I’ve been hiding out under a rock for the past two months. Part of the quietude here is because I’ve been working hard to write up my dissertation, which compares patterns of jaw growth in humans and the our extinct relative Australopithecus robustus. Even though I presented some extremely preliminary results last year, I’ve generally been hesitant to talk about my work here on Lawnchair.
But in an effort to break my dissertation silence, and to begin thinking about starting to consider crawling out from under my rock, here’s a pretty pretty picture I made:
The green box and whiskers are humans, and the blue boxes A. robustus. Each box and whiskers represent all the individual mandible “sizes” that can be calculated for each species in each dental stage (stage 1 has only baby teeth erupted, stage 5 has nearly all its teeth erupted). It’s sort of like a mandible growth curve for each species, but not exactly.
The problem is I want to see whether I can distinguish patterns size change, from infancy to just before adulthood, in humans and A. robustus. But fossils don’t preserve well, and not all specimens share all the same measurable parts. So I devised a special test that measures a mandible’s “size” based on the traits it compares with other individuals.
Now, clearly from the figure A. robustus and human mandibles differ in mandible size throughout childhood. But questions arise: given the range of size variation within each species (especially stage 4), what are the chances of seeing the same amount of size change between dental stages in each sample? What traits or measurements on the mandible are contributing to these differences? Do these ‘sizes’ reflect the development of each species’ unique mandible shape? Well you’ll just have to stay tuned to find out…
…Or you could check this poster I presented at this year’s annual meeting of the American Association of Physical Anthropologists.