Chimps.
They live in rainforests, subsist primarily on fruit, are hugely aggressive,1 a male is about 40 to 60 kg (88 to 132 lbs) and 10% body fat, a female about 32 to 47 kg (70 to 104 lbs). They live and forage in groups with explicit dominance hierarchies, and reproductive success and happiness (or at least lower levels of cortisol) is largely dictated by your place in that hierarchy.
Modern humans.
We live everywhere in the world, subsist primarily on junk and fast food, and are incredibly non-violent and non-aggressive for great apes. A male is maybe 75-120kg (165-264 lbs) and about 20-30% body fat, a female is about 60-90kg (132-198 lbs). We live in large groups within a mix of hierarchies, most of them ranked by “status” rather than explicit hierarchical rank. The status games the largest chunk of people in the West collectively recognize and play revolve around education and career and how much you make, although happiness and cortisol levels are “correlated but not tightly correlated” with those things.
How did we get here from there?
Broadly: we started walking, we got better at walking, then running, we got better at using tools, fire, and cooking, we got swole, we split into a couple of roughly-equal species who lived side by side for hundreds of thousands of years, then our line self-domesticated and in an eyeblink, wiped everyone else out.
And throughout all of this, our brains were getting steadily bigger.
The story I’m going to relate to you is pieced together from several books, but the biggest three are Richard Wrangham’s The Goodness Paradox, David Reich’s Who We Are and How We Got Here, and Svante Paabo’s Neanderthal Man.2
Also, all the high quality pics are from the work of John Gurche, who is like a one-man powerhouse of paleoanthropological modeling and recreation, and whose work I greatly respect and admire.
I’m not a paleoanthropologist - if I’ve made any mistakes here, I welcome correction and commentary. But this is my current best understanding.
Chimps and humans diverged 5-7Mya.3 The root of the divergence was a change in habitat, largely brought on by a change in climate to the cooler and drier driven by Milankovich cycles - chimps love rainforests, but as they contracted, there was an ecological niche that was relatively open in savannahs. The chimps that went out there and took advantage of that savannah niche started changing.
We started walking. First they changed into Ardipithecus and Sahelanthropous about 5Mya, which were more bipedal than chimps but still would have had funny, inefficient gaits due to non-inline toes and some other skeletal inefficiencies, and were still adapted for climbing in trees, as can be seen in their long arms and fingers.
We got better at walking. Then starting around 4Mya and going to about 1Mya were the habilenes, sometimes called Australeopiths.
They were slightly larger than chimps, with slightly larger brains, but still small skulls overall. There were roughly a half dozen of species of Australeopiths, with some more gracile and some more robust and plant adapted (judging from their teeth). They used simple cutters and scrapers (Oldowan tools). Some species were much stronger walkers, featuring inline toes and foot arches and other adaptations. There’s a famous set of footprints from a larger male, a female, and a child found in Tanzania. Their brain size was roughly 300-600 cubic cm (cc).
The habilene lineage continued with H Habilis and H Rudolfensis around 2.3Mya, with brains a couple hundred grams bigger. Habilis had a face closer to Homo Erectus, and Rudolfus had a face closer to Australeopiths. These had brains roughly 500-800cc, with Rudolfus larger in volume.
We started running, and got better at tools, fire, and cooking. Finally, we reach H Erectus around 2Mya (and going to about 200kya). If you’ve heard of Java Man and Peking Man, those were H Erectus. They were much closer to what we’d recognize as human, at least in their bodies. Tall and slender (males might be 6ft and 150lbs and ~10% body fat), and fully adapted walkers.
They had the “persistence running package.”4 Their tool use got more complex than H Habilis tool use, as they created the bifacial, tear-shaped Acheulean handaxe. They were hunter gatherers, used fire, cooked food.5
Cooking was a huge deal, as Richard Wrangham’s Catching Fire goes into at length. It converts indigestible starches to digestible starches, pre-processes food to be more readily digestible, reduces pathogens, and a host of other benefits.
Broadly, the brain and the gut in modern humans are each about a kilogram, roughly 1:1 vs the more usual 1:10 ratio in mammals, and cooking was foundational to allowing that massive 10x change.
