He still has that hair

Steven Pinker was saying that greatly extending the human lifespan is hard, maybe impossible: ” I suspect that death will never be conquered (though our lifespans will continue to increase, at least for a while). Any cost-free longevity gene or easily tunable molecular pathway would have been low-hanging fruit for natural selection long ago. Senescence is baked into most of our genome because of the logic of evolution: since there’s a nonzero probability at any moment that an organism will die in an unpreventable accident, making genes for longevity moot, selection tends to sacrifice longevity for performance at every level of organization. This means we’d have to know how to tinker with thousands of genes or molecular pathways, each a tiny (and noisy) effect on longevity, to make the leap to immortality. The low-hanging fruit is in fact at the other end of the lifespan and income scale. We’ve made massive global progress in reducing maternal and infant mortality and premature death, but we’re not seeing a cohort of billionaire centagenarians. ” Centenarians.

He’s got the argument backward: sure, natural selection has not favored perfect repair, so says the evolutionary theory of  of senescence.  If it had, then we could perhaps conclude that perfect repair was very hard to achieve, since we don’t see it, at least not in complex animals.*  But since it was not favored, since natural selection never even tried, it may not be that difficult.

Any cost-free longevity gene that made you live to be 120 would have had a small payoff, since various hazards were fairly likely to get you by then anyway…  And even if it would have been favored, a similar gene that cost a nickel would not have been.  Yet we can afford a nickel.

There are useful natural examples: we don’t have to start from scratch. Bowhead whales live over 200 years: I’m not too proud to learn from them.

Lastly , this would take a lot of work.  So what?

*Although we can invent things that evolution can’t – we don’t insist that all the intermediate stages be viable.

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76 Responses to He still has that hair

  1. Hence a wide body jet skips the flapping wings solution that has evolved so well.

  2. If we came across human remains from someone who had lived a substantially extended life / aged slowly, would it even be noticed? What would one look for?

  3. Anonymous says:

    Experiments with mTOR alone show Pinker to be quite wrong. In fact, we know the evolutionary theory of senescence is wrong too: all the genes we’ve found that play a strong role in lifespan are metabolic genes, and and the vast majority of them have nothing to do with reproduction. Hence, Kenyon’s view that tinkering with metabolism is the surest way to extend lifespan (and probably also why she’s working at Google now, because they’re serious about slowing aging). Additionally, much of the damage that we call “aging” likely begins before birth, not after maturity. The longer back we peer, the more aging-related damage we see: like the recent results showing that misfolded proteins that may or may not (depending on who knows what ultimate causes) become Alzheimer’s in some people begin accumulating around age 20 and probably well before that.

    • gcochran9 says:

      “we know the evolutionary theory of senescence is wrong too”

      What do you mean by “we”, kemosabe?

      • benhardisty1 says:

        There’s a reason the aging geneticists are leaving academia in droves to work in private industry and start-ups: the vast majority of aging-associated genes that have been characterized have nothing to do with reproduction, at least not directly. That’s why the medical aging people laugh at the disposable soma. It was a great idea when we knew nothing about how aging actually happens, but we know enough about it to see that there is something missing from the picture, something important. Of course, some still hold out hope that further work will indeed reveal that there bunches of small-effect alleles. That may or may not happen.
        And Kirkwood is still running around proclaiming that free radicals are the major cause of aging (e.g., they modulate his disposable soma) but that’s wrong too. They appear to a by-product, not a cause.

    • Josh says:

      Why is Google serious about slowing aging? Do their stockholders know about this?

      • benhardisty1 says:

        When Cynthia Kenyon discovered the first allele that contributes to aging, biologists were in a state of shock: they expected there to be a bunch of alleles of small effect scattered throughout the genome. Instead they got a small number of genes that are heavily involved with insulin signaling. Through effects on metabolism, these genes prevent cellular maintenance from occurring nearly fast enough to benefit lifespan. Theorists like Michael Rose had been proclaiming that evolutionary theory predicted that no genes with a large-effect on lifespan were ever likely to be found (and despite the genetics work, he still proclaims we can’t hope to slow aging). But they were wrong. I think Google is smart to get in on the action. David Sinclair’s work alone, at Harvard, will lead to aging treatments in the next 10 years I’d guess. Work on mTOR will also lead to extended lifespan. Not sure what Google’s Calico is up to precisely, but I’m going to bet that it is targeted gene therapies to slow aging.

