DISCLAIMER: This article was inspired by reading way too much Stephen Jay Gould, and its arguments are currently still being debated within the scientific community.
Much ink has been spilled refuting creationists’ sometimes sneakily intuitive and sometimes hilariously outrageous arguments. Such refutations are often done by clarifying misunderstandings about evolution that arise in the defence of creationism.
While many of us who support evolutionary theory like to think that we are substantially more enlightened, it seems that we also tend to hold ill-formed and erroneous beliefs about the evolutionary process.
I’d like to talk — in admittedly overly simplified terms — about some common misunderstandings about evolution that are held not only by creationists but by so-called “evolutionists” alike.
Many people view evolutionary change as occurring at a haltingly slow pace, with tiny phenotypic improvements continuously taking place over the long course of history, gradually improving a species’ “fitness” with their environment over time. Darwin himself promoted this view.
A noted problem with this is the lack of attention given to the rapid environmental changes that often occur. A group of organisms gradually refining and updating their fitness and survivability, becoming ever more adapted to environmental needs and pressures, presupposes the stability of that environment. However, environments change, and they change quickly. Ponds dry up, temperatures increase, food supplies diminish, predators increase, etc.. When catastrophic environmental changes occur, many members of a group of organisms can be wiped out. Those surviving may luckily possess some adaptive trait that made their continued survival possible. It is important to note here that whatever trait allowed their survival was not necessarily something that did so prior to the environment changing. In fact, it may previously have been a hindrance.
In this way, species may exist in relatively stable phenotypes until catastrophic environmental changes occur, at which time survivors, with their new traits that allowed their survival, multiply, passing on these new traits to their offspring. This view also explains the relative lack of transitional fossils in the fossil record, and was developed by palaeontologist Stephen Jay Gould with his colleague Niles Eldridge in 1972. They called it the theory of “Punctuated Equilibrium,” and while it has achieved widespread acceptance, it is important to note that it is not without its critics.
In a social psychology class a few years ago, I remember cringing as the professor stated that physiological traits that were not improving an organism’s survival would be selected out by evolutionary processes. I guess this would mean that male nipples are on their way out.
While it’s one thing to claim that maladaptive traits are “selected out,” it’s quite another to think that neutral traits would also be gradually removed. If neutral traits are not hindering an organism’s survival, why would their removal increase survival fitness and therefore be promoted by evolution? Are males without nipples having more offspring? Of course these types of neutral traits may end up getting removed from a population, but it wouldn’t necessarily be because they were maladaptive, since by definition these traits are neutral to survival. It is important to remember that evolution only works in concert with environmental pressures. If there is no environmental pressure to remove a trait, it can stay there indefinitely.1
As organisms evolve, they get increasingly more complex, right? Not necessarily. Again we must consider the environmental pressures acting in concert with the organism. Is it possible for environmental characteristics to “select for” a decrease in complexity? Of course it is, and it has happened several times throughout history, particularly in parasites (organisms that are great at Darwinian survival.) These organisms often do not require such extraneous features as locomotion nor digestion, and thus the loss of these features is favoured by evolutionary processes. In his book about life’s complexity “Full House” Stephen Jay Gould states that were he a betting man, he would “wager a decent sum on a small natural preference for decreasing complexity within lineages, and not for the traditional increase, if any general bias exists at all.”
We also tend to see evolution as a process which is continually making life on Earth more diverse while increasing the numbers of new types of organisms. To dispel this myth, we need to recall the distinction between “phylum” and “species.” Organisms can be grouped together according to their basic body plan. For example, arthropods are a group of organisms that have jointed appendages, an exoskeleton, and a body segmented into three parts. This basic body plan characterizes all members of the phylum arthropoda, which includes within it millions of different species (and includes crustaceans, trilobites, and insects.)
There are currently about 35-40 different animal phyla, which have remained fairly constant throughout their history on earth. These phyla burst on the scene approximately 530 million years ago in an event known as the “Cambrian explosion.” The term “explosion” was chosen to capture the sudden appearance of a multitude of a wide variety of organisms in the earth’s oceans. The main thing about this event was the appearance of an incredible diversity of different phyla. In fact, all phyla that exist today made their debut at the Cambrian explosion. But beyond this, a multitude of other organisms with body plans that would now seem bizarre and science fiction-y debuted as well (such as the five-eyed half-arthropod half-worm Opabinia.) These, of course, did not survive. This story of the Cambrian implies that the history of evolution is one of primary decimation; it is a story of the decreasing number of body plans (or “phyla”) as history has progressed. Within the phyla that did survive, an increase in the diversity of species has certainly occurred. However, new animal phyla (body plans) don’t arise as readily.
All of these above points can be marshalled in defence of an anti-progress view of evolution. Though this may sound politically incorrect, evolution cares not. Evolution proceeds not according to any future plan. It is without an end goal and devoid of purpose. It merely seeks to adapt organisms to their present environment where possible. Should that environment change, what was once a wonderfully adaptive trait can now become a maladaptive hindrance. The common thread throughout these points is the failure of many of us to remember the role of the changing environment in shaping the organisms living within it. An organism adapts to its local environment, and has no foresight about what that environment will look like in the future.
A brief quote from the book Wonderful Life, written by this article’s main source, Stephen Jay Gould, summarizes these sentiments and directs our thoughts to our own place in evolutionary history.
“Groups may prevail or die for reasons that bear no relationship to the Darwinian basis of success in normal times. Even if fishes hone their adaptations to peaks of aquatic perfection, they will all die if the ponds dry up. But grubby old Buster the Lungfish, former laughing stock of the piscine priesthood, may pull through — and not because a bunion on his great-grandfather’s fin warned his ancestors about a coming comet. Buster and his kin may prevail because a feature evolved a long time ago for a different use has fortuitously permitted survival during a sudden and unpredictable change in rules. And if we are Buster’s legacy, and the result of a thousand other similar happy accidents, how can we possible view our mentality as inevitable, or even probable?”
1 Please note that there are other forces in nature that shape an organism and population’s phenotype and genotype other than natural selection.