ASPM (Gene)

ASPM is a human gene whose defective forms are associated with autosomal recessive primary microcephaly. A new version of ASPM appeared about 5,800 years ago and has spread to half the world's population, especially Europe and West Asia.

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"ASPM" is an acronym for "Abnormal Spindle-like, Microcephaly-associated", which reflects its being an ortholog to the Drosophila melanogaster "abnormal spindle" (asp) gene. ASPM is located on chromosome 1, band q31 (1q31).

The mouse gene, Aspm, is expressed in the primary sites of prenatal cerebral cortical neurogenesis. The difference between Aspm and ASPM is a single, large insertion coding for so-called IQ domains.^[1]

According to recent research regarding human evolution and cultural development, the most recent ASPM gene variation arose about 5,800 years ago, roughly correlating with the development of written language, spread of agriculture and development of cities^{[citation needed]}. Currently, two variations of this gene exist: the older variation (pre-5,800 years ago) and the newer variation (post-5,800 years ago). About 10% of humans have two copies the "new" ASPM gene, while about 50% have two copies the "old" version. The other 40% of humans one copy of each. Of those with an instance of the new gene, 50% of them are a completely identical copy of the gene [2] suggesting a highly rapid spread from the original mutation. According to evolutionary theory, the rapid spread of a mutation (such as the new ASPM) through the population indicates that the mutation is somehow advantageous to the individual.^[3] As of today, there is no evidence to support the notion that the new ASPM gene increases intelligence, and some researchers dispute whether the spread of the gene even demonstrates selection^{[1] [2] [4][5]}. However, statistical analysis has shown that the older forms of the gene are found more heavily in populations that speak tonal languages like Chinese. [6]

Instead of the ASPM gene, the Chinese appear to have developed the DAB1 gene which also increases the density of neural matter, however, there is no evidence what either of these facts means, one is more intelligent than the other. [7]

References and notes

1. ^ Woods, R.P., et al. (2006). "Normal variants of Microcephalin and ASPM do not account for brain size variability". Hum. Mol. Genet. 15 (12): 2025-2029. doi:10.1093/hmg/ddl126.
2. ^ Mekel-Bobrov, N., et al. (2007). "The ongoing adaptive evolution of ASPM and Microcephalin is not explained by increased intelligence". Hum. Mol. Genet.: adv. access. doi:10.1093/hmg/ddl487.

1. ^  An IQ domain is a segment of DNA that codes for the IQ motif.

   IQ protein motif: [FILV]Qxxx[RK]Gxxx[RK]xx[FILVWY]

   The term "IQ" refers to the first two amino acids of the motif: isoleucine (commonly) and glutamine (invariably).

2. ^  Nitzan Mekel-Bobrov et al. (2005). "Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens". Science 309 (5741): 1720–1722.
3. ^  Mathias Currat et al. (2006). "Comment on "Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens"". Science 313 (5784): 172.
4. ^  following is one of a large number of similar news articles:

   Study Suggests Human Brains Still Evolving. Live Science: Human Biology. Retrieved on November 26, 2005.

5. Kniffin, Cassandra L. et al.. ABNORMAL SPINDLE-LIKE, MICROCEPHALY-ASSOCIATED; ASPM. OMIM at the NCBI. Retrieved on August 6, 2005.

   Bruce Lahn moving on to non-IQ projects?. Live Science: Human Biology. Retrieved on June 16, 2006.