    • benhardisty1 says:

      Of course, we could be wrong for a good reason: we just haven’t found the downside to these particular alleles. For example, the centenarians with their mutant mTOR alleles might have lower fitness. In fact, that may be fairly simple to test. They live longer, but have less offspring for some reason. Perhaps they develop slower. I’ll have to ask Ken Smith if TOR1 has been looked at in all of the ‘super ager’ databases he’s familiar with.

  4. AnonymousCoward says:

    Centenarians tend to have fairly hoary families, among which they’re an outlier.

    “Calment was born in Arles on 21 February 1875.[2] Her father, Nicolas Calment (28 January 1838 – 22 January 1931), was a shipbuilder, and her mother, Marguerite Gilles (20 February 1838 – 18 September 1924), was from a family of millers. She had an older brother, François, (25 April 1865 – 1 December 1962). Some of her close family members also lived an above-average lifespan, although none lived anywhere near as long as Jeanne: her older brother François lived to the age of 97, her father to six days shy of 93, and her mother to 86.”

    But there’s a fly in the ointment: the extremely high suicide rates among inuit when they start to feel “burdensome upon others”. That has to have a genetic component. How might that reflect upon the advantageousness of superlongevity in a species inclined to care for the injured and sick?

    Not only might there be no obvious incentive, there might non-trivial costs to superlongevity in a filial species like ours, more so than among tortoises and bowheads.

    • benhardisty1 says:

      Lifespan is highly heritable in the small number of QT studies done thus far. There are 6 large genome studies of centenarians that I’m a little bit familiar with and they all tend to have certain gene variants at higher frequency than non-centenarians that have been sequenced. I think APOE is the most common large-effect aging gene found in families of centenarians. That does beg the question though, if having the ‘good’ version of such an allele is good, how come these alleles haven’t spread to fixation? Further work will perhaps tell us why.

  5. spandrell says:

    I take it the idea is not to extend a 70 year old body for 130 years; it would be more like decay slowing down a lot, so that at 70 you’d look like 30, at 120 you’d look like 50, and so on.

    I’d say that the implications for population growth are horrible; but given current fertility rates in civilized countries, maybe a 200-year lifespan is the only way to get people to replace themselves.

    At any rate, even if Pinker got the evolutionary logic wrong; it’s still not gonna happen. We just don’t have it in us. The incentives aren’t there, it’s a lot of work, and we are increasingly unable to pull off big projects that don’t pay off in the next quarter. That’s getting worse before it gets better. If it does.

    • pyrrhus says:

      The long term (maybe even the short term) consequences of a technology that would allow some people to live hundreds of years can easily be imagined. If generally available, world population would run into a Malthusian wall almost immediately. If only available to the elites, resentment would likely turn violent in short order. So the elites would exert serious efforts to keep the process secret, but eventually it would leak out, with grim consequences…

      • spandrell says:

        “Generally available” is impossible. Food isn’t generally available. If this were to be developed, it could be widely available in developed countries, which are right now losing native population by the millions. No Malthusian wall in Europe or Japan.

        Of course if you introduced this in India or Africa they’d all starve. But they’re gonna starve soon anyway.

        • Kamran says:

          Starvation is excellent. Starvation and sterilization are IQ selection. I am from Turkey and I will introduce starvation and sterilization to increase IQ with my new political movement. I am seeking advice on new sterilization methods. Please contact me with advice: kamran0113@gmail.com

        • John Hostetler says:

          The problem in Europe is that there’s no wall, and no will. But there are Malthusian boats, many landing successfully for every one that gets on the news by sinking.

  6. j says:

    What hair? Is it a reference to “The Naked Ape” that still has some hair? Or to Steven Pinker’s toupee? Both? My next guess is that you started talking in parables.

  7. Sean says:

    I think the costliest things for the individual in terms of limiting lifespan would be the most necessary from the genes’ point of view. Reproduction is the most necessary and must be the costliest; so it would be the obvious target for life extension. Castration gives you an extra 7 years I believe.

    • reiner Tor says:

      I think evolution would prioritize and would try to economize on food for example. This sucks: I’d rather my body used up half of my fat reserves on a major overhaul and reparation process of my body. This would enable me to indulge in even more food than I currently eat, and at the same time make me younger. I could eat all trace elements if needed, too. Even if my body needed twice my current body fat reserves over the next year, it could easily make me hungrier, and then I’d eat still more. Actually, probably it needn’t make me hungrier at all, I’d eat a lot more if I wasn’t worried about my waistline.

