I get really confused and depressed when people misunderstand evolution badly enough to use the word microevolution. Creationists often love to fall back on the old “microevolution is real, but macroevolution is a lie!” trope. I don’t get it.
Microevolution is macroevolution. Evolution is evolution! What creationists call macroevolution is just evolution taking place over relatively long periods of time. What does that mean, “relatively long?” It means “long enough for populations to deviate enough from one another that we perceive them as different species.” The only part of that definition that differs from what they call microevolution is time.
Whoa there, I’d best back up a bit. What is microevolution? Well, according to biologists, it’s a bullshit word made up by ignorant creationists. According to those ignorant creationists, it describes changes that occur within a species, such as different breeds of dog. The reason I call these creationists ignorant is that this is evidence for, not against, the theory of evolution.
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Reading Richard Dawkins changed my life. Unlike so many of my fellow atheists, I actually discovered him first through his work in biology. I was aimlessly browsing my local library one day when I came across The Ancestor’s Tale. It’s a book describing evolution from a modernity-centric, backward-looking viewpoint, essentially beginning with humans and following the tree of life back in time to the “source.” It carries itself as a sort of narrative and describes key concepts in biology and evolution throughout in a way that I found easily understandable. (And I am not a biologist.) It was eye-opening for me because prior to reading it, the only significant experience I’d had studying inheritance was doing Punnett squares in seventh grade. (Seriously, that’s it. PS: They suck.)
The way most people think about evolution is entirely backwards. If you think evolution is any sort of active process that takes place in the background to drive a species towards being more capable of thriving in its environment, you’re suffering from the same misapprehension I was under. There is no guiding force. Evolution does not steer a species toward any goal. “Survival of the fittest” does not operate by making some individuals better at reproducing per se—it’s called “survival” because everything dies, but individuals with beneficial mutations die slightly slower. Organisms that lack these beneficial mutations (or that carry harmful mutations) are more likely to die off.
Another common misconception about evolution is that individuals evolve. They don’t. We don’t. You don’t. Once you’re born into the world, that’s it. There is no evolving for you. Pokémon is a damned lie. Only groups evolve—individuals may only bear mutations. When a group is isolated and enough of these mutations have spread throughout it, it is possible for that group to become a subspecies (like a dog’s breed: it has obvious traits that the main group does not—just for the record, no, skin color is not sufficient to classify people into different subspecies). Given enough time, these mutations will slowly create a scenario in which members of that group will no longer be able to produce viable offspring with the original population in the wild. When this happens, we say speciation has occurred. You know what that means? Speciation is just microevolution plus time. Thus, microevolution is macroevolution. Both are just plain-ol’ evolution. It’s the same damn thing. And at no point can a lizard ever give birth to a bird.
“But what about transitional forms?”
Oh yes, that question. Transitional forms indeed. The analogy that best helps me understand this idea is that of a clock. If you watch a clock, you will see the second-hand spinning, spinning, spinning, and the minute-hand sloooowly creeping along. Unless you stare at it for quite some time, you will fail to see the hour-hand moving at all. Yet the hour-hand is moving; it does not stop. What we call species represent positions on the clock—they’re the hour marks on the clock. Individual genetic mutations are the changes that take place on the second-hand. Mutations becoming predominant are the changes taking place on the minute-hand. They’re largely arbitrary designations.
You bear genetic material from both of your parents, but odds are high that your genetic code also carries with it mutations— essentially DNA that neither of your parents have. (But don’t worry, most mutations are harmless. You wouldn’t even notice ’em.) You exist as a fraction of a fraction of a second different from your parents. This is how it has always been; every child has always been of the same species as its mother. In truth, every organism is a transitional form between its parents and its offspring.
“But your children are the same species as you!”
This is true in exactly the same sense that 5:03:00000000002 PM is the same time as 5:03:00000000003 PM. We live in a world measured in seconds, but each second is broken up into smaller fractions. There is a point at which these fractions are so small that we cannot perceive them—the resolution of our minds is not precise enough to perceive this scale. So too with most evolution.
Most? Yes, only most. Evolution seems so slow for us because mutations take place on the generational level. The shorter a species’s life cycle, the more quickly we can perceive the effects of evolution. Genetic change in fruit flies is much more rapidly visible because their short lifespan means their evolutionary clock runs faster than our own. (This is why scientists often use them in genetic experiments.)
This observation’s most threatening implication is seen at the bacterial level. The discovery of antibiotics allowed us to fight diseases with never before seen effectiveness. Indeed, some diseases, such as smallpox, were entirely eradicated because the little critters that caused them had no defense against our superior antibacterial weaponry. Things are no longer so clear-cut; stories of the so-called superbug, MRSA, abound. Our application of antibiotics has become somewhat less than judicious, which is where natural selection comes back into play.
Except in this case, it’s artificial selection because we’ve guided it. Through the misuse of medicine, our own bodies occasionally become breeding grounds for new bacteria (and subsequently, new diseases). You know those commercials for products that say “kills 99.9% of bacteria?” Bacteria are living organisms, so what do you suppose happens to that surviving .1%? They breed more copies of themselves. In terms of medicine, if the reason that .1% survived is because they had a genetic mutation that caused them to survive the drug, their children will be equally likely to survive that drug. Through artificial selection, we’ve created various species of bacteria that resist our treatments. Sucks, doesn’t it?
That’s evolution. Anyone who says “Evolution is just a theory—it’s not a fact!” is just ignorant. MRSA is a fact. MRSA is the product of genetic change. This is a fact. The best scientific explanations for facts are called theories. Evolution is the theory that best describes the observed facts of mutation.
And now you know.