Darwin’s theory of evolution may well be the most important scientific breakthrough of all time. It describes how a simple iterative process applied over long periods can lead to results of staggering complexity. The ramifications of this are only now, over a century and a half after Darwin’s seminal work, beginning to be fully appreciated. The far-reaching implications of the theory are now categorized under the rubric of Universal Darwinism, a topic I will return to many times in these pages.
For the moment, I want to concentrate on what I believe are common, even pervasive, misunderstandings about how biological evolution works. Evolution is oft portrayed by (I’m sure, well-meaning) science based programs on television and other media as entailing gradual improvements which increase a species’ ability to survive. The term, “survival of the fittest”, is commonly understood to simply mean that species that have evolved better fitness are the ones that don’t die out. I think this completely misses the point of how evolution works. First of all, the emergence of species is the result of evolution, but it is not species themselves that evolve. Species die out and new species emerge, this is what is driven by the evolutionary process.
To understand what I mean it is important to understand why it is species that we speak of (as opposed to phyla or genera or any other taxonomic grouping in botany) when talking of evolution. The category species refers to a group of organisms that can reproduce with each other and whose offspring can also reproduce. Evolutionary processes occur within groups of organisms that reproduce together. (I should note that evolution can occur in organisms that do not employ sexual reproduction, and for which the term species as used here does not apply. Asexually reproducing organisms, and indeed entities which are not even organisms (e.g. software) can evolve, but the discussion for now will be limited to biological evolution of sexually reproducing species.) Evolution does not occur to an entire species at once, it occurs within a reproducing population. A reproducing population is a group of members of a single species that have the potential (due to proximity) to reproduce with each other. The members of this group are competing for a common resource which is in limited supply. The common resource I refer to is offspring. All competition for resources (food, water, safety, &c.) is subservient to the competition for this most vital resource.
Evolution by natural selection requires that not all members of the group will successfully acquire offspring. In other words, if all members of the group are able to successfully reproduce, there can be no evolution [of this type]. Evolution engineers new designs by virtue of the fact that organisms embodying less fit designs fail to reproduce. A mutation (or group of mutations) is important in the evolutionary sense only when those members of a reproducing group that don’t have it fail to reproduce. It is the dying-out of those entities without the attribute which is at the heart of evolution. One could say that the single most important process in evolution is a culling process. Therefore the statement that, for instance, some species of plant evolved thorns to keep from being eaten, is somewhat nonsensical. The mechanism is that an earlier plant species was less thorny, and some of the offspring of some of those plants were more thorny and by virtue of this survived. Ultimately all the less thorny plants died out. The more thorny plants have less thorny plants as ancestors. But to say that the less thorny plants “evolved” thorns is to miss the point that what the less thorny plants actually did was, in the long run, fail to have any more offspring.
Postscript:
The concept of an evolving species (i.e. speaking of evolving as something that species do) can be a very useful abstraction. The problem is that this manner of speaking is so often utilized that it can lead to misunderstandings as to what is really happening. Daniel Dennett has coined the term the intentional stance to refer to the way of looking at the actions of objects or the functions of systems as if they are enacted with intent. His oft cited simplified example is referring to the actions of a thermostat by speaking of it as “wanting to keep the temperature at the set value”. Now obviously the thermostat is just a mechanical (or electronic) device that harbors no such intentions, but looking at it as if it did can be a convenient and succinct way of describing its behavior. There is nothing wrong with using the intentional stance when describing evolution, but its overuse can lead to misunderstanding.