H Erectus brain sizes ranged from 600-1300 cubic cm brains over time and range, steadily getting bigger throughout the time they were around.
We got swole. H Erectus got swole at some point and became H. Heidelbergensis, who is important to our story as our own ancestor and the ancestor to a number of confrère species. Because it’s a huge pain to type out “Heidelbergensis” every sentence, I’m just going to call them HH.
So HH is around 600kya, persisting to 200kya. Much like H Erectus, they used fire, simple tools, they cooked. Males were 5’ 9” to 5’ 11” and 90-100kg (198-220 lbs), and would have been ~10% body fat, females were 5’ 3” to 5’ 5” and 70-75kg (154-165 lbs).
HH were absolute units. Those stats for males are a couple kg off of Phil Heath (7 time Mr Olympia), except they didn’t have gyms and steroids and protein powder, HH had to go out and hunt every calorie those muscles needed every day,6 and their workout plan was “I’m gonna go out and hunt a Wooly Mammoth with spears today.”
Speaking of spears, they had them. HH graduated to Levallois tools, which required more complexity, and also began creating spears and projectile points. HH had a big ole brain too - 800-1400cc, the upper end of which is basically “modern H Sap.” Brains had been steadily increasing in Homo for 5M years now.
So why is HH important, besides being the Mr. Olympia of our forebears and having a full sized brain? Well, they brought the next 3 lines of humanity into being - Neanderthals, Denisovans, and Archaic H. Sapiens.
We split into three species.
Denisovans hail from an HH population that migrated into Asia. We don’t know as much about the Denisovans, because all we have from them are some teeth and tiny bone fragments. They had very large molars, indicating they may have been adapted for eating fibrous plants. They were probably more robust than modern H Sap, but we don’t really know. They interbred several times with H sap somewhere in SE Asia, leading to high ancestry in Papuans, Melanesians, and Australian Aborigines, and ancestry in various Pacific island populations from subsequent outmigrations. All the samples of Denisovan remains we’ve found are in Siberia, but a larger range is assumed for various pretty good reasons, to extend across SE Asia.
One fun fact - we think the Tibetan altitude adaptation gene / ability came from Denisovans.
Around 500-700kya, an HH population in Europe started becoming the Neanderthals (H Neanderthalis), who persisted until about 30kya.
Like their HH predecessors, Neanderthals were robust, with some signs of cold-adaptation lowering their height, but retaining significant muscle mass and dense bones. Neanderthal males might be 5’ 5” to 5’ 9” and 75-100kg (165-220 lbs), and they would have been ~10% body fat. Once again, this is “bodybuilder” territory, but without gyms and protein powder.
Facial width indicates the *average* Neanderthal male had the same testosterone levels as a 1/10k human male today (far, far out in the tails of the bell curve), and this would have been true for HH as well. They had 1200-1700cc brains, with an average around 1500, slightly bigger than H Sap brains today.
Neanderthals interbred with both us and Denisovans, with multiple fairly significant cross-breeding events throughout our shared history.7 There is in fact a 50/50 Denisovan Neanderthal mix in the ancient hominin skeletons we’ve genetically sequenced.8
Culturally, they had no needles or awls, very limited fishing or seafood, and very limited migration or transportation of more than 25km.
They were almost certainly undomesticated, with higher reactive aggression and smaller group sizes as a result. There are multiple examples of self-cannibalism (Neanderthals eating Neanderthals).
Neanderthals and archaic H Sapiens actually lived in the same general area (the Levant and parts of the Middle East and Europe) for hundreds of thousands of years. Sometimes the balance would shift more towards one or the other, but it seemed a relatively stable equilibrium. This equilibrium was not to hold, however.
Archaic Homo Sapiens. 500-600kya lasting to 200kya. We got smaller - males would be 5’ 6” to 5’ 9” and 60-75kg (132-165 lbs) and around 10% body fat, females 5’ 2” to 5’ 4” and 55-65kg (121-143 lbs). This is still larger than modern H Sapiens,9 but smaller than our HH ancestors.
