Characteristics feature of elementary evolutional factors activity in human populations.

Date: 2015-10-07; view: 497.

In human populations activity of elementary evolutional factors has some characteristics feature. Influence of directional selection is slightly. Natural selection act during early ontogenesis mainly, especially in fetal age.

Here are some examples of natural selection act in human populations.

Natural selection against heterozygotes is rhesus incompatibility or Rh-incompatible. An Rh-negative woman has a heterozygous Rh-positive foetus. Because of placental barrier may be imperfect a foetus' Rh-antigen permeates into organism of the woman. And against the Rh-antigen an Rh-antibody produces. Then the Rh-antibody permeates into organism of the foetus again and promotes of erythrocytes superfluous destruction. Fetal erythroblastosis (or hemolytic disease of newborn) is developed. The disease is cause the increase of death rate. Hence heterozygouses are eliminated from population.

Natural selection against homozygotes is situations in which people (homozygotes) having sickle-cell disease (anemia) die. But heterozygotes having the anemia are alive. And frequency of heterozygotes especially increases in the regions, where there is malaria. It is because the vector of malaria – malaria mosquito – doesn't bite a sick by anemia.

Mutation process in human populations is like one in a population of any other organisms. However, frequency and intensity of antropogenic mutagens activity in human populations is bigger.

Human migration is very intense now. So, population structure of mankind is changing quickly. And classical populations are getting disappear.

But in population structure of mankind there are some isolations. Insulations of modern mankind have a social genesis. As examples of isolation are deme and isolate. Isolate is population in which the quantity of people is equal of about 1500 members, and percent of marriage within the population is about 90%, and the percent of migration during one generation is about 1%. Deme is population in which the quantity of people is equal of about 4000 members, and percent of marriage within the population is about 80%, and the percent of migration during one generation is about 2%. Growth of inhabitants during one generation is about 20% - 25%. For example there is a dunkers sect in the Pennsylvania state of the USA. The population has 27 families only.

The phenomenon of genetic drift among people takes place in small population (isolate for example). One kind of genetic drift manifestation named as “effect of progenitor”. Within the dunkers sect a frequency of the cases of grows of hair on the middle phalanx of fingers takes place more often than within other populations.