The Birth of the Brain
Today's episode with Dr. Josh Stout is about the growth of the brain, how we got such large brains and what might this mean.
Today's episode is all about the growth of the brain, how we got such large brains and what might this mean.
Eric 0:14
Friday, September 22nd. This is our second episode.
Dr. Stout 0:19
Hi, I'm Dr. Stout. Today's episode is all about the growth of the brain and how we got such large brains. We've been talking about AI in general mind, body evolution. And what. What? What does that mean?
I think of the evolution of the mind and body as completely a single thing that has happened to us or we have made happen. And this is often seen as separate ideas, and I want to really bring them together into a sort of single concept and then unite it with the implications for our evolution. So we often as biologists just think about particular aspects of our physiology and how they might have happened through evolutionary history, but we don't really think about what that means for our overall health and how we should be living. So I want I want to focus on both of these things at the same time, the evolution of our mind and of our physiology and how that will affect our health. So last week we were looking at as we left the rainforest and we became bipeds. So it's sort of our first 4 million years of evolution. And what that had done for our mind. So our minds were ever so slightly larger. Instead of, say, about 350 cc brain in a chimpanzee was maybe 450 brain in an australopithecine. Our teeth got really tough, so we developed jaws that were great for chewing and we developed a bipedal gait so that we could walk long distances without expending too much energy. So this was the time when we were really developing a a goal in our physiology for efficiency and for storing every possible calorie that we would get and not expanding it at all and whenever we could. So that was pretty much the scene for the first 4 million years. But then things began to change and it was another rather abrupt change, much like coming out of the jungle made us bipeds. It was a moment where we entered a new evolutionary niche, where we suddenly acquired large brains and what could have been driving this. So we were already quite good at finding our foods. We were good at social interactions. We could lie to each other, we could detect lies. We had large territories. We would have been able to work together. And we can see all of these things in chimpanzees. So these are things that our brains were already good at. What was what was driving the next change. So first of all, it was the beginning of the ice Age. So there was a another major climactic impact. Things got much drier, so things were even worse. And so we were already sort of the the the the poor relatives of chimpanzees out on the Serengeti without fruit, but having to dig for everything. And now things got even harder. And so we turned to a resource that was not fully exploited out on the Serengeti and that was scavenging. We became obligate scavengers and we started eating a lot more meat in our diets. And so the technologies that would have been developing at this time were the sharp stones. So Australopithecines would have had very simple tools which wouldn't left any any any particular remains behind sticks, maybe maybe some chipped rocks. There's a few out there that people think might have been purposely chipped for for a reason. And we know that there is even monkeys that will use stones to crack nuts and things like that. So the idea of stone tools and sticks wood would have already been in our lineage. But starting around 2 million years ago, you see a huge expansion in brain volume up to around, you know, six, 700 cc's. And this coincides with sudden arrival of stone tools. And so this would have allowed a new source of of calories. We would go to a carcass more able to slice it open, and we would have gotten things that other animals couldn't get. So we could cut through a thick hide that even a hyena wouldn't be able to get through an elephant's hide, probably for a couple of days. But a sharp rock can get in. And then we would have been able to crush a bone of a larger animal, like a like an elephant or a rhino that even a hyena wouldn't be able to bite through. And so one of the main things that we encountered would have been the muscle meat. We would not have been able to get as much in the way of of organ meat is probably why we don't like it. Most carnivores love organ. Meat has a lot more fat in it, but it doesn't preserve well while sitting out on the hot African sun. And so meats, dried meats, this is what we started to to look for. And bone marrow. Bone marrow is very fatty and would have been a great source of calories for our brain. Big brains. But there's one more capability that we we really need to think about that makes us human and that is our ability to throw. We don't think about it as central to being human on the way. We do, say our large brains, but it's actually directly connected to our large brains as we are developing to use the the left hemisphere of our brain is getting particularly selected for and we become handed. But this this region of our brain that eventually becomes the language region is also the region that controls throwing and targeting systems. So I think that the growth of the brain wasn't just about tool use tools enabled the growth of the brain and the growth of the brain enabled tools. But what I think got it going was throwing itself. So chimpanzees throw, but they don't do it very accurately. It's more of a display kind of arrangement. And if you imagine us out on the Serengeti without any defenses, probably the Australopithecines would have been doing inaccurate throwing from a very early time, just as you would see in a chimpanzee. And