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Some thoughts on evolution

No, this is not an Evolution Versus Creationism Death Match. Really, there's only so many times one can watch Godzilla squash Bambi before it ceases to be amusing any more.

Rather, this is a post intended to clear up some popular misconceptions about how evolution works. I've been meaning to write it for a long time, and some comments made at a Dragon*Con panel reminded me that I still haven't ranted about this in my journal. So, it's high time to get my rant on!

There are two popular notions about evolutionary processes that I hear all the time, often from folks who ought to know better, and they tend to get under my skin. The first is that evolution is no longer operating on human beings; the second is that evolution is goal-directed, that it makes a species "better." Ready? Here we go!

Evolution still operates on people, just as it always has

"Evolution is about survival of the fittest," people say. "Today, thanks to the miracles of modern technology, people who would have died a hundred or a thousand or ten thousand years ago can be kept alive. They don't die off, so their genes still spread. So that means we've stopped evolving."

Fine, except that it's wrong. Evolution isn't about survival of the fittest. That wasn't Charles Darwin's phrase; it was coined by Herbert Spencer, and was included in On the Origin of Species only at the fifth reprint, as it had become popular by that time.

But evolution is not, and never has been, abut "survival of the fittest." That's an overly simplistic and inaccurate view of how evolutionary processes work. Evolution is about the propagation of those genes which most enable an organism to...propagate its genes. What's good for the gene is often, but not necessarily, what's good for the organism; a gene that shortened its host's life by fifteen years but increased the probability that its host would reproduce by .01% would do quite well in the evolutionary game.

(As a segue, I've frequently heard an argument against transhumanism in general and life extension in particular that says "Mortality and a finite life expectancy must be good for us. If they were not good for us, then we would not have evolved to have a finite life span. So the fact that we have evolved in such a way means that there is some benefit to being mortal." This argument does not hold water, because the bulk of our evolutionary heritage comes from a time when most members of the species would die through accident, disease, or predation far, far before they would die of old age. A gene that conferred immortality offers no reproductive benefit to a species whose members are killed by leopards, diseases, tumbles off a cliff, or each other before they're thirty. Ergo, such a gene would not be selected in favor of. We have genes that confer mortality because there's no advantage to genetic immortality.)

Evolution is not about survival of the fittest. It's about the genes that spread. Evolution needs only three things to operate, namely:

1. A population whose individuals are different from one another;
2. A system whereby those differences are heritable; and
3. A system whereby those differences make a difference in how likely an individual is to reproduce.

That's it. That' all it needs. And yes, you have those things in humanity. We are not all the same; the differences between us can be transmitted to our children, and sometimes, those differences make a difference in how likely we are to have children, or how many children we have.

Contrary to the crude understanding of evolutionary processes so common in pop culture, it is not necessary for individuals who have a particular trait to die for that trait to be selected against. If a particular gene--a gene making its bearer more likely to have asthma, say--decreases the odds that a person will reproduce by 0.01%, that's enough. If even one person out of ten thousand has one fewer child because of a particular gene, then evolution is still working.

Modern medicine keeps many people alive today who would die in a pre-industrial society. That does not mean that people with detrimental genes have exactly the same number of children at exactly the same rate as people without that gene. As long as a particular gene has any impact on the number of children its hosts have, however slight, evolution still works.

Evolution is not goal-directed

Evolution does not make a species "better" for any value of "better" that people often use. Evolution favors genes that make its hosts more likely to reproduce. That's it. A gene that causes you to die of a horrifying, debilitating cancer after you hit menopause isn't going to be selected against.

Furthermore, evolution is completely blind with regards to "better" and "worse" as human values. At the panel, one person used Down's syndrome as an example of how evolution no longer applies to human beings. If people with Down's, he reasoned, have children, then how can evolution make the human species better?

This question falls down on a number of levels, and shows a lack of understanding of what evolution is. Down's syndrome is not generally heritable; it's caused by a particular genetic malfunction that does not, usually, affect the gametes.

But leaving that aside for the moment, let's assume that it is heritable. What does that mean? If people with Down's syndrome had more children than people without it, then from an evolutionary perspective, Down's syndrome would be "better." From an evolutionary standpoint, there is one and only one definition of the word "better," and that is "more likely to reproduce."

I mean, if you think about it, I am a worst-case scenario. I have not had children at all, and I have even opted for voluntary sterilization, so I never will have any children. My particular collection of genes is a dead end. I am, evolutionarily speaking, the poorest possible outcome. From the perspective of the processes we're talking about, a person who has Down's syndrome and has children is better than I am.

