Agriculture and cultural ecology

Your original claim:

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Heat kills brain cells. Since we were operating in a very hot niche, there was a need for redundancy, for backup brain cells-- hence, brain size increased.

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Falks theory involves cooling the brain, not having an enlarged brain to provide spare cells so you can afford to lose them. A criticism of the theory is more about how the brain can be enlarged, not why it grew larger. At any rate, your idea and Falks are two different things.

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Having seen the quality of your posts and witnessed the string of dishonest debating tactics, I know that you are full of sh*t. Your lame appeal to "I took some classes" only confirms the conclusion.
Those classes wouldn't have any relationship to that 'field work' you claim to have under your belt-- a claim you unceremoniously dropped when asked that it be substantiated?

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Excuse me? You started out with an idea that is ludicrous from the beginning. Then post a bunch of links that only counter your own claim. (i.e. showing how brain damage is actually prevented by an efficient cooling system.)What is your obsession with my credentials? You would do better to stay with the facts at hand. I don't feel compelled to share my personal history with anyone on a public forum, nor did I realize that it was required by anyone.------------------
Bringer of fire, trickster, teacher.[This message has been edited by Speel-yi, 10-09-2003]

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At any rate, your idea and Falks are two different things.

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Actually...1) Not my idea. I got it from a primatology/anthropology professor named Glassman, at SWTSU. It wasn't his idea either, but at the time he seemed to favor it and made a good case.2) I know it is a different idea. I said so in my post. I believe I wrote something like "I also like this theory of Falk's" Can't you read? I bet you can, but choose to misread instead.

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Excuse me? You started out with an idea that is ludicrous from the beginning.

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Ummm... no. I started out with an idea which you, from the beginning, have claimed is ludicrous but have provided nothing substantial to support that claim. In other words, you just keep repeating yourself and pretending to have said something worthwhile.

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Then post a bunch of links that only counter your own claim. (i.e. showing how brain damage is actually prevented by an efficient cooling system.)

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The presence of a cooling system is does not counter any claims I have made. For this objection to make sense one would have to assume that this cooling system prevents all-- not just some, but all-- heat related damage to the brain. This just isn't the case. Overheating does cause brain damage. I've provided more than enough proof to that effect.

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What is your obsession with my credentials?

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My obsession with your credentials? You've several times brought up your 'training' or 'experience' to buttress your position. What is the problem with asking that your support these claims?

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You would do better to stay with the facts at hand.

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I have. You, on the other hand, have cited your 'field work' and your education as evidence. This is an appeal to personal authority. It is fallacious. People with nothing to say use such things to try to bully others into silence. A bit hypocritical isn't it, to throw around your personal expertise and then complain when someone asks for verification?

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I don't feel compelled to share my personal history with anyone on a public forum, nor did I realize that it was required by anyone.

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You have felt compelled to BRING UP YOUR CREDENTIALS several times now. What you object to is having your bluff called. If you had half an education in any relevant field, you could have made an argument a thousand times better than the one you've made. I say this largely because you haven't made much of an argument at all, but have rather posted a huge string of logical fallacies. If you had a case, you wouldn't need the bully debate tactics.------------------
No webpage found at provided URL: www.hells-handmaiden.com[This message has been edited by John, 10-09-2003][This message has been edited by John, 10-09-2003]

I see that Dr. Glassman is an archeologist, you would do well to consult with him about lithic technology. It's a little more involved than you have made it out to be.You have contradicted yourself with your posts, I have only pointed that out. The idea that you started out with is not supported by any of the links that you have spammed the thread with.------------------
Bringer of fire, trickster, teacher.

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Although it can make your child and you uncomfortable, a high fever resulting from an infection almost never causes brain damage. It's not unusual for toddlers to run a temperature of 104 or even 105 degrees F (40 and 40.5 degrees C) when they're sick. The important thing to remember is that your child's temperature will stop climbing once it reaches a certain temperature it won't keep going up and up. Fevers due to infection rarely top 106 degrees F (41.1 degrees C). A small percentage of normal children between 6 months and 6 years of age may have brief seizures when they're running a high fever, but even these "febrile convulsions" very rarely cause brain damage.

