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tigtog (aka Viv) is the founder of this blog. She lives in Sydney, Australia: husband, 2 kids, cat, house, garden, just enough wine-racks and (sigh) far too few bookshelves.

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27 responses to “Natural vs Artificial Selection”

  1. Valerie

    “in the West, humans have virtually stopped evolving as the term is normally understood”

    Many of us in the US have been suspecting this for years.

  2. Oz Ozzie

    Talk about a biological perspective. I think that Darwinian selection is as active as ever. Just instead of dying, people are not reproducing. And the selection criteria are radically different. I look forward to finding out the long term effects with interest.

  3. tigtog

    @ Oz Ozzie:

    But that’s the point – people deciding to not reproduce is not Darwinian selection: it has nothing to do with external filters acting on one’s genetic characteristics.

    I agree that it is a form of selection (which was also the point the bioscientist was making), it’s just not a natural/Darwinian form of selection.

  4. Jennifer

    I saw an article about this somewhere, and I agree with Oz Ozzie. Darwinian selection is all about who reproduces. I don’t think it matters whether you don’t reproduce because you die, or because you fail to find a mate, or because you don’t want to – your genes still don’t get passed on. So the human race is still selecting by virtue of who reproduces and who doesn’t. My two children are the only grandchildren from either side of their family – which means that my parents are unlikely to be as successful, genetically, as my great-great-great-great-grandmother http://penguinunearthed.wordpress.com/2009/01/25/487/
    who has 15 A4 pages of descendents in her family tree. Just because my brothers have so far chosen not to reproduce (rather than having died in infancy) doesn’t change the outcome.

  5. Oz Ozzie

    tigtog – yes, it’s an interesting question as to what degree they *choose* and what degree this is an externally imposed choice. I think that darwinian selection is not a simple binary thing in this respect.

  6. Oz Ozzie

    bah. I missed a bit of this. You said: parts of the world where there is still appalling infant mortality and violence/war that results in many people dying before they get the chance to reproduce.

    Yeah. So is this natural? I think not. Again, it’s not a binary choice. Secondly, these places have high birth rates and very young populations – is this darwinian selection of the fittest? It almost seems like it’s encouraging the survival of the less fit. :-(

  7. tigtog

    @ Jennifer:

    Animal husbandry is fairly ruthless about deciding which of their animals pass on their genes – that is not Darwinian selection, it’s the very definition of the artificial selection that Darwin’s theory of natural selection was posited against.

    Natural selection (and I’m aware that there are quibbles) is where a population is engaging in reproductive behaviours at the instinctual rate and the environment (whether a wilderness or a manufactured environment) acts upon that population randomly as to whether those reproductive behaviours actually pass the genes on or not.

    Artificial selection requires intellectual analysis and planning applied to reproduction i.e. an ego actively prevents organisms from engaging in reproductive behaviours e.g. through contraception

  8. tigtog

    @ Oz Ozzie:

    Remember that Darwin never actually said “survival of the fittest” – that was a contemporary epitomising the book. Also, “fittest” is not an absolute, “fitness” is relative to the organism’s environment – organisms who are “fittest” in the desert are not the “fittest” organisms in a flooded river valley.

    In an environment of war and poverty, the fittest human organisms for that environment are the ones who breed young and often so that they have the chance that some of the offspring will survive. That is exactly natural/Darwinian selection.

  9. tigtog

    @ Oz Ozzie: (sorry, forgot to respond to this bit)

    parts of the world where there is still appalling infant mortality and violence/war that results in many people dying before they get the chance to reproduce.

    Yeah. So is this natural? I think not.

    What exactly about violence/war and high rates of infant mortality is NOT natural for the human species?

    Our stable, peaceful societies with low infant mortality are the populations that are UNnatural – don’t get me wrong, I’m all for the UNnaturality of a stable society with a long life expectancy, I just don’t see it as “natural” at all.

  10. Shaun

    Tig, the erudite bioscience type is Professor Steve Jones. I heard him on 702 with Adam Spencer and wasn’t that impressed with his argument.

    The part of his argument about the age of fathers was strange. In the past, father would likely to have been generally younger than today given general life expectancy.

    Jones also likes to mention that the Moulay Ismail of Morocco had over 800 children as some sort of evidence for powerful men having a greater number of children. But it can be easily argued that this is really an exception. The size of ordinaries families would have been a far greater influence than such outliers.

  11. Oz Ozzie

    @TigTog: What exactly about violence/war and high rates of infant mortality is NOT natural for the human species?

    Sigh. Yes. You’re right. But the extension of your argument seems to be that war is a logical outcome of the struggle for survival? I’ve never liked that, though it smells all too true.

