Question

How did Darwin explain the existence of different varieties of finches on Galapagos Islands?

Answer 1

A common ancestral finch population reached the islands. As descendants occupied different habitats and food niches, heritable variations in beak shape and size were favoured differently by natural selection. Over generations, the populations diverged and formed distinct finch species—an example of adaptive radiation, or divergent evolution.

The diversity of finches is explained by common ancestry followed by adaptation to different ecological niches.