We descended from HH too, but we haven’t always been “ourselves.”
Our immediate ancestor, archaic H Sap, didn’t have the characteristic rounded skull we use to identify H Sap skeletons, and had a wider and more robust face in males. Skeletons intermediate between them and us (so partially domesticated) were found in Jerbel Irhoud in present-day Morocco.
And what distinguishes “archaic H Sap” and modern H Sap? Domestication. Specifically, self-domestication.
We self-domesticated.
As we hear about in The Goodness Paradox, domesticated animals have a recurring package of traits:
Lower reactive aggression
Reproduce faster
Neotenic appearance and behaviors
Smaller brain
Smaller bodies
Lower sexual dimorphism
“Reactive” aggression there is contrasted with “proactive” aggression, which together cover the aggression scale. For the difference between reactive / proactive - think hot vs cold, or immediate vs premeditated.
What’s the difference between an undomesticated and domesticated hominid? An undomesticated hominid has greater sexual dimorphism, higher reactive aggression (and many more aggressive incidents in a given time period), and generally a more hierarchical society with an “alpha” male who has many more offspring. It means it’s harder to cooperate, that group sizes are lower,10 that breeding is much more interwoven with violence and dominance games,11 and that it’s a more violent society overall, because if leaving offspring (the primary drive in every animal ever) relies on being at the top of the hierarchy, people will always be coming at the king to get those sweet baby gains.
Modern Homo Sapiens has been domesticated, and we have all the physical and behavioral traits. It happened over time, of course - by 200kya our braincase was rounder and our faces smaller. At 40kya we had smaller more gracile skeletons overall. At 35kya sex differences in height and tooth size decreased (making us less sexually dimorphic), and brains finally became 10-15% smaller.12
Wrangham’s best guess of when self domestication started was 500-700kya, ie soon after H Sap and Neanderthals split, so we were likely archaic H Sap for 200-400k years, on a trend of continuing self-domestication.
What was the biggest consequence of self-domestication? Because we were less reactively aggressive, we were now able to live in larger groups.
Larger groups led to better cooperation and much more technical advances. Ancient tool development is typically divided into lower Paleolithic, middle Paleolithic, and Upper Paleolithic,13 and upper was driven by domesticated modern H Sap, and represented a step-change in creativity and range.
The Aurignacian, Gravettian, Solutrean, and Magdalenean tool eras all happened in this short span. Tools got much more complex, much finer, and more diverse. Art and symbolism exploded similarly. It was like the Renaissance, but you know, for hunter gatherers.
This is interesting, because it implies that despite HH and Neanderthal brains being basically human in size (and presumably capability), there wasn’t much change in the areas we might expect - better tools, art, more complex problem solving - for hundreds of thousands of years. And we DO see this effect with culturally modern, fully domesticated H Sap, with the same sized or smaller brains. The fact that this is true - that we don’t see the direct fruits of modern-sized brains as we’d expect, in technology and culture, for hundreds of thousands of years,14 is in my own opinion supportive of Geoffrey Miller’s theory that brain size was largely driven by courting and sexual selection rather than literal survival advantages, because H Erectus and HH existed across Eurasia and Africa and seemed fine survival-wise for a long time with basic lower and middle Paleolithic tool packages.
The big change that allowed the explosion of creativity and technology was self-domestication.
The Category Killer
Because we lived in larger groups and used natural resources better (as both archaic and modern H Sap), we competed for resources with other groups of ourselves. Much in the same way the intense competition and warring in Europe between relative technological peers led to a rapid accretion of technological advances and better warfare tactics and strategies, eventually going out and conquering and colonizing the rest of the world, so our domesticated H Saps followed the same path.
The touch of the divine
At some point roughly 60-50kya, for reasons that are still not clear,15 there is no change in brain sizes, but a massive change in technology, art, symbolic thought, and culture (the Cognitive Revolution). “Culturally modern” H Saps were born.