It frustrates me that American culture is so divided and American politics is so wrapped up in the idea of evolution, yet very few people even understand what "evolution" is. They feel passionately about it, but they're incapable of articulating the most basic principles of evolutionary biology.

Rant off.

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Comments

( 49 comments — Leave a comment )
joreth
Sep. 4th, 2007 09:26 pm (UTC)
Unfortunately, I get into that same argument all the time. I feel your pain. My favorite is the idea that humans, because we use tools, are somehow "cheating" and are outside the spectrum of nature because they don't understand that our brains that came up with the idea to use the tool is as much of an evolutionary survival trait as the claws and fangs of the other animals. I have also referenced your blue-green algae post in the anti-human movement that is related, that we are somehow exempt from or outside of the laws of "nature".
red_girl_42
Sep. 4th, 2007 09:54 pm (UTC)
This is wonderful--thank you! I may have to add this to my memories as it touches on a couple of my own pet peeves about people's "understanding" of evolution.

Another couple of pet peeves of mine:

1. People assuming that if you say that something is an evolved trait, you must also be claiming it's a morally defensible trait. An example of this is when some scientists suggested that rape is an evolved behavior that has allowed men with little access to willing women to propagate their genes anyway. There was a huge feminist uproar about this--not attacking the actual science behind the suggestion, but attacking the idea that anyone would even dare voice this hypothesis. Evolution isn't morally based. Sometimes we evolve in ways that are politically incorrect. I don't think it's really fair that men are on average bigger and stronger than women, but I shouldn't attack scientists who study this and find it to be true. When a scientist tells us what *is,* they aren't telling us what *should* be. Nor are they telling us that we have no choice in the matter. Our genetic makeup isn't the only factor that governs our behavior.

2. Similarly, and also something you touched on...I hate when people assume that an evolved trait is necessarily the ideal one. For instance, people promoting that "hunter-gatherer diet" claim that because we evolved in hunter-gatherer societies, a diet similar to that of our ancestors must be the healthiest one we can eat now. But just because our bodies adapted to survive and reproduce in certain limited conditions, that doesn't mean other conditions can't be even better. It's not like our ancestors had the opportunity to try. Certainly, some products of agriculture/industrialization *are* unhealthy for us, but others (such as access to dairy products, so that pregnant mothers don't wind up losing teeth with every child) are most definitely a good thing. The mother who loses all her teeth in childbearing (because the human body is designed to feed the fetus first, the mother last) is just as much of a reproductive success as today's toothy mom. But I'll take my cow's milk and pearly whites over a gummy stone-age grin anyday.
boigrrrlwonder
Sep. 5th, 2007 12:36 am (UTC)
1. People assuming that if you say that something is an evolved trait, you must also be claiming it's a morally defensible trait. An example of this is when some scientists suggested that rape is an evolved behavior that has allowed men with little access to willing women to propagate their genes anyway. There was a huge feminist uproar about this--not attacking the actual science behind the suggestion, but attacking the idea that anyone would even dare voice this hypothesis. Evolution isn't morally based. Sometimes we evolve in ways that are politically incorrect. I don't think it's really fair that men are on average bigger and stronger than women, but I shouldn't attack scientists who study this and find it to be true. When a scientist tells us what *is,* they aren't telling us what *should* be. Nor are they telling us that we have no choice in the matter. Our genetic makeup isn't the only factor that governs our behavior.

In a society when one of the dominant discourses is "natural = acceptable" (think about how much investment has gone into finding a gay gene and the argument that gay people are born gay as a means to justify gay rights), what good can come from a study that argues that rape is an evolved behavior? Furthermore, a lot of evolutionary biology, when studying humans, often reflects the sexism of our society (for example, how common it is to assert that women want monogamy while men want nonmonogamy in evolutionary biology).
(no subject) - catwoman980 - Sep. 5th, 2007 03:41 am (UTC) - Expand
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6_bleen_7
Sep. 4th, 2007 10:02 pm (UTC)
Very nice rant! A couple of comments:

People who claim we've stopped evolving because we've cured most major causes of death are more than wrong; they're ironically wrong. If genes predisposing to nearsightedness, say, proliferate and become common because myopia no longer confers a selective disadvantage—that's evolution! Moreover, infant and childhood mortality, while greatly reduced, is far from abolished even in industrial nations, and there, natural selection still has room to act—and, as you mention, anything that prevents reproduction is as bad as death, from an evolutionary perspective. Studies of population biology indicate that that very small differences in fitness—undetectably minuscule differences—can drive big changes over the long haul. Hence, we still have plenty of opportunity to evolve, despite our greatly extended lifespan.

