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The Most Important Event In History (Big Brains Require An Explanation, Part VII)

Timeline of hominin evolution

Click to see the timeline again at full size.

We’re taught, as schoolchildren (usually around sixth grade) that the invention of agriculture is not only the most important event in human history…it’s when history began! Leaving aside for the moment the awkward facts that its effects on human health and lifespan were so catastrophic as to move Jared Diamond to call agriculture “The Worst Mistake In The History Of The Human Race”—and that the invention of agriculture apparently coincides with the invention of organized warfare, among other “inhuman” practices—we need to ask ourselves which milestone is more important…

…a change in technology, or the invention of technology itself?

(This is Part VII of a multi-part series. Go back to Part I, Part II, Part III, Part IV, Part V, or Part VI.)

The First Technology: Sharp Rocks

The most important event in history happened approximately 2.6 MYA. First, some genius-level australopithecine (probably with the Pliocene version of Asperger’s) made an amazing discovery:

“If I hit two rocks together hard enough, sometimes one of them gets sharper.”

However, this discovery is insufficient by itself, for reasons we learned in previous installments:

“Intelligence isn’t enough to create culture. In order for culture to develop, the next generation must learn behavior from their parents and conspecifics, not by discovering it themselves—and they must pass it on to their own children.”
“The developmental plasticity to learn is at least as important as the intelligence to discover. Otherwise, each generation has to make all the same discoveries all over again.”
The Paleo Diet For Australopithecines

It’s likely that the idea of smashing rocks together to create a sharp edge occurred many times, to many different australopithecines. The real milestone was when the other, non-genius members of the tribe understood why the sharp rock their compatriot had was sharper than the ones they found lying about; learned how to make their own sharp rocks by watching their compatriot making them; and perhaps, having learned, actively attempted to teach others how it was done.

Yes, chimpanzees use sticks to fish for termites, and short, sharp branches to spear colobus monkeys in their dens. It’s likely that our ancestors did similar things—though since wood tends not to fossilize, and a termite stick looks much like any other stick, we’re unlikely to find any evidence.

Most importantly, though, and as we’ve seen in the last six installments, the archaeological record describes slow, steady changes in hominin morphology* up until the discovery of stone tools…

…after which the rate of change accelerates rapidly. So while there may have been previous hominin technologies, none of them had the impact of sharp rocks (“lithic technologies”). We’ll explore those changes in future installments.

(* Morphology = the study of physical structure and form)

What Use Is A Sharp Rock?

“And what use is a sharp rock?” we might ask.

Well, to a first approximation, human history is sharp rocks! Recall that anatomically modern humans appear between 200 KYa and 100 KYa, depending on region…so from their first use perhaps 3.4 million years ago, to their purposeful creation 2.6 MYA, and until the first use of copper perhaps 7,000 years ago (which postdates agriculture by several thousand years), the entire narrative of human evolution has been powered by sharp rocks.

The answer to this question (“What use is a sharp rock?”) shouldn’t be a surprise—especially given the Dikika evidence we explored in Part IV. And since the abstract below is a dense brick of text containing much important information, I’ll split it into pieces and discuss each one. (All emphases are mine.)

Journal of Human Evolution
Volume 48, Issue 2, February 2005, Pages 109–121
Cutmarked bones from Pliocene archaeological sites at Gona, Afar, Ethiopia: implications for the function of the world’s oldest stone tools
Manuel Domínguez-Rodrigo, Travis Rayne Pickering, Sileshi Semaw, Michael J. Rogers

“Newly recorded archaeological sites at Gona (Afar, Ethiopia) preserve both stone tools and faunal remains. These sites have also yielded the largest sample of cutmarked bones known from the time interval 2.58–2.1 million years ago (Ma).”

“Cutmarked bones” = bones scored by the scraping and chopping of sharp rocks.

“Most of the cutmarks on the Gona fauna possess obvious macroscopic (e.g., deep V-shaped cross-sections) and microscopic (e.g., internal microstriations, Herzian cones, shoulder effects) features that allow us to identify them confidently as instances of stone tool-imparted damage caused by hominid butchery.”

The cutmarks are not the result of any natural process. They are the result of deliberate butchery—hominids scraping meat off of bones, or smashing them for marrow.

