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The Most Important Event In History (Big Brains Require An Explanation, Part VII)
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May 20, 2012
7:25 am
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Cameron, Tx
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Vizeet: go to megafauna.com, read, and then come back.

May 20, 2012
10:30 am
vizeet
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@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.

May 20, 2012
10:51 am
Neal Matheson
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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.

May 20, 2012
3:56 pm
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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!

vizeet:

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.

DT:

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.

Neal:

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.

JS

May 20, 2012
10:17 pm
Neal Matheson
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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.

May 20, 2012
10:25 pm
Neal Matheson
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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.

June 4, 2012
2:46 pm
jesse
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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?

June 5, 2012
6:22 pm
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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.

jesse:

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!

JS

October 6, 2012
10:29 pm
Adam
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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?

October 7, 2012
4:41 am
Alex
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Adam, the site completely mangles long URLs. Try using a URL shortening service, like http://tinyurl.com/

October 12, 2012
1:04 am
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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.  

Alex:

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).

JS

December 8, 2012
4:23 pm
Katherine
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"“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.

December 17, 2012
3:09 am
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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.

JS

February 15, 2013
9:54 am
Alexander
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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.”

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

Full Talk here:

February 15, 2013
9:55 am
Alexander
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February 15, 2013
11:15 pm
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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.

JS

February 20, 2013
9:32 am
Alexander
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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."

February 22, 2013
8:41 pm
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"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.

JS

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