Perusing my AJPA RSS feed, I came across an interesting abstract (see attempt at citation below). This article tests three different hypotheses for cranial robusticity in modern humans: genetic, mastication, and climate, and finds that mastication doesn’t seem to explain the robusticity of some populations. I didn’t read the article, just the abstract (it’s summer, and I was perusing), but it got me thinking. If we find population variation that is not based on climate or diet within modern humans, could this have been the case in more ancient hominids? My memory for australopithecine crania is terrible, but I keep thinking of all the different sized “erectines” and “habilines” we looked at in 565 – that sample definitely represented different levels of robusticity. I’m not really sure where I’m going with this (I probably should have read the article and thought about it for a day or so to collect my thoughts, but I’m impatient and felt like posting). I guess I’m just trying to link what we know about modern humans to what we think we know about other hominids. Thoughts? Did anyone else look at this article? Did you find it interesting or dull or poorly written or irrelevant? Is everyone having a good summer so far?
Baab et al. (2009) Relationship of Cranial Robusticity to Cranial Form, Geography and Climate in Homo sapiens. American Journal of Physical Anthropology – June 25.
Lawn Chair Anthropology 
I also just skimmed the abstract. What I recall about erectines (Anton's "size considered" paper) is that the major "erectus" cranial features are more pronounced at larger sizes. So bigger individuals tended to be more 'erectus-like.'Spoor presented similar stuff at the Paleo meetings last year. Basically he just ran a bunch of linear regressions, with cranial capacity as the proxy for size and saw how each trait scaled with brain size. I think his results corroborated Anton's.The habiline stuff is just weird and problematic. The most 'erectus' like of all the crania generally attributed to habilis is KNM-ER 1813, which is also the smallest of all. Baab herself has some recent, interesting papers on the erectine crania (I think in JHE), which would be good follow-up reading to connect her most recent paper on humans to earlier Homo.
Hmm, maybe I'll have to check out Baab's other work. This article suggested that the big-are-always-more-robust rule didn't work for modern humans, so it'd be interesting to see what she has to say about erectines. Thanks!