    • reiner Tor says:

      Forgot to mention that I’d prefer death over life without balls.

  8. MawBTS says:

    Why do so many birds have long lives?

    My (indifferent) understanding is that genes that allow for long lifespans pay off in stable, low-risk environments. Macaws, albatrosses, and condors don’t seem to fit the proverbial bill.

    • benhardisty1 says:

      The bird species whose genomes have been studied have variants of alleles that protect them from free radicals. They generate far more free radicals but are protected from damage due to them. Or they are protected for a longer period of lifespan perhaps?

  9. IC says:

    Bacteria or many single cell organisms are technically immortal. Gametes are immotal technically. We are just vehicles for gametes. As vehicles, we are disposable tools for gametes, and we are replaced just like vehicles by gametes.

  10. Jerome says:

    The idea that longevity is not selected depends upon the idea that reproduction ceases with increasing age. To use Dawkins useful formulation, a set of genes that can continue to make faithful copies of itself indefinitely is certainly more likely to have multiple copies of itself walking around than one that ceases after a fixed span. I don’t think this puzzle has been solved yet. There are still a couple pieces missing.

  11. Ilya says:

    If one has read Nick Lane (http://www.nick-lane.net/double-agent%20theory.pdf), it seems that the quickest payoff would be from tinkering with genes in mitochondria — especially, ones responsible for its membrane — in order to mimic the metabolic efficiency (and relative longevity) of bats.

    Of course, humans would need to experiment on mice, rats, and monkeys first, but it looks like things like that are doable, if only some very rich people / government consistently funded such research.

    • Ilya says:

      Just to add: bats live 40 years. Rats — 4 yrs (in captivity). Hence, if we translate it into a potential for improvement, achieving a factor of 8 to 10 times lifespan for humans (i.e. >500 years!) seems to be within the realm of achievable.

      • Sean says:

        Long lived creatures : Storm Petrel – nocturnal, Bats -nocturnal, Naked mole rats – live underground (and don’t show signs of aging even in their latter years).

        So much for the sunshine vitamin.

        • gcochran9 says:

          Tortoises, parrots, elephants, you’re wrong.

          • Ilya says:

            Yes. Looks like animals with either (relative to their size):
            1) Slow metabolism (whales, elephants, tortoises, naked mole rats).
            2) Very efficient metabolism (bats, most flying birds).

        • setstamov says:

          It is about level of predation and hazardous environment. Bats have less natural predators than mice. Air is less hazardous environment than land. All avians benefit, so genes from longevity would make better sense there than on the ground, full of cats. The mammals still pay their tool on the dinosaur epoch they developed as a specie. For 150 millions of years mammals had been living as a prey in an extremely hazardous environment overshadowed by superior creatures; life expectancy at birth way too short – could have been 2-3 years at most, so zero selection for longevity genes, cell regeneration and continuous tooth replacement. All contemporary mammals age (aging as a decrease in fitness), no exception, unlike fish and reptiles -most – or many -of them do not. Birds seem not to experience the process of aging to the same degree as mammals as well. It’s something about predation and life expectancy in accordance to the hazards of the environment – and it is something about being a mammal. When the mise learn to fly they start living as the avians – selection for longevity begins. Quickly. It is a long hanging fruit for the evolution – given the right selection pressure.

          • Ilya says:

            @setstamov: given their small size and high metabolic rates (especially , when not sleeping), bats outperform humans in terms of lifespan (in context of relative body size and metabolic rate sense). As I’ve said above, metabolic rate is indeed very important, but not the whole story when it comes to lifespan.

            According to Nick Lane, the main advantage of bats and flying birds is their very efficient metabolism, metabolism that can ramp up and down very organically, due to need for wing flapping. It becomes possible via very well protected mitochondrial membranes, inside their cells ( as they age they also leak much less than regular mammals’). I provided a link to his paper above.

            In any case, there is truth to your argument regarding being prey negatively affecting lifespan. I would say, however, that the main effects come from selecting for high maneuverability and reaction time, via need to maintain higher basal metabolic rates (http://www.sciencedirect.com/science/article/pii/S0003347213003060).

  12. magusjanus says:

    Curious if Greg has any thoughts on Aubrey DeGrey and the whole SENS idea.