“In addition, preliminary observations of the anatomical placement of cutmarks on several of the recovered bone specimens suggest that Gona hominids may have eviscerated carcasses and defleshed the fully muscled upper and intermediate limb bones of ungulates—activities that further suggest that Late Pliocene hominids may have gained early access to large mammal carcasses.”

Mark those words “early access”, because they’re extremely important. But what do they mean?

These observations support the hypothesis that the earliest stone artifacts functioned primarily as butchery tools and also imply that hunting and/or aggressive scavenging of large ungulate carcasses may have been part of the behavioral repertoire of hominids by c. 2.5 Ma, although a larger sample of cutmarked bone specimens is necessary to support the latter inference.”

“Early access” means that by 2.6 MYA, our ancestors didn’t always have to wait until the lions, giant hyenas, sabertoothed cats, and other predators and scavengers all ate their fill before running in and grabbing a few bones to gnaw scraps from and break for marrow. It means that we were very likely to either have killed these large animals ourselves—or to have been fearsome enough to “aggressively scavenge”, which means somehow forcing the killers away from the carcass.

Since our ancestors were much smaller than modern humans, and the predators much larger and more numerous than today’s, I believe that hunting is more likely than aggressive scavenging. For instance:

Yes, Gryka could do this.

Pachycrocuta: 1   Your head: 0
Click for an article about the skull-crushing hyenas of Dragon Bone Hill.

And a moment’s thought should convince anyone that a large dead animal wasn’t much good to our ancestors without sharp rocks to butcher it with. (Imagine trying to gnaw your way through elephant hide—or even antelope hide.)


The most important event in our ancestors’ history was learning how to make sharp rocks from another australopithecine. The technology of sharp rocks took our ancestors all the way from 2.6 million years ago to the Chalcolithic and Bronze Age, just a few thousand years ago.

Furthermore, as we learned in Part II, the Paleolithic is defined by the use of stone tools known to be made by hominins. Therefore, since the Gona tools are the earliest currently known, the Paleolithic age begins here, at 2.6 MYA…

…and so must any discussion of the “paleolithic diet”.

Live in freedom, live in beauty.


This series will continue! In future installments, we’ll look at what happens once australopithecines start regularly taking advantage of sharp rocks.


Permalink: The Most Important Event In History (Big Brains Require An Explanation, Part VII)
  • Joel Zaslofsky

    I’m really loving all these installments. You’ll get no argument from me about the most important event in our history although I’m going to have to think about this one a bit.

    Let’s just say that with a headline of “The Most Important Event In History” you didn’t let us down with some useless drivel. Thanks again for great stuff!

  • Daniel

    Great article, JS.

    I for one am not disappointed about your silence on the drama.

    This and MDA are the only sites I refer beginners to. For many reasons.

    It would seem only logical to me that we’ve been hunters since leaving the trees. Maybe there was a period of scavenging, but bc the apex predators of the day were bigger, stronger, and had claws and large teeth (you know), we would have had to rely on our brains to develope hunting strategies. Like the sneak attack. Gorrilla warfare type.

    In all likelihood our brains got bigger and we got smarter bc we had to to survive. As stated in the previous installments, there wasn’t just one factor in this. Primates aren’t big cats; perhaps our brains have been all we ever had? I think it’s a matter of what we are, combined with what we are not, combined with survival pressures that forced bigger brain development.

  • Howard

    I would bet that the making of sharp rocks also roughly coincides with the production of fire-on-demand, especially since one of the best substrates for the creation of sharp rock happens to be flint.

  • Lauren

    @Daniel, I like the (unintended?) pun on guerilla warfare 🙂

    J.S. I appreciate that you’ve nominated the *lateral transmission of knowledge*, specifically related to sharp rocks, as the turning point; one without the other is nothing.

    Whenever I read about the development of stone tools I recall the ground south of Addis (nowhere near the Afar region, but archeologically rich nonetheless), which is littered with obsidian flakes. You cannot leave the road without risking your tires, feet, shoes. Once you’ve seen the ground glitter with natural knives it makes way more sense, this jump to tool use – even a very basic intellect can extrapolate ‘this cuts me’ to ‘I can use this to cut something else’. It’s the deliberate shaping of those tools for your own purposes, and doing so for and with others away from areas in which the landscape does most of the work for you, that is key to our development.