In our last outmigration from Africa, the “culturally modern” H Sapiens completely dominated and wiped out every single confrère hominin species everywhere modern H sap ran into them, likely due to larger group sizes, distance weapons, and better coordination and cooperation leading to better war technology, tactics, and strategy. We were a “category killer,” and the category being killed was “all other hominins in our ecological niche,” because we wanted it all for ourselves.16
Remember now, that Neanderthals were absolute units, massively bigger than us, with massively higher testosterone, and correspondingly higher strength and physical capability. They were the very definition of an alpha Chad. In a one-on-one match, or even a two-on-one match, they would surely dominate most H Saps, archaic or modern, and would be able to throw them around like toys.17 And yet the Herculean adonises were utterly dominated and wiped out by us tiny, domesticated things. It must have felt like being overwhelmed by an army of Furbies. Furbies who came en masse, and fought really well.
And this is the real takeaway, I think. Whenever people like Andrew Tate says they wish they lived in a world of might-make-right, where Nietzchean supermen could stride like roughshod Herculean gods over their lessers, we can tell them: we already tried that. Our direct ancestor was that, our hominin brother species the Neanderthals were that, and we absolutely dominated them on every front, and wiped them (and every other hominin alive at the time) from existence.
Focus on what matters - cultivate friendships, join large groups working together to drive technological advance, and live in large groups for the exchange and improvement of ideas and to foster creativity. It was our recipe for success 50kya, and it’s what led us to being the dominant species on the planet.
I think we should think of this when we’re tempted to “other” and “outgroup” people with different politics, too. Better cooperation and understanding was literally our superweapon. If we mess it up, and nuke each other or create a malevolently used AI, or get pwned some other way, it will be because we’re so busy arguing about pronouns and gun control that we don’t have the collective coordination capacity to discern and enact the right decisions. And that’s on us for indulging in our weaknesses rather than our strengths.
About 600-1000x as aggressive as modern humans by many measures.
Honorable mentions: Geoffrey Miller’s The Mating Mind, Dan Lieberman’s The Story of the Human Body and Robin Dunbar’s Grooming, Gossip, and the Evolution of Language.
Throughout this article, I’ll be using Mya and kya, which are respectively “million years ago” and “thousand years ago.”
Nuchal ligament, large semicircular canals, Achilles tendon, short toes, large butt. Persistence running likely started with scavenging - if you run as soon as you see vultures, you can get to freshly apex-predator-killed animal remains before heynas and other opportunistic scavengers get there, and get some meat.
Cooking as of 1Mya, prior to that they cut and tenderized food with tools, which also makes the food more digestible and releases more calories to be absorbed, but to a lesser degree than cooking.
Both HH and Neanderthals likely had primarily meat-based diets. We know this from Neanderthals thanks to isotope and tooth enamel analysis, and infer backwards to HH. So they *literally* had to go out and hunt their food every day, because plants weren’t a big portion of their calories.
The majority of the breedings (which recurred on a large scale over many thousands of years) were male Neanderthal and female H Sapiens. Obviously, the original gigachads stealing our women.
Denisova 11, a female fossil from ~90kya with a Denisovan mother and Neanderthal father.
Well, not modern AMERICANS, who average 5’ 9” and 86kg (190 lbs) in males, but a lot more of that 86kg is fat (26kg roughly, vs 7kg of fat in archaic H Sap that height).
But modern H Sap Hadza (a hunter gatherer tribe in Tanzania), males are roughly 5’ 5” and ~45-55kg (100-120 lbs), so ~20kg less than archaic H Sap.
Neanderthal groups, for example, were typically the size of only 1 or 2 families of immediate relatives, consisting of 10-30 people.
Archaic H Sap, partway on the road to domestication, had groups of roughly 20-50 people.
Modern H Sap had groups of 20-100 people.
Higher aggression tendencies really makes cooperation and collaboration harder. Those smaller Neanderthals group sizes also whacked them on genetic diversity, which was much lower than in H Sap.
In chimpanzees, males routinely go and beat up on females “just to show them they care.” In fact, one of the major “coming of age” behaviors seems to be doing this - beating up each female, one by one, once a male chimp is an adult. In alternately horrifying and grimly amusing “through a mirror darkly” fashion, this seems to be a sign of regard and affection. In fact, each female has a particular male who beats her most often / most severely - and it is that male who most frequently fathers her next child.
