Not really. That's a theory and it is one that is hard to disprove experimentally. It is a much stronger theory than evolution, saying that every action is correctly designed to optimise gene transmission. Essentially it is trying to say that we are at a global maximum in a space that is probably more nonlinear. In fact our genes may well be suboptimal in some respects even if you think they have "control". The contortions people go through to try to justify homosexuality as a genetic thing are one example of many. In fact diversity is an advantage in a varying environment so many traits must be suboptimal.

>Not really. That's a theory and it is one that is hard to disprove experimentally. It is a much stronger theory than evolution

This isn't right at all. The idea that our behaviors are shaped in ways that increase our fitness follows necessarily from the theory of evolution. If we believe that behaviors are influenced at all by our genes, then behaviors that are detrimental get weeded out. What's left over was more fit for that environment. There is mountains of evidence that our behavior is affected by our genes.

That is not to say that all behaviors are optimal at all times. For one, our environment has changed monumentally in just the last few hundred years. Behaviors that were optimal back then may not be now. Also, there are multiple levels when considering optimal behavior. Behavior that is suboptimal for the individual can still be optimal for the gene causing that behavior. Homosexuality for example. It may be true that the homosexuality gene is optimally propagated when its in 10% of the population (look up evolutionary stable strategy).

I recently read about a study that claimed the male homosexuality gene when in a woman greatly increased her sexual attractiveness and sexual aggressiveness. When it's in a man it makes him homosexual. I'm sure its too early to take this as fact, but this scenario would lead to a non-zero optimal distribution of that gene in the population.

> The idea that our behaviors are shaped in ways that increase our fitness follows necessarily from the theory of evolution.

This is a misreading of evolution. To start with, we are not optimal. Not even locally optimal. No species is. Who is the optimal human? Is that person alive today?

Second, you haven't considered timescale. You say "get weeded out". How long does that process take? Suppose all behaviors are directly influenced by genes. A low-impact detrimental behavior - let's say a tendency to pick one's nose in public - faces essentially no evolutionary pressure, and so will persist effectively forever. Rather, it would be long enough as to make it nearly impossible to tell if that behavior is a beneficial or detrimental one.

How can you tell that the behavior you are examining increases fitness or decreases fitness but happens to be in the same genome as something else which greatly increases fitness?

Suppose that a subpopulation of humans acquires the 'hunk/babe' mutation and also acquires the nose picking mutation. The first gives an strong genetic advantage, and the second a very minor disadvantage. Over 1,000 years, this subpopulation dominates the overall human genetic makeup. Some researchers then point to the increase in nose picking in the general population and conjecture that nose picking must have conferred some genetic advantage. But this is wrong. Nose picking came along for the ride.

(For purposes of that thought experiment, assume also that the environment is unchanged during that time.)

Third, the coupling between behavior and genes can be extremely tenuous. 300 years ago you could look at European populations and conclude that they were genetically predisposed towards monarchy. Some believed that this was the natural order of things. Where's the gene for democracy? 1000 years ago you could conclude that there was a genetic predisposition towards Catholicism. What genetics caused people to chose that over, say, Zoroastrianism?

Did you skip my second paragraph? I completely agree with your point that observing a behavior now does not imply that it is optimal.

Of course I don't believe there is a "Monarchy" gene any more than I believe there is a juggling gene. These behaviors are too complex to be determined by any given gene. But probabilities and predispositions come into play. Genes that influence behaviors that create predispositions for certain complex behaviors in certain environments will still have selective pressure exerted on that 'ultimate cause' gene.

I object to the statement "our behaviors are shaped in ways that increase our fitness follows necessarily from the theory of evolution."

That is a individual-centered view of evolution. But evolution works on genes, not individuals. Had you said "our behaviors are shaped in ways that increase the fitness of our genes" then I would have agreed.

In your second paragraph, you said "Also, there are multiple levels when considering optimal behavior."

I disagree. There is only one level - that of the genes. If you're a Tasmanian devil and part of you mutates to produce the cancer which is devil facial tumor disease, and that cancer spreads to all of the other Tasmanian devils, and kills off the species, then evolution doesn't care. That set of genes managed to transcend the individual and survive without it. (Which is a good thing since it kills its host.)

Elsewhere in this thread I gave a model where two independent mutations occur at effectively the same time in the same person. One is a big advantage, the other a minor disadvantage. Both together still convey a big evolutionary advantage. This means that the minor disadvantage is very likely to spread into the entire population, because it's part of the same genome as the big advantage.