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To damage the brain, a fever has to go as high as 107 or 108 degrees F (41.6 or 42.2 degrees C). This rare kind of fever is generally the product of heat stroke or a severe bacterial infection. A temperature this high can start to break down the nervous system, and, in rare cases, may lead to brain damage or other long-term problems.

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Pretty simple to read.From the site:Page Not Found | BabyCenterThen using some simplistic argument about brain volume without addressing the complexity is ludicrous as well. Glial cells are important and any site posting rubbish about the brain being composed of neurons should have any information taken from it with a large grain of salt.Link #2: Neuroscience For Kids - glia

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The brain is made up of more than just nerve cells (neurons). Although there are about 100 billion neurons in the brain, there are about 10 to 50 times that many glial cells in the brain. But do you hear much about glia? NO! Because neurons get all the attention, you don't hear too much about glia. Although glia cells DO NOT carry nerve impulses (action potentials) they do have many important functions. In fact, without glia, the neurons would not work properly!

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And then:

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The brain is the only tissue in the body where we don't know the function of the major cell type," said Barres. Glia make up approximately 90 percent of the cells in the human brain, and yet researchers have assigned mainly passive functions to them. Some glia wrap around nerve cells and insulate them with a protein called myelin. Glia at synapses act both as a physical barrier that prevents crossed wires and as a disposal unit that mops up extra messenger molecules released by nerve cells.

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But now a particular kind of brain cell, which for decades had been passed over as relatively insignificant, has gained elevated stature. Glial cells were thought to be merely menial laborers of the brain, shuttling nutrients and removing waste. New studies are showing, however, that these cells are a major source of neurons. With a little coaxing, they may someday be veritable neuronal factories, used to produce neurons for patients in need of brain repair.

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From the site: Page not foundAll of the above demonstrate that the brain is composed of more than one type of cell. The brain also is very complex it's not a general purpose organ that simply gets filled up with information as it goes along through life. Pinker among others has been working on this for years. How this evolved is not a simple question to answer.Page Not Found | MIT - Massachusetts Institute of Technology------------------
Bringer of fire, trickster, teacher.

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I see that Dr. Glassman is an archeologist, you would do well to consult with him about lithic technology.

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I know, or knew, Glassman because I took a dozen of his courses.

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It's a little more involved than you have made it out to be.

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More glib BS. Maybe I should call you 'spiel.' Oldowan toolkits are not complicated. Hell, they are mostly unmodified flakes. Acheulean tools are a bit tougher, but still not that hard. Our ancestors survived for about 2 million years using first one then the other, so I guess they adequate.

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You have contradicted yourself with your posts, I have only pointed that out.

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You have been incoherent, spiel. That hardly counts as 'pointing.'

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The idea that you started out with is not supported by any of the links that you have spammed the thread with.

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More BS. Simple senseless repetition. You can't create even a bad argument to support your claims.Spam the thread? LOL... not tired of the bully tactics yet are we?------------------
No webpage found at provided URL: www.hells-handmaiden.com

Guys, I sit here reading your last bits and I can't tell you is making more sense than the others.John the last half of your last post is a bad example: Or rather a good poor example.
Both of you have asserted away without pointing out why you are saying these things.First Spiel says John has contracdicted himself. I can't tell where he did cause Spiel doesn't say so.Then John says Speil has been incoherent but doesn't repeat where or in what way.Then it carries on in this vein.It is extra work to make each post more self contained or refer directly to the relevant previous posts but it makes the argument easier to follow and increases the chances of getting your opponent pinned down.I'm enjoying this one cause I'm not at all sure in my own mind who is where or who is right or wrong. Let's see who can be most convincing.[This message has been edited by NosyNed, 10-09-2003]

The first assertion I have made is that the human brain evolved to handle complex tasks such as toolmaking.John believes that there is no need for a large brain because foraging is easy, so his explanation is that the large brain evolved because hominids lived in a hot equatorial environment and a large brain meant that there would be plenty of spare cells to carry on the work after some of them had been killed off by heat.I then have pointed out that the brain does not get killed off by heat since the body strives to maintain thermal homeostasis (98 degrees for us) and the brain is cooled to this temperature.He did mention the Falk theory. This idea is that the blood supply to the skull relies on small vessels to keep the large brain cool. But Falks idea only explains how a brain can be enlarged through efficient cooling, not why it became large in the first place.John stated:

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The brain is cooled by its blood supply, not by evaporation from its outer surface. You are complaining that the engine block cannot cool itself but you are forgetting about the radiator.

