A study of hominin dispersal out of Africa using computer simulations.

A study of hominin dispersal out of Africa using computer simulations is presented. Attention is focused on the joint probability of the colonization of Western Europe later than 1 Ma and that of Eastern Asia prior to 1.6 or 1.8 Ma, as current archaeological estimates suggest. We found that the determinant factor to hominin dispersal is the mode of hominin movement. If the movement of all populations is uniform and their number great enough, greater than 300 in our models, then such movement favors the colonization of Eastern Asia and Western Europe at more or less the same time. On the other hand, the colonization acquires prominent probabilistic features if the number of populations migrating is small enough, smaller than 10 in our models, or when all hominin populations may move but there are only a few with much higher mobility. In this case, the joint probability for the earliest dispersals of hominins in Western Europe after 1 Ma and Eastern Asia prior to 1.6 Ma ranges from 0.02 to 0.05. The single probability of colonization of Western Europe after 1 Ma is very high, about 0.5 for the majority of the colonization routes, whereas the corresponding probability of the colonization of Eastern Asia prior to 1.6 Ma is ten times lower, about 0.05. The least probable event is the earliest colonization of Java prior to 1.6 Ma, to which our simulation attributes a probability of ca 0.01. Deserts, mountains, and mountain ranges may delay the arrival at a certain location; nevertheless, their effect on the joint probability is very small.