    Seems like we’re still pretty far from what he’s talking about, but a targeted “engineering” like approach to the problem seems (to the very amateur me) like the right approach. And instead of trying change metabolism (VERY complex) to not lead to aging we rather try to focus on actual dealing with the damage and correcting it via bioengineering. Rather like we accept how a car will take damage on the road, but it’s easier to fix damage as it occurs in a targeted fashion and occasionally replace parts instead of making the car impermeable to damage from the start.

    Seems intuitively to me like the right way, though of course we don’t have the technology yet for most of what he talks about it seems to at least offer a “path” towards negligible senescence.

    • Mark P. says:

      Aubrey de Grey is an amusing crank, mostly, though perhaps a useful one in the longer term. That said —

      The car-repair metaphor isn’t invalid. In that context — somewhat humbler than de Grey’s — ‘of course we don’t have the technology yet for most of what he talks about’, is NOT an assumption I would necessarily make.

      Consider already-emerging technologies for organogenesis/regenerative medicine like decellularized organs —

      — and some of the possibilities that gene-editing via CRISPR suggest. There are other tends, too.

  13. Charity to Pinker says:

    Is Pinker necessarily contesting the view that things would be even worse if there had been strong selection for long lives and it hadn’t worked?

    If I was trying to reconstruct his argument to make more sense I would focus on the point that weak selective pressure for longevity means that many different systems start breaking down at the same time. Cancer, heart disease, dementia, all increase together with age, so if you cure one or even a few you still die a few years later of the remaining causes.

    What do you think of Aubrey de Grey’s attempt to catalog and estimate the scope of multifactorial causation (he clumps things in 7 broad categories), i.e. “SENS”?

    “This means we’d have to know how to tinker with thousands of genes or molecular pathways, each a tiny (and noisy) effect on longevity, to make the leap to immortality.”

    This is less defensible though.

    “I suspect that death will never be conquered (though our lifespans will continue to increase, at least for a while)”

    This is trivially true for physics reasons because of the end of the universe and running out of free energy. But it seems foolish with respect to aging: never is a very long time. After a billion years of trillions of genetically engineered supergeniuses and then intelligent computers working on the problem it wouldn’t be solved? Not plausible.

  14. James Rafael says:

    “Lastly , this would take a lot of work. So what?”

    So we might as well just wait until you baby boomers, the worst people in the history of civilization, are all dead.

    Maybe we’ll start when Ray Kurzweil eats it.

    • j says:

      Someone said that in science, wrong theories dont die, progress comes when old professors die. Or something to that effect.

      • Maciano says:

        In that case, we should encourage anti-aging for everyone, except scientists?

      • Andrew says:

        That was Max Planck.

        “A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”

        I get odd looks when I say the short version.

        “Science progresses one funeral at a time.”

        • j says:

          Thanks. Death is not an error or misfunction of an organism but it is a built in function necessary for the survival of the species. The social benefit of people living much longer is negative: the scientific contribution of old people is zero. Death is necessary and good. Look at Japan today. What we have to do is not to conquer death but prolong youth.

        • Erik says:

          There’s a positive feedback loop in there somewhere. Science progresses, bigger and better weapons get invented, leading to more funerals.

      • Dave Pinsen says:

        “Science advances one funeral at a time” – Max Planck

    • Toddy Cat says:

      “So we might as well just wait until you baby boomers, the worst people in the history of civilization, are all dead.”

      I’ll bet that the Millennials are worse, by far. They have already caused a lot of damage, and worse will follow. As Hegel said, the owl of Minerva flies at dusk…

  15. Dale says:

    Of course, the straightforward way would be to select humans for longevity. The easiest way to do that is to prevent anyone from reproducing until they’re 40. That would put immense selective pressure against senescence before that age, regardless of the amount of unavoidable death before 40. After that, keep pushing the minimum age for breeding up so as to shear out 20% or 30% of the population in any generation because they can’t reproduce after that age, either due to senescence or death.

  16. Brian says:

    Like Pinker, I was born in September 1954. He still has hair, I don’t. “If ya got it baby, flaunt it.”

  17. ziel says:

    The most obvious problem with greater longevity is the existential threat it would pose to Whigism, as its continued viability relies heavily on the early demise of those on the wrong side of history.

  18. Pincher Martin says:

    Greg writes:

    Bowhead whales live over 200 years: I’m not too proud to learn from them.

    I once read a book about whales that claimed one Bowhead was hauled up recently which still had a nineteenth century harpoon in its body.