  • tess

    this series gets better all the time — thanks, J!

  • Daniel Taylor

    @lauren: that was a joke for JS. 😉

    Not sure why that comment was posted as guest tho….I switch my iOS devices too much.

    Also @lauren: I read a legend that after Bowie had broken his first “Bowie” knife he had a second one made from a meteorite that his master blacksmith (forgot the name) had found. How awesome a knife would that have been?

    I love obsidian and had my wedding ring made from it and titanium. Yes, it’s black…. 😉

  • Neal Matheson

    I have to agree that the idea of early hominids making a meaty living by scavenging has never really made sense to me. To my knowledge there are no scavenging apes beyond very occasional opportunism.
    I made most of my points in this post; (link)

  • Joel:

    I believe the invention of technology was a more important milestone than any specific application of it…especially when the archaeological record indicates that things started changing rapidly (in relative terms) soon afterward.


    I'll be putting the pieces together both as I go and in the conclusion, but yes, those are important elements.  You're getting a bit ahead of me, which is good because it means I've clearly presented the information so far.


    So far the earliest evidence for use of fire is perhaps 1 MYA — and it's sparse until much later, meaning that it's unlikely we depended on it for cooking or had the ability to create it at will, vs. using it when we came across it.  Grass and brush fires are reasonably common in grassland Africa.

    Making fire with percussion is a much more complicated problem than making a sharp rock.  It's quite difficult, as anyone who's ever tried it can attest, and that's with a pre-chipped flint — and steel (and where would one get steel?  In the wild one would require some sort of pyrite…another rare type of rock), not to mention things like tinderboxes full of charred cloth.  There's a reason survival kits contain magnesium or mischmetal instead.

    Remember, the pace of progress was slow back then.  Tt took nearly a million years for our ancestors to figure out how to sharpen both sides of a rock (Oldowan vs. Acheulean industry — this is a bit of an oversimplification, but not much.)    

    I'll discuss this subject at length in the future.


    Absolutely.  The population genetics from the previous chapter shows us that almost all beneficial individual mutations will be lost.


    Glad you enjoy it!  This is when things start getting interesting.


    An obsidian/titanium ring would be beautiful!


    As the series continues and wraps up, I'll present what I believe to be the most likely timing for the scavenging/hunting transition.  There's actually some good evidence for it…and while nothing is certain, I believe one “most parsimonious explanation” stands out.


  • Fmgd

    Nice article, and we’ve finally hit the paleolithic, I was looking forward to this.

    Also, I appreciate your posture. I don’t really know what all the arguing is about, but the civil yet objective air here is pretty good.

  • Leslie

    I think of early humans being much more pragmatic than modern man spoiled by what we consider the most elementary inventions such as fire and cutting tools. More like Gricka’s ‘people’ for whom survival demanded the sensibility to consider every second of every day, where to source food, protect from injury, and care for young. When I read comments from clueless people that early humans were incapable of hunting an auroch or mastadon, or whatever, I wonder if they’ve considered if it were possible given a knowledge passed through generations and hunting since childhood, and level of fitness only realized by someone who lives off the land. Sure, dump some citykid in a bush and he/she might last 3 hours, but what about a person raised from infancy for survival? Necessity truly is the mother of invention … need to develop a way to do something that means life or death? Lots of necessity there for invention.

  • Txomin

    A progress from blunt to sharp rock is not the most likely possibility. It does not seem this was an eureka moment (as opposed to, say, a true artifact such as the invention of wheel).

    Sharp rocks (as found) were used for a very very long time. Sharp rocks lost their sharpness, sometimes gradually, sometimes abruptly, by being continuously stricken against hard objects… which was after all their purpose.

    There were times, however, when a lucky strike made the rock sharper, sometimes gradually, sometimes abruptly. Multiply this by a gazillion times and you have a more likely possibility, namely, the sharpening of rocks began as attempts at very small repair. Most failed.

  • Fmgd:

    Now that the evidence is much less sparse, I won't have to go into so many individual fossil examples!

    And I understand what the drama is about, but I feel no need to participate in it or contribute to it.  There's plenty of science to explore.


    The examples of modern hunter-gatherers should be more than sufficient to disabuse people of that notion.  African Bushmen are perfectly capable of taking down elephants without guns…in fact, the bigger and slower the animal, the easier it would have been for our ancestors to kill.  But we'll get into that discussion later.

