How many ways can we make a home? I remember as a child walking through the corridors of the American Museum of Natural History and gawking at the many dioramas which combined realistic painting with artifacts or copies of natural and prehistoric settings. I saw homes of our ancestors built from mammoth tusks in Siberia. I saw tepees with animal skin wrapped around a cone of trimmed saplings. I saw igloos built from blocks of ice or compact snow. Outside the museum I saw the swank apartments of those who lived on Central Park West and imagined the view of Central Park they enjoyed. I contrasted that with our own Brooklyn cold water flat with a coal stove in the kitchen. In books I saw castles and mansions that housed the privileged and log cabins that Presidential candidates promoted as their identification with the underprivileged voter or common man.
In a similar way there are many mechanisms by which evolution occurs. There is natural selection in which adaptive traits survive, thus providing the genetic basis for them that enters a new generation and this in turn changes the gene frequency of the population. There is the “founder effect” in which a small number of individuals enter a new niche and reproduces rapidly in large numbers to create a population that differs in appearance from its original source. There are hybrids that undergo a doubling of chromosome number and thus establish a new self-reproducing species. There are developmental mutations that can multiply body parts or organs like wings, limbs, or eyes. There are other developmental mutations that place organs in different parts of the body producing new variations in a species. One of my favorites is a process called neotony in which juvenile or embryonic features are carried into adult stages. In the 1920s such neotonous species were found in salamanders in caves, the fertile adults sporting gills which are normally absorbed in the related species living outside the caves.
We humans have a neotonous origin from out primate ancestors because we have prolonged child-raising period compared to other primates which are sexually mature and functionally adult in fewer years. The most recently studied neotonous organisms are the birds that had a dinosaur-like ancestry. They miniaturized as they shifted from living on land to living in trees and then to the skies as they developed wings for flight. Their eyes are larger (like an embryo’s) in proportion to their bodies. We do not reflect as much as we should on these neotonous traits in the evolutionary process, and most of the debates about Creationism and Intelligent design are waged over natural selection which is only one of many ways evolution works.