Single gene mutations and the evolution of the human brain.
While it has been firmly established that bipedalism came much earlier in the evolution of our ancestors, the evolution of a comparatively large brain and the cultural (and eventually linguistic) evolution that accompanied its development is often what people think of when they attempt to answer questions of what it is that defines ‘being human’. Some recent research into microcephaly (see citation at the bottom of the post), a condition that causes a given individual to develop a much smaller and less convoluted cerebral cortex than others (see pictures below), has possibly given some insight into how it is possible for human brain size to be dramatically altered by mutations in even single genes.
It was demonstrated in the research that a mutation of a single gene (NDE1) involved in cell division yields the microcephalic state shown in the image provided. In an evolutionary context this is of interest as it demonstrates that, in general, a mutation in a single gene could have large-scale consequences for brain development and perhaps it was such a single gene mutation in the past that sparked the evolution of the ‘human defining’ big brain and consequent increases in cognitive abilities.
I’m aware that the connection made here is somewhat simplistic, but it will be very interesting to see what future research into single gene mutations relating to brain development reveals.
Image produced by the Yale University School of Medicine.
“The Essential Role of Centrosomal NDE1 in Human Cerebral Cortex Neurogenesis”
Mehmet Bakircioglu, Ofélia P. Carvalho, Maryam Khurshid, James J. Cox, Beyhan Tuysuz, Tanyeri Barak, Saliha Yilmaz, Okay Caglayan, Alp Dincer, Adeline K. Nicholas, Oliver Quarrell, Kelly Springell, Gulshan Karbani, Saghira Malik, Caroline Gannon, Eamonn Sheridan, Moira Crosier, Steve N. Lisgo, Susan Lindsay, Kaya Bilguvar, Fanni Gergely, Murat Gunel, C. Geoffrey Woods
The American Journal of Human Genetics – 28 April 2011