The biological factors like the size and composition of population produce social changes. The phenomenal growth of population in the 19th century has led to vast social changes and brought problems.
Food problem, housing problem, unemployment, poor health, poverty, low standard of living and the problems are its direct outcome. But there are also countries where there is the problem of under-population.
The falling rate of population has posed a serious problem for countries like U.S.A., U.S.S.R. and Sweden. It is said that such countries are facing the threat of “race suicide”. It has its own political implications also. Further, the proportion of younger people is decreasing in few countries like U.K., U.S.A., Sweden, etc.
The death rate has fallen and hence the number of the old is increasing. It has its social implications. Some social arrangement such as taboos on inter-marriage, customs respecting the age at marriage, persecution of the minorities, war, etc. tend to lower the biological quality of the population.
Hence the increase and decrease in population, a change in the ratio of men and women, changes in rates of birth and death are likely to affect our social system. The relations of man and his society to the biological environment are more dynamic than those of man and his society to the physical environment.
The latter submits to his use and abuse. But the biological environment which is inherently unstable responds rather than submits to man’s uses and abuses. It is more sensitive. Hence man has to fight against the diseases, harmful bacteria’s, weeds, wild beasts constantly.