Return to the Hobbit ...brain/body mass differ in selection process

Homo floresiensis, a pygmy-sized small-brained hominin popularly known as ‘the Hobbit’ was discovered five years ago, but controversy continues over whether the small brain is actually due to a pathological condition. How can its tiny brain size be explained? Researchers have tackled this question in the context of a comprehensive assessment of the evolution of brain and body size throughout the larger primate family.

Nick Mundy and Stephen Montgomery, from the Department of Zoology at Cambridge University, UK, and colleagues from Durham University used previously published data from living and extinct species to reconstruct the pattern of brain and body mass evolution in primates. According to Nick Mundy, “Our results provide robust confirmation for the suggestion that strong evolutionary trends have governed the expansion of the primate brain. In contrast, body size evolution has not tended to increase in primates, implying brain and body mass have been subject to separate selection pressures and supporting the findings of previous studies in other taxonomic groups that these two highly correlated traits can show differences in their patterns of evolution”.

Brain expansion began early in primate evolution and has occurred in all major groups, suggesting a strong selective advantage to increased brainpower in most primate lineages. Despite this overall trend, however, Mundy and his colleagues have identified several branches/lineages within each major group that have shown decreasing brain and body mass as they evolve, for example in marmosets and mouse lemurs. According to Mundy, “We find that, under reasonable assumptions, the reduction in brain size during the evolution of Homo floresiensis is not unusual in comparison to these other primates. Along with other recent studies on the effects of ‘island dwarfism’ in other mammals, these results support the hypothesis that the small brain of Homo floresiensis was adapted to local ecological conditions on Flores."

http://www.biomedcentral.com/bmcbiol/

Source: Alphagalileo 27/01/10

Evolution of the Human Gait

Professor Matthew Bennett has been awarded a Standard Natural Environment Research Council (NERC) grant worth £880,000, in collaboration with Professor Robin Compton of Liverpool University, to continue research into the evolution of the human gait in our ancestors.
In 2009, Professor Bennett was the lead author of a landmark paper published in the acclaimed journal Science which revealed new evidence of early human development. The study, which featured on the front cover of Science, concluded that footprints discovered near Ileret in Northern Kenya were left by one of our evolutionary ancestors, Homo erectus.
Professor Bennett and an international team of colleagues believe that the prints, made between 1.51 and 1.53 million years ago, show clear evidence that Homo erectus had a modern foot anatomy and function, and walked much like we do today. This important feature is viewed as vital to the shift in cultural and biological adaptations of Homo erectus, believed to be the first species to migrate from Africa.
The footprints are preserved in fine-grained mud on two distinct sedimentary layers in a single outcrop at Ileret. These surfaces have been dated precisely via volcanic ash layers and digitally scanned by Professor Bennett to create three-dimensional digital elevation models accurate to a fraction of a millimeter. Laser scanning not only provides a unique method of analysis, but also allows for the footprints to be preserved where they are and shared digitally around the world.
“I’m delighted that Professor Compton and I have been successful in obtaining this funding which will mean that our work on these ancient footprints can continue,” said Professor Bennett. “The award will help to fund vital resources in the lab and in the field and should lead us to uncovering further evidence of early man’s development.”