Strength and heritage
Thus, large and strong males are more successful in reproduction. Their chickens inherit these characters. Therefore, after many generations males have become successively larger. This explains the great difference in size between the cock and the hen – it is larger than among any other bird species!
Natural selection
We have seen that, with time, males have become larger through a quite natural process, in which hens select strong males. In science, such a process is called "natural selection".
Sexual selection
Thus, the hen decides which cock will father her chicks. Since the selection here is based on one sex's choice of partner, this type of natural selection is called "sexual selection".
