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When Darwin published On the Origin of Species 166 years ago, there were, naturally, misunderstandings. In an 1860 review, Richard Owen, a leading Victorian scientist, rhetorically asked whether evolution by natural selection continuously operated through time. “Unquestionably not,” Owen wrote.
Au contraire. The theory of evolution, masterfully crystallized by Darwin, shows how, over generations, populations of organisms have been shaped by natural selection. And given our current understanding, how this process continues even today.
Evolution is elegantly simple, in some ways simpler—or at least, more apparently straightforward—than many other key concepts in science. However, its apparent simplicity continues to attract a disproportionate number of misconceptions, as though to fill in the spaces surrounding what people know … or think they know.
As an evolutionary biologist who has also spent decades as a university professor, I’ve come across plenty of strongly held misunderstandings about evolution and how it works. It’s not necessarily that a little learning is a dangerous thing; rather, a little learning leads to a lot of misconceptions. Here are 10.
1. Evolution is “only a theory”
It is indeed a theory, in the technical sense. The trouble here is the meaning of theory. In science, a bona fide theory doesn’t lend itself to “only.” A theory is an explanatory paradigm that has stood the test of theoretical coherence and—most important—empirical validation. So, if someone tells you that they have a theory that Elvis still lives, you might or might not want to correct them about Elvis, but you definitely should downgrade their “theory” to a hypothesis (more accurately, a ludicrous notion). The theory of evolution resides comfortably among other powerful fellow theories, including the germ theory of disease, the theory of continental drift, atomic theory, number theory, the theories of general and special relativity, and quantum theory.
Within evolutionary theory there are certainly many competing hypotheses, such as regarding the role of nonadaptive genetic change, the levels at which natural selection operates, the extent to which evolution is always gradual or occasionally involves large steps). Some people seize upon these and other tweaks in the most powerful theory in biology to suggest that the whole edifice is crumbling. However, such debates and modifications are precisely what one expects from a vibrant and productive theory, the result being that evolutionary biology is regularly strengthened by the fine-tuning.
We can be confident that, once life emerged, its subsequent course was evolutionary.
2. “Survival of the fittest” means that evolution favors those who are “strongest”
For evolution, the “fittest” are not necessarily the most physically fit, although being in good physical condition is nearly always an adaptive advantage. “Evolutionary fitness” refers to reproductive success; more precisely, it’s a measure of the success of genes in getting themselves projected into the future and is achieved in many ways—including the ability to obtain food, to avoid becoming food for someone else, to overcome diseases, to adjust to local weather and climate, attract mates, and so forth. In a pioneering research report, male European red deer who were smaller and who bore less impressively developed antlers were often more “fit” than the hulking males, because these “sneaky fuckers” (don’t blame me: This descriptive phrase is part of the technical literature) copulated with the females while the more massive bulls were busy fighting antlero-a-antlero with other more physically developed specimens.
A related and equally misconstrued phrase is “nature red in tooth and claw.” This comes from Lord Tennyson’s poem “In Memoriam A.H.H. 1883,” which was actually written before the publication of Darwin’s Origin of Species. In some cases, notably predation, natural selection indeed involves red teeth and gore-bedecked claws. Sometimes, bloody competition characterizes intraspecies competition, but mostly it operates via differential reproduction—whereby some individuals and their genes leave more descendants than their competitors—which sometimes favors cooperation rather than violence. In any event, the key is reproductive success, not necessarily fighting prowess.
3. Evolution explains the origin of life (or it’s supposed to)
Evolution explains why organisms are connected as well as how they have changed … once they exist. It does a marvelous job explaining the origin of new life forms from old ones, and also how and why some organisms have not changed over vast periods of time. But it doesn’t purport to explain how life initially arose from non-life. Hence, it’s inappropriate to criticize evolutionary biology for not having (yet) solved this puzzle, which is primarily a job for biophysics, biochemistry, and geology.
Evolutionary biology may indeed help explain the initial appearance of life—my guess is that it will contribute significantly—but that isn’t its particular remit. That said, whatever the initial chemical interactions and combinations that first created living molecules, we can be confident that, once life emerged, its subsequent course was evolutionary.
4. Evolution acts for the good of the species
This might be the most widespread misunderstanding. It’s easy to see why: Because natural selection rewards adapted genes and individuals, populations come to be composed of individuals and genes that are relatively well adapted, that are good at solving the various challenges that environments throw their way. And so, by and large, species are well adapted to their situations. Imagine, counterfactually, that a species was not the result of natural selection’s sifting and winnowing, but rather was stocked with a random array of living things that aren’t adapted to their environments and hence, to their lives. It wouldn’t be a “good”—biologically successful—species. But most extant species do a pretty good job of existing and reproducing. When a species is on the verge of extinction, moreover, there is no evidence that evolution works especially hard to keep it extant, such as by increasing reproductive rates, energetic efficiency, and the like.
