Several news items have appeared lately about human evolution. This article from the New York Times examines some new evidence in the debate over the disputed new species, Homo floresiensis. Small hominin fossils discovered on the Indonesian island of Flores are believed by some to represent a newly discovered species of humans, and by others to be the bones of modern humans, perhaps adapted for island life (which often reduces the size of a species over time) or perhaps suffering from congenital disorders. Now another set of fossils from small humans has been discovered, this batch on a Micronesian island. The new fossils share some facial traits with the Flores fossils, but had bigger brains and are believed to be smaller versions of modern humans, suggesting that perhaps the Flores bones are not a new species either. There’s no end in sight yet for the debate, which the article summarizes.
This article from Live Science covers a new study into skeletal differences between humans and Neanderthals, our fellow hominins who likely shared the planet with us before dying out around 30,000 years ago. After examining human and Neanderthal skulls, a research team concluded that the differences between them are random individual characteristics and not evidence of any evolutionary adaptations that gave humans the edge over Neanderthals. One possible conclusion is that it was not a physiological or anatomical difference that made us better equipped to thrive on the planet, but some kind of social or cultural edge. On the other hand, Erik Trinkaus, Neanderthal researcher at Washington University in St. Louis and unconnected with the recent skull study, sees very little meaningful difference of any sort between the two species, and argues that perhaps it was just luck that led to the success of humans and the death of Neanderthals.
And finally, going much further back in time, recent research suggests that bipedalism did not arise relatively recently in the hominin lineage but goes clear back to a species called Orrorin tugenensis. This very early hominin lived in Africa around six million years ago, somewhere around the time that the chimpanzee and human branches diverged from each other. Measurements of fossil thigh bones indicate that it walked upright on two legs some of the time and also spent some time climbing trees on all fours; biomechanically its gait differed from that of modern humans. Walking upright evidently has a longer and more complicated story than we knew before. This story from US News & World Report has the details.