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I stated:

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So since the brain is cooled by the blood supply, there should be no lost cells with adequate blood flow. There would be no need to have spare cells hanging around and metabolizing food you could put to good use like pumping blood around. You would also benefit by having a smaller brain in any event.

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There is the central flaw in his argument. The blood supply cools the brain, the brain doesn't need the extra cells because they don't die in the first place.In any event, it is unlikely that the brain enlarged to provide extra cells for the function for early hominids. Neural tissue is energetically expensive consuming 16 times as much energy per pound as other tissue. About 20% of modern human energy expenditure is spent on providing the electrochemical gradient for the brain to function in the first place. A reduction of any unneeded tissue would be evolutionarily favorable since an organism that needed less energy to survive, would have more available energy to produce offspring.There must be a cost benefit to the presence of a large brain and one probable benefit to the high cost of a big brain would be the commonly cited social forager model.RE: Oldowan choppers/flakes and Achulean hand axesThe limiting characteristic for making anything more complex than an Oldowan tool is the thumb of the Australopithecines, the ability to grasp items is fairly limited for these hominids. The evolution of the Erectus thumb allowed for the Achulean hand axes and these are in fact somewhat difficult to make. The point being that the limiting characteristic for making a more complex tool is the ability to grasp the raw material to make the tool as well as the chipping tool used on the hand axe.Achulean hand axes appear as cranial capacity increases, it might be a coincidence, but I don't think so.------------------
Bringer of fire, trickster, teacher.

Thank you Speel. That presents your views pretty clearly.John? Care to be as clear?I don't remember more than assertions about a big brain being needed for back up and for cooling. Is that what you are claiming?

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Pretty simple to read.

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Yes, it is. Tell me again why this demonstrates that heat does not cause brain damage?

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Then using some simplistic argument about brain volume without addressing the complexity is ludicrous as well.

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What are you talking about?

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Glial cells are important and any site posting rubbish about the brain being composed of neurons should have any information taken from it with a large grain of salt.

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I know they are important. Read your past few posts. You have been acting as if glial cells were packing peanuts. Your objection was that brain size isn't selected for in a hot environment because heat does not kill neurons but glial cells. The implication is that glial cells are NOT important. It also implies that glial cells do NOT contribute to the size of the brain. Both implications are absurd. I think you realize that or you would not be making a 180 degree turn.

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All of the above demonstrate that the brain is composed of more than one type of cell.

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No kidding?This isn't even an issue. This hasn't EVER been an issue. This is your red-herring. I haven't said "Heat selects for neurons." Or "Heat selects for glial cells." I have consistently argued that hot environments select for BRAIN SIZE-- that would be THE WHOLE DAMN BRAIN. The size increase could be neurons, glial cells or jellybeans. It doesn't matter.I have stated that neurons can be killed by heat. They can and are. I haven't said, as one would expect having read only your reply, that ONLY neurons die. Nor have I said even that the increase in brain size was due primarily to an increase in neurons. All I have said is that heat kills BRAIN cells, and that this would provide a selective pressure for larger brained individuals.To refute this idea you need to...1) show that heat stress does not kill BRAIN cells-- not neurons, not glial cells, just brain cells. You can't do this. Heat stress kills cells.2) Show that the cells which do get killed are not important. You appeared to be taking this route when you first seperated my 'brain cells' into neurons and glial cells and pointed out that most damage is to glial cells, as if this somehow doesn't effect the brain's functions. Can't do this either. Neurons and glial cells are both necessary.3) Demonstrate that healthy brain cells will not takeover for damaged cells. Again, you can't do it.4) Indicate that a large number of cells would not be beneficial if one's brain were damaged. Can't do it. Redundancy is a good thing.5) Demonstrate that hot environments do not put people at risk for heat stroke. Again, can't do it.So there you have it.Now, your idea, that big brains evolved because foraging requires it kinda gets hung on the fact that most animals forage and most don't have big brains.------------------
No webpage found at provided URL: www.hells-handmaiden.com

