Common Myths About Evolution
This Robust and Unifying Idea is the Source of Much Misunderstanding
Feb 13, 2009
2009 marks the 150th anniversary of the publication of Charles Darwin's On the Origin of Species, a landmark work that transformed the biological sciences and caused a drastic shift in humankind's perception of itself and its place in the world. Evolutionary theories had been propounded before 1859, but it was Darwin's key insight into the mechanism of natural selection - a concept independently discovered by Alfred Russel Wallace - that provided the means through which we understand how evolutionary change occurs.
Since Darwin's day, scientists have built and expanded upon the original idea, collecting mountains of data in the form of fossils, comparative DNA studies, and direct observation. Despite this, however, there is a great deal of confusion and misinformation circulating in the public. Some of it can be blamed on the creationist/intelligent design movement, who seek to discredit evolution because it conflicts with their theological notions; some arises from inadequate science education and distorted portrayals of evolutionary theory in the popular media. A compendium of common misconceptions would include the following:
Evolution is "Progressive"
This myth took hold of the public imagination in the 19th century and never really let go, leading in some cases to wrongheaded ideas about race and eugenics. Even today, editorial cartoons parody the famous "march of human progress," with a modern man heading up a line of more "primitive" ancestors; many people still think of evolution as a ladder with modern humans occupying the top rung by virtue of their superior intellect and environmental mastery. There is, however, nothing to suggest that evolution is going anywhere, and it is certainly not heading toward some future state of perfection. Creatures of the past were not necessarily less fit or somehow "worse" than their modern counterparts; they were simply adapted to the circumstances they lived in at the time, becoming larger or smaller, simpler or more complex, or changing not much at all. Natural selection does not have a goal of creating the optimum individual; it is simply a process by which species adapt well enough to propagate their genes.
Evolution is "Random"
This myth is popular among creationists, who compare evolution to a tornado tearing through a junkyard and miraculously assembling a 747. But this is a false analogy that betrays a fundamental misunderstanding of the "ratcheting" action of natural selection. The only truly random factor in the evolutionary equation is mutation - genetic mutations are indeed random errors arising within individuals of a given population. These mutations, however, are only the raw data on which the non-random process of natural selection can work. Neutral mutations are ignored; harmful mutations are usually flushed out of the population (unless they happen to convey a benefit that outweighs the harm - the mutation that causes sickle-cell anemia, for example, also confers resistance to malaria). But advantageous mutations, even if slight, can give the individuals who possess them a competitive edge, and this enables them to leave behind more offspring, on average, than their mutation-free brethren. Over many generations, the trait spreads and may even amplify to the point where a new species splits off from the original one. So while the mutation rate is certainly random, natural selection works upon these mutations in a highly systematic way.
"Humans Came From Monkeys"
This is a common shorthand phrase for expressing humans' evolutionary lineage, but it is not technically correct. Another often-heard phrase is some variation of, "If we came from monkeys, why are there still monkeys?" This misunderstanding may be partially traced back to the "ladder" idea again, where evolution is perceived as a linear progression, with one species replacing another. Humans clearly did not replace apes or monkeys, but we did share a common ancestor with them, just as, going back to the origin of unicellular life some 3.7 billion years ago, we share a common ancestor with every living thing on the planet. The story of life is one of constant branching and splitting, more like elaborately tangled vines than a ladder. In the case of humans, at some point roughly five million years ago, the common ancestor we shared with chimpanzees diverged, perhaps due to a change in local environment. One group forged the path that eventually resulted in modern chimpanzees, while the other group traveled a different path and became us. Human beings are thus simply another offshoot of the richly complex matrix that makes up the diversity of life on Earth.
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