this would have been pretty effective. We know that today there are groups in Africa that are, you know, herding cows. They see a lion coming. They'll just throw clods of dirt at it and the lion will go away because a lion can't stand having, you know, something hits it in the eye. It will go hungry for a couple of days. If it chips a tooth on something, it might starve to death. So lions not going to mess with you if you are if you're if you're throwing rocks and objects at it, you know it's going to run away. And this was probably our number one defense out on the Serengeti. And I what we see in association with the brain getting larger is changes in the body itself. And so some of these would have been for any kind of tool use. We got stronger thumbs and shorter fingers that allowed better gripping so now we could grip a stick and hit something with it. But this is also the grip that allowed us to hold a stone and throw it properly. Now, why do I think this is not just a matter of, say, the ability to hit something with a stick or a club or, say, hitting one rock against another, but it was actually throwing is you see changes in the shoulder and the waist that are specific for throwing. If you think of a baseball pitcher leaning back, rotating the waist, Homo Erectus could do this in a way that the Australopithecines could not chimpanzees could not chimpanzees with throw sort of sideways from their elbow, whereas a baseball pitcher is reaching way back, are asking their back, twisting their waist. That flexibility is something that first occurred in in the same group that had the first larger brains. And so there's a direct connection between the growth of the brain and the ability to throw and which is interesting in terms of, you know, thinking about health aspects that while we have evolved as these very efficient machines that are storing calories, we've also evolved in things where we have we have the evolutionary ability to produce explosive energy, very, very quickly. And that's directed probably not the way modern baseball pitchers are. I don't think it's good for you to pitch for 3 hours at 100 miles an hour, but I the development of of of being able to throw something targeted ten, 20, 30 times a day is part of our evolutionary history. And I think it's something that we've neglected in sort of most of our ideas of exercise. Maybe in the martial arts, you'll get explosive power like that. But combining it with full rotation with the idea of the arm flexing backwards, these are things that are central to our evolutionary history and we should be able to do it with both hands. Now, we became right handed probably because it gave us just a slight edge to the left side of our brain is a little bit better at targeting, a little bit better coordination. And even a tiny edge was going to give you a big advantage. But traditionally people have been able to throw with both sides. There is there is there is, you know, account of the Europeans landing on terrible off waggle and meeting a one of the inhabitants. And, you know, of course, it didn't go well. And so the first thing we did was shoot him as soon as we saw him. And he he then started picking up rocks after he'd been shot, dodging side to side, throwing with both hands. He took out three people before they brought him down. Finally, he broke a guy's collarbone, knocked two guys in the head, knocked, you know, they were they were he almost took out a group of Marines just throwing rocks at them.
So this was something that that that people could do really well. I you know, there are still people out there who can who can just go out and kill a rabbit. You know, I had friends who were trekking in Mongolia and the guy said, I'm going to get you dinner. And they looked around and it was just grassland in all directions. And he went out and came back with two rabbits and he just thrown rocks at them. This is something that is in our history, and we certainly know a baseball pitcher can do it, but it's something that we all can do, maybe not at that level. You know, I've clocked my own ability to throw at something and it's not great. I could barely break 40 miles an hour, but that would be enough to, you know, throwing a baseball sized rock would, if definitely throw it accurately. If you could throw it actually, you know, and that was the speed I from about 20 or 30 feet, I could mostly hit something at about 30 to 40 miles an hour, which is not great. I would really, really hurt whatever I was throwing it out. So throwing became central to who we were. But then we have to think about what happens next. You know, in our in our progression. So Homo Erectus would have become suddenly one of the top dangers out on the Serengeti. By throwing rocks at things, we are now able to stand down most things during the day, at night, we can't see as well. We have to gather and find some sort of defense. But during the day out in the Serengeti, we can throw rocks at almost anything. And most things are going to be deterrent, not an elephant or a rhino, but the predators are. We're now much, much safer from the predators because we can do this. It's going to take a lot more lions to take us down. And so what became our new threat was each other. And so now we're running into the problem of we have to fight other groups of humans. And so what this would have been called was confrontational scavenging. And so this would have started off. You see the birds gathering, you run to the carcass, you slice a piece of meat from the carcass, and then you run away before the bigger predators get there. And so that was sort of the general model. And there would have been some, you know, hyenas and lions coming. We would have thrown rocks at them, cutting off that piece of meat, defending it long enough, and then going away.
