While explaining the concept of natural selection, we have stressed the fact that natural selection is synonymous with differential or non-random reproduction. Natural selection aims at the multiplication of those genes that contribute to the reproductive success of the population. In other words, if any gene does not in any way contribute to the reproductive success of the species, the chances are it may be eliminated from the population. Certain critics of Darwin pointed out that the common altruistic behaviour of individuals provided evidence contrary to the theory of natural selection, Whether it is so or not, will be discussed in the following subsections.