Darwin’s Finches… The Galapagos finches are one of the most famous illustrations of natural selection in action. Michael Denton explains why these birds are a double-edged sword for Darwinian theory. For more information about Michael Denton, or to purchase his new book, “Evolution: Still a Theory in Crisis.”
…The Galápagos finches put on display the two strict requirements that must be present in order for natural selection to work its magic. If these two factors are not present, natural selection is impotent to change any creature at all, much less create a new species.
First, the finches’ beaks are clearly adaptive. Each distinct variation gives the lucky individual a definitive leg-up in its specific environment. There is an obvious, practical reason why the differentiation is helpful to the species in question. This is absolutely essential in order for natural selection to pick between variations in species. Natural selection can only “see” those variations that are adaptive — causing one individual to live, and carry on its genes, and another to die and not leave offspring. If a variation is neutral or does not somehow increase fitness in the specific environment the creature lives in, Darwin’s mechanism cannot select it.
Second, there is a functional continuum among the finches’ beaks. That is, between a finch with a tiny beak and a finch with a large beak, there are tiny, step-by-step changes, and each change makes the creature slightly more fit in its environment. This is also essential for natural selection to work.
The problem for Darwinian theory comes in explaining evolutionary change where, unlike the case of Darwin’s finches, these requirements are absent. First, there may not be a continuum. That is, natural selection cannot make large jumps or drastic changes. There must be small steps. Secondly, each single step must be beneficial to the individual. It is not enough for the first and last versions of the adaptation to be helpful — all the intervening steps must increase fitness as well.
There are examples of creatures throughout the biological world that break one or both of these rules. Many creatures just don’t fit the natural selection story like the Galápagos finches do….