Eric 12:44
Because you're a sharp stone and you're throwing stones become important.
Dr. Stout 12:49
Well, you need the sharp stones to cut with, but you also need things to to, to, to to throw at at the predators. But that could have been almost anything. Clods of dirt, rocks. But yeah, the stones would have hurt more. And having a sharp stone would have been particularly useful for for both slicing and, you know, it might have hurt more. But when it came to other members of our genus other Homo Erectus now now we had another issue they could throw at us. And so you have two groups who are able to throw clods of dirt and rocks at each other. And this is when I think we combined our number one tool, the sharp stone, with our throwing weapon. And so we sharpened hand axes all the way around. So they were like throwing stars. And this wasn't a hunting tool, primarily, in my opinion, although it could have been, I think they would have been generally too valuable to use that way. Most animals that you could kill with the stone, you could kill with just a random stone, but a sharp stone would have been particularly effective against a another human who was standing there naked screaming at you. It would a sharp stone, even if it didn't kill them, would definitely do some damage. So, you know, even at 30 miles an hour, not, you know, your best throw, if you just winged them, they would be in big trouble. And so this became the one thing that we made more than anything else in our history was the hand axe, because it was our knife, it was our weapon. It was the thing you went away with holding it in your hand because you had to have some way of defending yourself. And I think it led to some interesting aspects of our psychology so that we're very aggressive. If you have a bunch of people with stones, whoever is not the most stones and is throwing them well, well more rapidly is going to be winning any kind of contest. So having a pile of stones and a lot of people is the way you win any kind of territorial battle. But what happens when you have one person against one person? Let's say it's a male male competition for a mate. So you've got two guys fighting over someone or you've got just got two guys who've met each other at the edges of a territory, right? So they've met each other at the edge of a territory. Each one's got their hand axe. How's that going to go. If you're the first one to throw you lose. The other guy is going to run right up to you and hit you from four feet away with his hand axe, or he'll just stab you because you don't have a hand axe anymore. And he and he's got a sharp knife. So it became an advantage, an evolutionary advantage to not be the first one to throw, particularly in interplay, personal interactions. So we while we became very aggressive and we got really good at throwing sharp things at each other and were able to defend large territories this way, we also figured out a way to not kill each other. And this is something you see amongst dangerous animals, you know, throughout the animal kingdom, particularly with male male competition. So people some people have these weird ideas that hand axes were for display and that the beauty of your hand axe was to attract a mate. But I find that a bit of a stretch. I think they were for what they look like they were, they were knives and they were for cutting and they were for chopping and they were also for throwing. And if you think about male male competition with dangerous animals, you have things like the, you know, the elephant seal slashing at each other. But they make sure that they have, you know, enough blubber so they're not killing each other when they slash each other's throats, you know, more typically you can think of something like, you know, bighorn sheep or a or a stag to stags are clashing antlers. Those antlers are full of spikes that could easily kill each other, but they run head on to each other and then it becomes a shoving contest and the biggest stag wins without killing the other one. And so this is how evolution figures out ways to deal with the danger that we present to each other where whoever passes on their genes wins the competition. So everything matters. If that involves killing the other person, so be it. Passing on your genes is all that matters. But if we kill each other all the time, we won't exist. And we are.
Eric 17:05
None of us will get to pass on you.
