You Don’t Know Shit About Evolution

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Original copies of "On the Origin of Species" by Charles Darwin
Wellcome Collection, CC BY 4.0 , via Wikimedia Commons

You don’t know shit about evolution.

Yeah, okay, so I just use that challenging language to grab your attention and make you read this. So what? It’s not the first time or the last, so get over it. You and I both know that, in truth, you probably know at least one thing about evolution. But, lemme tell ya something… there’s a good chance that some of the things you think you know about evolution, ain’t true. Even if you’re a scientist. Even if you’re a biologist, maybe. There’s a lot of reasons for this. Maybe you were taught inaccurate or outdated information at school. Maybe you’ve absorbed some misconceptions without even realizing it. Maybe something just seemed to make so much sense that you never questioned it. And yeah, maybe it never really mattered a lot to you, because it didn’t impact your day to day life.

But lemme tell ya something else. Evolution is the foundational principle of modern biology. It’s basically the Theory Of Everything for the life sciences. It ties all of biology together. Physicists have been searching for their version of evolution for, like, forever. They get so mad that Darwin managed to link together everything in biology back when they still used wooden sailboats. And here physicists are today with crazy-assed, futuristic, Star Wars level shit like the Large Hadron Collider, and they STILL aren’t much closer to figuring out a unifying theory for physics than they were back then. We never make fun of them for it, of course. That would be unprofessional.

But the point is, if you think that anything related to biology, anything at all, is important, then a basic and accurate understanding of evolution is also important. I don’t care if you’re talking about medicine, ecology, agriculture, genetics, or anything else, evolution underlies all of it. It’s probably a good idea to make sure you’ve got your facts straight. You don’t need to be an expert (I’m certainly not!), but you can at least make sure you don’t carry some of these common myths around with you. Evolution is just too big of a deal to get wrong. Even a casual understanding of it can shape how you think about life and the world around you, so don’t fuck it up. Now, there’s too many misconceptions, mistaken beliefs, and outright lies to cover them all in one sitting. And yeah, outdated information too. News Alert: Darwin didn’t get everything right! I mean, they were still using wooden ships, for crying out loud, what did you expect? But I’ll hit a few of the big topics, the ones you’re most likely to be lugging around with you, along with the mistaken belief that black licorice is edible, and that the Charlie Brown cartoons were funny.

First off: Evolution theory says NOTHING about the actual origin of life. It has everything to say about life once it got going, but that’s it. Evolution theory doesn’t claim to know, or to really care, how life got going on this rock. Maybe it was a supernatural deity, or an alien civilization, or cells hitching a ride on a meteorite, or just some crazy-assed chemistry. So, let me just stop you right there. The question of how life began is a separate issue. And while it’s obviously an important one, the answer to it doesn’t actually change anything about what came next. You can fill in the blank with anything you like, and nothing about our understanding of evolution would really change. We know more or less what the earliest organisms must have been like. The details about how they formed aren’t going to change much, if anything, about the details of everything that came after. It’s interesting, important, profound even, but it’s not a topic that evolution theory is much concerned with. It’s a whole separate thing.

Okay, that’s the easy one out of the way. Next up: Natural selection. Turns out, you don’t know shit about natural selection, either. That’s right, we’re now in a sub-blog-post!

You Don’t Know Shit About Natural Selection

Natural selection. You’ve probably heard this term used a lot, but it’s rarely actually explained. The short and simple version is this: traits that increase the chances of an individual surviving long enough to successfully reproduce are more likely to be retained in a population. Traits that decrease the odds of this will tend to be eliminated. Maybe you’ve heard it described as “survival of the fittest”. And… well…. kiiiiiiind of. That’s an easy phrase to remember, but it ain’t exactly like that. First off, natural selection is more like “survival of the good enough”. Because it’s not like the absolute best survivors get to reproduce, and everyone else fails. Plenty of less-than-perfect individuals are going to make it as well. Unless the population is undergoing a pretty dramatic, stressful situation, the second place survivors are probably reproducing, too. And third and fourth place. I mean, did you make it to the playoffs? Good enough. Doesn’t matter if you bring a trophy home, as long as you… umm… squirted out some babies out there on the field. Uh. I think I just screwed this metaphor up. Or not. I don’t really watch sports. Do they ever involve giving birth? In public?

