The point mutation which made humanity

By Razib Khan | August 16, 2011 1:30 am

Steve Hsu points me to a piece in The New Yorker on the science and personality of Svante Pääbo. The personality part includes references to Pääbo’s bisexuality, which to me seemed to be literally dropped into the prose to spice it up. Of course it was the science which I found interesting. There are many more bisexuals than there are heterodox scientists. And yet like many researchers of yore it seems that Pääbo is out to find the genes which make humanity distinctive as we understand it (if the reporting is accurate, which I don’t take as a given). There are some interesting tantalizing clues littered about; some genes implicated in autism seem to exhibit Neandertal vs. modern human differences (with the Neandertals carrying the autism-implicated variants).


But here’s a consideration: what if the premise that there are a set of traits which are disjoint between Neandertals and modern humans is false? What I’m saying here is that there are traits which are fixed and universal within a species, and totally differentiate species x from species y. Anatomically and behaviorally modern humans seem to be exceptionally strange creatures. As noted in The New Yorker this lineage was the one responsible for many of the megafaunal extinctions and the push into Oceania and the New World. And yet do we have to presume that whatever characteristics differentiated behaviorally modern humans from other human lineages were universal to all of the former and totally absent from the latter? It may be that the difference is not one of quality/kind, but of quantity/degree. In other words, a particularly novel personality type may have transitioned to critical mass amongst the neo-Africans ~50,000 years before the present, but that personality type may not have been universal, and may even have been present at far lower frequencies across the other branches of humankind.

If the above proposition is assumed, then the quest to find the “gene which made humanity” is going to be much harder. You can’t just compare a few Neandertals to humans, but would need many more Neandertal samples. That’s because there may not have been a gene which made humanity, but a subtle complex of numerous genetic and cultural changes which transitioned at a critical point. Do remember also that it may be the nature of statistical genetics that there are some loci where Neandertals and modern humans differ in totality, but these are the “genes which make us human” only if you presume that there are some genes which make all modern humans human and all Neandertals not quite human.

To be concrete about this idea, what if the archetype of the visionary/mystical leader with charisma is responsible for the distinctiveness of modern human groups? This is not a common individual, but not exceptionally rare. Most humans are not particular visionary, nor are they prone to mysticism. Perhaps the difference between Neandertals and behaviorally modern humans was less about large between group differences in individual level traits, and more about the fact than Neandertals simply lacked the leadership cadre which behaviorally modern humans possessed. In this scenario most modern humans are just like Neandertals, lacking vision, drive, and proximate insanity. Neandertals would not have had their Alexander the Greats, but perhaps they would not have had their Adolf Hitlers.

  • Konkvistador

    But to think thus further upsets our tenuous claim to specialness, especially if say most of humanity rather than a small fraction, dosen’t share X which helped our species out compete them. How dare you make us think slightly discomforting thoughts?

  • http://walled-in-pond.blogspot.com Woody

    In my view, “humanity” is an (inadvertent) cosmic experiment testing whether “life” can survive ‘intelligence.” The ‘null hypothesis’ appears safe…

  • Peter Ellis

    That all sounds frightfully “Atlas Shrugged”, until you reflect that a society composed of nothing but visionary leaders might be… a little prone to internal dissent?

  • http://blogs.forbes.com/johnfarrell John Farrell

    Razib, are you implying there was no clearly defined ‘ontological leap’ from the animal to the human??? I’m going to have to clear this with the CDF in Rome.

    ;)

  • rimon

    Razib, fantastic points. and I agree with you about the bisexuality line. It seemed gratuitous, especially since the article goes on to say that he is married to a woman now. Who cares who he dated in college?

    What I always wonder about the supposed extinction of the neanderthals at the hands of modern humans is this: why are people so sure that the neanderthals were hunted nearly to death, and not just absorbed into the modern population? in central asia, for ex., we don’t assume that the earlier European types were completely wiped out by the later arriving Asians, we know they mixed together to create the populations we see today.

  • miko

    I was thinking along similar lines while reading this… Paabo (and most people) want to explain group/society differences as if they can be linearly extrapolated from individual behavioral phenotypes. Everything that makes humans interesting is about groups of humans–individual humans are not smart, innovative, curious or creative unless they are in social environments that encourage and allow these things.

    My own guesses (borrowed mostly from others): what gave raise to modern humans is not so much about cognitive abilities, but our ability to live in larger groups at higher densities. This could have to do with diet, pathogen resistance, or behaviors not directly related to intelligence, such as aggression or fearfulness. While we’re extraordinarily efficient at large-scale violence in recent eras, individual humans are, by most mammalian standards and certainly by primate standards, extraordinarily conflict averse (i.e. the domestication hypothesis).

  • Robert

    In some countries, Alexander the Great is considered to be at the same moral level at Adolph Hitler.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    #4, lol.

