Notable: Synchotron analysis of early hominin teeth

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Notable paper: Smith TM, Tafforeau P, Le Cabec A, Bonnin A, Houssaye A, et al. (2015) Dental Ontogeny in Pliocene and Early Pleistocene Hominins. PLoS ONE 10(2): e0118118. doi:10.1371/journal.pone.0118118

Synopsis: Tanya Smith and colleagues report on the largest-ever study based on synchotron scanning of juvenile teeth from early hominin species. They examined 25 specimens that represent Australopithecus anamensis (from Kanapoi, Kenya), Au. africanus (from Sterkfontein and Makapansgat, South Africa), Paranthropus robustus (from Swarkrans and Drimolen, South Africa), and early Homo (species unidentified, from Drimolen, South Africa). They examined the growth increments of the teeth, showing that these early hominin samples have a substantial variation in the periodicity and formation time of their molar crowns.

Interesting because: We would like to know more about the growth and development of fossil hominins. The formation of enamel in teeth happens at a characteristic rate, leaving growth increments that can be examined microscopically. The synchotron scans allow this enamel formation to be studied non-destructively. Up to now, conclusions about the growth rate of early hominin teeth have been based on very small samples. Looking at the larger sample has yielded a broader picture of variation, while supporting differences among species (like the apparently faster development of P. robustus teeth.

More: The teeth in this study all come from juvenile specimens, and yield a more precise estimate of age at time of death for them. Some of them were surprisingly older than originally thought, some younger. Again, the better data yield a picture of variability. It’s great that the authors put this into the open access PLoS ONE so that it can be widely read, because it’s a good empirical paper.