The L1Hs preTa subfamily of long interspersed elements (LINEs) originated after the divergence of human and chimpanzee and is therefore found only in the human genome. Thirty-three of the 254 L1Hs preTa elements are polymorphic for the absence/presence of the insertion, making them useful markers for studying human population genetics. The problem of homoplasy, however, can diminish the value o...