The ongoing adaptive evolution of ASPM and Microcephalin is not explained by increased intelligence.
Recent studies have made great strides towards identifying putative genetic events underlying the evolution of the human brain and its emergent cognitive capacities. One of the most intriguing findings is the recurrent identification of adaptive evolution in genes associated with primary microcephaly, a developmental disorder characterized by severe reduction in brain size and intelligence, reminiscent of the early hominid condition. This has led to the hypothesis that the adaptive evolution of these genes has contributed to the emergence of modern human cognition. As with other candidate loci, however, this hypothesis remains speculative due to the current lack of methodologies for characterizing the evolutionary function of these genes in humans. Two primary microcephaly genes, ASPM and Microcephalin, have been implicated not only in the adaptive evolution of the lineage leading to humans, but in ongoing selective sweeps in modern humans as well. The presence of both the putatively adaptive and neutral alleles at these loci provides a unique opportunity for using normal trait variation within humans to test the hypothesis that the recent selective sweeps are driven by an advantage in cognitive abilities. Here, we report a large-scale association study between the adaptive alleles of these genes and normal variation in several measures of IQ. Five independent samples were used, totaling 2393 subjects, including both family-based and population-based datasets. Our overall findings do not support a detectable association between the recent adaptive evolution of either ASPM or Microcephalin and changes in IQ. As we enter the post-genomic era, with the number of candidate loci underlying human evolution growing rapidly, our findings highlight the importance of direct experimental validation in elucidating their evolutionary role in shaping the human phenotype.
Mekel-Bobrov
Nitzan
N
Department of Human Genetics, Howard Hughes Medical Institute, University of Chicago, Chicago, IL 60637, USA.
Posthuma
Danielle
D
Gilbert
Sandra L
SL
Lind
Penelope
P
Gosso
M Florencia
MF
Luciano
Michelle
M
Harris
Sarah E
SE
Bates
Timothy C
TC
Polderman
Tinca J C
TJ
Whalley
Lawrence J
LJ
Fox
Helen
H
Starr
John M
JM
Evans
Patrick D
PD
Montgomery
Grant W
GW
Fernandes
Croydon
C
Heutink
Peter
P
Martin
Nicholas G
NG
Boomsma
Dorret I
DI
Deary
Ian J
IJ
Wright
Margaret J
MJ
de Geus
Eco J C
EJ
Lahn
Bruce T
BT
D000293:Adolescent; D000328:Adult; D000483:Alleles; D005075:Biological Evolution; D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism; D018797:Cell Cycle Proteins; D002648:Child; D003598:Cytoskeletal Proteins; D019143:Evolution, Molecular; D005190:Family; D005260:Female; D005838:Genotype; D006801:Humans; D007360:Intelligence / Q000235:genetics*; D008297:Male; D008831:Microcephaly / Q000235:genetics; D008967:Molecular Biology; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009929:Organ Size; D020641:Polymorphism, Single Nucleotide
C467202:ASPM protein, human; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; C460645:MCPH1 protein, human; D009419:Nerve Tissue Proteins