In a classic study of blood types in Italy Dr Luigi Cavalli

In a classic study of blood types in Italy, Dr. Luigi Cavalli sforza (1969) found that small, isolated towns in mountain regions had reduced genetic diversity within populations, but showed significant genetic differences from one town to the next. In valley regions with more movement of people from place to place, he found more diversity within the population of any given town, and fewer differences between towns. If you consider your genetic simulation to represent one mountain town, and other lab groups to represent different mountain towns, can you explain Cavalli-Sforza\'s results? How could you alter this lab procedure to simulate what happens in the valley towns?

Solution

The genetic history of a group of populations is usually analyzed by reconstructing a tree of their origins. Reliability of the reconstruction depends upon the validity of the hypothesis that genetic differentiation of the populations is mostly due to population fissions followed by independent evolution.

Most patterns found in the analysis of human living populations are likely to be consequences of demographic expansions, determined by technological developments affecting food availability, transportation, or Military power. During such expansions, both genes and languages are spread to potentially vast areas.

The first tree of evolution based on gene frequencies of living humans was published 34 years ago. It was based on genetic distances among 15 populations, 3 per continent, calculated from 5 blood groups, with a total of 20 alleles. The number of genes used was admittedly small, but it was practically impossible to get more information at that time.

The most important difference is in the position of Europe, which with neighbor joining branches out first after the splitting of Africans and non-Africans and with maximum likelihood is the last but one.