The Great Game

While religious leaders continue to lobby for the removal of evolution from the high-school biology curriculum, a Canadian researcher has documented extremely convincing evidence that speciation—the evolution of one species into two separate species—does occur.

Darren Irwin is an assistant zoology professor at UBC who has been studying Eurasian warblers for many years. In 2001 he reported in Nature magazine that the warbler species Phylloscopus trochiloides (greenish warbler) was what is known in biology as a “ring species.”

A ring species is an organism that originated near an inhabitable obstacle and slowly spread around that obstacle, eventually meeting itself at the other side. In the case of P. trochiloides, the species originated in Southern Asia and the obstacle was the treeless Tibetan Plateau. After spreading northwards through Nepal and China, greenish warblers from east and west converged in Siberia.

Irwin explains, “The genetic evidence reported in the 2001 paper was only based on a few genes. In 2002 we started using a new genetic technique that examines variation in dozens of genes.

“This more comprehensive look at genetic variation showed that there is a gradual genetic change around the ring, but distinct differences between the two Siberian species.

“These results strongly support the theory that the two Siberian forms of greenish warbler evolved into different species while still being connected by a chain of populations through which gene flow could occur.”

One of these gradual genetic changes is in the warblers’ song patterns. Moving west from Bangladesh, warblers increasingly favour one song pattern; moving east they favour another. In Siberia, where the two groups meet, neither group recognizes the others’ song. Because warblers choose mates based on song patterns, these two groups do not mate. “If two groups do not exchange genes through reproduction, they are on separate evolutionary pathways and therefore they are separate species,” Irwin says.

Since Darwin published Origin of Species in 1859, many religious leaders have gone to great lengths to convince the public that the concept of evolution is a theory, not a scientific fact. Their reasons for this are understandable: evolution stands in direct opposition to Biblical mythology. When I asked Darren Irwin whether his research had established evolution as a fact, his answer was enlightening:

“Scientists are never able to completely prove any theory. Science is a process by which incorrect theories are shown to be incorrect, leaving us with the theories that are most consistent with the evidence.”

“The theory of evolution is one of the most successful theories ever, in the sense that it is highly consistent with abundant evidence. We understand the mechanisms by which evolution operates, and these mechanisms have actually been observed on short time scales. This establishes evolution as a more successful theory than the theory of gravitation. The theory of gravitation is also consistent with evidence, but we don’t yet know how it works.”

The theory of gravitation, however, does not contradict religious doctrine, and so is universally accepted. (Link)