From “Studying bat skulls, evolutionary biologists discover how species evolve” (Eurekalert, November 23, 2011), we learn that the explanation for why there are so many species of bats is new food sources:
hey investigated why there are so many more species of New World Leaf-Nosed bats, nearly 200, while their closest relatives produced only 10 species over the same period of time. Most bats are insect feeders, while the New World Leaf-Nosed bats eat nectar, fruit, frogs, lizards and even blood.
They found that the emergence of a new skull shape in New World Leaf-Nosed bats about 15 million years ago led to an explosion of many new bat species. The new shape was a low, broad skull that allowed even small bats to produce the strong bite needed to eat hard fruits. The rate of birth of new species jumped as this new shape evolved, and this group of bats quickly increased the proportion of fruit in their diet. Change in shape slowed once this new skull had evolved.
It can be difficult for evolutionary biologists to demonstrate that traits related to anatomical changes, also called “morphological innovations” such as a new skull shape, give certain groups a survival advantage when new food sources, such as hard fruits, become available.
It is difficult in this precise case, as a matter of fact.
The science-based question is not why it would benefit a species of bats to speciate further and vary their food sources, but why they – but not other species of life forms are able to do that. Many life forms simply go extinct if conditionschange.
For this finding to count as an actual explanation, the researchers must first establish that any life form can speciate limitlessly, offered the opportunity. Although that may be a tenet of some versions of Darwinism, it is just not evident in nature. So we are still looking for an explanation for why some species speciate much more readily than others.
It’s interesting that two of the life forms that resonate most with humans – cats and dogs – speciate rather reluctantly.