Besides that, natural selection isn’t really about survival of an individual. It’s actually about survival of a trait within a population of individuals. That can mean a physical trait like having no chin and squinty little eyes, a behavioral trait like being a terrible smartass, or something more subtle like not being able to taste the difference between a gourmet meal and a frozen dinner. Since I don’t plan on having children, though, we’ll never know if this combination of traits contributes to natural selection or not. But natural selection isn’t about me, the individual. I’m gonna die eventually one way or the other. But my traits, at least the ones that are based in genetics and are therefore inheritable, could survive in the population. If, you know, I made a baby. And if these traits helped any particular individual to survive, then they would be selected for. If they made it harder for an individual to survive and breed successfully, then they would be selected against. That’s natural selection. “Survival of the traits that are pretty okay,” is a much better description than “survival of the fittest”, but it just isn’t as catchy.

illustration from 1768 showing a mermaid and other weird critters having really nothing to do with evolution at all
The evolution of the… mermaid? Manatee? Whatever that guy down in the corner is? They didn’t get it all right back in 1768

Oh, and natural selection ain’t the only game in town, either. Evolution and natural selection are so strongly associated with each other that the two terms are often used interchangeably, but they’re not the same thing. Natural selection is just one of several forces that drive evolution. The other main one is genetic drift. This is not what happens when a “Fast and Furious” movie takes a sci-fi twist with genetically engineered cars that slide around turns. Genetic drift is basically what happens when different mutations randomly spread throughout a population. A genetic mutation that has a strong influence on the survival or reproduction of an individual will be selected for or against, but a mutation that has a weak effect or no effect can become dominant in the population, or become rare, just by chance. That’s genetic drift.

For example, if 5% of the population has a gene that makes them love K-pop, but a freak accident involving a hurricane and a cargo ship full of fertility drugs causes that 5% to have more offspring per individual than the rest of the population, you could end up with 15% of the population trying to out-stan each other on the BTS sub-reddit. That gene isn’t helping them to survive or reproduce any more, or less, than folks with the reggaeton gene or the elusive Swedish viking metal gene, but genetic drift gave it a chance to spread throughout the population anyway. It’s not likely to happen for any one trait, but with thousands, or tens of thousands of genes, and multiple possible mutations for each one, it’s going to happen sometimes.

Lemme just leave you with one more tip about natural selection. Natural selection does not just select for the fastest, or the biggest, or the strongest, or the smartest. Natural selection works on whatever traits help individuals, or hurt them. Sometimes being bigger or faster might be beneficial to survival. But if food is scarce, then smaller individuals that need less food to survive might be favored over large individuals. And we see this when we look in the fossil record. Sometimes species evolve to become smaller, structures become simplified, brain size decreases. Being fast or strong or smart aren’t inherently good things. What’s “good” is whatever works. If today that means being small and slow and staying hidden, then that’s what will be selected for, not being faster and stronger.

Back To… You Don’t Know Shit About Evolution

Which actually leads nicely into the next thing you may have gotten wrong about evolution. This one is a doozy, widely believed and very incorrect. It’s actually what many people have been taught in schools… hopefully not lately, but nothing would surprise me. I’m talking about the evolutionary ladder. Let me tell you everything you need to know about the evolutionary ladder in two words:

Total bullshit.

Let me make sure we understand what I’m talking about, though. Maybe you’ve seen an illustration of the evolution of the horse. Because we have a pretty good fossil record of horses, they have often been used to teach evolution. The classic chart shows a series of, usually, five horse species. They start with an animal called the Eohippus, considered the first real horse, or close enough to still call it one, at least. Eohippus was a cute little guy, about the size of a fox, with four toes. The old school chart then shows the next four species all in a line, each one getting progressively bigger and with smaller or fewer toes, until you end up with the modern domestic horse, with its large size and single toe. This is the classic evolutionary ladder. It’s a very satisfying story about striving towards progress and some ideal of perfection. And it’s garbage.

Evolutionary ladder of the horse, which is incomplete, misleading, and generally rubbish
Mcy jerry at the English language Wikipedia, CC BY-SA 3.0 , via Wikimedia Commons

Don’t misunderstand me… each of those extinct horses was just as they described, and really did live in those time periods. The chart doesn’t lie about anything, not exactly. But it does misrepresent the history of horses. There were dozens of species of horses in prehistoric times, not just five or six. You can’t represent them all by picking out the ones you like best and ignoring the others, but that’s basically what they did for a long time. The second species often shown in that sequence of five horses was the Mesohippus. This group of horses didn’t show up until 20 million years after the Eohippus. It was NOT the next group of horses to show up, there were a number of others before that. The reason they don’t like to show earlier species of horses in their little evolutionary ladder? Because in between those two groups, horses didn’t get any bigger at all. For 20 million years, or about a third of the entirety of horse evolution, horses developed many species, but they all stayed around the size of a small dog. There was no inherent drive towards bigger horses. Little horses did just great for a long time. But that didn’t fit the notion of an evolutionary ladder, constantly striving towards some goal that was supposedly better, so they just skipped all those guys. They were inconvenient.