    This could have to do with diet, pathogen resistance, or behaviors not directly related to intelligence, such as aggression or fearfulness

    sure. but the thing that seems to weight it to something cognitive is the weird encephalization of the lineage. humans are to some extent sui generis. but our diet or immune system don’t seem qualitatively special. i’m not saying i know the solution, but i’m thinking we need to suspect it isn’t quite banal or typical, because it doesn’t seem like sentient hyper-cultural species are very common in the history of earth.

  • juan

    Wouldn’t the genes of this tiny leadership caste quickly spread throughout the population? The charismatic, visionary leader who hangs onto his sanity seems to have extraordinary reproductive success even today. Pre-birth control we get Genghis Khan levels of reproduction.

  • http://backseatdriving.blogspot.com/ Brian Schmidt

    In-group cooperation seems to be highly effective among modern H sapiens. Charismatic leadership could be a driver of that, as could other genetic tendencies.

    If the critical mass Razib refers to needed to change from 80% prevalence in Neandertals to 95% prevalence in moderns, they’ll need lots of genetic samples to work it out.

    The role of memetic/cultural evolution makes things even murkier – what if it was a cultural change/innovation that made it all happen, and not easily traceable to genetics? While we’re clearly genetically distinct from Neandertals and I think it’s highly likely to have made a difference, what happened in Africa is less clear.

  • juan

    Could we have genes that somehow get activated if we sense we are in a leadership position vs a regular drone? Kind of a mild social insect architecture. Cognitive pathways that either don’t get built, or don’t get activated if we aren’t in a high status position? Clearly we are built to sense status. It seems that for some people, and maybe most, their behavior can change fairly dramatically depending on their social status. They will behave much more charismatically in a high status position, but can function as a lower status worker bee if necessary.

    Don’t we see this with celebrities? Someone who goes from struggling musician to global rock-star, or waiter to movie star. Does being shown constant respect and admiration change neural architecture? Is it just the plasticity of our brains? As more people defer to us and respect us, our neural pathways devoted to discerning and deferring to the goals of other people wither, and the pathways devoted to expressing our own goals grow.

  • dave chamberlin

    There was no point where mutation made humanity. But there was one where long mixed hybridization between Neaderthals and near moderns out of Africa did. Proven? No. Probable? For now.

  • gcochran

    One of the key features of really truly behaviorally modern humans was the ability to make water crossings. Perhaps
    Neanderthals and other archaic humans had a specific speech deficit – they were were unable to say “arrrr, matey”.

  • Tom Crispin

    There was a SF short story circa 1950 (I don’t recall the title or author), the premise of which was that “humans” were omni-present throughout the galaxy, but that earthlings were uniquely capable of coordinated group behavior (in particular military behavior).

    The consequences were similar to Razib’s thinking, although the “humans” managed to win in the end.

  • Neuro-conservative

    Razib — I follow your general logic, but I’m not sure how you got from there to the leadership hypothesis.

    In any event, I might sooner hypothesize that followership (including features such as mirroring, empathy, and docility) is a more likely substrate of human success.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    , but I’m not sure how you got from there to the leadership hypothesis.

    just something i threw out. i have no idea what the difference is.

  • chris y

    Neandertals would not have had their Alexander the Greats, but perhaps they would not have had their Adolf Hitlers.

    I’ve always considered that the principal difference between those two was the technology available to them. (one of the few advantages to life in the palaeolithic was that the technology for mass murder was comparatively restricted.)

  • http://qpr.ca/blog Alan Cooper

    Well, Neuro beat me to it, but I too am inclined to suggest that perhaps what distinguishes “humanity” is the “capacity” for suppressing one’s own intellect and immediate interests in favour of some socially determined doctrine and leadership. Perhaps this does lead to greater reproductive success for individuals who can affiliate with such groups, and perhaps those of us who are too “bright” to be fully “human” might then be well advised under most circumstances to mimic the general dimmness rather than fail the test of credulity and get pruned as defectors from the common interest.

  • imnobody

    (Let me express my opinion, although I am pretty ignorant about this area. Razib, if I make some mistake, please tell me why I am wrong).

    ” That’s because there may not have been a gene which made humanity, but a subtle complex of numerous genetic and cultural changes which transitioned at a critical point.”

    I think this is the most likely scenario. The genetic changes may have been not only new alleles but also a greater frequency of alleles that were already present in the Neandhertal. This is similar to the fact that African people are adapted to malaria: it’s not only that they have specific gene adaptations, it’s that they have a bigger proportion of alleles that help to resist malaria (these alleles are present in other populations but with a lesser frequency, because natural selections don’t favor them).

    Anyway, how do we know that early modern humans were that different from the Neandhertal? If I am not wrong, the “great leap forward” was about 40,000 years ago, when culture is supposed to have been created. Maybe the early modern humans were very similar to Neandhertal and it was only about 40,000 years ago that the genetic and cultural changes happened and this made a difference.

  • Bob Dole

    “some genes implicated in autism seem to exhibit Neandertal vs. modern human differences (with the Neandertals carrying the autism-implicated variants).”

    https://secure.wikimedia.org/wikipedia/en/wiki/Talk:Causes_of_autism#Neanderthal_Admixture_Hypothesis

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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