You know the feeling when  you’re scrolling on the Internet and you see a video of  someone doing something wild, like doing parkour off a rooftop or something?

The kind of thing that makes you  think “holy cow, that’s so risky. Why would anyone ever do something like that?” Well, some people are just  risk-taking adrenaline junkies.

We know a fair amount about  the psychology and neuroscience of what scientists call “high  sensation-seeking individuals”. But what’s less clear is why it’s a trait that exists in the population in the first place. And to answer that question, we may need to look at our closest living relatives: chimpanzees. [♪INTRO] Whether it’s skydiving, running with the bulls, or motocross racing, dangerous activities seem like a prime opportunity for  natural selection to kick in.

Like, you’d think that most daredevils would end up taking themselves out of the gene pool. And if that’s true, you’d expect  risk-taking to be extinct. Unless, of course, it does more good than harm.

And as with many traits, one of  the best ways we currently have to study the evolution of risky  behavior is by taking a look at our closest relatives, chimpanzees. More  specifically, their eating habits. Stay with me, because I  promise this will make sense.

Chimps mainly eat fruit, which is a pretty low stakes food, as far as collecting it goes. A much higher stakes meal would be, well, steaks. Not only does hunting for meat  require you to leave the safety of the group, it also puts you at  risk of getting hurt while chasing your meal of choice.

You end  up using a ton of energy, and your prey could even turn  the tables and attack you. Despite that, chimps do hunt,  mainly for red colobus monkeys. Hunting these monkeys is worth  the risk for all the delicious nutrients they get from meat  that they can’t get from fruit.

So it might seem like that’s where  that risk-taking trait comes in handy. Individual hunters put themselves at risk, but they get a chance to  nab some precious calories. That’d be a great way to continue your genes, and would reward risk-taking behavior.

Except chimps don’t hunt  individually, they hunt in groups. And the spoils are shared  amongst participants of the hunt, and sometimes members of their  larger social cluster too. So if you’ve got a good  chance at getting meat anyway, why should any one individual risk getting hurt?

Thing is, if the entire group  thought that way, then no one would ever hunt, and there’s not  going to be any meat for anyone. And once one individual starts a hunt,  others are more likely to join in. Researchers have also seen  that the more individuals out on the hunt, the better  the chances of success.

This catch-22 means that there’s  an incentive to join in on a hunt that’s already going, but way less  pressure to be the one to start it off, which is why researchers wanted  to dig in and understand what social pressures are at play  when it comes to starting a hunt. And they’ve discovered that  there are some individuals who are much more likely to  initiate hunting than others. So, the researchers call these guys – and yes, it’s mostly males – impact hunters.

Not only are the impact hunters  the most likely individuals to initiate a hunt, but when they aren’t around, foraging groups are less likely to hunt at all. So it’s not like others step up to  fill that role in their absence. There’s something unique  about these specific chimps.

And the weirder thing is, they aren’t necessarily better hunters than other chimps in the group. Only one of the impact  hunters that the researchers identified had a consistently  higher rate of catching their prey. So their main value seems to  be that they just initiate the risky behavior of hunting, not  that they pull it off every time.

They do the dangerous thing, and then other chimps join in the hunting effort. And again, more chimps, more success. So for these impact hunters, being  the one that sets the hunt in motion does mean they have a better  chance of getting meat, but only because it means that everyone has  a better chance of getting meat.

It’s not necessarily that  being a daredevil increases survival rates of the  individual, but of the group. What’s good for the goose is  good for the gander, or rather, what’s good for the chimp,  is good for the other chimp. There’s another benefit for these chimps, too.

Their oxytocin levels shoot way  up after they hunt as a group, which facilitates group bonding and cooperation. And researchers suspect that  cooperation itself is part of what’s led both chimpanzees  and humans to thrive. So if there’s potentially a group  evolutionary advantage for individual risk-takers in chimpanzees,  maybe there is for humans, too.

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The physiological mechanisms for risk-taking seem to be similar in chimps and people. In both species, adolescents  engage in more risk-taking behaviors than adults too, so there’s a basis for comparing risk-taking across the species boundary. And sure enough, there is evidence that key individual humans catalyze violence, too.

Except in humans it’s less  about starting off a hunt, and more about what’s called  coalitionary violence, basically one group of people  engaging in violence against another. Less of a bar fight and more of  a rumble, West Side Story-style. But probably with less dancing.

Anthropologists think that  coalitionary violence may be relevant to the development of complex  social behaviors, like warfare. And while there’s been tons of  research on the reasons for war, we know a lot less about who actually  starts wars, and how they do it. Just like with chimps, there’s a tension between risk and reward of being the one to shoot first.

In other words, we want to know if there are impact soldiers that kick off the whole thing. By going to war, every single soldier in all of the armies involved is going  to be putting himself at risk of being killed or  maimed or captured, but he’s putting himself in that position  for the benefit of the group. And those benefits often aren’t going to be directly felt by any individual combatants.

It’s not like every single one is going  to get a share of the spoils of war. They might just win something  abstract like reputation benefits, or something not all that  shareable, like more territory. And that’s only if you win.

Putting yourself at risk for  something you won’t directly benefit from isn’t a very good deal in  the grand scheme of evolution. This is where key individuals come in. With humans, impact fighters  are a little more complex than just whoever’s the first  one to run into the fray.

These individuals change the  cost-benefit ratio somehow, making the group think that the potential benefits  of fighting outweigh the risks. Maybe they provide coordination,  or some sort of specialized knowledge, or take on a larger  share of the costs themselves. Importantly, these individuals  aren’t necessarily the leaders, kings, or alpha  males in the group of humans.

Instead, their role in starting  violence is due to things like their social network, their  physicality, or their expertise. Or there may be personality factors at play. Whatever it is they’re  offering, they tip the scales towards going to war, either  by making the potential costs lower or the potential rewards greater.

Which raises the question of…why? It seems like it’d be a lot better for  our individual and group survival if we hadn’t evolved to go to war and  were more about peace and love. But for one thing, the kind of group aggression needed for war can help cement group cohesion, because it helps to establish an  in-group, the people fighting with you, and an out-group, the people fighting against you.

That group cohesion may have played a role in humans’ ability to engage in the large-scale cooperation that has allowed  for us to flourish as a species. Stuff like sharing workloads,  helping each other build complex structures, establishing trade  networks, or all the other ways that we benefit from having a group working  together towards a common goal. There’s also some evidence  that being on the winning side of a conflict increases social status  and reproductive opportunities, which means going through a war and winning may be better for you socially  than not going to war at all.

But no one person can gain  that advantage without lots of people being willing to put  themselves at risk of not surviving. So it’s possible that risk-taking  does have an evolutionary advantage, not because it gets individuals more resources, or because chicks dig scars, but  because it’s good for the larger group. But how does that tie back  to the whole daredevil thing?

After all, people aren’t like,  skydiving as a form of coalitionary aggression, although that  would be really fun to watch. So it’s pretty hard to see how that particular behavior might benefit the rest of us. It’s possible that what’s  happening here is just a result of a less dangerous society,  since most of us don’t need to hunt down prey or  fight to defend our territory.

So for the people with a risk-taker mentality, the only other way to satisfy the urge to take a risk is through bungee jumping, or whatever. So it may be that the instinct  that evolved in some people to put themselves at risk is getting redirected to put themselves at risk performing wild stunts. It’s the same mechanism, just a different context.

For all of the daredevils out there taking seemingly stupid risks,  thank you for your service. I, on the other hand, will be  keeping my feet firmly on the ground. [♪OUTRO]