Then we look at the end of the horse chart, represented by one or two species before we hit the modern horse. That’s fine, but that one or two species is standing in for MOST of the species of horses that ever existed. The horse family went nuts about 15 million years ago, with dozens of species all existing around the same time. It’s crazy to show one species and let it represent all of that diversity. And guess what? They didn’t all get bigger. Some of the last horses to go extinct before modern man showed up weren’t much bigger than that early Eohippus. We had horses the size of dogs and horses the size of horses, running around all at the same time. There was no inherent drive towards bigger horses. Sometimes horses stayed the same size. Sometimes they got smaller. Sometimes some got bigger while others got smaller. There was no evolutionary ladder. There wasn’t even an evolutionary tree, with a single trunk and a few side branches. There was an evolutionary bush, with many branches and twigs all over the place, and many lineages were important and continued on until relatively recent times. But that’s messy. That doesn’t tell a story about progress. That’s chaotic, and we humans don’t like that. We want everything to be nice and orderly, tidy. But the real world ain’t like that, folks.

Oh, and the other example of an evolutionary ladder you may have seen is the chart with some sort of ape-like creature on the left, a “caveman” with a spear in the middle, and a modern human on the right. Same deal, it’s bullshit. There have been many species of humans and human-like creatures. Though we don’t seem to have been as successful and diverse as the horses, there were still multiple human species existing at the same time for most of our evolution, sometimes even living in the same areas together. There was not a regular, linear progression from something that walked on its knuckles, to us. There were many twigs and branches, and just like the horses, guess what? One of the most recent human species to vanish, Homo floresiensis, was small. At 3 feet tall, it was so small that it’s called the hobbit. But having a little guy show up right before the end doesn’t make for a nice progression. That doesn’t imply that taller is better, which is the story we want to tell ourselves. Instead, here’s a human species that survived up until only 60 thousand years ago, and it was only three feet tall, much smaller than its predecessors. Like I said, evolutionary ladders are bullshit. Nothing about evolution is that orderly.

historical satirical drawing of Charles Darwin
Not everyone was a fan of my man, Chucky D.

Evolution in the Fast Lane

The last thing I want to hit you with for now is the notion that evolution takes a long time. We often think of evolution as taking place over millions of years, which is how Darwin envisioned it. In fact, he was worried that geography would prove his theory wrong, because in his day, the Earth was only thought to be 100 million years old. This wasn’t nearly enough time to explain everything in the fossil record using evolution theory. We know now that it’s at least 4.5 billion years old, more than enough to account for all of evolution. But the thing is… evolution doesn’t always happen by tiny little incremental steps. It often does, it’s true. Those horses probably slowly got bigger, or smaller, over hundreds of thousands of years. But, as usual, evolution turns out to be messier than that. It can go in leaps and bounds sometimes. Sometimes simple changes in genes, or even just in the timing of when genes are expressed or “turned on”, can result in significant changes in an organism. And when the pressures selecting for one trait over another are very great, evolution can happen rapidly. Maybe the traits needed for a population to survive a new environment are very rare. Maybe a species suddenly has great opportunities for exploiting new resources. There’s many ways it can happen, but evolution doesn’t have to take a million years. It can take 10 thousand years. Or ten generations. Or literally overnight.

My favorite example of rapid evolution is the case of the Lake Victoria cichlids. Lake Victoria is a huge lake in eastern Africa, straddling the borders of Uganda, Tanzania, and Kenya. It contains over 500 species of a type of fish called cichlids (pronounced sick-lids), most of which are found nowhere else in the world. Now…this by itself is amazing diversity. There’s some dispute as to how many of these species are truly species, because many are very similar and the definition of what a species actually is, is pretty… umm… fishy. But even if you cut that number in half, it would be an astounding variety of fish. And that’s just the cichlids, there are other types of fish in the lake as well. But here’s the amazing thing.