We see this all the time. As a trivial example, about 8% of our genome is made up of endogenous retroviruses. These are viruses which incorporated themselves into our DNA, and then a host mutation killed them off. They are no longer do anything for us. But our body spends a slight amount of energy transcribing them. No advantage plus slight disadvantage => net negative. Still, the evolutionary pressure to remove those bits of dead retroviruses is so weak that they have persisted for millions of years. We share some of that DNA with chimpanzees, for example.

There was likely never a time when those genes gave any advantage to an individual or even were net neutral, which is why I object to the statement "behaviors that are detrimental get weeded out."

Your statement assumes an infinite amount of time in a stable background - but species live for only a few million years (on average) and the background is always changing, so your statement isn't useful.

Yes yes, I read the selfish gene too. I don't mean that as a slight, as most of my significant understanding of evolution comes from that book. Yes, ultimately its about genes attempting to propagate themselves. But completely ignoring higher "levels" of selection is overly reductionist. It's like saying consciousness is simply chemical reactions firing in the brain. While technically true, this analysis is not at the correct level of abstraction for maximum understanding (also the same reason why we don't program in assembly).

Genes create behaviors in their host organisms. This is a large class of affects that genes have that ultimately exert selective pressures. This is the correct level of abstraction to understand this mechanism. Similarly for analyzing unfit behaviors for an individual that are ultimately fit for the group as a whole, thus the behavior is not completely weeded out.

I haven't read "The Selfish Gene" though I know of Dawkins' views. My original basis for understanding evolutionary thought comes from Gould, and you can see that influence here in my opposition to the view that behaviors have a direct genetic basis. Wikipedia summarizes his (and my) viewpoint nicely:

Gould's primary criticism held that human sociobiological explanations lacked evidential support, and argued that adaptive behaviors are frequently assumed to be genetic for no other reason than their supposed universality, or their adaptive nature. Gould emphasized that adaptive behaviors can be passed on through culture as well, and either hypothesis is equally plausible. Gould did not deny the relevance of biology to human nature, but reframed the debate as "biological potentiality vs. biological determinism". Gould stated that the human brain allows for a wide range of behaviors. Its flexibility "permits us to be aggressive or peaceful, dominant or submissive, spiteful or generous… Violence, sexism, and general nastiness are biological since they represent one subset of a possible range of behaviors. But peacefulness, equality, and kindness are just as biological—and we may see their influence increase if we can create social structures that permit them to flourish."

My resolution to the issue is to take the strict view that biological evolution only deals with genes, and that other mechanisms can be and are better at describing what you've termed the "higher levels" of selection.

The usual analogy is to computers, where software is constrained by the hardware, but still highly flexible. My own analogy is to think of weather. Fundamentally it's based on quantum mechanics, and at a higher level as particle dynamics, but weather forecast models use neither approach because because the minutia of those lower levels -- the detailed collision dynamics of a specific O2 against an N2 for example -- don't appreciably affect the large-scale weather. In fact, non-quantum mechanics can give rise to similar effects. There is no need to consider the effect of the weak force in order to predict tomorrow's weather.

Instead, weather is much more tractably understood as the gas law, along with parameters for "turbulent diffusion, radiation, moist processes (clouds and precipitation), heat exchange, soil, vegetation, surface water, the kinematic effects of terrain, and convection." It's absolutely true that weather is based in quantum mechanics, but it's not true that a quantum mechanics approach is the best way to understand the weather.

And I assert that that is the same for higher level behaviors, including even culture. Yes, there's an ultimate genetic basis somewhere in the depths, but a natural selection model based on genes is a poor instrument for understanding most human behaviors, and the attempts to do so have all had a sense of post hoc justification rather than having good experimental evidence.

Eg, just because certain dynamics models give rise to, say, homosexuality in a population, doesn't mean that those models reflect the actual process which gave rise to homosexuality in humans. It only means that gene-based evolution does not preclude an evolutionary model for homosexuality.

In any case, I gave a specific example of how an unfit behavior can spread to the entire population. It arises through a mutation, and that mutation happens to be in the same genome as another recent mutation which greatly improves fitness. This unfit behavior is both unfit for the individual and unfit for the group, but the negative consequences are so minor that there's little evolutionary pressure to weed it out.

I even gave the specific example of the endogenous retroviruses, which compose some 8% of our genome, which take some energy to maintain, and some of which are believe to have been inserted during a plague some 60 million years ago, though some are more recent. I find it hard to believe that any of those genes were ever beneficial to an individual or to the group, and yet after millions of years they still have not been fully weeded out.

