Overturning a Common Theory of Darwin's Evolution: Birds Reveal It's Not 'Be Different or Die'

Scientists may have just overturned a common theory of evolution. They've found that species living together are not forced to evolve differently in order to avoid competing with each other. The findings reveal a new aspect of evolution.

In order to learn a little bit more about species evolution, the researchers focused on ovenbirds. This group of birds is one of the most diverse bird families in the world. In order to learn a bit more about these birds, the researchers compared the beaks, legs and songs of over 90 percent of ovenbird species. They then sequenced genes and took measurements.

So what did they find? It turns that although bird species occurring together were consistently more different than species living apart, this was simply an artifact of species being old by the time they meet. In fact, once variation in the age of species was accounted for, coexisting species were actually more species evolving separately. This is opposite to Darwin's view.

"It's not so much a case of Darwin being wrong, as there is no shortage of evidence for competition driving divergent evolution in some very young lineages," said Joe Tobias, one of the researchers, in a news release. "The reason seems to be linked to the way new species originate in animals, which almost always requires a period of geographic separation. By using genetic techniques to establish the age of lineages, we found that most ovenbird species only meet their closest relatives several million years after they separated from a common ancestor. This gives them plenty of time to develop differences by evolving separately."

The most surprising discovery, though, was that species living together had songs that were more similar. This in particular challenges longstanding ideas since the standard view for the last century has been that bird species living together would have to evolve different songs in order to avoid confusion.

"The reasons for this are difficult to explain and require further study, but they may have something to do with the advantages of using the same 'language' in terms of similar aggressive or territorial signals," said Tobias in a news release. "For instance, individuals of two closely related species with similar songs may benefit because they are able to defend territories and avoid harmful territorial contests not only against rivals of their own species but those in other species coexisting in the same places and competing for similar resources."

The findings reveal a bit more about the process of evolution. By taking the evolutionary age of species into account, the scientists managed to uncover exactly how this process occurs in species that are in the same general location.

The findings are published in the journal Nature.