Forces of Microevolution

In the language of Kraus and White (1956) we can say that microevolution is generally "very slight changes in gene frequencies that occur generation by generation in populations of various sizes". Though in the modern genetic concept evolution is nothing but a change in gene frequencies genera­tion by generation, yet as has already been stressed the study of morphological characters and the nature of their changes should not be ignored while dealing with human evolution. No doubt, morphological forms represented by anthropometric measurements and somatoscopic observations are traits of continuous variation and are determined by several loci and hence may be regarded as polygenic, yet as has been stated by Oliver and Howells (1957)   that these traits comprise a  complete field of human variation in shape and size , in addition comprising modification by environment and the differentiation  and relationship of populations—in short, all the proceses of  the microevolution".

Microevolution and macroevolution and are basically the same; one does not differ entirely from the other. The study of one helps in understanding the other. Therefore, Dobzhansky (1964: 17) has clearly stated that "the terms 'macroevolution and ‘microevolution’ are comparative terms, and have just descrip­tive significance; they involve no distinction in the fundamental causal agencies". "Cumulative effect of microevolution through ages leads to macroevolution. An effective breeding population during a certain period of time at a specific level should be taken into consideration to study microevolution".

There was a time when it was believed that human races are unchanging and static. Physical traits distinguishing one ethnic group from another were supposed to be constants. However, in the event of admixture ethnic groups may change assuming new characteristics. For any variation or for any 'intermediate' population hybridization was a common explana­tion, because of lack of evolutionary concept. In classical anthropology, populations are described in terms of the statistical averages of characters. Franz Boas (1911 et seq.) opened a new chapter in physical anthropology by demonstrat­ing the plastic nature of those metric traits causing change in the statistical averages. This may result in the formation of a 'new' population distinguishable from the parental population. Thereby, dissimilarities between the ancestral and the descendant populations may develop.

Questionnaire:

• Explain about Forces of microevolution?