Why did our species survive?

Today, we're the only living member of the genus Homo and the only living member of the subtribe Hominina. Along with chimpanzees and bonobos, we're all that remains of the tribe Hominini.

But the fossil record tells us that wasn't always the case. There were, for instance, at least eight other species of Homo running around this planet at one time. So what happened to them? What makes us so special that we're still here? And isn't it just a little weird and meta to be fretting about this? I mean, do lions and tigers spend a lot of time pondering the fate of the Smilodon?

Today, starting at 12:00 Eastern, you can watch as a panel of scientists tackle these and other questions. "Why We Prevailed" is part of the World Science Festival and features anthropologist Alison Brooks, genome biologist Ed Green, paleoanthropologist Chris Stringer (one of the key researchers behind the "Out of Africa" theory), and renowned evolutionary biologist Edward O. Wilson.

You can also join in a live conversation about the panel, which I'll be hosting. Just post to Twitter with hashtag #prevail, or join us at UStream.


  1. Based on how Civilization games go for me, humans got far ahead technologically, the other species got scared and declared war, and then we wiped them out because they started it.

    1. Not necessarily, Manuel. 
      There’s really good evidence that “we” interbred with them. Don’t think you can essentialize Homo Sapiens as killers and other Homo species as our victims. Evidence shows something a lot more complicated.

      1. There’s evidence we interbred with them when they were technologically ahead.  Microlithic tools were a technology we learned from them in the Mousterian, in the few thousand years we interbred, in the Levant, shortly after we left Africa.   
        The absence of mitochondrial DNA is interesting.
        We didn’t breed with their women. Seemingly.

        1.  Well, if there are no mitochondrial lineages from these species, it just means there are no unbroken all-female lines from them to us. There could easily be other females in the lineage.

          I can also imagine that such interbreeding occurred, but that the females tended to raise the offspring among their own kind instead of among humans, which could account for those genes lineages not surviving.

          1.   Some men of our species will have sex with goats or cars. 
            Knowing that, it would be outright silly to think such interbreeding between modern men and archaic women didn’t occur. 
            There are several possible explanations for the lack of matrilineal Neanderthal DNA. 
            A combination of some of those are most likely. 

      2. I’d wager a bit of both, and as Manuel says, indirectly as well: we tend to outcompete rival species in our niche so effectively that mass extinctions follow us everywhere.  Take the recent studies on African predator diversity during the emergence of the Homo genus.

    2. “We killed them” is only really a half answer (if it is even true).  The question you naturally half to ask is why it didn’t go the other way?  Most related species that were comparable were omnivores, and assuming that look anything like most other apes, perfectly capable of violence.
      The knee jerk reaction is to declare humans violent brutes, but it might have been admirable traits.  It might be that humans, when feeling threatened, were better at banding together to take on a threat.  It could be we were better at cooking.

      I would be shocked to learn that it is just that we have a personality better predisposed for war.  We really just are not that naturally violent.  It takes shocking little effort to get a few million humans to behave civilly with each other.  Sure, in big cities you have violent crimes, but they are pocket change in the grand scheme of things.  There is good reason to believe that non-agrarians who didn’t own anything more than what they could carry were even less inclined to start chopping each other up.

      1.  Depends on the resources available relative to the population.  It’s my (admittedly shallow) understanding that, for example, the indigenous cultures of New Guinea are horrifically violent, while those of the Amazon Basin by and large are not.

        1. The indigenous culture of New Guinea are also agrarians.  They don’t plant massive fields of wheat, but they farm and don’t move around as much.  They have “stuff”.  There is a strong argument (though hardly consensus) that agrarianism is what turns people nasty.  Agrarianism is what lets people settle down and become easier targets.  You accumulate valuable positions, the things you own can become complex and hard to replace, and you can own more than you can hold.  

          The amount of stuff nomadic bands who can’t own more than they carry is pretty minimal.  Take out “stuff”, make everyone equally poor/wealthy, and the things left to fight over shrinks considerably.  Its a theory.  Sadly, by the time we started to ponder this sort of things, all truly nomadic hunter/gathers had been wiped out.  

