Species: Paranthropus robustus
The above classification was taken from ‘Human evolution: taxonomy and paleobiology.’ Wood, B.A. and Richmond, B. J. Anat., 97: 19-60. and is used, more or less, in the second edition of Conroy’s Reconstructing Human Origins. There are other classifications out there, each with their own advocates, but I kind of like this one. The more I think about it the more it grows on me (although I should point out that taxonomy isn’t something I have spent a lot of time learning about – I keep meaning to change that but never seem to have the time). I will also point out that I am still on the fence about the whole Paranthropus thing.
Paranthropus robustus (SK-48 is pictured left) dates to between 2-1 MYA and are found at Kromdraai, Swartkrans, Drimolen, and Gondolin. Endocranial capacity averages around 450 cc. Body weight estimates range from 30 kg in female to 40-60 in males (these estimates were based on the diameter of the femoral head). The cranial vault is thin walled and has well developed sagittal and nuchal crests. The forehead doesn’t rise much above the orbits and the browridges are prominent. The midfacial and jaw regions show a number of traits, such as the anterior pillars, related to the large masticatory system. Dentally, the posterior cheek teeth are large and low cusped and the anterior teeth are reduced. There is a high incidence of anterior crowding, something seen in Homo sapiens for different reasons, and the canine are reduced. The enamel on the molars is thick. The mandible is large as it houses the large molars and provides attachment areas for the masticatory muscles (as do the sagittal and nuchal crests). Postcranially, Paranthropus robustus displays traits that are more human-like than ape-like, they walked bipedally, for example. Finally, there is some evidence that Paranthropus robustus was a tool user. Some artifacts have all the hallmarks of being used for termite fishing.
Eurydice, skull top, and Orpheus, mandible bottom.
As you may have guessed, I chose Paranthropus robustus for this week’s “Know Your Primate” because of the recent Science article. Greg Laden has an excellent post on the subject and since I largely agree with it I won’t comment further. Well, strike that, one of the things that is getting some play in the news is the way the number of fossils we have changes the questions we can address. In this case because the researchers used about 35 specimens they were able to ask some pretty sophisticated questions about the variability displayed by Paranthropus robustus.
Although I will say that the paper in question is a good example of why I mention the sex of animals that are forced to leave the group and talk about the groups composition of each species in this series.
DNH 7, SK 48, SK 12, and SKW 12 (from left to right)
Update 1: Sorry, my brain was elsewhere and I left the last sentence half finished. That has been corrected.
Update 2: Kambiz has an interesting take on the new paper