Thank you, ned. I was about to abandon the topic as a waste of time.First, what Speel wrotes in reply to your post may be his position, but he misrepresent the flow of the thread.This thread started as a discussion about the origin of agriculture. Speel's claim being that foraging takes more intelligence than farming. The first few posts will make that clear, though it doesn't really matter right not. Then in Post #6, he asks... To which, in Post #12, I respond... In return, Speel asked... In other words, the claim is made that our brains enlarged because we needed a large brain for foraging. Foraging is presented as the driving force. Speel's post to you is the first mention in this thread, as far as I remember, of the brain evolving to make tools. Of course, the obvious response is that this can't possibly be the case because if foraging were the key then a lot of animals would have big brains similar to ours. Most animals forage, after all. This is essentially the response I gave in Post #15. I quote that portion in full. The second paragraph, I believe, provides that clear statement of my position.Speel's reply, in Post #16, and my reply that post in Post #17, flesh out some more detail.Now, I have some further comments.I do want to point out a couple of key phrases from my initial statement. "I am not sure if there is a consensus in the field..." And "the theory I favor" And "the initial push to big-brains..." This latter is important because it puts the theory into an evolutionary timeline. This applies to very early hominid evolution-- right as our brains were starting to grow. This makes it applicable to late A. afarensis and early H. habilis. This does correspond with the appearance of the Oldowan tool kit. Climate changes force the Australopithecines out of the trees and out onto the plains where they encounter the big predators. On the plain, there is nowhere to hide. Foraging and hunting is risky, but there is an unexploited window. The other hunters are quiet during the hottest periods of the day, so the risk of predation goes down during that time. And, the prey also suffers from the heat and become more vulnerable. That is the niche into which our ancestors moved. These ancestors had nearly nothing in the way of weapons. They had stone choppers or hand-axes, but these would have been useless for hunting. This, on top of the fact that we aren't very strong, nor are we fast. So how do you hunt? You start chasing an animal and simply don't stop chasing it until it drops. Of course, since we are living in the middle of the day a big issue is heat. Our ancestors had been walking erect since the earliest specimens of A. afarensus, and this stance provides some advantages in hot climates, as I believe I have mentioned. Some consequences would be a reduction in surface area exposed to the sun and to the heat radiating from the ground. Our upright bodies are fully exposed to the wind, which aids us in cooling.In other words, our ancestors moved onto the grasslands and had adaptations which allowed them to exploit a niche in that environment. Exploiting this niche increased the pressure selecting for those adaptations to heat. One of those adaptations is more redundancy in the brain. Chasing an animal in the noonday equitorial sun is bound to put an animal at risk of overheating. Overheating causes the brain a great deal of stress, as well as stressing other organs of course, and hence the selection for redundancy and thereby for larger brains. There were adaptations occurring in the body and the brain, each effecting the other. There are numerous substantial feedback systems that would factor into the account. For example, hunting in mid-day gives us an advantage. This advantage inceases protein intake, which makes a larger brain possible, which increases the need for protein. Eventually these adaptation created a decently enlarged brain. Exploiting the capabilities of this enlarged brain shifted selective pressures. The brain got co-opted, for things like speech, for example.Speel's major objection to this idea so far is something like 'heat doesn't damage the brain' and therefore there would be no need for redundancy. It is all to easy to demonstrate that heat does damage the brain. A variant is that 'heat doesn't damage neurons but only glial cells.' Why Speel's thinks the need for replacement neurons would increase brain size while the need for more glial cells wouldn't is beyond me.That should do it. Perhaps, at least, I'll get some real debate.------------------
No webpage found at provided URL: www.hells-handmaiden.com

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1) show that heat stress does not kill BRAIN cells-- not neurons, not glial cells, just brain cells. You can't do this. Heat stress kills cells.

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The heat required for damage is 106 F or higher, found only in the highest of fevers and extreme heat stroke. Both are not part of the evolutionary environment. The body in hot environments keeps the brain well within by sweating and limiting exposure to the sun with the upright posture.

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2) Show that the cells which do get killed are not important. You appeared to be taking this route when you first seperated my 'brain cells' into neurons and glial cells and pointed out that most damage is to glial cells, as if this somehow doesn't effect the brain's functions. Can't do this either. Neurons and glial cells are both necessary.

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Good to see you are beginning to understand the brain is not just a glob of indiscriminate tissue. Both types can replicate; glial can do it faster although they are also more susceptible to damage due to the cell replicating cycle. Point here, not only are their two basic types, there are a myriad of neuron type. Interneurons and pyramidal are two types for example.