When before in the previous 200-300k years they were getting larger, going from 1200-1300 cc to roughly 1500cc.
Tool development prior to modern H Saps was glacially slow. The lower Paleolithic period is ~3.3Mya to 300kya, a full 3 million years, during which there were minor changes as the H Habilis Oldowan toolset was upgraded to the Australeopith Acheulean toolset. Notice who else is in here? H Heidelbergensis, for a good part of it’s temporal range, with a full size brain but limited tool advancement (basically spears and projectiles). Neanderthals for probably 100-200k years too, and who had essentially the same tool package as HH until the Levallois techniques were formed in an area where H Saps and Neanderthals lived near each other and could trade or steal tool technologies from each other.
The middle Paleolithic is 300k - 45kya. This is the time when archaic H Sap and Neanderthals and Denisovans are all cruising around and interbreeding, with none achieving real dominance over another in terms of macro population distributions. Development was faster, but still slow - we got the Mousterian / Levallois tools out of this, with a broader range of tools and more complexity.
Finally, there’s essentially a step change and we get the upper Paleolithic, which is 45k-12kya. Basically, hunter gathering until agriculture. There was a dramatic acceleration in tool development, driven by fully domesticated, culturally modern H Sapiens.
Actually H Erectus itself, which existed up to 200kya, shows the whole brain size evolution with very little tool, art, or symbolism development corresponding with a doubling in size, with earlier specimens having 600-800cc brains 1-2Mya, and later specimens at 400kya having 1200-1300cc brains, but tools largely staying Acheulean.
Look at this graph - https://imgur.com/GF9KJGB - specifically look at the “technological progress” line chart at the bottom any time before 200kya, and the huge upslopes in brain sizes amongst multiple species (Erectus, Heidelbergensis, archaic H Sap), extending well into modern H Sap ranges during those times, but with “progress” basically flat nonetheless.
Speculations include FOX gene mutations and / or esophogeal changes allowing greater capacity for language, changes in brain organization or wiring, larger groups leading to greater idea exchange, a creativity or technological tipping point achieved after a slow and steady increase, and more.
And I personally find it rather ominous and telling that essentially every other archaic hominin (H Erectus, H Heidelbergensis, archaic H Sap itself, possibly others like H Naledi), who were all global in extent and had survived multiple climactic shifts, lasted til ~200kya, which is right about when modern H Sap would have been fully domesticated, and even though the technological Upper Paleolithic tool and creativity explosion hadn’t happened yet, at this time they would have had the 2-3x bigger group size and the famous human predilection for slaughtering outgroups that is so perfectly balanced by the greater ingroup cohesion and lack of aggression.
I’m not suggesting a previously unknown outmigration from Africa of moderns, I’m suggesting archaic H Sap - which we know had been undergoing domestication selection for hundreds of thousands of years - got domesticated enough in its global range to wipe out everyone else around then, because that’s about when moderns got domesticated enough in Africa. Then we moderns wiped them out when we expanded and took over the entire earth, which becomes an ongoing trend (Yamnaya, etc).
Speculation, yes. But to me, it’s telling in the same way that “as soon as H Sap enters a new landmass, all the megafauna go extinct an archeological eyeblink later.”
Remember, Neanderthals probably had 30kg+ on non-archaic H sap hunter gatherers (Hadza men are 5’ 5” and 45-55kg vs Neanderthals of the same height at 75-90kg) , and that was 90% muscle. They would have had 10-20kg on archaic H Saps.
And if 10kg sounds low - that’s 22 pounds, 20 of which is muscle - that’s an entire weight class in most size-categorized athletics today. How happy would YOU be going up against somebody with 20 lbs more muscle than you? And that’s basically the floor of the size difference, the biggest Neanderthals could have been 5 weight classes above an H Sap (50kg, 110 pounds bigger).
They would have also been stronger from higher free testosterone levels in the blood, on top of the extra muscle mass.