A Creation Neither Perfect Nor Complete – Darwin and Early Theories of Evolution
In a relevant side note to history: the famous pea plant experiments of the German monk Gregor Mendel—first presented as a paper to a small, non-comprehending audience in Brűnn, Germany in 1865—were virtually unknown to Darwin and his contemporaries. Mendel’s work on the inheritance of traits in plants actually held the key to the unknown agency of species change that so bedeviled Darwin. Darwin’s theory of natural selection (and later, sexual selection), powerful as it was, could not explain how any original variation in appearance could arise and spread throughout a population (Note: DNA was discovered in the 1860’s by Swiss biologist Miesher, but its function/purpose remained unknown until the 20th Century)
In fact, it was on this point that the now famous Darwin would receive his fist major challenge to his theory of natural selection. The challenge would come from a Scottish engineer named Fleeming Jenkin. Jenkin, whose work would come to serve as the cornerstone for the 20th Century science of population genetics, presented a convincing mathematical challenge to Darwin: any new, “fortuitous” variation would be quickly “swamped” (outnumbered) by more pervasive traits, and would be quickly eliminated from the population, due to numerical inferiority. Thus natural selection—what Darwin had posited as the agency responsible for spreading fortuitous traits throughout a species—was insufficient and inadequate in explaining how any variation could take hold and persevere (the specific example here being the male peacock’s colorful plumage).
Darwin, recognizing the mathematical power of this argument, would come to express some self-doubt as to his over-reliance on this agency, and, in later editions of The Origin of Species, he would include consideration of Jenkin’s argument. This problem of how to explain spontaneous variation within species, and its spread throughout a population, was so vexing to Darwin that he would, in his later years, fall back on a somewhat more subtle Lamarkian explanation for the cause of this variation (Darwin posited the subordinate and malleable character of the “germ plasm” in receiving “messengers” from somatic cells with acquired traits).