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3) Demonstrate that healthy brain cells will not takeover for damaged cells. Again, you can't do it.

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They do take over all the time, it is not that the number of neurons involved in the brain structure, it's the number of synapses between them. Axons grow and meet during development and during brain damage repair. It takes time though, not going to happen overnight.

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4) Indicate that a large number of cells would not be beneficial if one's brain were damaged. Can't do it. Redundancy is a good thing.

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Up to a point redundancy is good, there are costs and benefits. If the costs outweigh the benefits, then redundancy will not be selected for. There are structures that are unique and can't be replaced. Broca's area is an example and Broca's aphasia is debilitating. The other various apahsias are also devastating.

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5) Demonstrate that hot environments do not put people at risk for heatstroke. Again, can't do it.

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Heat stroke is uncommon, the cooling system works fairly well. The damage does not always result in cell death anyway. Cell damage and cell death are not the same thing. They will stop firing, but that does not mean that they are dead. In time damaged cells can recover.

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So there you have it.

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Now, your idea, that big brains evolved because foraging requires it kinda gets hung on the fact that most animals forage and most don't have big brains.

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Most animals have built in adaptations for hunting; humans have to rely on tools. Instead of fangs, we use sharpened sticks. An improved sharp stick will result in more successful hunting. Instead of powerful jaws to crush skulls and long bones for marrow, humans rely on pointy rocks with edges. A better tool kit requires a better brain. Then you also have to consider that 2 hunters will probably have better success than one and 3 probably more than 2. When you have a social group involved, you have to have a communication system to hunt more efficiently and then to fairly divide the spoils. What the scenario is, is the evolution of co-operative behavior.And if you even begin to consider the dynamic of women, the scenario gets even better since they have another tool kit plus you have the negotiation between men and women to produce offspring, which is the bottom line in evolution.Evolution of cooperative behavior site:http://www.pscs.umich.edu/research/carReports.html------------------
Bringer of fire, trickster, teacher.

This is helping. Maybe a summary of a thread every 50 or 60 posts isn't a bad idea.However, let me see if I understand the two positions. Basically the issue is what selective pressure(s) helped start the brain size increase in hour pre-hominid to early hominid ancestors.One side suggest that this was the advantage of tool making and complex omniverous food obtaining methods. The other side says the brain evolved to increase resistance to heat and therefore allowed hunting in hotter weather. I'm a bit confused but it appears that he resistance was obtained by allowing for death due to the heat through redundancy.What is there in the way of evidence to support each side?Not a lot I don't think. It appears that we have evidence that it take very great heating to kill brain cells. The need for redundancy isn't clear to me and the agrument doesn't seem to hang on much else.It has been suggested that the enlarged brain then became co opted for other uses. It is not at all clear to me that it makes sense that a complex *heat producing* structure would evolve to handle a high heat enviroment. Wouldn't large ears have been better?The whole foraging is hard or isn't hard argument seems to be pointless to me. At some point in our evolution the large brain became and advantage from the things it allowed us to do. This may have been fancier weapons and their use, it may have been language, it may have been other socialization. Why can't we keep backing this up to our earliest ancestors? Each increase in size confered some advantage directly from the intellectual capability it gave us.Right now I'm not convinced that the heat resisting redundancy is all that strong an argument.

If you are inclined, read the paper by Sahlins. The work done by foragers could be termed skilled since they do learn many thigs we don't have to think about.http://www.appropriate-economics.org/materials/Sahlins.pdf------------------
Bringer of fire, trickster, teacher.

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The heat required for damage is 106 F or higher...

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Ok. Go outside, at the equator, in the middle of the day, and run for four hours. 106 is very easily accomplished. It can happen in a matter of ten to fifteen minutes once the body's cooling systems shut down, and those systems would be severely strained by persistence hunting. You just aren't putting it all together. Heat kills thousands of people every year.

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Both are not part of the evolutionary environment.

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Lets see. You just said that fevers and heat stroke are not part of an evolutionary environment. But there ARE extreme fevers and heat stroke and these occur in organisms which are evolving, therefore your statement in absurd.

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The body in hot environments keeps the brain well within by sweating and limiting exposure to the sun with the upright posture.