(I do realize that these remaining sequences do not cause overt behavior. About all they do is take up time and energy during cell duplication. But that's still a behavior, and you have not placed a limit as to what evolution considers as a behavior or not.)

Thanks for your detailed response. I originally misunderstood your point, I thought you were essentially arguing a reductionist view of considering genes and only genes. I agree with much of what you have written, although I personally would fall more on the biological determinism side, where our genes constrain our behavior far more than people generally accept. But that's just my personal view and its certainly up for debate.

My personal view is that the belief in biological determinism is too widespread. Up until the mid-1800s, nurses were often men. Nightingale's views played a big role in making nursing a female dominated field, partially justified by saying that women are naturally nurturers. It's all too easy for people to argue that sex-based, race-based, etc. roles have a biological basis, when it's actually cultural determinism. And we know this because things have changed in timescales that aren't possible under a genetic basis. But it's easier to assume things are because they are than it is to change one self and the views of others.

In any case, I think this thread is nearing the end. I thank you for your participation and consideration.

And my thanks to everyone who chimed in. I found it an insightful discussion. A great example of the reason to keep reading the comments on Hacker News.

> this analysis is not at the correct level of abstraction for maximum understanding

That, by the way, is exactly the reasoning I used when dismissing the claim that "women have affairs to increase the genetic diversity of the sperm that compete for her egg". There are various different depths of causality and levels of abstraction at which one could view women having affairs. That particular level is one which provides almost no explanatory benefit.

(Unrelated point below.)

In addition, it may also be wrong. At previous points in time scientists have claimed that there was an "obvious" evolutionary reason why women DIDN'T have affairs. The argument, as I have heard it, states that in primates the male of the species gets the most genetic diversity by having as many children as possible with as many females as possible. But since the female is limited by biology to a fairly small number offspring, she is better served (evolutionarily) by remaining loyal to a single male in order to increase the degree to which he will help provide for her offspring and thus increase their survival rate. (Remember: it's not the number of offspring, it's the number of offspring times their survival rate that counts.)

Of course, this theory was in vogue at a time when lots of people (erroneously) believed that men had affairs but women didn't. MY conclusion is that it's extremely easy to fool ourselves with evolutionary-sounding excuses for social and cultural behavior and that one should approach any such explanation with extreme skepticism.

> This is a misreading of evolution. To start with, we are not optimal. Not even locally optimal. No species is. Who is the optimal human? Is that person alive today?

Optimal refers to having the highest probability of surviving and reproducing in the given environment. Since humans dominate the earth, we are more optimal than any other species of animal.

From a genetics standpoint, the most "optimal" human would bear as many children as possible while still maintaining the earth as a hospitable environment, and minimize all potential risk factors that could harm his or her children. So yes, there is a theoretical maximum for evolution that we haven't reached, but we will likely never reach it.

> Second, you haven't considered timescale. You say "get weeded out". How long does that process take?...How can you tell that the behavior you are examining increases fitness or decreases fitness but happens to be in the same genome as something else which greatly increases fitness...Some researchers then point to the increase in nose picking in the general population and conjecture that nose picking must have conferred some genetic advantage. But this is wrong. Nose picking came along for the ride.

Meiosis randomly splits chromosomes via crossing over, then pulls out one half of the chromosomes (23) to later pair with the 23 chromosomes from the other zygote (sperm or egg cell). After enough iterations this process can isolate genes that increase or decrease fitness.

> Third, the coupling between behavior and genes can be extremely tenuous. 300 years ago you could look at European populations and conclude that they were genetically predisposed towards monarchy. Some believed that this was the natural order of things. Where's the gene for democracy? 1000 years ago you could conclude that there was a genetic predisposition towards Catholicism. What genetics caused people to chose that over, say, Zoroastrianism?

Culture certainly affects behavior, yet humans have sex and produce kids in every culture. When it comes to survival and reproduction, genetics preempts culture when it comes to individual behavior. Democracy isn't an individual behavior, it's a cultural idea. People typically live under whatever government they're born into. Same with religion.

It seems logical that women could be genetically predisposed to desire multiple partners in order to increase the variety of genes and thus enhance the fitness value of their offspring. However, I do not know how you could prove or disprove this idea.

> Since humans dominate the earth, we are more optimal than any other species of animal.

