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[QUOTE]Originally posted by DD'eDeN: [QB] Lefties and lingos - not linked? <http://www.amazon.com/Handedness-Brain-Asymmetry-Right-Theory/dp/184169104 6> Some researchers still in 2002 claimed to support the monogenic theory, suggesting that handedness is determined by a single genetic locus with 2 alleles. But with the advent of advanced molecular & genetic techniques, the foundation of monogenic theories has become increasingly shaky, not just for handedness, but for many complex traits, e.g. for skin color & height, some cancers & other multifaceted diseases. Clyde Francks : "Many human traits that are continuous in nature in the population (e.g. height, weight, blood pressure, aspects of brain lateralization) are likely to have complex contributions to their variability, both genetic & environmental. As neuroscientists, we are very puzzled that there is this weird link between left-handedness & cerebral organization." Even with the knowledge that traits as complex as brain lateralization & hand preference were unlikely to have a simple genetic foundation, Somers admits that he sought the elusive single gene that could explain the well-established behavioral distribution: "I was hoping to find the major gene that linked language lateralization & handedness." So a few years ago, he & colleagues tracked down families in a Dutch village that had a bizarre demographic trait: disproportionately large numbers of southpaws, going back generations. Somers cs studied the genetic makeup of 355 people from 37 large families that comprised generations of lefties, performing genetic linkage analyses of left-handedness, atypical lateralization & degree of language lateralization in the brain. Although they identified genome regions that were linked to all of those phenotypes separately, none of the regions overlapped. J Neurosci 35:8730-36, 2015 <http://www.jneurosci.org/content/35/23/8730.short>, The finding "overturns this older idea of a shared gene," and serves as strong evidence that monogenic theories of handedness or language lateralization are incorrect: "It is more complicated, and it is more in line with many recent findings that traits are composed of many genes rather than single genes." [/QB][/QUOTE]
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