Question

With respect to evolution, consider two organs, X and Y in our body. Organ X is more complex and larger in size in humans as compared to that was present in Homo erectus (Primitive Human species). Organ Y was functional in Homo erectus but not in today's humans. Identify which organ has undergone progressive and which has undergone retrogressive evolution. Why?

Answer 1

In progressive evolution, an organism or an organ undergoes changes that are progressive or that are more complex as compared to their previous forms. These changes are aimed at increasing the adaptive fitness of an organism. So, organ X becoming more complex and larger in size in humans as compared to what was present in Homo erectus is an example of progressive evolution. In retrogressive evolution, an organism or an organ moves to its simpler form, both structurally and physiologically. Hence, organ Y shows retrogressive evolution.