<P> Human genetic variation is the genetic differences both within and among populations . There may be multiple variants of any given gene in the human population (genes), leading to polymorphism . Many genes are not polymorphic, meaning that only a single allele is present in the population: the gene is then said to be fixed . </P> <P> No two humans are genetically identical . On average, in terms of DNA sequence, each human is 99.5% similar to any other human . Even monozygotic twins, who develop from one zygote, have infrequent genetic differences due to mutations occurring during development and gene copy - number variation . Differences between individuals, even closely related individuals, are the key to techniques such as genetic fingerprinting . </P> <P> Alleles occur at different frequencies in different human populations, with populations that are more geographically and ancestrally remote tending to differ more, a phenomenon known as isolation - by - distance . The differences between different populations represent a small proportion of overall human genetic variation . Populations also differ in the quantity of variation among their members, with greatest diversity among African populations . This is consistent with the theory that humans recently migrated out of Africa . Populations also vary in the (always small) proportion of DNA they received from archaic hominid populations, such as Neanderthals and Denisovans . </P> <P> The study of human genetic variation has both evolutionary significance and medical applications . It can help scientists understand ancient human population migrations as well as how different human groups are biologically related to one another . For medicine, study of human genetic variation may be important because some disease - causing alleles occur more often in people from specific geographic regions . New findings show that each human has on average 60 new mutations compared to their parents . </P>

Where do we find the highest genetic diversity among human populations