Starting with Fossil Hominins

Today we  started our discussion of human evolution through the fossil record and we were able to cover fossils from our split with Pan to Lucy (A. afarensis). I started by reviewing the parts of the cranial and post-cranial anatomy that paleoanthropologists use to discern changes in the hominin line – these features include, 1) movement of the foramen magnum anteriorly, 2) reduction of facial proganathism, 3) elimination of the honing complex, 4) shortening of limbs relative to the body plan, and 5) a shift in the shape of the dental arcade (U-shaped to parabolic).

I also took the opportunity to explain that taxonomies are made by scientists and that scientists typically fall into two camps, lumpers (who see similarities) and splitters (who see differences), and that species classifications can vary depending upon who is constructing the taxonomy.

We started with the pre-Australopiths (Orrorin, Sahelanthropos, and Ardipithecus) and I reviewed the fossil finds, features that were derived with later hominins and those that were ancestral or primitive – each of these has reason to be put into the hominin line, despite ancestral traits.

From Ardipithecus, I reviewed A. anamensis, A. afarensis, and A. africanus, following the same strategy as before. With these three, I took some effort to explain how some of this variation could also be accounted for because of geographical separation, but that all were bipeds, a necessary feature for Australopiths.
I also reviewed the Laetoli footprints and they tells us about bipedality at around 4 mya.

45 minutes passed quickly today and I didn’t even remotely get to address tool making, later Australopiths, or any of the Homo line.  All for next time!


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