Evolution Without Darwin
It happens, and scientists are finally seeing it.
Darwin suspected it, but he would roll over in his grave if he knew how his dogma on adaptation and natural selection is changing. His original teachings are still not accepted by fundamentalist religious people. The new thinking would make them both apoplectic! Evolutionary thinking is finally beginning to mature past Darwin's explosion onto the science scene, after 159 years of stagnation. Forty years ago, there was another explosion in the science world. Stephen Jay Gould published a paper called The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme. What it proclaimed was heresy in biology. Simply put, Gould said that not all adaptations are adaptations, some things are by-products that an organism can put to use, but they were not naturally selected. He likened these abilities to the spandrels in the church of San Marco. A spandrel is a triangular shape created when a dome is added to a rectangular room with arches between the arch and the wall. Artists used these spaces for artwork. Gould saw traits that were like spandrels—the body is a restricted form (the rectangle), and the dome was an adaptive trait. In between were usable by-products—the spandrels.
San Marco Spandrels
We have a big brain that evolved because of the food we ate five to eight thousand years ago. A by-product of that is language. Another is being able to make tools, and so on. Some people found a new religion with these ideas, and others refused to give up pure Darwinism. The dust hadn't settled on that when Gould and colleague, Elizabeth Vrba came out with a paper on exaptation and the related term co-option. A trait can evolve because it served one particular function, but subsequently, it may come to serve another. The classic example is feathers. They originally formed on dinosaurs for insulation. At some point in the evolution from dinosaur to bird, they became displays in mating rituals, and then birds used them for flight. They still provide insulation and display, but now there is flight.
The order and arrangement of the bones in the four limbs of land-dwelling animals are an exaptation for walking on land, since these limbs originally evolved for navigating water; by contrast, changes to the shape of the bones and to the musculature are adaptations, Gould and Vrba wrote.
The FOXP2 gene is causing a disturbance these days, because not only is it a requirement for speech, it apparently has a strong use in digestion. Evolution is packed with examples of exaptation. Mammals used the sutures between the skull bones to squeeze the larger head of offspring through the birth canal. Host organisms found new purposes for viral genetic material left behind and metabolic enzymes came to refract light rays through the eye’s lens. Repetitive DNA sequences known as transposons come from viruses. At the time they wrote their paper in 1982, Gould and Vrba suggested transposons might serve no direct function at first, but may be used to great advantage later on. It has since been discovered that transposons play a huge role in pregnancy. “They come from viruses, but they can be utilized for something they are not built for,” said Gunter Wägner, an evolutionary biologist at Yale University.
The problem is that not every part of an organism can be broken down into evolutionary parts. If something existed it had to be because of the Darwinian concepts of natural selection of adaptations. However, in the Spandrels paper, Lewontin and Gould point this inconsistency out by choosing the non-biological example of the Church of San Marco. With this analogy, they have created a platonic form of what a perfect spandrel is, more precise and pure than any biological example could be. Only years after construction did the spandrels get put to use and become functional in themselves. Slowly, today's evolutionary biologists are accepting spandrels and exaptations. Some of them are daring enough to use the words and those who cannot speak the words "spandrel' and "exaptation" or write them yet, have those concepts swimming in their minds.