| Abstract: | Provins (1990) has suggested that the apparently low incidence of left-handedness on the island of Tristan da Cunha is the result of social pressures such as deference to authority and group conformity, and that “any genetic factor determining left-handedness must be very weak”. Here we use a large number of Monte Carlo simulations (n = 10,825) of the growth of the population of Tristan da Cunha from 1827 to 1961, to show that if the original population was randomly selected from a large population with a typical gene-frequency, then a combination of founder effects, genetic drift and evolutionary bottlenecks can readily explain the fairly low incidence of left-handedness that was found. Indeed in 15% of the simulations the c-allele, which is postulated to be responsible for left-handedness, has disappeared entirely, resulting in a population with no left-handers at all. The data from Tristan da Cunha are therefore entirely compatible with a genetic model of left-handedness. |