It is estimated that something like 99 percent of species that have existed are now extinct, so if evolution is working for the good of species, it has done a terrible job! What really argues against “good of the species,” however, is the actual way natural selection operates. Although it is possible that species sometimes compete, and, as a result, better adapted ones replace their poorly adapted alternatives, evolutionary competition takes place almost entirely within species, not between them. The process is more potent in proportion as the unit of selection is more reductive: groups more than species, individuals more than groups, and genes more than individuals.
It’s no more likely that natural selection could create an organism than that a tornado could assemble a Boeing 747.
5. Evolutionary theory says that living things are the result of chance
No, it doesn’t. There’s a half-truth hidden here; actually, less than half. Natural selection’s power comes from differential reproduction, the logical, unavoidable process whereby some genetic variants are more successful—more fit—than others. As such, its raw material comes from genetic diversity, which is produced by mutations and, in the case of sexually reproducing species, the reshuffling of genes via meiosis and sexual recombination. These processes are essentially random. But that’s just the source of the building blocks employed by natural selection. Natural selection definitely isn’t random—it does the heavy lifting and fitting together, by picking and choosing among various options, with some genes being projected into the future more than their alternatives—i.e., our old friend differential reproduction once again. Then the process happens over and over, repeatedly retaining those that are more fit and abandoning those that are less so.
The renowned astronomer Fred Hoyle made an especially egregious blunder when he claimed that it is no more likely that natural selection could create a functioning organism than that a tornado could pass through a junkyard and assemble a Boeing 747. That would be a stupendously unlikely chance event, and it’s not the way evolution works. Rather, natural selection accumulates adaptive concatenations, mixes them every generation with new, randomly generated ingredients—a process that, over time, is spectacularly effective in producing immensely nonrandom outcomes, much more complex than a mere jet plane.
This also speaks to a closely related misconception, that natural selection is a purely negative phenomenon—removing the “unfit”—and so it couldn’t be responsible for the evolution of positive, complex traits or organisms. Here again, we’re dealing with much less than half a truth. Natural selection indeed selects against the unfit, but because it retains the more fit each generation, and then builds upon the results with every succeeding generation, the result is phenomenally creative. It’s really an unavoidable statistical process, analogous to being dealt, say, 13 cards, then aiming for all diamonds by discarding spades, clubs, and hearts, then getting more cards and doing the same thing over again. It would take very few such repeats before you had all diamonds, an outcome that would almost never happen by chance alone. The only difference is that when it comes to evolution by natural selection, the outcomes are far more nonrandom, and thus, in a sense, much more creative.
6. Because we rely more and more on brain power and less and less on our muscles, human beings in the future will have big heads and small bodies
Although so extreme as to appear a bit silly, this misconception unknowingly reflects a widespread version of Lamarckism, aka the inheritance of acquired characteristics. We learn in school that Jean-Baptiste Lamarck was wrong, that giraffes didn’t evolve long necks because they stretched to reach leaves. Rather, selection favored giraffe ancestors that were more fit because they had longer necks, both to reach higher foliage, and also—as revealed by recent research—to battle other giraffes).
Bodies often change because of use and disuse, but these effects are not inherited, no matter how tempting this “explanation.” Thus, weightlifters develop big muscles but these acquired traits are not passed on genetically, because information flows from nucleic acids via RNA to proteins and hence bodies, not the other way. Advances in epigenetics have shown that, in some cases, parents’ experiences can impact their offsprings’ genomes by attaching certain chemical combinations (especially methyl groups) to DNA. This doesn’t introduce new genes; rather it impacts the expression of existing ones. Hence, it adds a wrinkle to our understanding of evolution, but doesn’t replace Darwinian evolution with a Lamarckian alternative. The only way future people will have bigger heads and smaller bodies is if such individuals persistently have more children … which seems unlikely, albeit not altogether impossible.
It is similarly easy to get hung up on the Lamarckian assumption that insects, crustaceans, fish, and amphibians that inhabit pitch dark caves are often blind because they stopped using their eyes, which therefore disappeared. Not so. These evolutionary changes, which are entirely compatible with Darwinian natural selection, occur because eyes are useless in the dark—hence, they lose the selective advantage that they convey in lighted environments—and, moreover, they take energy to produce while also being vulnerable to injury and infection. So, go ahead and exercise, use your brains, and hang out in dark places if you wish … but your offspring won’t have larger biceps, bigger heads, or smaller eyes as a result.
Field studies have documented a dizzying array of evolutionary changes deriving from natural selection.
