Smell and Cognitive Development -- "Sex bias in copy number variation of olfactory receptor gene family depends on ethnicity"

"the most polymorphic CNV-enriched OR cluster in the human genome, located on chr 15q11.2, is found near the Prader–Willi syndrome/Angelman syndrome bi-directionally imprinted region associated with two well-known mental retardation syndromes. As olfaction represents the primitive cognition in most mammals, arguably in competition with the development of a larger brain, the extensive retention of OR pseudogenes in females of this study, might point to a parent-of-origin indirect regulatory role for OR pseudogenes in the embryonic development of human brain."

http://journal.frontiersin.org/article/10.3389/fgene.2013.00032/abstract

I have a vague memory of reading about the link between cognitive evolution and olfactory (smell) receptor genes. I was putting together a presentation on the neurogenetics of smell for a continuing education day for science teachers, and I stumbled on this paper.

The paper starts from the fact that there is a lot of variation between humans in the number of copies of certain olfactory receptor genes. This means that some people might have a lot more of a certain receptor than others, and be more sensitive to certain odors or have the ability to distinguish similar odors that other people can't.

The authors basically find that this copy number variation might be associated with a gene-regulation change that causes mental retardation. They suggest that the olfactory system competes with higher cognition (thinking, attention etc...) for resources during development, so that if you have a lot of different receptor genes and