By Bruce Bower, Science News
Right-handedness reaches back a half million years in the human evolutionary family, at least if scratched-up fossil teeth have anything to say about it.
Stone-tool scratches on the front teeth of Neandertals and their presumed European ancestors occur at angles denoting right-handedness in most of these Stone Age hominids, just as in human populations today, say anthropologist David Frayer of the University of Kansas in Lawrence and his colleagues.
Scientists have linked prevalent right-handedness in human populations to a left brain hemisphere that controls right-sided body movements and enables critical language functions. Given the new tooth evidence, populations of largely right-handed Neandertals and their predecessors must have possessed a gift for gab, Frayer’s team proposes in a paper published online April 14 in Laterality.
“Findings so far suggest that most European hominids were right-handed by at least 500,000 years ago,” Frayer says. “A capacity for language appears to have ancient, not recent, roots.”
Along with widespread right-handedness indicating that these ancient hominids possessed language-ready brains, humanlike inner-ear fossils show that Neandertals’ ancestors could hear all the sounds employed in modern tongues, Frayer asserts.
Other researchers contend that, based on vocal-tract reconstructions informed by skull and upper-body fossils, Neandertals were physically incapable of articulating some modern speech sounds. In these scientists’ view, language as spoken today originated in Homo sapiens sometime after 200,000 years ago.
Frayer’s findings coincide with previous reports of right-handed sharpening patterns on 120,000-year-old Neandertal stone tools (SN: 11/21/09, p. 24), remarks archaeologist Natalie Uomini of the University of Liverpool in England.
“This new study points to a strong right-hand preference at the group level, and very early on among hominids,” Uomini says.
Handedness may exist among chimpanzees and other nonhuman primates (SN: 4/9/11, p. 11), although to a lesser extent than in people.
To discern ancient hand inclinations, Frayer employed a method developed by paleontologists who excavated 500,000-year-old fossils of Neandertal ancestors in northern Spain. Experiments conducted by the Spanish team indicate that when using a stone tool to cut a piece of meat by biting down on one end and holding the other end taut, right-handers make accidental scratches that angle in a consistent direction. Similarly, left-handers make scratches angled in the opposite direction.
Magnified images of front teeth from 17 European Neandertals that lived between 130,000 and 30,000 years ago revealed scratches consistent with right-handedness in 15 cases and left-handedness in two cases.
Comparable scratch data from front teeth of 12 Neandertal ancestors, previously obtained by Marina Lozano of Universitat Rovira i Virgili in Spain and her colleagues, denoted right-handedness in each individual.
Frayer calculates that between 0.8 percent and 22.8 percent of these Neandertal and ancestral Neandertal populations were left-handed. Even at the high end of that range, right-handedness would have been far more common than left-handedness.
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