardi lived in along with its arboreal and terrestrial abilities suggest that Ardipithecus ramidus would have been arboreal to gather food and may have walked upright short distances while carrying food. This also suggests that Ardi lived in groups, which would have helped them gather enough food to survive. As an intermediate hominin Ardi would have been comfortable in the trees or on the ground but unlike what the study suggests, I believe that Ardipithecus ramidus was fully bipedal, even if it was not quite as functional of an upright walker as modern humans. It is difficult to assume factors of behavior from fossils, however I think that most of the evidence points to Ardi living in at least small groups and gathering and carrying food from the trees to the ground in order to survive.

The image on the left shows how Ardipithecus ramidus may have walked, the image on the left shows and artist's reconstruction of how Ardi may have gathered food from the trees in groups.

Bibliography:

Sarmiento E, Meldrum D. 2011. Behavioral and phylogenetic implications of a narrow allometric study of Ardipithecus ramidus. HOMO - Journal of Comparative Human Biology [Internet] 62:75–108. Available from: http://uw8rw3ad9q.search.serialssolutions.com/?genre=article&issn=0018442x&title=homo - journal of comparative human biology&volume=62&issue=2&date=20110101&atitle=behavioral and phylogenetic implications of a narrow allometric study of ardipithecus ramidus&spage=75&pages=75-108&sid=ebsco:sciencedirect&aulast=sarmiento, e.e.

Image from: http://ardipithecusramidus.yolasite.com/resources/Ardipithecus_ramidus.jpg