LOL! You are amazingly self-centered. Yes, humans are the most numerous mammal, with rats second. There's 50 billion chickens. By your definition, chickens are more optimal than humans. The nematode populations are measured in up to millions per square meter. With an estimated 1 million species of nematodes, the average nematode species population is comfortably higher than that of humans. There's an estimated one to ten quadrillion ants in the world across 22,000 species, so about 500 billion ants per species, on average. Again, higher than the number of humans.

There are about 1 million wheat plants per acre and 60 million acres planted gives a wheat plant population of over 1 trillion. (It hard to find numbers for non-commercial plant populations.)

But wait! Why look at multicelled animals? Bacteroides fragilis, Bacteroides melaninogenicus, Bacteroides oralis, Enterococcus faecalis, and Escherichia coli are found in basically every person's gut, so there's definitely way more of each of those species than humans. To say nothing of those species populations elsewhere. It's really hard to find estimates of the total number of a single bacteria species.

Would you care to revisit your statement that humans "are more optimal than any other species of animal"? At the very least you should acknowledge that chickens are more optimal than humans.

> the most "optimal" human would bear as many children as possible while ...

You wrote "his or her children" but you meant to write "descendants." In any case, you are viewing things on the wrong level. Evolution works on genes, not individuals. Humans, like other primates, are social beings. It is part of our evolutionary strategy to help others of our species, especially those we recognize as family. You'll easily notice that other mammals don't all follow the strategy you say is the evolutionary mandate. The naked mole rat is a favorite example; only the queen and one to three males reproduce, while the rest are sterile workers. Why do those workers work if they don't have children?

Some animals eat their own young, or preferentially feed the strongest (hence how cuckoos get others to raise their young) and leave the weak to die if there isn't enough food. These are obvious counter-examples to your assertion that parents "minimize all potential risk factors that could harm his or her children."

In addition, why did you choose a definition of "optimal" based on population count instead of, say, species longevity? Surely the Queensland lungfish, where fossils identical looking to the modern form exist from 100 million years ago, has a stronger claim to being optimal than H. sapiens' scant 500,000 years.

> After enough iterations this process can isolate genes that increase or decrease fitness.

Obviously. My point was regarding the length of time it takes. If "enough iterations" for humans is 50,000 then 1.5 millions years is longer than H. sapiens has been around. Now factor in that most mutations are either neutral or negative, and you end up with a lot of slightly detrimental mutations which last for a very long time. How then do you tell that an observed behavior, with no obvious, direct benefit (like nose picking) is evolutionarily beneficial or detrimental but following along on the coat tails of a more beneficial mutation?

My definition of optimal was in terms of control over the environment. We could kill all 50 billion chickens if we wanted to.

If we want to redefine optimal to mean quantity of genes in the environment, then humans don't come out on top right now, but we could if we wanted to; I am sure that if we desired we could set up a lab to replicate more of our genetical material than any other species has in the environment.

Also, by this definition the most optimal human would theoretically attempt to turn all of the matter in the universe into copies of his/her genes.

A gene for a behavior that affects the number of sexual partners an animal has would likely have been selected for or against long before H sapiens evolved, thus enough iterations have occurred to weed out polygamy in mammals if it was a detrimental behavior. As for your ride-along-nose-picking thesis, I suppose it could be true. Nose picking only recently became a detrimental behavior in terms of evolutionary timescales.

I figured you would say that about chickens. Basically, if you pick a definition which only works for humans, then sure, humans are going to be the winner. You might as well say that humans are the most optimal because they are the only ones to have put satellites into orbit around Mars. True, but not a useful species comparison.

Tell me, can you even apply your concept of "wanted to" to any other species? Which are the most successful fish species by this definition? Could any species of ant ever "want to" kill all humans? If they really wanted to, could they succeed?

As it stands then, your definition is useless, and propaganda for the supremacy of the humans species.

If we go extinct tomorrow - pretend this is the height of the Cold War and WW3 starts, with 50,000 nuclear weapons going off across the surface of the planet - then would an alien observer say that we were a successful species, because of our massive effect on the ecosystem, or would they say that we were a dismal species, which only lasted for a few hundred thousand years?

If we go extinct next year because of a hyper-virulent virus which kills only humans, would you say that that virus is more optimal than humans?

Your answers probably say more about you than provide a useful guide to how to measure evolutionary success.

As to the amount of genetic mutation present, that's just silly. There's 844 million tons of maize harvested each week, with plenty left as chaff. Assuming an average human mass of 65 kg and a population of 7 billion gives 460 million tons of people. Corn DNA is slightly larger than human DNA and plant cells tend to be smaller than animal cells. By the mass or count definition, corn is more successful than humans. There's 651 million tons of wheat harvest each year, but wheat's genome is 5x bigger than humans, so there's certainly more wheat DNA in the world than human DNA.

