Another creationist myth has bitten the dust, although that's unlikely to stop it being repeated. A new species emerged under the eyes of biologists able to study it closely, and it happened faster than anyone expected. Appropriately, the species is a Galapagos finch, one of the subfamilies crucial to Darwin's world-changing revelation.

The diversity of the Galapagos Islands has created multiple niches for finches, leading them to evolve different-shaped beaks and varying body sizes in order to take advantage of the variety of food sources available. Yet even Darwin himself doubted evolution would happen fast enough for us to detect it in real time. “We see nothing of these slow changes in progress, until the hand of time has marked the lapse of ages,” he wrote. 

Bacteria evolve so fast that microbiologists can indeed bear witness to the appearance of new species, but vertebrate zoologists are seldom so lucky. So when the famous finch trackers Drs Peter and Rosemary Grant of Princeton University noticed something new on the island of Daphne Major, they were deeply hesitant to claim what they were seeing was more than just a variety of an existing species.

Other scientists were more audacious, and three years ago the suggestion that the Grants had potentially described a new species as it appeared reached the wider community. Now the Grants have published a paper announcing what they once described as “highly unlikely”; the appearance of a self-contained population in just two generations as the result of the arrival of a single stray bird on Daphne Major. Moreover, the events appear to be even more surprising than previously suspected.

The story began in 1981 when an unusually large male with a distinctive beak arrived on Daphne Major. "We didn't see him fly in from over the sea, but we noticed him shortly after he arrived. He was so different from the other birds that we knew he did not hatch from an egg on Daphne Major," Peter Grant said in a statement. Initially thought to be a hybrid of two other species from a nearby island, genetic sequencing has now shown the new arrival was a Geospiza conirostris from Española island, 100 kilometers (60 miles) away.

Dubbed "Big Bird" by the graduate student who noticed him, the immigrant charmed a local female medium ground finch (Geospiza fortis) and established a family of hybrids. The unusually shaped beaks of their offspring proved suited both to eating Tribulus seeds of all sizes, where many finches are restricted to eating only large or small ones, and eating cactus nectar that only some other species can reach.

Galapagos finches choose their mate in part based on beak size and shape, but apparently, most of Daphne Major's other inhabitants found nothing sexy in such diverse mouthparts. Moreover, although Big Bird's mate apparently found his offshore accent delightful, other females of her species disagreed, so the pair's descendants bred almost exclusively among themselves, rather than with members of the island's three pre-existing species.

"A naturalist who came to Daphne Major without knowing that this lineage arose very recently would have recognized this lineage as one of the four species on the island. This clearly demonstrates the value of long-running field studies," said Professor Leif Andersson of Uppsala University, Sweden. Along with the Grants, Andersson has announced the results of the sequencing of the genome of Big Bird and many of his descendants in Science, confirming it took just two generations for a new species to appear.

Daphne Major's tiny size and the Grants' outstanding attention to detail mean we have a record of the mating history of every Big Bird descendant. Nevertheless, until recently the Grants were doubtful if the birds they observed met the requirements to be considered a new species, rather than simply a variety of a pre-existing one. Yet the family is establishing its own successful niche, having grown to eight breeding pairs and 23 individuals after six generations.

The survival of the new lineage remains perilous. The population peaked at 36 in 2010 before some bad seasons reduced it. Climate change or introduced species could make Daphne Major less comfortable for finches in general, in which case the smallest population could easily be the first to die out. In the meantime, however, the Grants have a front row view of a species establishing itself, something previously only seen in butterflies, and outside the animal kingdom.