    It's instructive to remember that intelligence must be for something or it never would have arisen!  In other words, intelligence must have had survival value

    …and that is the reason this series exists.  If we didn't need intelligence to survive, we never would have become intelligent!  Therefore, it's important to figure out what intelligence is for.  

    I'm glad Gryka's story resonated with you.


    We'll never know the exact thought process that led to tool-making.  However, we must keep in mind that it had to have been very difficult for our small-brained ancestors, and understandable only to the smartest few — otherwise they would have come up with it long before!  

    Here's an analogy: a physical simulation of a motorcycle wheel on smooth pavement involves no less than the solution to five simultaneous linear equations.  (And this is a simplified model: a realistic model involves more.)  The percentage of humans who can comprehend the physics and mathematics required to understand that simulation is extremely low…let alone the percentage who could envision and write it in the first place!

    Inventing and comprehending stone tool manufacture with a 400cc brain would have been a similar problem.  Only the smartest australopithecines would have been able to make the connection.  

    With the benefit of hindsight, a brain over 3x as large, and thousands of years of cultural knowledge, it's easy to say how we would have solved the problem…but that doesn't tell us anything about how our ancestors did it.


  • Txomin

    That’s actually my point. The manufacture of sharp rocks is unlikely to have happened all at once and as the result of searching for a “solution”.

  • js290

    re: Aggressive scavenging…

  • Txomin:

    Great!  I wasn't quite sure what you were getting at.  AFAIK, most important discoveries throughout human history have been made by accident.


    I knew what that video was going to be even before clicking the link — but for those who haven't seen it, it's a great reminder that humans with stone-tipped projectile weapons are enough to scare off even the biggest, most deadly predators.  Thanks for posting.


  • Neal Matheson

    With reference to that video, Lions have been hunted/killed by H.sapiens for a very long time. No animal on planet earth doesn’t know we are extremely bad news. Modern H.sapiens pushing a lion off a kill doesn’t say much about what happened in prehistory.
    J; I don’t really like the hunting or scavenging split. There are no terrestrial scavengers, not a one a scavenging ape would be a unique mammal let alone primate. I know there is evidence for the behaviour but even modern HG people scavenge. I have scavenged if you want to see collecting road kill that way. I was watching the Frank Forencich talk from AHS 11 when he said “we weren’t hunter we were hunted” again this split. Take a walk through bear country or lion country and yep you are back to being in the hunted category.

  • vizeet

    “I believe that hunting is more likely than aggressive scavenging”

    I think there is a problem with this also because our ancestor’s weapons were very crude that time and may not be good enough to kill large animals. I think we may be using techniques like trapping and scaring instead of direct hunting.

  • vizeet

    The video is nice but it does not prove anything because it is recent and these carnivores have gone through massive killings after invention of guns. So they fear humans and the tribe is just using their fear.
    In India there is a place called Sunderban, lions there don’t fear humans because they are in advantage over us because of geography of the location.

  • vizeet

    I remember in one of the episode in Discovery channel a animal behavior researcher was explaining that 150 years back there was no such thing as non-maneater lion/tigers. This behavior is consequence of recent massive killings.

  • Daniel Taylor

    Vizeet: go to megafauna.com, read, and then come back.

  • vizeet

    @Daniel, sorry for commenting without going through the website.
    I’ll read it soon.
    True humans were responsible for killing of large animals. In my understanding these large animals were not carnivores. Carnivores did extinct due to humans because they had to compete with humans for food. This won’t make them fear humans, so the argument does not apply to lions as in the video.

  • Neal Matheson

    Hi Vizeet, Heidelbergensis was killing adult male rhinos with sharpened sticks, while Neanderthal used fire hardened sticks for elephants. In hominid hands sticks and/or stones are really effective weapons.

  • Neal:

    While we don't know exactly when humans became fearsome enough to push lions off a kill, there is fairly strong evidence for it — which I'll present in future installments.  I don't think we're there yet at 2.6 MYA.

    The hunting/scavenging dynamic is actually more complicated than most think, and it's not as simple as “you're a hunter” or “you're a scavenger”.  This issue has come up repeatedly in my studies of spotted hyenas, and I may have to write an article about it!