It is fun to try to identify evolutionary forces in modern Western society. Teenage depression? Drunk driving? Inability to cope with noise pollution? A big problem in doing so is that our environment—which by now is largely a product of our own society—keeps changing so quickly. And, needless to say, the change is accelerating.

One can also argue that in the context of overpopulation, "voluntary" sterility (i.e., sterility when fertility is physiologically possible) confers a selective advantage, albeit a very indirect one, in that it can prevent a population from destroying itself through overconsumption. Definitely there are animal species whose fecundity diminishes after reaching a certain population density.

Actually, in your list of three requirements for evolutionary change, natural selection is not strictly required. If a population is very small, random chance will do the trick (i.e., genetic drift). Drift, however, is not likely to spur large changes in modern human populations, as mobile as most of us are.

Some very intriguing recent work has been done looking at genes that have undergone recent positive selection in humans. Many, like the lactase gene in Northern Europeans, have probably been favored by the advent of agriculture some twelve millenia past.
(Deleted comment)
tacit
Sep. 5th, 2007 03:22 pm (UTC)
Re: Fitness
Fair enough. The word "fitness" in a narrow biological sense is appropriate.

There's a common problem in science, that goes beyond evolutionary science, which is that scientists often use words in very specific ways that don't mean the same thing as the vernacular. You see this among some of the weird, New-Age "woo woo" interpretations of quantum mechanics, which are almost always predicated on the mistaken idea that our minds can affect the physical world at the quantum level. These silly notions almost always come from the fact that people hear the physicist talking about an "observer," and believe that the word "observer" means "person looking at something," when to a quantum physicist the word "observer" means "anything whose state depends in a thermodynamically irreversible way on the state of the thing with which it interacts."

So, yes, "survival of the fittest" is meaningful in the biological sense of the word "fittest," but not in the common vernacular sense of the word "fittest."
pstscrpt
Sep. 5th, 2007 03:48 am (UTC)
Evolution favors genes that make its hosts more likely to reproduce. That's it.
Well, not quite. It favors genes that make its hosts likely to reproduce, its offspring likely to survive long enough to reproduce, and maybe a couple more generation that it can have a direct effect (depending on the species).

Women hit menopause because they help their descendants survival better by helping out as grandmothers than by continuing to attempt reproduction themselves. Men don't because reproduction doesn't much affect their usefulness to later generations.
tacit
Sep. 5th, 2007 03:23 pm (UTC)
Okay, fair enough. Evolution favrs genes that make its host more likely to reproduce successfully; in social animals, successful reproduction may depend on more factors than just popping out the pups. :)
peristaltor
Sep. 5th, 2007 04:21 am (UTC)
Nice rant. By any chance, have you read Philip K. Dick's The Golden Man? Dick understood evolution. Because of that story, more than any other, he says, he got lots of bitchy letters from folks who didn't.
tacit
Sep. 5th, 2007 03:28 pm (UTC)
I haven't! I'll have to look for it now.

In, y'know, my copious free time. Heh, heh.
(no subject) - peristaltor - Sep. 5th, 2007 08:06 pm (UTC) - Expand
mr_z
Sep. 5th, 2007 04:58 am (UTC)
One interesting argument I've heard is, roughly, "Evolution would never have favored something as smart as man, or advances that cause us to live as long as we do, because evolution only favors traits that get you to reproductive age and help you reproduce."

Erm...

Stable society, lots of food stores, lots of infrastructure, medicine, etc.... That all favors lowered infant mortality. And let's face it: Generational continuity helps.

Smart communities are more successful and thus have more successful offspring. The "excess" capacity of the human mind enabled it to adapt its environment to suit its needs as much or more than the human needed to adapt to the environment.

This argument was particularly interesting to me, because it came from my highly educated Uncle, who was a Master's in psychology. I still wonder where that disconnect is. I couldn't write his argument off as ill informed, but I still don't think it's sound. (His argument specifically was that the human brain could not be the result of evolution, because it was too well organized, and far beyond what evolution might favor in any sort of incremental approach.)
mr_z
Sep. 5th, 2007 05:03 am (UTC)
...amending the argument I was rebutting....