  2. “And isn’t it just a little weird and meta to be fretting about this? I mean, do lions and tigers spend a lot of time pondering the fate of the Smilodon?”
    We humans have distinguished ourselves by virtue of our tool making ability. Our most powerful tool is language. Lions and tigers can only grunt, while we articulate. They don’t ponder the fate of other species because grunts can only get one so far down the line in intellectual pursuits.

  3. There’s the possibility that we’re seeking causation where there is none. Why can’t it just be luck? Random rotten awesome luck. We weren’t any smarter, stronger, more violent, etc. Than the others at that stage. There’s some evidence that we might have been more “creative” whatever that means, but blah.

    1. Quite. Suppose that at some point in the earth’s history, round about ‘now’ (in geological terms) one particular species of half a dozen or so similar ones has outlasted all of the others. How unlikely is it that they’re going to think they’re especially better than the others?

  4. That’s what all those alien stories come from ;). And I’m sure that we survived because we are both very intelligent and very hostile towards our own and other species.

    Edit: this was a reply to Maggie Koerth-Baker’s post but after login it was placed at the bottom of the list of comments.

  5. Isn’t it just a little weird and meta to be fretting about this?

    The ability to ask this sort of question may be an expression of a characteristic that allowed our species to survive.

    There’s an interesting theory that psilocybin had plenty to do with it.  The mushrooms grow on bovine dung, and nomadic man followed the herds, so they bumped into the shrooms all the time.

    In small amounts, psilocybin increases sensory perception.  Good for hunting = more food.
    In larger amounts, it increases libido.  Coupled with more food = tribes grow.
    In very large amounts, often and communally, abstract thought is nurtured.

    The “stoner caveman” theory makes sense, but it doesn’t explain why other kin species did not bump into this happy accident.

  6. Got to wonder if there was ever some advanced bonobo offshoot, working on higher mathematics and having lots of sex, not even thinking of war until we came over the hill.

  7. I have to say I’m a little taken aback by the hubris implicit in the headline “Why we prevailed”. Geologically speaking, isn’t it a little too soon to tell? We’ve been here for, like, five minutes.

  8. I’ll go out on a limb tying a few things together.   One of the things mentioned is early humans trading networks.  And more efficient food collection.  With that you have higher population density and with the trading networks comes disease.  The burdens that keep populations down..  Humans could thrive at higher Malthusian thresholds than the other hominids. Consider that other hominids almost surely were subject to the same diseases as us, suffered as well when there was famine.  Likely the mere presence of modern humans pushed them above the threshold where long term survival wasn’t possible.

  9. We probably interbred out of convenience.  Meanwhile, we had the most convoluted cortex, so we could figure out how to outwit every other species, as well as mother nature, oceans, mountain ranges, famines, disease, etc. We were fast and light, moving around a lot, and developed incredible overland stamina.

    Now, we are nearly at the maxima of these abilities to help us survive, as resources dwindle, diseases become harder to fight, and the earth gets overcrowded.  So we will have to find new ways to reduce, reuse, recycle, and change our cultures to solve the problems.

  10. I mean, do lions and tigers spend a lot of time pondering the fate of the Smilodon?

    I prefer to think that they do.

    1. Yep, that’s what house cats ponder while sitting by the windowsill all day, staring out into infinity and beyond.
      Then when their ears prick up for no apparent reason, they are receiving transmissions from entities in another dimension!

  11. Wilson makes it pretty clear in The Social Conquest of Earth that he thinks we made it because of a hugely unlikely series of fortunate adaptive mutations, but that we prevailed over the other contemporaneous hominid lines because we wiped them out. The extinction timeline is pretty supportive — Neandarthals seemed to be doing okay till we showed up. It seems even more likely when you consider how many other mammalian species started getting a lot more scarce when we showed up. Maybe it’s our deodorant.

    1.  In the talk they mentioned that Homo Sapiens tried to move out of Africa more than once only to see the Neanderthals make a comeback and wipe us out from the Middle East. Ultimately our species returned the favor in spades but whatever edge we had was probably not quite so big as we’d like to think, at least in regards to the Neanderthals.

  12. Something’s wrong here, 26 comments so far (actually, 27 with this one), and the BB main page still says “o Comments” for this thread.  All other posts yesterday and today display a correct comment counter.

    1. That comment count thing is dodgy. It’s almost never accurate even if it appears about right.

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