http://medicalxpress.com/news/2012-05-extra-gene-drove-instant-human.html
In NOT A CHIMP I devote one chapter, called MORE IS BETTER, to the extent to which phenomena like gene duplication have driven human evolution and widened the genomic gap between humans and our near neighbours - chimpanzees. Evan Eichler's work was heavily mentioned in the book and in this recent report on his work with Franck Polleux, an expert in brain development at The Scripps Research Institute, they make trenchant claims for the dramatic effects of gene duplication at crucial points in our hominin evolutionary history that may have been very important in brain growth and development - and unique human brain anatomy. The gene in question is SRGAP2. Here's a section of this Medical Express report which encapsulates what happened and why it may be very important:
""There are approximately 30 genes that were selectively duplicated in humans," said Franck Polleux. "These are some of our most recent genomic innovations."
Intriguingly, many of these genes appear to play some role in the developing brain. Polleux and Evan Eichler, a genome scientist at the University of Washington, focused their expertise and attention on one of the genes known as SRGAP2. This gene has, in fact, been duplicated at least twice during the course of human evolution, first about 3.5 million years ago and then again about 2.5 million years ago.
The new work shows that the second and relatively recent duplication event produced only a partial copy of the gene. This copy acts at exactly the same time and place as the original, allowing it to interact with and block the ancestral gene's function.
"This innovation couldn't have happened without that incomplete duplication," Eichler said. "Our data suggest a mechanism where incomplete duplication of this gene created a novel function 'at birth'."
Interestingly, the novel gene appears to have arisen just as the fossil record shows a transition from human's extinct Australopithecus ancestors to the genus Homo (as in Homo sapiens), which led to modern humans. That's also when the brains of our ancestors began to expand and when dramatic changes in cognitive abilities are likely to have emerged."
The gene is involved in neuronal migration to appropriate parts of the developing brain from the epithelium from which neurons bud off. It also seems to govern the complexity of projections any neuron can develop - a key factor in eventual complexity of interconnectivity of neurons - network.
Are we humans simply remodelled apes? Chimps with a tweak? Is the difference between our genomes so minuscule it justifies the argument that our cognition and behaviour must also differ from chimps by barely a whisker? If “chimps are us” should we grant them human rights? Or is this one of the biggest fallacies in the study of evolution? NOT A CHIMP argues that these similarities have been grossly over-exaggerated - we should keep chimps at arm’s length. Are humans cognitively unique after all?