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Then how do you explain the many cases of heat stroke that are recorded every year? If the cooling system were perfect, as you seem to imply, there would be no cases of heat stroke, ever. This is not the case. You've made a claim that is 100% contrary to the facts.

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Good to see you are beginning to understand the brain is not just a glob of indiscriminate tissue.

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Where did you get the idea that I think of the brain as a glob of indiscriminate tissue? This is absurd. I've said nothing close to that. Kindly provide proof or stop posting this misrepresentation.

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They do take over all the time

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Then there is no argument. My point stands.

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Up to a point redundancy is good, there are costs and benefits.

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Then my point stands.

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Heat stroke is uncommon, the cooling system works fairly well.

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Yes, it does work well, but heat stroke is not uncommon in people who perform strenous work/exercise outside during the middle of the day at the equator. You aren't factoring everything in the picture.I live about 30 degrees North of the equator and in the middle of summer twenty minute outside can make you faint, and that is when doing next to nothing.

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The damage does not always result in cell death anyway.

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It doesn't necessarily have to result in cell death. If the damage is severe enough to limit the damaged cell's functions, then redundancy would be a good thing.

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It takes time though, not going to happen overnight.

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Exactly... which is why redundancy is a good thing. Having a partially functioning brain while your cells heal would be very bad.

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Most animals have built in adaptations for hunting;

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And none of them outside our line have developed a big brain, as would be expected if it were as critical to hunting and foraging as you pretend.We share most of our physical characteristics with the other primates. None of them have developed a brain like ours, yet they get along just fine without it. This suggests that it isn't needed for hunting and gathering. There has to be something else.

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humans have to rely on tools.

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The australopithecenes did not, and in the transition between them and genus Homo is where you see the first rise in brain size and then the emergence of crude stone tools.If you plot the development of stone tools against the rise in brain size you'll notice that brain size increases very quickly while tool complexity increases only a little bit. It does not make sense.

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Then you also have to consider that 2 hunters will probably have better success than one and 3 probably more than 2.

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Quite a few predators hunt in groups of two, three or even more. African wild dogs, for example, live in packs of ten and hunt cooperatively-- not all ten, some of these would be pups, for ex.-- achieving a success rate of 80%. No webpage found at provided URL: http://www.wildwatch.com/resources/mammals/wilddog.aspAustraelopithicenes appear to have lived in small groups, not large ones. Social structure couldn't have been the key factor. Numerous primates live in cultures of ten or more, yet they haven't developed the big brain either.

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What the scenario is, is the evolution of co-operative behavior.

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But one must ignore the cooperative behavior in other animals that has not resulted in large brain sizes.I agree that the brains we have now are the result of selection for certain of the brain's cognitive abilities, but this didn't provide the initial push toward brainy-ness. You, in other words, are well into H. habilis or erectus. I am talking about the transition between A. afarensis and H. habilis-- the beginning of the trend toward large brains. I've stated this before as well.

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And if you even begin to consider the dynamic of women, the scenario gets even better since they have another tool kit

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Show me the tool kit difference between 'male' oldowan or acheulean tool kits and 'female' tool kits.

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you have the negotiation between men and women to produce offspring

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Common to all primates.------------------
No webpage found at provided URL: www.hells-handmaiden.com

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The heat required for damage is 106 F or higher...
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Ok. Go outside, at the equator, in the middle of the day, and run for four hours. 106 is very easily accomplished. It can happen in a matter of ten to fifteen minutes once the body's cooling systems shut down, and those systems would be severely strained by persistence hunting. You just aren't putting it all together. Heat kills thousands of people every year.

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It's a minor cause from a statistical standpoint. Long before a forager would die from heat stroke, he'd probably be dead from another heat related illness. Heat stroke kills by stopping the heart and many of these cases involve temperatures below 106 F. The least of your worries is losing brain cells because you will die from heart failure first.

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Lets see. You just said that fevers and heat stroke are not part of an evolutionary environment. But there ARE extreme fevers and heat stroke and these occur in organisms which are evolving, therefore your statement in absurd.

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See above.

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Then how do you explain the many cases of heat stroke that are recorded every year? If the cooling system were perfect, as you seem to imply, there would be no cases of heat stroke, ever. This is not the case. You've made a claim that is 100% contrary to the facts.