He argued that the additional mental capacity that allows seemingly endless human innovation was such a departure from what had come before, and mostly favorable to people after they had had offspring such that it could not possibly be a successful or meaningful selection criterion.

Therefore it had to come from "somewhere else." (aka God.)

I'm pretty much the only agnostic / atheist in my family, so.... I just let that lay where it fell...

(I call myself agnostic for my family's sake, but the longer the go, the more atheist I feel.)
(no subject) - tacit - Sep. 5th, 2007 03:32 pm (UTC) - Expand
(no subject) - mr_z - Sep. 5th, 2007 03:53 pm (UTC) - Expand
(no subject) - tacit - Sep. 5th, 2007 04:00 pm (UTC) - Expand
ktar
Sep. 5th, 2007 08:02 am (UTC)
While Darwin didn't use the phrase "survival of the fittest," the term is used worldwide in any center of learning with a biology department. It's used for a a very good reason too.

"Survival of the fittest" absolutely describes how evolution works. It does, perfectly.

However, it has nothing to do with physical fitness, or mental acuity, or being all badass and scary. It means how well an organism "fits" into a specific environment.

As an example, lets say we have two types of hares, black hares and white hares. They are genetically identical except for a single (or several if you wish) gene(s) that do nothing except determine the colour of the hares. Now lets say they're living in the Tundra.

Usually, the white hare "fits" better, because his white fur will blend in and give him more camouflage than the easily seen black hare.

THAT is what "survival of the fittest" means. It's not that the term doesn't apply, it's that people misuse it, and it's depressing.

If you think that people misunderstanding evolution is annoying, trade me places. Every university course I take that even begins to mention evolution, Darwin, or even biology in general spends at minimum 1/2 a lecture explaining what evolution actually is, and how not to misunse the term "survival of the fittest."
indywind
Sep. 5th, 2007 01:51 pm (UTC)
Tacit, have you read David Brin's article "Neoteny and two-way sexual selection in human evolution"? I think you'd find it fascinating.

Online here.
tacit
Sep. 5th, 2007 03:53 pm (UTC)
Interesting article. I think it has a couple of flaws, the most major of which is a focus on pair-bonding as "the" evolutionary strategy of human reproduction; most evolutionary biologists who study human breeding strategies think it's more complex than that.

A human female has an evolutionary advantage in choosing mates who will stick around and help raise the young, for reasons which the article goes into at length. But there is also an evolutionary advantage in fathering multiple children with multiple fathers. Multiple fathers means a wider assortment of genes in the offspring. Since a woman always knows that any child she has is genetically hers, it pays to have as wide a genetic assortment of fathers as possible, because if she puts all her genetic eggs in one basket--fathering all her children with one father--then her young may all be vulnerable to, for example, a particular disease or parasite to which the father happens to be particularly vulnerable.

There is no one singe "best mate." A mate who is physically strong, who cares for the children, and who is otherwise genetically desirable but who contains a genetic weakness that is lurking beneath the surface may doom all of a woman's offspring. Women who were strictly monogamous faced a tiny, but nevertheless still present, genetic risk; women who fathered children with many males could, to a tiny degree, offset that risk.

So in other words, there is an evolutionary advantage to be pair-bonded in a long-term relationship with a mate, but to cheat on that mate with other males! Women who do this have a greater chance of having at least one of their children survive a calamity to which their long-term mate has some particular genetic susceptibility, such as disease.
(no subject) - indywind - Sep. 6th, 2007 01:13 pm (UTC) - Expand
much_ado
Sep. 5th, 2007 02:41 pm (UTC)
redhotlips suggested you might find this article from yesterday's Toronto Globe & Mail an interesting dovetail about the purposeful evolution of monogamy as a direct correlative (and, according to the article's author, totally necessary) foundational link to democracy.

the whole article had me so infuriated i threw things, and i'm still angry about it this morning. i'd be interested to hear your take on it.
tacit
Sep. 5th, 2007 03:34 pm (UTC)
That's the kind of article that could only come from a politician with an axe to grind, not a scientist. Given that its author is a professor of politics and not an evolutionary biologist, its conclusions are about what I'd expect. This is clearly a man who has never actually attended so much as a freshman-level class in evolutionary biology.

I briefly thought about writing a point-by-point rebuttal, but what's the point?
sarahmichigan
Sep. 5th, 2007 02:58 pm (UTC)
I just finished reading "Origin" not too long ago, so this was a good refresher, though I knew these things already.