    @Shaun: I read somewhere that some % (5%?) if humans can trace their ancestry to Genghis Khan – apparently he was prone to enjoying the spoils of war. I can’t recall where I read this.

  12. tigtog

    @ Oz Ozzie:

    But the extension of your argument seems to be that war is a logical outcome of the struggle for survival? I’ve never liked that, though it smells all too true.

    I don’t know that it’s a logical extension, just that violence/war appears inevitable wherever resources are scarce and the rule of law is not firmly established.

  13. fuckpoliteness

    Enjoying the spoils of war=euphemism for raping women during war. Just thought I’d point that out since it seemed important. Not to biological arguments, just to, you know decency.

    fuckpoliteness’s last blog post..Ok, I’m going in…

  14. tigtog

    @ Shaun:

    What I don’t like is the conflation of evolution with natural selection so entirely. Darwin’s Theory of Natural Selection was subtitled as a theory of evolution, not the theory of evolution. Evolution will still occur even if natural selection’s significance drops compared to the significance of various styles of artificial selection.

    I didn’t even hear the older males claim in my small snippet: your own objection is entirely correct, but what about the other things he’s overlooking? Even in the West, he’s barking if he thinks that there are fewer old dads today than there were in ages past – a combination of the later age that both men and women start families anyway, plus all those blokes out there going on their second and third rounds of starting a family.

    Obviously a very Western-centric view and full of fallacies even when that restriction is taken into account. (off to read PZ’s fulminations now)

  15. Rebekka

    “Darwinian selection is all about who reproduces. ”

    Actually not quite. It’s about random mutation, and sex selection – the characteristics in the opposite sex that we find attractive (like peahens obviously find large and funky tails attractive in peacocks).

  16. Mindy

    Yeah, the hubby heard the bit about the older dads thing and got the full ‘oh so it’s only about the menz is it?’ when he told me about it later because it was hot and I was cranky and in the mood to shoot the messenger. We then went onto the ‘male body default’ setting in medicine and I swear he looked green when I told him about the old ‘take the penis and split it up the middle’ thing.

  17. Torri

    I remember watching a program on evolution recently which looked at populations where AIDS was rampant and apparently some sex workers had developed a resistance to AIDS. It was at once fascinating that humans were still developing resistances and also mind numbingly depressing to know it was necessary from lack of other help.

  18. Shaun

    @ Oz Ozzie, about 16 million men from the areas where Ghengis Khan share the same Y chromosome. It is likely (but unproven) that this came from Khan during his conquests. However it is not not natural selection that caused the spread. It is the result of social pressures.

    @fuckpoliteness, good point which was on my mind reading up on Ghengis Khan. More than one article claimed him to be a great lover or superstud rather than the reality of him raping women selected from the conquered population.

    @tig, yep I agree there is a very Western centric view to the whole argument and that natural selection is not all there is to evolution.

    @torri, I was reading something the other day and there is supposedly a gene that is starting to spread through populations in Africa that confers some immunity against AIDS (sorry no source).

  19. tigtog

    @ Shaun:

    The horde of Genghis Khan probably already mostly shared the same Y chromosome anyway – it was a homogeneous and isolated population out there on the steppes, and probably exhibited a strong founder effect. There’s no reason to suppose the the originator of that particular Y-chromosome was Genghis.

    So it wasn’t that he necessarily personally raped (or sexually exploited the destitute widows and daughters of slaughtered defenders in the best case scenario) all the women of the region, just that there was a hell of a lot of it happening from the horde as a whole.

  20. Shaun

    @ tig

    From what I understand markers in the Y-chromosome were used to trace it back back to one person around the time Ghengis Khan started his empire. As Ghengis Khan left no DNA it can’t be proven it was him but there is a strong suggestion it was. Though the origin of the Y-chromosome may have been a few ancestors back anyway.

  21. Ariane

    From the perspective of something so global as evolution, I find it hard to understand how there is a distinction between natural and artificial.

    The interactions and feedback loops that create evolution are much more complicated than genetic make-up meets environment. All species affect their environment as much as it affects them. The human environment now includes a lot navel gazing and self-created tools used for saving lives and blowing them to bits. But just because we have become rampant in our impact on the environment, I just don’t understand where we managed to transcend natural, at least in this context (I do think the idea of natural has a place in the assessment of foodstuffs, for example). The fact that we may be the biggest source of the environmental factors that are shaping us now, doesn’t sever us from the natural world.

    This is not to say that a touch more navel gazing about what direction all this might be taking us is misplaced. And I am suggesting thinking more about our environment and the pressures it places, not on who should be choosing to reproduce.

    Ariane’s last blog post..A day in the life of Tokyo

  22. tigtog

    @Ariane:

    From the perspective of something so global as evolution, I find it hard to understand how there is a distinction between natural and artificial.