Dr. Stout 17:07
And we're a communal species and we live in communities. And so if you wipe out the rest of your community, you're actually starting to cost yourself something. There's it's always difficult to come out with a sort of a a way for defending any kind of of group evolution. But you can certainly see if the people next to you are, you know, related in some way and they have some of your genes. Not killing them is in favor for your evolution. And we would have been living with other males who are relatively related to us. And so killing them was probably a bad idea. So backing down became something that we were able to do to scream at each other, wave the stones back and forth, and then step back. And so one of the interesting things that you see at this time is our australopithecine. Males are about twice the size of the females. Homo Erectus males are 20, 25% larger than the females. So we're becoming in some ways more egalitarian. If you think about the way different primates mate, where you see males and females of the same size, that's a monogamous relationship. What you're seeing here is something I probably with male male competition, possibly some sort of polygamous relationship, multiple wives, sometimes one, sometimes more depends, but competition even between males for mates with perhaps the ability to not kill each other for it. So actually backing down sort of a mutually assured destruction seems to be basic to the way we think about things. The interesting thing is this is probably when when a more advanced form of language is also developing. So as tools are developing and we're seeing the growth in the left hand side of the brain, we're also developing the regions, same regions of the brain that we now see call, you know, the language regions. This is sort of a more old version of thinking about the brain, but the linguistic regions of the brain are the same ones that control eye things like hand-eye coordination and the ability to do small movements with the fingers that you would need for tool use and swinging a hammer or something like that. And they're definitely the same regions that involve throwing. And I think it's really interesting the way the way language is built with a subject and a verb and an object kind of copies the way we think, where we throw something at something. I throw the rock.
Eric 19:42
Out.
Dr. Stout 19:42
At the other person, and that this is a sort of grammar that's built into the actions themselves. And so the grammar portions of the brain are also the ones that control targeting a hammer onto the thing you're hitting. These are the same the same regions that are controlling these small movements. And the the, the, the intent behind hitting something is the same ones that are controlling things like syntax and word formation. It's the Broca's and Wernicke's areas of the brain are the same ones that are controlling a lot of tool action and in my opinion, auto throwing. Now, again, these are this is old ways to think about the brain. Like, say if you imagine an atom is something with a nucleus and electrons spinning around it, you are about a hundred years or more out of date. But it's a good way to think about an atom, right? So thinking about the brain with language regions that are then controlling and talking to each other in particular areas like this is, is a somewhat out of date way of thinking about the brain. But but it's useful and useful model. It's a useful model. And it's and it's not completely inaccurate. Right. It it it is somewhat true and can can be used that way. So we definitely are seeing the left hand side of the brain getting larger. We're seeing the right hand side of the body's bones getting thicker. So they're being used more. We're becoming more fully right handed. And we're we're probably developing the ability to have language at this time and other physiological changes. So the the throat is starting to change. A chimpanzee can breathe and drink water at the same time, whereas you as a human cannot do this. And more humans would survive if we could, right? So we have to get the Heimlich maneuver or we die when we choke on something. This is an evolutionary cost. So why did we do this? Why did we we we lowered our larynx, we lowered our voice box. And probably it has something to do with communication. And that communication was very important to us or we would have not taken on this cost. And so sort of piggybacking on this development of the brain having to do with confrontational scavenging, having to do with throwing sharp rocks at each other, we were also building the nature of language into our brain. And so it's it's built on what we were doing, the idea of hitting something with something else. It's built on the already existing Machiavellian sort of ways of manipulating each other. And now we've done this into our display activities. We've got this into into the tools we're using and how we how we interact with each other has all been associated now with language. And so now we can do with sounds coming out of our mouth. What we could only do physically before that. So the way a chimpanzee would say comfort another chimpanzee, we can now
perhaps do with sounds, right? So we don't know exactly when language is starting, but we're seeing the region of the brain and we're seeing physiological changes that one would expect if language is happening at this time. Right. So not saying that chimpanzees don't have very fine brains that are very good for social interactions and that they are, you know, a fully sentient species, but they don't have the same linguistic capabilities that we do. Their brains simply are not as large. There are many things they can't do that we can, such as chipping rocks with a pattern and a form that you can actually see the form happening, you know? So this is probably where we're getting the beginning of mental images that we can then copy into a particular shape. All of these things having to do with the beginning of abstract language where we're saying sounds that represent something many animals.
Eric 23:27
Can do this now, this is what you see, the beginnings of which you talked about in the in the last conversation when we began to imagine the tubers under ground.