7. Gaps in the fossil record argue against evolution
Of course there are gaps in the fossil record! It’s remarkable that we have any such records at all, given how unlikely it is that any given dead critter will be fossilized and preserved, to which we must add an additional low probability that these remains will be discovered and recognized as such, perhaps hundreds of millions of years later. Although the evolutionary process is continuous, physical evidence of long-ago critters is therefore unavoidably rare and discontinuous. And yet, we have an extraordinary parade of fossilized intermediates linking fish and amphibians, reptiles and mammals, reptiles and birds, land-dwelling mammals with marine species, and many more.
As for “missing links,” picture a line between two taxonomic groups, with as yet unidentified species connecting them; now, identify something between (linking) them: Now you have two new missing links! So, any time we find intermediate forms, there will necessarily be “missing links,” because every time a linking specimen is found (such as the discovery of Australopithecines linking nonhuman primates and Homo sapiens), new missing links are produced. In short, the more fossils, the more “missing links.”
8. Human beings aren’t evolving any more
We are. It’s just that evolution is typically a very slow process, limited by selective pressures (differences in the reproductive success of different traits and the genes that underlie them), along with generation times. And so, we can’t readily observe evolutionary change in our own species, unlike what’s readily apparent in, for example, field studies of Galapagos finches, or the evolution of pesticide or antibiotic resistance in living things that reproduce rapidly. Any time some individuals and their genes are experiencing differential reproduction, evolutionary change is the result. Among our ancestors, selection may well have worked against genes that produced susceptibility to diabetes; now, with insulin, this evolutionary change is likely relaxed. Human beings have recently evolved the ability in some populations to prosper at high altitudes, to be increasingly resistant to malaria, to favor lactose tolerance, and many other adaptive traits.
It is possible that human beings in the future will have evolved the ability to function and reproduce readily with microplastics and “forever chemicals” in their blood, not to mention Strontium-90 in their bones and DDT in their fat, or maybe enhanced ability to manipulate computer screens, if such individuals have more kids. Each person’s genotype is fixed, so as individuals, we don’t evolve biologically. But Homo sapiens does, and will continue to do so, unless all people and their genes reproduce identically.
9. Because of evolution, living things are always getting “better”
Not necessarily. Early in the Earth’s history, a few billion years ago, life was very simple. Since then, it has evolved increasing complexity and enhanced ability to flourish in a variety of environments. In that sense, living things have gotten “better.” But any notion of improvement is subject to human-centered bias. Here’s a selection from the 1923 poem “Progress” by renowned evolutionary biologist Julian Huxley (son of “Darwin’s bulldog,” Thomas Huxley, and brother of Aldous):
The Crab to Cancer junior gave advice:
“Know what you want my son, and then proceed
Directly sideways. God has thus decreed—
Progress is lateral; let that suffice.”
Darwinian Tapeworms on the other hand
Agree that Progress is a loss of brain, …
Living things have been honed by evolution to do an excellent—or at least, an adequate—job of living their lives and reproducing; accordingly, no species has “progressed” further than any other. We evolved big brains. A sign of progress? Well, bats have evolved sonar and flight, sharks have “progressed” beyond us in swimming and electroception, dogs in olfactory acuity and hearing, and so on.
It is also tempting but misleading to think that free-living organisms—especially vertebrates such as ourselves—have progressed beyond those sneaky, regrettable, and “less competent” parasites. And yet, there are substantially more of the latter than the former. How do we know this? Because inside every vertebrate there cavorts a multitude of parasites, from macroscopic worms to an array of microscopic beasts. Necropsies have found that most every animal is host to, well, a host of parasites. So, if abundance is a sign of progress, maybe parasitism is the winner! Or maybe we shouldn’t think in terms of evolutionary “progress” at all.
10. Evolutionary biology isn’t a science because it’s a historical phenomenon and can’t be tested
Biologists make all sorts of predictions based on evolutionary theory, and often they are fulfilled. Notably, differential reproduction (whether observed in nature or a laboratory) nearly always causes a shift in a population whereby some traits are subsequently represented in greater frequency. Evolutionary change is predicted and observed in laboratory populations whenever the reproductive rate of a study species is fast enough, whereupon change can be observed in years, months, weeks, even—in the case of microbes—days. Field studies have also documented a dizzying array of evolutionary changes deriving from natural selection.
Many sciences, notably astronomy and geology, engage uniquely with historical phenomena (we can’t experimentally manipulate stars or continents), and yet they generate impressive empirical testing, often based on detailed observational regimes along with falsifiable predictions. And there is no question of their status as bona fide sciences. Evolutionary biology is no different. 
Lead image: Uncle Leo / Shutterstock
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