    Cool story, even if it’s probably apocryphal.

  19. Portlander says:

    This is a topic I harp on every time it comes up… what’s with all the billionaire octogenarians? Something is definitely going on there. The obvious answer is HGH, but that seems too pedestrian for a billionaire.

    Why not whole blood transfusions from Chinese orphans? Hell, it’s in Reuters. And for those that may not have noticed, Buffet’s son is big into Chinese philanthropy. Seems like a cover story any CIA spook would appreciate.

    I have neither the means nor the network to get such off ground, but I think an orphanage that sidelines with a CSA for plasma, whole blood, and human breast milk to the world’s oligarchs, despots, and dictators is a veritable gold mine. With an orphanage one could maintain tight control on inputs and assure clients a wholesome, high-quality product. It also has up-sell written all over it. Single-source breast milk from a 125 IQ, EDAR positive, 16 y.o.? We got that. Single-source whole blood from an 18 y.o., Div II varsity caliber male? We got that. Oil revenue a little thin (heh) this year and need to value shop for 10-14 y.o. multi-source plasma? We got that.

    • Patrick Boyle says:

      Speaking of breast milk. You know who Luciano Pavarotti was? Do you know who Mirella Freni was? Some would argue she was the greatest lyric soprano of the twentieth century. She was as accomplished as Pavarotti and almost as famous.

      It’s a little strange that they were both came from the same town. It’s a little more odd that they were born at nearly the same time. But what really screws with your noodle is to realize that they shared the same wet nurse. Two of opera’s most renowned artists each had a nipple at the same time on the same woman.

    • “Why not whole blood transfusions from Chinese orphans?”

      While we are writing plausible science fiction, let’s go whole hog. The Reuters article throws out the “Ponce de Leon molecule”. Ha! If there is such a thing to be exploited at some future date that approaches the lofty title of the Ponce de Leon molecule the most likely source isn’t young blood but our own stem cells. I am not saying there isn’t good to be had from old farts getting young blood transfusions but where I would guess the real pay off will come in medical treatments that actually result in life changing anti-aging treatments is in our better understanding and manipulation of stem cells. It is going to be a real interesting century science wise and I hope to cackling in an old peoples home keeping up on the latest breakthroughs.

      • Portlander says:

        Plausible science fiction? Not saying there isn’t good to be had? Well, with back-handed compliments like that… 🙂

        Patiently waiting for a stem cell breakthrough real-soon-now™ is, of course, exactly what they want the hoi polloi doing. As for billionaires with all this time, energy, and inclination for jet-setting to world conferences, corporate mega-mergering, and rabble rousing up the Diversity, sure perfectly normal. Up at 5:00, nap at 2:00, and we too could conquer the world. Haha… reminds me of that Seinfeld episode.

    • MawBTS says:

      Don’t forget the fecal transplants.

      Perhaps (among Fortune 500 execs) a standard retort to “you’re full of shit” is “yes. An eight-year-old Armenian’s, to be exact.”

    • benhardisty1 says:

      There are bizarre experiments I came across writing my thesis proposal last year: 1) blood from young mice does seems to be beneficial when infused into old mice, 2) liver chunks taken from live young mice can be transplanted into old mice and it appears to increase lifespan and healthspan. Very interesting stuff!

  20. On Pinker’s side of the argument the only known anti aging strategy that works is calorie restriction. Well that sucks. I can live a bit longer if I’m hungry all the time. On Cochran’s side of the argument we have a number of closely related species that have very variable average life spans. Horses for example live an average of 20 to 30 years. Donkeys live an average of 30 to 50 years. The Japanese are the human equivalent of a donkey with an average lifespan of 86 years while the horse equivalent (excluding the African craphole) just might be ex NFL players whom kick the bucket at an average age of 55 to 60.

  21. jamzw says:

    It should seem obvious that, were human lifespans to increase three times, and all while in the general physical condition of a nineteen year old, actual evolution would necessarily slow to a crawl–both genetically and environmentally.

    “Never do today what you can put off to tomorrow”–Alfred E Neuman

    • Mark P. says:

      But then, if we developed the technology to increase human lifespans three times, we’d also have the capability to engineer our own evolution as we will. So it’s all good.

      Or not, depending on your socio-religious preconceptions about “eugenics”/self-directed human evolution, etc.