    If you read “The Old Way” (one of the books on my Recommended Reading list) you'll see that the Kalahari Bushmen lived in lion country without the benefit of guns — or, indeed, anything but small poison arrows that take a day or more to kill their target.  And though lions were frequently seen in and near camp, they did not attack either the Bushmen or the researchers who made first contact with them.  So though the Bushmen's behavior was most certainly constrained by lions, there was apparently some sort of mutual respect in human prehistory that prevented the lions from simply massacring humans.  

    I highly recommend the book, as it shows that the issue is more complicated than “everything was a maneater” — and that animals are smarter than most of us give them credit for.


    Megafauna is a great book, and I highly recommend it.  I think it's a bit liberal in its acceptance of early dates of fire usage, though for opposite reasons than Wrangham — but that's mostly a nitpick.


    Absolutely.  Look up the Schoningen spears…and recall that H. heidelbergensis was much taller, heavier, and stronger than modern humans.

    Also keep in mind that much of the African megafauna is extinct — most likely because it was either slower, stupider, or otherwise easier to hunt than the remaining elephants, rhinos, hippos, etc.


  • Neal Matheson

    Hello, A friend of mine has stayed with the bushmen many times. I have asked hime about their relationship with the big preadators they share their home with. He said that one time he arrived they gave him a rather small (and to my mind silly) spear and told him never to leave it behind as lions were close by. Other times they haven’t bothered, when leopard tracks were spotted in the camp they gathered the children together and kept and eye on them.
    He said that when out hunting in the bush one hunter stays awake at all times during the night, but that in general they have no fear of lions etc but more a healthy respect.

    I don’t really buy humanity (if that’s the right term) being much of an agent in mega fauna extinctions. I honestly think it’s an issue where a lot of scientific objectivity gets lost.

  • Neal Matheson

    P.S. It is often said in popular media that the mesolithic inhabitants of Britain stuck to the coasts for fear of the large animals, bear auroch moose wolf etc, in the interior. Despite the fact they hunted them (starr scarr) and that hunter gatherers and in fact industrial peoples often live along side such animals today.
    The rather more likely explanations of poor surivival of relics in the interior forests and excellent fishing by the coasts are often ignored.

  • jesse

    this series got me thinking, what with this big brain and all…. Big brains lead to big intelligence. Based on our understanding of the past can we predict the theoretical intelligence limit for our genetic line and how close we are to it? Are we getting smarter? Are the outliers in intelligence significant enough to be selected for? Ignoring any theories about the agricultural diet limiting our brain size etc… which may or may not be true… I’m thinking much bigger picture and I figure in time the agricultural stuff will all work itself out and we’ll be back on track.

    So where are we headed?

  • Neal:

    That information about Bushmen and lions is consonant with the other accounts I've heard.  Remember that, to an animal in the wild, even a minor injury can easily result in death (no one is going to feed while you recover) — so even if lions can usually kill humans, it's probably not worth the risk to attack a human unless they're obviously alone, unarmed, etc.


    I'm not conversant enough with the neuroscience to understand the theoretical limits of human intelligence.

    Unfortunately, without some form of selection pressure, we're headed — on average — down the slope of a slow but inevitable degeneration.  Most point mutations are either neutral or deleterious, and we're accumulating them rapidly.

    The complicating factor is that while natural selection isn't currently acting on humans as a whole in a meaningful way, sexual selection and differential reproduction are absolutely occurring.  For most animals, reproduction is dependent purely on survival to reproductive age, at which point an animal will bear as many offspring as it believes it can provide for.  In contrast, human reproduction is dependent on socialization and acculturation, many humans choose not to have children even though they easily could…and given our huge population and diversity of appearance and culture, mate choice becomes far more complicated than just “young, healthy, and fertile?”  The consequences are far beyond the scope of a comment!


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  • Adam

    I'm sure you've seen this, right? Earliest Porotic Hyperostosis on a 1.5-Million-Year-Old Hominin, Olduvai Gorge, Tanzania

    Hunting definitely by 1.5mya because scavenging would not provide enough meat to cause such nutritional adaptations (due to seasonal availability + actual amount of flesh available). Do you agree? If so, we can say hunting certainly happened by 1.5mya, if not the 2.6mya you suggested. Your idea that hunting predates aggressive scavenging is very interesting, and I would probably agree with it. The paper indicated that competition for meat was low in certain areas, so would that indicate more support for hunting before agressive scavenging?