Haplochromis degeni, one of the many species of Lake Victoria cichlids

15,000 years ago, Lake Victoria dried up completely. Gone. Nothing but dust. No water, no fish. Which means that every single species of Lake Victoria cichlid, which remember, are not found anywhere else in the surrounding area, must have evolved within the past 15,000 years. 14,600 if you want to get picky about it. Now, that would be an amazingly short period of time for just a few new species to evolve. But for hundreds to develop from what we think were just a few ancestor species that colonized the new lake… that’s bananas. B-A-N-A-N-N-A-N… shit, I screwed it up. You get it, though. It’s insane. We think part of how they did it was that the species that colonized the new lake were pretty genetically diverse, maybe even hybrids with genes from multiple species. Add to that a lake with a diverse array of habitats and food sources, and species started popping off like swollen ticks on a mule. I don’t know if that’s actually a saying, but I want it to be. Point is, with a lot of genetic variation and strong pressures causing different traits to be selected for, evolution and new species can develop rapidly.

So what about evolution happening in just ten generations? Easy peasy. Remember, evolution is just a change happening in a population. It doesn’t need to lead to a new species. There are many species around the world that we have observed evolving in real time, before our eyes. A wildfire can trigger local insect populations to switch from having mostly bright colors to mostly dark, blending in better with the new landscape. Introduce a predatory fish into a pond where none had been before, and watch in a few years as the other fish start maturing at a younger age as they race to reproduce before they get eaten. There’s a species of mosquito that only lives in subways like the London Underground, and are thought to have evolved there over just a couple hundred generations. That’s not just a different color variation, mind you… these mosquitoes are different enough that they can’t breed with their closest relatives. They’re a entirely new species. And that’s not counting intentional, deliberate evolution caused by selective breeding of domesticated plants and animals. You may not think of a new breed of dog or variety of rose as being evolution, but technically it is.

Spontaneous Speciation

Okay, so evolution can happen pretty fast. But… overnight? It’s weird, and it’s not an adaptation so much as a freak accident, but it happens. It involves some sciencey jargon, so bear with me. There’s a thing called polyploidy. Humans, and most animals, are diploid. This just means we have two sets of chromosomes, two sets of genes. The “di” means two. Polyploidy, then, means having multiple sets of chromosomes. A triploid individual has three sets, a tetraploid specimen has four sets, and so on. This is typically a very bad thing in animals… it’s fatal in humans, for instance, and leads to an early death of the fetus. But in plants… plants fucking love that shit. They actually seem to do better when you toss extra sets of chromosomes in there. Now, there’s different ways that plants can become polyploids, such as two different species hybridizing, or something unusual, like a cold snap, shocking the sex cells as they form. Regardless, depending on how things shake out, it’s possible for weird little polyploid seeds to develop. If one of those seeds survives and grows into a mature plant, it may be fertile but unable to reproduce with the species that its parents belong to. It may only be able to breed with other weirdo polyploid plants. Thus, BOOSH! A new species of plant, overnight. Now, that’s obviously not really natural selection, and there’s no guarantee that the new species will survive for long. But it does happen, and while the results may not be visible right away, every once in a while a new species of plant does arise this way, seemingly appearing out of nowhere. And once that weird polyploid freak does start breeding successfully, of course, natural selection kicks in just like normal.

So there you go. Evolution ain’t what you thought it was. Or maybe it is. You keep acting like I know you, but I don’t. Probably. Maybe. Are you Dave from across the street? Because that would be weird. Anyway, I honestly think the points I’ve brought up here can really help you think about the world around you. Especially about how natural selection works. Remember, it’s not survival of the fittest, it’s survival of the traits that are pretty okay. Evolution doesn’t drive species towards some ideal or perfect form. “Good enough” often wins the day. So everything… every living thing… is the result of messy, chaotic imperfection. It has to be. Any species that becomes completely perfect, is a species that’s completely unable to adapt to new situations. So remember that, the next time you’re embarrassed because your eyes are squinty, or because you’re not much of an athlete, or you’re frustrated that you’re hard wired to be a night owl and sleep when you’re supposed to be working and work when everyone else is sleeping. Remember that those variations are actually critical to natural selection and evolution, because something that’s simply good enough for now, could become essential tomorrow. When civilization collapses and we all form into nomadic tribes, struggling for survival in the wastelands, I’ll be the one protecting the rest of you by staying up all night to guard the camp while you sleep. So you better be nice to me, Dave from across the street, or you’re gonna wake up screaming as the mutant cannibals drag you off into the night while I just stand by and watch.

And that’s natural selection.

MORE READING:
Ugly but informative list of evolution misconceptions
Lake Victoria cichlid evolution
Evolutionary Ladders Are Fake News

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