West of Zimbawbe, near the Zambezi river, lives a relatively isolated tribe known as the Doma (Wadoma and Madumo), who have an interesting feature. A majority of its members were born with a genetic mutation known as ectrodactyly which affects the development of fingers and toes.
The conditon results from a mutation of chromosone number seven and causes a 'split ' or division in the digits, often resulting in a lobster-like appearance of the hands and feet. In the case of the Doma it is primarily the feet which are affected and their three middle toes are missing. As a result, the tribe has become known as the 'two-toed' or "ostrich" tribe. The mutation survives because the gene pool among the Doma is small and they live in relative isolation.
The Doma speak a combination of Chikunda (Portuguese) and KoreKore, which is the language of the Mkorekore tribe. In order to survive, they depend on hunting, trapping wild animals, fishing and gathering wild fruits, roots and honey.
The interesting thing is that, because the gene is dominant, and so many tribe members have the condition, to the Doma the appearance of the toes is quite natural and accepted as a normal variation within the tribe.
The tribe are particularly interesting to biologists because they provide a rare example of genetic effects in a small population, however both the area and the tribe are not easily accessible.The Doma like to keep to themselves and their home is high in the Chiruwa Hills.
An Englishman called Charles Sutton was reputedly the first white man to encounter the Doma in the early 1950s. At the time he was working as a recruit for the British South Africa police and got posted to several rural stations and in the course of his work, eventually he came cross the Doma. His frst sight was of an old man sitting among clay pots outside an "impoverished" grass hut:
"From the light of a burning fire I could see astonishment written all over the man's face, especially looking at myself, as he later revealed that I was the first white man he had seen, and the first to come to that area...
I asked the old man, Mhoramasaka, why he and his followers wanted to stay in the hills, away from civilisation, and not move to the villages near the Zambezi River. He said that they were quite contented with their life, and the way in which they were living - this being the only life they knew."
Genetic drift is a genetic sampling error that can only occur within small, isolated populations. It signifies a change in the gene pool of a small population that has happened purely by chance and can either mean genetic traits get lost from a population or they becoming widespread, irrrespective of the survival or reproductive value of the involved alleles (one member of a pair of genes).
Such chance events make a huge difference to the genetic make-up of an isolated tribe, as is the case with the two-toed Doma. In a larger population the electrodactyl would have become recessive as it is not biologically favourable.
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