A closer look at identical twins shows they are not so identical after all. Differences start to appear as early as the first stages of development, before embryos form a mass of cells, The Guardian reports. Mutations during cell replication resulted in, on average, 5.2 of these genetic differences in each twin pair in a new study, scientists reported yesterday in Nature Genetics. Researchers say the findings can help us better understand human development and improve studies that use twins to look at the genetic and behavioral impacts of nature versus nurture.
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