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With almost complete certainty, I can predict that you, dear reader, are right-handed. If I were a betting man, I’d put money on it. I’d make the same bet if you were reading this in India or Iowa, Kansas or Kathmandu. And a hundred years from now, I’d make the same bet again.
I can be so sure of myself not because I am some prodigious prognosticator, but because about 90 percent of humans are right-handed. That phenotypic ratio—nine right-handed people for every lefty—is relatively stable, not just across cultures and geographic regions, but perhaps across the span of human evolution. The archaeological record suggests that hominins were predominantly right-handed as far back as 2 million years ago,1 and a 2010 study of the wear patterns on 32,000-year-old Neanderthal teeth found that this extinct cousin of Homo sapiens was likely about 88 percent right-handed.2 It’s a ratio that has baffled scientists for more ...
