After: Het ontstaan van soorten (Natuur en Techniek, 1983)

After Whitfield: De evolutie van het leven (1994)

The most common way of speciation is the one connected with geographical isolation. Two populations of the same species get separated from each other because of the formation of a mountain range, a sea or another barrier. Gradually the populations are going to differ from each other because they adapt to different circumstances or simply by coincidence. It is also possible that mutations occur which change the hereditary characteristics more abruptly. When in the course of time the populations happen to meet again, there are three possibilities: 1. there are so many and/or drastic changes that they do not recognize each other anymore. There is no interbreeding. New species have come into being. 2. there are certainly differences, but the populations are still interbreeding with fertile offspring. Two races of the same species have come into existence. In fact races are the preliminary stages of new species. 3. there are hardly any differences and everything stays as it was. Examples of geographical barriers are a mountain range, a sea, land, a river, a desert and ice. Speciation by geographical isolation is called allopatric speciation. Allo = another place, patria = homeland. The name comes from Mayr. Know more? Geographical isolation

In this way also the human races will have come into existence: by geographical isolation. Populations (tribes) will have developed in certain directions, while living separated from other populations. In mankind (Homo sapiens) no new species has been formed, for the races are mutually perfectly fertile. This is probably a consequence of the fondness of travelling of our species. Eventually man has overcome all barriers with the consequence that gene exchange has always persisted. However, there have existed different Homo species. In any case in different times, but also simultaneously like the Neanderthal and Homo sapiens. And still more recently Homo floresiensis and modern man.

Evolution 16

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