In any case, you're again too focused on the individual. Evolution only cares about genes, not individuals.

That's why your correct extrapolation - "the most optimal human would theoretically attempt to turn all of the matter in the universe into copies of his/her genes" - shows that that definition of optimality is invalid. Individuals aren't relevant. There's no guarantee that duplicated genes in cloned copies of a single individual are better at survival than having a mix of genes spread across a heterogenous population.

And your last paragraph shows that you don't understand the effect of mutation in evolution. All you are thinking of is the weeding out part.

Mutations occur all the time. Humans have about 0.003 mutations per genome per generation. For every 4000 births, there is a mutation. Few are improvements. Nearly all have no effect or are negative. Suppose one mutation has a really good advantage, and the only child from that person both 1) inherits the gene and 2) has a brand new nose picking mutation which confers a slight negative effect. Then that person's children will inherit both mutations. The really good one is going to spread, and the new, detrimental mutation will also spread -- even though it doesn't help improve survivability!

According to this article (http://www.eurekalert.org/pub_releases/2012-12/nifm-sfe12061...) homosexuality is epigenetic and not genetic (i.e. is not related to a specific gene, but to chemical differences that affect the expression of genes).

I completely agree with you. I don't believe that every action is correctly designed to optimize gene transmissions and I think you put it into very eloquent words with: "it is trying to say that we are at a global maximum in a space that is probably more nonlinear."

However, I think that there are certain actions that we take that are clearly defined by our genetics, like the fact that we eat, or that we have sex. And having affairs is one of those.

That we have sex is defined by our genes; who we have sex with is a choice we make by thinking about it, not something pre-encoded by our genes, as you are trying to say.

Which actually makes sense given your premises. A good evolutionary "strategy" would be to evolve brains that can make choices far more complex (literally, inelligently) than what can be pre-encoded by genes that change slowly and mutate randomly.

In summary, you are implying that when you have an affair, it's not a choice, but it's determined by your genes. Thus, it's not a moral issue; you have no choice. Thus, you can justify having any particular affair by claiming "genes," and you should just forgive any particular affair your wife has for the same reason. And I'm saying, no, it's a choice.

A cursory glance at discussions online regarding relatinoships and attraction would show that most people would say they don't decide who to be attracted to, that it simply is what it is.

Just because we can show that cheating has evolutionary benefits and thus people are likely prediposed to cheat in certain situations does not eliminate any moral considerations. Morality is precisely the idea of overriding any base instincts with what we "know" to be proper behavior. Claiming your genes made you do it is no more a loophole for morality now than "the devil made me do it" was before the discovery of DNA.

There was actually a study that showed female rats are more attracted to (read: had sex with) male rats with very different immune systems. The way she senses this is by the pheromone (smell) he gives off and as a consequence, her offspring have stronger immune systems.

In other words, this study suggests at least to some degree we don't even choose who we have sex with. Haha.

The purpose of my comment was to point out that humans have a (sophisticated) brain, something critical that you had overlooked, and you still seem to have missed that.

You argued that "who we have sex with is a choice we make by thinking about it, not something pre-encoded by our genes." I was trying to suggest maybe the opposite is true to some extent by sharing that study regarding the rats with you. Female rats unconsciously have sex with male rats whose pheromones smell like their immune systems are very different, in other words, who they select as mates is something pre-encoded in their genes.

Are you arguing that because we have brains we can 'override' what our genes would otherwise have us do?

there's a lot of stuff that people do that has nothing to do with thinking, and i'd argue that the idea of "intelligent choice" explains pretty much nothing in the context of mating/pairing. example: why are some people of the opposite sex "your type" and some not?

I agree absolutely it is more likely. And I read The Selfish Gene. But how could you disprove that theory? it is sort of too obviously true, if you see what I mean. Which is why I brought up the homosexuality counterexample. So I don't think it should be taken as undeniable, even though it is plausible.

I see what you're trying to get at. You're saying that "x% of children are not genetically related to their fathers because women have affairs to increase the competition for her egg" is a theory, not to be taken as something true.

I didn't mean to make myself sound like that I was saying it was. I was just suggesting something and I agree with you: it is plausible, but it is still a theory at the end of the day.

We're on the same page. :)

I rarely read discussions between 2 people beyond the 3rd or 4th reply, but this one kept me wanting to see how this goes, very well concluded. This is the reason I love HN, quality of discussion is much better than any other place.