Professor John Frink
03-05-2007, 05:17 PM
Acceleration of adaptive evolution in modern humans.
Humans vastly increased in numbers during the past 40,000 years. Recent surveys of human genomic variation have suggested a large surplus of recent positive selection, indicated by excess linkage disequilibrium and skewed SNP frequency spectra. We applied estimates of prehistoric and historic population sizes to estimate the importance of population growth in explaining the number of recent adaptive mutations. Our estimates are consistent with genomic evidence in suggesting that the rate of generation of positively selected genes has increased as much as a hundredfold during the past 40,000 years.
Do skeletal features reflect this genomic evidence of selection? Under positive selection, rapid appearance of new variants during the terminal Pleistocene and early Holocene would cause maximal phenotypic change during the last 2000-4000 years. We compared original and published series of Holocene cranial data from Europe, Jordan, Nubia, South Africa, and China, in addition to Late Pleistocene samples from Europe and West Asia, to test the hypothesis that the genomic acceleration in positive selection correlates with phenotypic evolution during this time period. A constellation of features in the face and cranial vault, notably including endocranial volume, changed globally during this time period and documents common patterns of selection in different regions. Holocene changes were similar in pattern and chronologically faster than those at the archaic-modern transition, which themselves were rapid compared to earlier hominid evolution. In genomic and craniometric terms, the origin of modern humans was a minor event compared to more recent evolutionary changes.
http://www.physanth.org/annmeet/aapa2007/aapa2007abstracts.pdf
Humans vastly increased in numbers during the past 40,000 years. Recent surveys of human genomic variation have suggested a large surplus of recent positive selection, indicated by excess linkage disequilibrium and skewed SNP frequency spectra. We applied estimates of prehistoric and historic population sizes to estimate the importance of population growth in explaining the number of recent adaptive mutations. Our estimates are consistent with genomic evidence in suggesting that the rate of generation of positively selected genes has increased as much as a hundredfold during the past 40,000 years.
Do skeletal features reflect this genomic evidence of selection? Under positive selection, rapid appearance of new variants during the terminal Pleistocene and early Holocene would cause maximal phenotypic change during the last 2000-4000 years. We compared original and published series of Holocene cranial data from Europe, Jordan, Nubia, South Africa, and China, in addition to Late Pleistocene samples from Europe and West Asia, to test the hypothesis that the genomic acceleration in positive selection correlates with phenotypic evolution during this time period. A constellation of features in the face and cranial vault, notably including endocranial volume, changed globally during this time period and documents common patterns of selection in different regions. Holocene changes were similar in pattern and chronologically faster than those at the archaic-modern transition, which themselves were rapid compared to earlier hominid evolution. In genomic and craniometric terms, the origin of modern humans was a minor event compared to more recent evolutionary changes.
http://www.physanth.org/annmeet/aapa2007/aapa2007abstracts.pdf