One example of this come from a gene responsible for the growth of the beak of a finch. Scientists have shown that by simply activating the gene BMP4, the birds grow beaks up to twice as large as ones without. The gene is present in all types of finches, but is only activated in some types. Dr. Sean B. Carroll says that these discoveries really "blow people´s minds to know that changes once thought to be extremely complex can really be quite simple mutations." This may not be THE driving force in evolution, but it´s presence as a major one is definitely gaining credibility among many scientists who study evolution.