I’m spending most of the day writing now, and it’s difficult to find time to read scientific papers and report on them. So do excuse me for a while if I summarize new findings from (reliable) journalistic results, even though I’ll scan and link to the original paper when possible.
There are two evolution-related findings of note this week. I’ll highlight one today and one tomorrow.
First, Homo floresiensis, the three-foot “hobbit” human whose remains were discovered on the Indonesian island of Flores in 2003, has now been designated as a real species truly distinct from H. sapiens. This species lived fairly recently—38,000-12,000 years ago, when modern humans were already colonizing the New World—but is very distinct from H. sapiens. Because of its size and the resemblance of the skull to those seen in certain human diseases (hypothyroidism, microcephaly, etc.), some scientists speculated that this was not a tiny archaic species living at the same time as modern humans, but simply a single pathological individual of H. sapiens.
A new analysis by Baab et al. (link and free download below) suggest however, that this really was a tiny hominin species. Extensive morphological analysis of the single existing skull from Flores, along with modern H. sapiens, both “normal” and suffering from a variety of syndromes suggested to have produced the Flores skull, as well as a variety of early hominin species, shows that the Flores skull is more similar to that of H. erectus than to nearly all pathological specimens, and is thus likely to truly represent a new species. (See the New York Times report by John Noble Wilford.)
Here’s a cast of the “LB1″ skull from Flores (the only existing one) that was used in the authors’ analysis:
Note that this hominin came up only to your hips (check out the reconstruction at Washington’s Museum of Natural History), and had a brain about 400 cubic centimeters: one third that of modern humans and the size of one of our earliest hominin relatives, Australopithecus afarensis. Here’s how the hobbit compares to a modern human:
Here’s the figure from the Times:
The authors of the paper conclude with the following paragraph, allowing one possible pathology as an explanation:
Our analyses corroborate the previously suggested link between LB1 and fossil Homo and support the attribution of this specimen to a distinct taxon, H. floresiensis. Furthermore, the neurocranial shape of H. floresiensis closely resembles that of H. erectus s.l. and particularly specimens of early Eurasian H. erectus, although it is unclear whether this latter affinity is best attributed to a close phylogenetic relationship or to a size-related convergence in shape. These results also counter the hypotheses of pathological conditions as the underlying cause of the LB1 neurocranial phenotype, with the possible exception of posterior deformational plagiocephaly, a condition without significant adverse health effects/
Baab, K. L., K. P. McNulty, and K. Harvati. 2013. Homo floresiensis Contextualized: A Geometric Morphometric Comparative Analysis of Fossil and Pathological Human Samples. PLoS ONE 8:e69119 EP -.