Since the tribes practised far more in-breeding than out-breeding, the tendency was toward forming not only verbal linguistic groups, but biological varieties; the weaker the tribe, the fewer the captures, the greater the isolation and harder the conditions - producing dolichocephaly, dwarfism and other retrogressive characteristics.
What causes gigantism and dwarfism among many species arriving on oceanic islands such as the Seychelles?
Dwarfism from impaired longitudinal growth of bones is a recessive trait that affects males more strongly than females.
As soon as indiscriminant breeders started to flood the market, aberrations such as dwarfism in Toy Poodles appeared, along with a host of genetic problems that dedicated and diligent breeders are still trying to irradicate to this day.
Achondroplasia: a disorder of bone growth that causes the most common type of dwarfism.