Humans ARE still evolving. I think the so-called "obesity epidemic" is overblown BS, but it is true that the average 10-year-old-boy and the average teenage girl today are about 10 pounds heavier than the same boy or teenage girl in the 1950s. They're also about 1 inch taller today.
tacit
Sep. 5th, 2007 03:57 pm (UTC)
It's hard to say whether that's a genetic evolutionary adaptation or an environmental issue, though. Most of the studies I've read attribute the increase in height among modern humans to better nutrition rather than genetics; our ancestors had the genes which would let them reach our height, but lacked the nutrition to get them there.
(no subject) - nornagest - Sep. 6th, 2007 09:32 am (UTC) - Expand
(no subject) - indywind - Sep. 6th, 2007 01:38 pm (UTC) - Expand
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(no subject) - pstscrpt - Sep. 10th, 2007 03:20 pm (UTC) - Expand
(Deleted comment)
indywind
Sep. 6th, 2007 02:04 pm (UTC)
Here's one general-audience article. Are we still evolving?

You'll likely want to do your own research on the points that are relevant to you.
(Anonymous)
Sep. 6th, 2007 08:35 pm (UTC)
Why evolution is a Mythology
Many people, when they can't provide evidence for their theory, adopt the strategy of falsehood. Such is the case with many of those who have fallen victim to the propaganda of renowned evolutionists.

If evolutionists want to end the arguments all they have to do is, get their brilliant heads together and assemble a 'simple' living cell. This should be possible, since they certainly have a very great amount of knowledge about what is inside the 'simple' cell.

After all, shouldn't all the combined Intelligence of all the worlds scientist be able the do what chance encounters with random chemicals, without a set of instructions, accomplished about 4 billion years ago,according to the evolutionists, having no intelligence at all available to help them along in their quest to become a living entity. Surely then the evolutionists scientists today should be able to make us a 'simple' cell.

If it weren't so pitiful it would be humorous, that intelligent people have swallowed the evolution mythology.

Beyond doubt, the main reason people believe in evolution is that sources they admire, say it is so. It would pay for these people to do a thorough examination of all the evidence CONTRARY to evolution that is readily available: Try answersingenesis.org. The evolutionists should honestly examine the SUPPOSED evidence 'FOR' evolution for THEMSELVES.

Build us a cell, from scratch, with the required raw material, that is with NO cell material, just the 'raw' stuff, and the argument is over. But if the scientists are unsuccessful, perhaps they should try Mother Earth's recipe, you know, the one they claim worked the first time about 4 billion years ago, so they say. All they need to do is to gather all the chemicals that we know are essential for life, pour them into a large clay pot and stir vigorously for a few billion years, and Walla, LIFE!

Oh, you don't believe the 'original' Mother Earth recipe will work? You are NOT alone, Neither do I, and MILLIONS of others!

PS: Please don't lie about the 'first life' problem, scientists are falling all over themselves to make a living cell. Many have admitted publicly that it is a monumental problem. And is many years away from happening, if ever. Logical people understand this problem and have rightly concluded that an Intelligent Designer was absolutely necessary. Think of it this way, if all the brilliant scientists on earth can't do it, how on earth can anyone believe that it happened by accident?????
tacit
Sep. 6th, 2007 09:44 pm (UTC)
Re: Why evolution is a Mythology
If evolutionists want to end the arguments all they have to do is, get their brilliant heads together and assemble a 'simple' living cell.

Already being done.

http://www.theglobeandmail.com/servlet/story/RTGAM.20051219.wxlife19/BNStory/specialScienceandHealth/

http://news.bbc.co.uk/2/hi/science/nature/6733797.stm

http://www.cbc.ca/technology/story/2007/08/20/tech-life.html

That's not relevant, though. We do not have to be able to 'invent' gravity to know that it exists, nor be able to create a star from scratch to know how starts form, develop, and die.

By the way, it's "voila," not "walla."
Re: Why evolution is a Mythology - james_the_evil1 - Sep. 9th, 2007 12:09 am (UTC) - Expand
Re: Why evolution is a Mythology - peristaltor - Sep. 26th, 2007 02:48 am (UTC) - Expand
Re: Why evolution is a Mythology - tacit - Sep. 26th, 2007 02:07 pm (UTC) - Expand
Re: Why evolution is a Mythology - peristaltor - Sep. 27th, 2007 08:10 pm (UTC) - Expand
Re: Why evolution is a Mythology - tacit - Sep. 27th, 2007 08:18 pm (UTC) - Expand
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