Archive for the ‘ASPM’ Category

My ‘HUMAN’ brain

A reconstruction of Australopithecus afarensis

Image via Wikipedia

Having a great time reading Michael Gazzaniga‘s new book, “Human – the science behind what makes us unique” and thought I’d see to what extent his conclusions might square with genetic data on population history and natural selection etc. and also evaluate my 23andMe profile to see to what extent I’m carrying the latest greatest derived alleles (more human-ish) or the older clunkier ancestral alleles.

I’ll try and keep updating this post as I work my way through the book. Here goes:

Chapter 1: Are human brains unique ?
Big Brains and Big Ideas ? (p.10) – In this section discussing how brain size may or may not relate to function and specialization of function, there are a number of genetic factors which have been linked to brain development and natural selection. Most well reported [doi: 10.1126/science.1116815] are the A44871G and C45126A variations in the ASPM gene. My 23andMe profile shows a GG and CA at these sites (rs964201 and rs3762271 respectively). Apparently, the G-allele (rs964201) and the A-allele (rs3762271) are derived, so I’m feeling very unique having scored 3/4 in this first query!

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Human evolution mural at Dover High School
Image by Colin Purrington via Flickr

Comparisons of human genome variation within and across closely related species have great potential to reveal ways in which the brain and mind of modern humans may or may not have differed from our hominid ancestors. Such comparisons have recently revealed a great many genomic targets of natural selection, some of which are expressed in the developing brain, and, hence, might provide clues to the mental life of our ancestors. Variation in two such candidates ASPM (rs964201) and MCPH1 (rs2442496) arose approximately 50,000 years ago and show strong positive selection in the lineage leading to humans. What do these genes and common variants do ? Do they affect language acquisition ? Social behavior ? Intelligence ? Any type of process that might smack of something uniquely ‘human’ ? In their paper [DOI], “Investigation of MCPH1 G37995C and ASPM A44871G polymorphisms and brain size in a healthy cohort“, Dobson-Stone et al., used structural MRI to determine whether differences in whole brain volume or grey matter volume might relate to either or both of these variants. Although no evidence was found that relate these common variants (rare mutations can cause microcephaly) their methodological approach seems like a fantastic strategy for gaining insights into our human origins.

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