Welcome! This is the web site for Adam M. Goldstein, Ph.D. I am an historian and philosopher of science, bibliographer, and ontology designer. I invite you to learn more about my work by exploring this site. Happy browsing! I hope you will email me at agoldstein [at] iona [dot] edu.

My site's title is from Sewall Wright, who claimed that adaptive evolution is most probable when a "shifting balance of factors" interact with one another: chance (random drift), natural selection, and the migration of organisms. Whether this theory is correct is not clear; its charm, however, is indisputable.

The most general conclusion is that evolution depends upon a certain balance among its factors. There must be gene mutation, but an excessive rate gives an array of freaks . . .; there must be selection, but too severe a process destroys the field of variability, and thus the basis for further advance; prevalence of local inbreeding within a species has extremely important evolutionary consequences, but too close inbreeding leads merely to extinction. A certain amount of crossbreeding is favorable but not too much. In this dependence on balance the species is like a living organism. At all levels of organization life depends on the maintainance of a certain balance among its factors. ("Mutation, Inbreeding, Crossbreeding, and Selection in Evolution")

The image above represents the role of chance in adaptive evolution, as Wright sees it. Suppose a species occupies a local maximum of mean fitness such as one of those to the right of the diagram. Because these local "peaks" of fitness are separated from the global maximum by "valleys," the latter is inaccessible by selection, which causes the population to remain at the local peak. Enter chance: a chance event can carry a population across a valley to the slopes of the global peak, which selection will cause it to ascend, ceteris paribus. Chance, together with other factors, provides "a trial and error mechanism by which in time the species may work its way to the highest peaks in the general field."