What is true about the isolated small tribal populations?

The acquired character such as strong muscles of a wrestler obtained by regular exercise will not be transmitted to the next generation. Gene pool of a population will consist of a large number of genes which will vary in their frequencies. These frequencies also depend on proportion of various genotypes in the total population. Small tribal population will have small gene pool. Hereditary diseases like colour blindness will spread in isolated population due to inbreeding. There is a decline in population as boys marry girls only from their own tribe, this is due to absence of gene migration/gene flow.