25 March 2004
Brain versus brawn: Myosin mutant's moment in human evolution
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The cranial vault in many primates, including chimps, gorillas (cover, upper skull) and extinct hominids such as Australopithecus, is encased by large, well anchored muscles (shaded red) that power the bite. These muscles are relatively smaller in humans, with attachments that leave several cranial growth sites, sutures, unencumbered (lower skull). The discovery of a mutation that disrupts a motor protein that uniquely powers these muscles suggests human evolution was spurred on by abrupt muscle fibre shrinkage (background, compare upper to lower). A 'molecular clock' dates the mutation at 2.4 million years ago, just before the genus Homo appears in the fossil record. Simultaneous reduction of muscle volume and bite force could have left the cranium free to expand to accommodate an evolving brain.
Myosin gene mutation correlates with anatomical
changes in the human lineage
HANSELL H. STEDMAN, BENJAMIN W. KOZYAK, ANTHONY NELSON,
DANIELLE M. THESIER, LEONARD T. SU, DAVID W. LOW, CHARLES R. BRIDGES,
JOSEPH B. SHRAGER, NANCY MINUGH-PURVIS & MARILYN A. MITCHELL
Nature 428, 415–418 (2004); doi:10.1038/nature02358
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Human genetics: Muscling in on hominid evolution
PETE CURRIE
A molecular difference in the jaw muscles of human and non-human primates
has tantalizing echoes in the fossil record. Was this divergence a central
event in the evolution of the skull of modern hominids?
Nature 428, 373–374 (2004); doi:10.1038/428373a
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