Darwin's Finches - the Possiblilties

Whilst Charles Darwin was on his travels to Galapagos Islands in 1835, he came across a variety of the animals he observed in South America. In addition, he noticed that the finches had different featured on both lands and he thought these variations are what made it possible to survive on Galapagos Islands. This observation inspired Darwin's beliefs in natural selection, leading to his theory of evolution. Challenging his theory however, was the possibility that the finches on Galapagos Islands weren't linked to the ones in South America via distant ancestors, but instead a completely different type of bird altogether.

It's known that the finches on Galapagos Islands had arrived there during a storm and their features modified accordingly to their diets (e.g. finches eating cacti need strong beaks to break down the prickly texture). To Darwin, it was obvious that the plants and animals in the Galapagos came from the Americas and were very different from those back in Britain and the rest of Europe.

On the other hand, at the time of Darwin's exploration, most people thought that God created everything and many people thought that living populations never changed. Though most male/female finches were black or female brown in both America and Galapagos, it would have been easy to think that they weren't all finches. There were differences in beak size, head shape, diet and colour.

Taking all of this into account, Darwin's theory seems to be the most plausible. As there are differences between the environment in South America and Galapagos Islands, you would expect come differences in the finches - they would have to adjust to the new habitat of Galapagos. Also, the similarities of the finches overrule the differences; with the same structure of beaks, short tails, form of body and plumage, the likelihood of them deriving from a common ancestor is very high.