Peter and Rosemary Grant were able to show evidence for the Theory of Evolution by Natural Selection using 40 years of data following two species of finches on Daphne Major. By banding and taking samples from as many birds as possible, the Grants found support for all four of Darwin’s postulates. The first of thing that is necessary for a population to undergo evolution is that there must be variation among individuals. Before the drought in 1977, the Grants recorded variation in the beak sizes of both the medium and large ground finch population. It was also observed after the drought, as there was enough variation that a small subset of the medium ground finch population survived based on having a larger beak size. The second postulate is that variation is heritable. This was observed after both the severe drought and the El Niño events that posed strong selection pressure on the finch populations. The Grants reported that the average beak size of the generations following the events were close in size to the surviving individuals. Genetic research into the finch populations showed the presence of the ALX1 gene, a heritable trait controlling for gene size.…show more content… This is obvious in the drought which caused 4 of every 5 medium ground finches to die, due to their inability to crack open the large seeds that were the only food available. Due to this change in food source, the finches with large beaks had a selective advantage, allowing them to survive the drought and have large beaks persist into future generations. The El Niño caused a similar selection event, but finches with small beaks had a selective advantage, as the seeds in abundance were small and soft. A variation in success was also observed in the 2003 drought, were medium ground finch with large beaks saw a significant reduction in population as they were not as efficient at opening large seeds as the large ground finches on the