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See above again.

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Where did you get the idea that I think of the brain as a glob of indiscriminate tissue? This is absurd. I've said nothing close to that. Kindly provide proof or stop posting this misrepresentation.

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Yes, it does work well, but heat stroke is not uncommon in people who perform strenous work/exercise outside during the middle of the day at the equator. You aren't factoring everything in the picture.

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If this were true, then the equatorial countries would be depopulated in no time at all.

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I live about 30 degrees North of the equator and in the middle of summer twenty minute outside can make you faint, and that is when doing next to nothing.

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Suggestion, stop using alcoholic beverages when it's hot out and hydrate adequately. I regularly spend a great deal of time outside in hot weather, I have no problem with it at all as long as I drink water and ingest an adequate amount of salt. In other words, what may make you faint won't have that big of an effect on me.

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It doesn't necessarily have to result in cell death. If the damage is severe enough to limit the damaged cell's functions, then redundancy would be a good thing.

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and...

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Exactly... which is why redundancy is a good thing. Having a partially functioning brain while your cells heal would be very bad.

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But there is no evidence that brain damage or cell death has anything to do with the evolutionary chain of events that led to modern humans.

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And none of them outside our line have developed a big brain, as would be expected if it were as critical to hunting and foraging as you pretend.

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All else being equal, overly large brains should be selected against. That's the $64,000 question.

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We share most of our physical characteristics with the other primates. None of them have developed a brain like ours, yet they get along just fine without it. This suggests that it isn't needed for hunting and gathering. There has to be something else.

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There's a few features we do not share, one of which is the more numerous sweat glands. Another of which is the bipedalism and this gets refined in erectus with an improved arch for walking. Human foraging is significantly different from arboreal primates. Hominids are thought to have been able to access resources not available to other primates or carnivores. We moved into an available niche that required a capacity for remembering resource location and also that there was a selective pressure for the social environment. Wild carnivores will hunt socially but they are not as adept at detecting cheaters. Often in forager societies, a generous hunter will have better reproductive success than a more proficient one. It's very much about inclusive fitness.

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The australopithecenes did not, and in the transition between them and genus Homo is where you see the first rise in brain size and then the emergence of crude stone tools.

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Australos have about the same brain size as chimps and they used Oldowan tools while chimps do not.

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If you plot the development of stone tools against the rise in brain size you'll notice that brain size increases very quickly while tool complexity increases only a little bit. It does not make sense.

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It makes sense from the standpoint of social hunting. The tools were adequate for what they were used for. Tools became very complex while the brain did not increase in size.Hint #1: The structure of the brain is supected to have changed though, early erectus had a cerebellum of about 66 cc while modern humans have one twice that size.Hint #2: Huntingtons Disease damages the cerebellum and victims first have difficulty walking and then eventually lose their memory. (See "Trinuclueotide repeat expansion disorders" for more.)

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Quite a few predators hunt in groups of two, three or even more. African wild dogs, for example, live in packs of ten and hunt cooperatively-- not all ten, some of these would be pups, for ex.-- achieving a success rate of 80%.

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Austraelopithicenes appear to have lived in small groups, not large ones. Social structure couldn't have been the key factor. Numerous primates live in cultures of ten or more, yet they haven't developed the big brain either.

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But one must ignore the cooperative behavior in other animals that has not resulted in large brain sizes.

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I agree that the brains we have now are the result of selection for certain of the brain's cognitive abilities, but this didn't provide the initial push toward brainy-ness. You, in other words, are well into H. habilis or erectus. I am talking about the transition between A. afarensis and H. habilis-- the beginning of the trend toward large brains. I've stated this before as well.

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We can see cooperative behavior from eusocial insects and they don't have much in the way of brains at all.Australos were probably not persistance hunters, the case against that would be the flat feet they had. Habilus is also probably an australo since the morphology is more australo-like than homo-like.What you are talking about is exaption and it does occur. However, if Falk is correct, robustus didn't need a cooling system since it stayed in the forest (highly debatable) and early "gracile" types developed the cooling system rather than an energetically inefficient replacement system.

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Show me the tool kit difference between 'male' oldowan or acheulean tool kits and 'female' tool kits.

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Female kits would involve things that don't preserve well. like sticks to dig with.------------------
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