  • Alex

    Adam, the site completely mangles long URLs. Try using a URL shortening service, like http://tinyurl.com/

  • Adam:

    I've seen that paper, and it's indeed useful…but there's more direct evidence for hunting at 2 MYA, which I'll get into in future installments.  

    Frankly, “man the scavenger” is a politically motivated belief that I don't find any basis for in the evidence, nor any plausible causal chain of events including it that leads to 1300cc brains.  


    That'll help.  I try to edit them in retrospect, but what I really need to do is get off this commenting/forum software (which will require $$$ to convert all the existing comments).


  • Katherine

    ““Man the scavenger” is a politically motivated belief that I don’t find any basis for in the evidence”.

    It’s certainly closer to the truth than “man the herbivore” which vegans repeat.

  • Katherine:

    I've made the point many times that “man the herbivore” was a partially-quadrupedal 60-pound ape with a brain the size of a modern chimpanzee.  Whether vegans know it or not, that’s what they aspire to devolve into.  It doesn’t take a big brain to pick fruit and dig tubers…

    …and even chimpanzees hunt and kill colobus monkeys, consuming roughly one McDonalds hamburger worth of meat each day during the dry season.  It’s not clear how far you'’d have to go back to find an herbivorous direct ancestor (our knowledge of diet that far back is speculative), but it seems likely we’re back into the Miocene by that point.


  • Alexander

    I’ve been perusing the site and I’m always pleased to learn something , I was just wondering if you used this concept put forth By Daniel Wolfpert that, “We have a brain for one reason and one reason only — and that’s to produce adaptable and complex movements.”

    “You may reason that we have [brains] to perceive the world or to think, and that’s completely wrong.”

    Full Talk here:

  • Alexander:

    It's true that the end result of brainpower is to move our body around in some useful way.  However, that ability is shared by our common ancestor with chimps and bonobos…and with every other animal.  The question I'm asking is not “What are brains good for?”  It's “Why did humans develop such big brains, in comparison to our common ancestor with chimps and bonobos?”

    It's not our motor cortex that grew by a factor of four, either.


  • Alexander

    Ah the motor cortex of primates serves a very important purpose for the eventual development of the first sharp rocks though , conscious control of individual muscle groups.

    From Wikipedia:

    “In the course of evolution a tendency to develop increasingly more complex brain structures and cortical densification can be observed. Cortical densification describes the increased shifting of control processes into the cerebral cortex. The motor cortex is a relatively recent development and occurs only in mammals. The execution of movement in fish, amphibians, reptiles and also birds is regulated by a core part of the brain called Archistriatum, in mammals the corresponding part of the brain is called Striatum, which is also involved in the execution of movement.

    Especially primates have a highly developed motor cortex. In addition, separating them from all other mammals, they have many monosynaptic, thus direct connections from the motor cortex to the motor neurons in the brain stem and spinal cord. This leads to the conclusion, that only primates have a conscious, planned and finely graduated movement of single muscles, whereas the execution of movement for most other animals is probably more automatic and without the possibility of deliberate interference. In comparison to primates, ungulates have a relatively weakly developed pyramidal tract, which ends in the neck region of the spinal cord (Intumescencia cervicalis) and plays an important part in the production of facial expressions. As for dogs, while about 30% of the pyramidal fibres reach the loin region of the spinal cord (Intumescencia lumbalis), those fibres always end on interneurons, never directly on anterior horn cells.

    Consequently, a complete impairment of the motor cortex in one hemisphere of the brain never leads to hemiplegia in non-primates, but rather to contralateral disorders concerning postural reflexes. Over the course of their evolutionary process, humans developed considerable control over their hands and articulatory muscles. Furthermore, humans have a uniquely high potential to learn new sequences of movement throughout their life.

    Please note that no citations are provided for the above material.”

  • “Please note that no citations are provided for the above material.”

    At least whoever wrote that passage is honest!  As for myself, I'll wait for some citations.

    Furthermore, even if that were all true, it still begs the question “Why did humans develop such big brains relative to the primates we're most closely related to, let alone primates in general?”  Again, it's not our motor cortex which grew by a factor of four.


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