What did darwin notice about life on the galápagos island

On the Galapagos Islands, Darwin notice several types of finches that varied from island to island, where each finch species had different kinds of beak depending on the available food on the area. That discovery  helped him to develop his theory of natural selection where he concluded that as the finches  are adapting to their new environments and food sources, they gradually evolved into different species.

Ithink the dna sequences may vary but the amino acid sequences are identical.