Question

Which evolutionary force (genetic drift, natural selection, or sexual selection) is more likely driving the speciation of Homo sapiens? Why?

Answer 1

According to Darwin, the driving force behind evolution is a phenomenon that he called natural selection. Today we know that natural selection is not the only mechanism of evolution, but it has certainly played a preponderant role.

Giraffes, for example, did not get their long necks by stretching them to reach the leaves on trees (which is what people thought before Darwin). Instead, within the entire giraffe population, some individuals underwent mutations that gave them slightly longer necks than other giraffes. This gave them an advantage, because they could obtain food more easily. Hence they remained in better health and so produced more descendants. These descendants inherited their slightly longer necks. If food became scarce and giraffes needed to be able to reach the highest branches of trees to survive, then those giraffes with shorter necks would die, leaving the entire habitat to the giraffes with longer necks.

Lastly, for Darwin, not only were organisms’ physical characteristics subject to natural selection, but so were their psychology and behaviour, thus explaining for the first time how all of the highly sophisticated instincts observed in the animal kingdom may have come to be.