    Natural selection is likely to throw up more mutations than artificial selection, because artificial selection is based on the selector’s arbitrary criteria through both controlled mating and culling/neutering of those organisms who don’t fit the criteria.

    There’s an environmental cull in natural selection, but it’s an impersonal filter that doesn’t target superficial phenotype traits in an organism – it’s purely survival-enhancing traits. There’s more chance for successful mutants to thrive if they’re not arbitrarily culled based on headshape or leg-length or adiposity, and those successful mutants are where eventual accumulated variations that could lead to speciation arise.

    I mainly posted on this because in my time on talk.origins I was continually amazed at the denialists who came in saying that natural selection doesn’t explain everything and therefore evolution doesn’t really happen, only to be confused and enraged when the t.o. mob shrugged and said “Yeah? Who ever said that natural selection explained everything about evolution anyway?”, as if actual evolutionary biologists were the ones who’d given them their simplistic understanding that Darwin=Evolution in the first place.

  23. tigtog

    @ Ariane:

    And I am suggesting thinking more about our environment and the pressures it places, not on who should be choosing to reproduce.

    Sorry I neglected to respond to this part: that is an excellent point.

  24. Ariane

    @Tigtog, I understand your point, although there are plenty of “natural” examples of phenotype selection – peacocks and other ridiculously shaped species, although they are probably conspicuous exceptions. It just feels arrogant to me to suggest that because we are self-aware of the processes we are imposing, that makes us apart from natural selection, rather than a new version of it. I guess ultimately I’m railing against the nomenclature, rather than refusing to accept there is any qualitative difference.

    My understanding, although it is gleaned from New Scientist and Discovery channel, and therefore potentially completely dodgy, is that some animals have selected themselves to extinction, without dramatic environmental change – they have essentially chosen non-viable traits (either directly or indirectly) to choose to mate with. Firstly, is that garbage? And secondly, if not, is that natural or artificial selection?

  25. tigtog

    there are plenty of “natural” examples of phenotype selection – peacocks and other ridiculously shaped species, although they are probably conspicuous exceptions…I guess ultimately I’m railing against the nomenclature, rather than refusing to accept there is any qualitative difference.

    The nomenclature suffers from the general usage/jargon usage divide, no argument. Which is why some people prefer to use the term Darwinian selection, to emphasise that there are other selection pressures that act on populations. Darwin used the term “natural” to mean unmodified by humans, but we do tend to have a better understanding that humans are not above nature these days, hence why it strikes you as a problem. However, I find that this approach would make the word “artificial” obsolete as a distinction, because humans are the artificers, so if everything humans do is natural, then nothing is artificial, is it?

    Anyway, sexual selection as per peacocks etc is certainly part of Darwinian selection, but it is not a conscious process, and in wild populations the reproductive behaviours are otherwise unmodified.

    Artificial selection is when an external selector not only chooses which phenotypes shall mate, but comprehensively modifies reproductive behaviour through neutering/contraception/sex separation etc.

    In human populations, fads in mate selection are largely subconscious (Darwinian) but in the age of mass media these fads are disappointingly receptive to commercially manipulated beauty ideals (artificial), and their reproductive success is modified by individual decisions regarding barriers to reproduction (artificial). This is where the term social selection or cultural selection is useful.

    Humans have basically been culturally selected since the time of agriculture, or at least since the first cities. Depending on who you read, this has increased our genetic diversity because of all the “weak” mutants who now survive to reproduce, and this is a good thing, or the lack of selection pressure favouring the dominance of “strong” mutant traits has led to human variation/speciation stalling, and this is a bad thing.

  26. Ariane

    Indeed, my instinct is that from an evolutionary point of view, nothing humans do is artificial, so I like cultural or social selection better as a description. Of course, I’m sure the bio-science world doesn’t care much what I like. :)

    And I genuinely think we should be taking a long hard look at our social selection processes – agents telling us what is attractive in a mate, agents creating an expectation of stupidity and blind acceptance rather than intelligent and independent thought – all sorts of things having complex and utterly non-understood effects on our population. Now that we have a conscious element to our evolution, whatever you call it, we need to have a meta-consciousness of it too.

  27. tigtog

    my instinct is that from an evolutionary point of view, nothing humans do is artificial

    Intentional barriers to normal reproductive outcomes is both artificial and evolutionarily significant, is my analysis.

    I’m not entirely unsympathetic to your objections to “artificial” in the general discourse being equated with “unnatural” (get me going on the whole “natural food” and “chemical free” advertising sometime) but I think that’s too superficial a view: we need a word that describes intentional modification of the environment around us as distinct from a spontaneously arising environment, distinct from an environment changed as an unintended consequence, and can you think of a better one?

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