Charles Darwin recognized adaptions in the beaks of finches as being due to natural selection, and now modern researchers have identified a gene in the bird responsible for their shapes.
Charles Darwin, a 26-year-old naturalist, arrived in the Galapagos Islands in 1835. After landing off the HMS Beagle, he was surprised to find that each island seemed to have a different species of finch. Birds he collected were later found to belong to 15 species within the subfamily Geospizinae.
A gene called Alx1 was recently found by researchers to vary between birds possessing rounded or pointed beaks. Slight variations in this gene were also shown to exhibit some variation, even among birds in single species. Investigators examined the genomes of 120 birds, representing all of Darwin's finches.
Medium ground finches, or Geospiza fortis, are known to have undergone significant genetic changes during the mid-2000's, after a larger finch invaded their habitat. During the 1970's, a severe drought in the islands reduced the number of seeds available to birds. The seeds which did survive the event were larger and tougher than normal, making it difficult for smaller birds to feed. Within a generation, beak sizes increased in newborn birds. A few years later, the weather patterns changed, resulting in the proliferation of smaller seeds. Again, the birds adapted, and smaller beaks once again became more common.
Different versions of Alx1 were found to correlate to specific beak shapes in the finches. In humans, this same gene is associated with frontonasal dysplasia, a birth defect that can result in misshapen faces in babies.
"The researchers hypothesize that smaller variations in ALX1 could be responsible for the diversity of face shapes among people," Sarah C. P. Williams wrote in Science magazine.
Naturalists believe finches first landed in the Galapagos Islands roughly two million years ago, and the birds developed specific adaptations to live in one region or another. On islands where insects are common in trees, the finches learned to live in trees and eat bugs. Finches on islands where seeds were readily found on the ground adapted to that feeding method.
"One might really fancy that, from an original paucity of birds in this archipelago, one species had been taken and modified for different ends," Charles Darwin wrote in The Voyage of the Beagle.
This new study could assist researchers not just in studying finches, but also the development of faces in people.
"I would not be surprised if it turns out that mutations with minor or minute effects on ALX1 function or expression contribute to the bewildering facial diversity among humans," Leif Andersson of Uppsala University stated in a press release.
Identification of the genes responsible for beaks in Darwin's finches was detailed in the journal Nature.