Dr. Stout 23:37
Right. So what we well, all animals have some way of modeling the world around them. All of this is involving imagination in some way, because modeling the world around you, in your brain is imagination. But yes, now this is coming to an another level where it's not just imagining how I can fool someone else with my ideas, but it's it's it's imagining. What does a rock look like when I look at a rock? How am I going to get this hand axe out of the rock? Imagining the hand in the rock is is a whole nother level of imagination. And so it's not art yet, but it's definitely a concept in our head that we can now make and we pass this down. And so hand axes become the number one thing that gets made. We see them everywhere they spread across the world. There is hand axes in every place that people have have have gone because this was what we made for the next 2 million years or so everywhere. And interestingly, if you go to some of these sites in Africa where people were making hand axes, you'll find them just heaped on the ground. Everywhere you look, it's just piles of hand axes. And so this would have been associated with the first development of a true home base where, you know, a an australopithecine would have been roaming from place to place. There were probably trees they liked to go to because they were great for shade near a river, etc.. But now it's worth stockpiling weapons so that if another group of Homo erectus comes along and you're the ones with a pile of hand axes, you can throw hand axes all day, How many hand axes can they have? They can have two, right? So you now have a defensible area. It's not the same as having a roof and walls, right? We're not in houses yet. We're not even in tents. But having a defensible area with a giant pile of your weapons gives you a place sort of that is that is more significant rent than the rest of the territory around you. Right. So there was probably shade, there was probably water. That was a reason to have this spot, but also access to good stones and then building up a pile of them where you live became important. So this is also building up the idea of connection to a place. So certainly chimpanzees would have had territory, but with the development of language, we're starting to build larger communities with language. We can we can we can interact with larger groups, we can defend larger places. And now we're connected to particular places to to to the land, because that's where our hand axes are, and that's where we get the rocks that we use to make them. And so we were certainly still nomadic. We're moving from place to place. We probably had several home bases that we'd move through seasonally as as systems change and as weather changed.
So these were these were sort of a combination of mental and physiological changes that are going hand by hand, hand in hand at the same time. This is why I say that the mind and the body are not two separate things. These are happening absolutely together. So as we get changes in the shoulder blade that allows us to bring our hand behind our own bodies, we're also getting a larger brain that allows us to talk to each other. And so we're getting the ability to have a a mental concept that we can shape in language in some way so we can say a word in our head and then we can say it out loud. Right? So chimpanzees have communication, but they probably don't have this sort of secondary linguistic aspect in their own brains when they're doing it. It's hard to say what humans do. We have, you know, two levels. We have the underlying thoughts and we have the language. Our thought is not simply language. Language happens after thought, but we organize our thoughts with language. And so this is this is now a capability that we're developing and we're able to now build, as I said, communities and home bases and a group of people who interact with each other with language. And so now this is how we, we, we we comfort each other, how he threatens each other, how we organize, right. So our our hunting ability becomes much more advanced at some point in sort of the first million years of of Homo Erectus, we start developing these new capabilities where we go from being confrontational scavengers, running out to a carcass, scaring off the other scavengers, scaring off the older humans, stealing a piece, running back to actual hunters, and we start becoming more organized and we can chase animals to a particular direction over a cliff. Maybe. I don't know if Homo Erectus was doing that much, but certainly we could. We could organize ourselves to to maybe even run down animals.
Eric 28:25
Because of language.
Dr. Stout 28:26
Because of language, and because of our, you know, ability to talk to each other about what we're going to do, make plans the same way we're able to pass on the concept of hand handshakes. Now, a lot of this stuff can be done without language, right? So a wolf can organize a wolf pack and go off and do a hunt without without language. I suspect I could make a hand axe If I could make a hand axe. They're not that easy. But someone could make a hand axe and you could learn how to do it without ever using language. Right? You could just copy their activity. But language makes all of this easier. You can say, No, no, no, not like that. Right? You you you can do things with language that is more difficult without it. Now, I don't think we had the fully developed language that we do today. It wasn't it wasn't at that level yet. And we can see it in the physiology. So I mentioned the throat dropping. This happens over the course of a human's life. So we start off as babies who can nurse and breathe at the same time. That's important, right? And we have little turned up noses and we can and we can suck while we breathe through them and we don't drown. So over the course of our lifetime, or all the way through puberty, our larynx is dropping and we are learning to form words. So a four year old having difficulty with words. Some of it is simply