The spread of alphabetical writing may have favored the latest variant of the ASPM gene.
ASPM, a gene that regulates brain growth, has evolved considerably in the primate lineage that leads to humans. It continued to evolve even after the emergence of modern humans, with the latest ASPM variant arising about 6000 years ago somewhere in the Middle East. The new variant then proliferated within and outside this region, reaching higher incidences in the Middle East (37-52%) and in Europe (38-50%) than in East Asia (0-25%). Despite its apparent selective advantage, this variant does not seem to improve cognitive performance, at least not on standard IQ tests. At present, we can only say that it probably assists performance on a task that exhibited the same geographic expansion from a Middle Eastern origin roughly 6000 years ago. The closest match seems to be the invention of alphabetical writing, specifically the task of transcribing speech and copying texts into alphabetical script. Though more easily learned than ideographs, alphabetical characters place higher demands on mental processing, especially under premodern conditions (continuous text with little or no punctuation, real-time stenography, absence of automated assistance for publishing or copying, etc.). This task was largely delegated to scribes of various sorts who enjoyed privileged status and probably superior reproductive success. Such individuals may have served as vectors for spreading the new ASPM variant.
Frost
Peter
P
Anthropology Department, C/o Bernard Saladin d'Anglure, Université Laval, Québec, Canada G1K 7P4. peter_frost61z@globetrotter.qc.ca
D000818:Animals; D001921:Brain / Q000254:growth & development / Q000502:physiology*; D019143:Evolution, Molecular; D014644:Genetic Variation; D006801:Humans; D007802:Language; D008037:Linguistics / Q000639:trends*; D009419:Nerve Tissue Proteins / Q000235:genetics*; D011323:Primates / Q000235:genetics; D014956:Writing
C467202:ASPM protein, human; D009419:Nerve Tissue Proteins