Darwin’s Finches Show How Genes Shape Evolution

Darwin’s finches have shown scientists the genetic mechanisms that explain how birds develop varying beak shapes in regards to fluctuations in their environment. The research involves the quintessential Galapagos finches Charles Darwin used for his research on natural selection. Originally, he was prompted to use finches as the basis of his research due to the diversity in beak size of the birds.

In a study published in the journal Nature, scientists identified a gene that has an important role towards influencing the shape of beaks, making them more blunt or more pointed. The variation in beak sizes and shapes allows different types of birds to feed on different types of food. For instance, birds with skinnier, longer beaks are able to reach into small holes in trees to dig out insect larvae, whereas birds with larger, blunter beaks are better able to eat bulky, tough seeds.

Lead author of the study, Leif Andersson, a geneticist at Uppsala University in Sweden, stated by using modern technology and advanced genetics, scientists are able to pinpoint single genes that contribute to the notion of natural selection, or adaptive evolution.

Around 1.5 million years ago, the ancestors of finches immigrated to the Galápagos Islands from South America. Since then, the pointed-beaked successors have evolved into 15 narrowly related species, donning different beak sizes, feeding behavior, body sizes, and even songs. The study unearths the aspects regarding their evolution, down to the genetic level. This research is based on the genetic mapping of 120 birds across all finch species, Darwin examined.

Scientists compared the genetic information of two species of finch, with blunt beaks, with two that had pointed beaks. They found 15 regions within their respective genomes that were different from one another. One gene that stood out among the 15 regions was ALX1. ALX1 is a portion of genetic machinery essential for cranial development in humans and many vertebrates. For example, if a child is born with craniofacial deformities, like a cleft palate, the ALX1 gene was turned off.

Decades ago, Peter and Rosemary Grant, researchers at Princeton University, used a species of finch, Darwin’s favorite finch, the medium ground finch, to demonstrate that a specific species can endure rapid and continuous evolutionary changes. Explicitly, the beak size and shape of the birds adapted over just a few generations, from severe fluctuations in their surroundings. The Grants stated that the discovery of ALX1 was exhilarating, it is the first observed instance of a specific gene controlling beak development, varying both species-wide and among individuals.

Scientists also found the bird’s genes go through what is called hybridization, when two genes are swapped between species, allowing for greater, more specific evolutionary characteristics. Professor Steve Jones of the University College London said it is a surprise to geneticists that a gene has been transferred between species.

Genetic researchers have stated that a large portion of evolution happens from random mutations, some that give a species an advantage and some that lead to the detriment of a species. Though, Darwin’s theory of natural selection favors mutations that allow for a species, in this case finches, to thrive in its environment and to engage in further, advantageous evolution.

By: Alex Lemieux

Sources:

Wall Street Journal

National Geographic

CBS News

Picture: Sergey Pisarevskiy – Flickr License