      More interestingly, I’m not seeing much notice being taken here of the fact that we already have the tech for much the above coming within reach, via CRISPR and other already-occurring trends in organogenesis/regenerative medicine like decellularized organs.


      It’s going to be an interesting century. Once these technologies develop a little further and the wealthy start availing themselves of these possibilities, the inequalities in lifespans — between 60-some years and 120 years by 2040 is not an outlandish projection — will be impossible to ignore for even the most brainwashed of us proles to ignore.

  22. melendwyr says:

    Wheels aren’t all that easy to make, but not fantastically difficult – yet evolution never produced them. It’s not that physiological immortality is impossible, but I suspect the human mind has an inherent expiration. Even accounting for decay, aged humans have certain unsettling traits in common.

  23. albatross says:

    There are a lot of bits of us that seem to wear out over time, at many different scales–accumulated genetic damage in cells, wear and tear on joints, accumulated plaques in arteries. My guess is that even if we can address some of the biological process of aging, there will still be a fair bit of repair work needed to keep a 100-year-old guy feeling young.

  24. j mct says:

    What Pinker wrote is just bass ackwards wrong, ‘sacrificing performance’ is specifically and exactly what senescence is. One might say that performance (in the reproduction system too) is sacrificed for more and better performing, especially while young, offspring, and one might make a case for this. With some species that might work, especially amongst females.

    In addition that would only matter for females and there is no reason why there couldn’t be dimorphism in aging, because there is, just not as much as one might expect. There is a soft sort of cap to how many calories a bull elephant can devote to reproduction. So if it’s only a question of resources, i.e. how many calories are eaten, why should a fifty year old man who eats as much as he does as he did when he is twenty, get fatter rather than younger. Fatter is better but obviously getting younger would add to fitness too, and if eternal youth were a solvable engineering problem one would expect to see it.

    Per Dave above, as is well known, eating less slows down aging, which, if aging is a question of using finite resources, is exactly the opposite of what one would expect. It’s almost as if a multicellular organism like a man slows down tissue repair and the like, he postpones death. Why would that be?

    The whales do look interesting though and though it might take a long time to find out anything useful from them, I’d think if I were in aging research I would study them.

  25. Mike K says:

    A motivated and intelligent person is several times as productive, in whichever endeavor – work and fun, than a duller person. The same guy could be an order of magnitude more productuve yet if he lived in society geared for the average IQ of 130, not 80. I guess that’s how super-rich might live, having minions to deal with red tape and formalities…

    (Smart and motivated) one could do a lot more living in the current lifespan if humanity changed along the lines much less technically sci-fictiony than physical longevity would require…

  26. Jaim Klein says:

    Roman patricians, Chinese mandarins and English colonials had dozen educated secretaries and assistants to make them more productive. Seneca had seven literate editors to write his books.

  27. skepticdonkey says:

    How does “evolution” favor or invent something? I thought it was a materialistic mechanism. It is teleology when Aristotle talks about the ends of such and such, but not when Darwinists do it? Why, because it’s shorthand in one case and…what…in the other? How does “evolution” “know” about the accident? After all, reproducing is the only thing that matters….so where is the theory that accounts for why there might be a tradeoff involved. A tradeoff because of what?

    One thing I never understood was why this kind of reasoning displayed by both Cochran and Pinker in this post is never applied to the theory of natural selection itself. How can it be that a gene that provides a favorable adaptation to a certain environment is not blotted out because of an accident or the incidental death of the organism before it can reproduce? How can there ever be enough “time” for natural selection to work?

    • gcochran9 says:

      First, imagine that you’re not an idiot.

      Next, consider that mutations can change behavior, which they can. Some of those mutations, not many, could change behavior in a way that worked better, leed to more offspring. They would tend to spread. For example, let’s suppose that it made the animal avoid some predator a bit more than before. That can only be an advantage if it doesn’t interfere too much with other functions, such as getting enough to eat. There are many possible strategies ( different degrees of predator avoidance, say) but only a very narrow set of them are going to increase reproduction, because multiple considerations exist (have to eat, have to avoid being eaten, have to mate, etc. ) so we talk about tradeoffs. If we were consciously designing this animal, we would be aware of these multiple considerations, could analyze them (look at the tradeoffs – that’s engineer talk) and pick the ones that would work best. At least we could if we were smart enough. But if you pick strategies randomly, the ones that work are the same ones that we would have chosen through analysis – by thinking about the tradeoffs and payoffs.

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