they don't have the apparatus that they will later in life to make those sounds. And so we're seeing this in the in Homo erects. So Homo Erectus would have had a throat, something like a six year old. So not fully developed by modern human standards, but certainly one that is they would not have been able to eat and drink at the same time area and breed at the same time. And they would have been able to make more complex sounds than they did before their larynx drops. So we're seeing a physiological advancement in language, but it is not physiologically complete yet. They they don't have the same kind of of innovation. They don't have we have really I we have really precise control of our of our of our chest, of our tongues of of of the apparatus for speech. This is not as developed yet in Homo Erectus. So they would have definitely not have any opera singers. They would have had the diaphragm control, they wouldn't have had the breath control to make the kind of sounds that are modern human can make. But they're on their way. They're vastly beyond what a chimpanzee could do. And the brains are about twice the size of chimpanzees at this time. So, you know, 700 cc's as opposed to 350. So this is a major, main, major change. And it's a major change in our way of life. We are now, as I said, meat eaters. We're not just I digging up roots and occasionally, you know, catching a lizard, but we're on purpose going for large animals because these are the ones that are less that the predators are less able to get into and take away. Right. So if something catches a rabbit, we're not going to get any of that rabbit. But if something kills an elephant or an elephant just dies so nothing can get through the hind. So we might be the first to get through that high if something else is sort of burrowed into its stomach and has eaten all the contents of the stomach, we can still cut away the hide and get to the meat. We can, with a stone tool, take out the joints in the leg and take out a whole leg and run away with that. So where we're eating the things other things don't like to eat, we're able to get at them in ways other things aren't able to do. And then we can take a big rock and we can break a bone with it. We even a bone of an elephant and get to the very rich, fatty bone marrow inside. So these are our new techniques that we develop. The basically, the moment our brain increases, we develop these techniques. And we couldn't have gotten these techniques without our brain increasing. I think the piggyback chicken and egg here, I think the piggybacking started with throwing that it was something we were doing already. And as we got better at throwing, we could get carcasses more easily because we could scare off the predators simply by throwing clods of dirt at it, something that chimpanzees already do. So it's already in our behavior. We got incrementally better at this, and then suddenly we got a lot better when we combined it with sharp things that could cut into the into the meat. So just like moving out of the Serengeti, there wasn't a million years of slowly becoming a biped. There was We lived in the jungle and then suddenly you see several bipeds happening at the same time. There's almost no intervening moment. So you have a whole bunch of bipeds living out on the Serengeti for 4 million years, chewing roots, and then suddenly one of their brains expands roughly double. And in like a hundred, 200,000 year period, we go from sort of transitory Homo Habilis to Homo Erectus, and then we stay that way for the next 2 million years.
Eric 33:18
A transition takes place over a hundred million years.
Dr. Stout 33:21
100,000.
Eric 33:22
So 100,000 years, yes.
Dr. Stout 33:24
And then we stay that same way, more or less for about the next 2 million years, with our brains slowly growing, but our physiology just staying kind of the same.
Eric 33:32
It's such rapid, rapid change. This slowed by stasis.
Dr. Stout 33:36
This seems to be the way evolution often happens when when a new ability is developed, you select for that ability very, very quickly. And then once you've solved the problem you're trying to solve being a biped or being intelligent, now you have a new evolutionary niche that you fill, and so you then try and maximize the ability within that niche, but your evolution slows down. And so sometimes this is called punctuated equilibrium. Some people call it evolution by jerks. It's like a just sudden, like something changes and then you're sort of at a new level. It's not that it's in a moment. It could be, but mostly it's not. In a moment. A momentary change would be something.
Eric 34:16
Thousand years is 100,000 years.
Dr. Stout 34:17
Yeah. It's time. It's time. Yeah. Sometimes there are things when, say, let's say, two chromosomes get fused together. You can't. You can't. That that's a new species in a moment. And then evolution could after that. So sometimes that could happen where it really is instantaneous. But I'm not talking about that. I'm talking about a series of of, you know, incremental changes, but they're selected for so heavily, whoever throws the rocks better gets more food, and then that quickly turns into whoever throws the rocks better, gets more food and more mating opportunities because we compete with each other. And if you're getting food and mating opportunities, evolution loves you. And so, you know, we went in that direction very, very quickly. Yeah.
All right. I guess I will go on in this direction. So next week I'll be talking about AI, further development of the imagination, and we'll get into things like art and aesthetics and how we got up to, you know, modern language as it is today and what kind of things that would have been associated with how we lived, what our diet would have been, what kinds of exercise we would have been doing at this time, say 200, 100,000 years ago in that range.
Eric 35:30
All right. Excellent. Well, thank you very much. See you next time.
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