Encephalization of early hominids

Discussion in 'General Science & Technology' started by Billy T, Mar 5, 2015.

  1. Trippy ALEA IACTA EST Staff Member

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    Right, so cooking allowed the growth in brain size driven by heat stress to occur. What's your point, precisely?
     
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  3. Trippy ALEA IACTA EST Staff Member

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    You've tried this bullshit before and you were wrong to dismiss it then, and you're wrong here (on both counts) as well.
     
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  5. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Cooking was essential for brain size increase - heat stress is a hypotheses at best, and not very plausible as the bigger brain needs more cooling - an extra biological cost or just adds to the heat stress.
     
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  7. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Instead of attack me, why not give the link I requested you to or attack the idea the six links suggest is essential for larger brain?
     
  8. Trippy ALEA IACTA EST Staff Member

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    Cooking provides no explanation for larger brain-sizes because it provides no evolutionary selective pressure. It's not very plausible as the bigger brain requires more nutrients - an extra biological cost.
     
  9. Trippy ALEA IACTA EST Staff Member

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    Read for comprehension:

     
  10. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Agreed. Cooking made possible the bigger brain, was not any selective pressure for it. That selective pressure was fill in the great increase in newly available time. The brain size would stop increasing when the new activities it allowed were not an improvement in the benefit cost ratio.
     
  11. Trippy ALEA IACTA EST Staff Member

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    Because my schedule is totally the same as yours...

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    I've relayed the essentials of the hypothesis, I've given you a rough idea of how recently I have seen something (it's implicit - likely to have been in the last few weeks, or maybe month or two).

    There is a paper on arxiv on the matter that's more recent than anything you've posted.
     
  12. Trippy ALEA IACTA EST Staff Member

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    Do you even stop to think about what you're posting before you post it?
     
  13. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    OK -then up my request. I need now two links you have said exist.
     
  14. Trippy ALEA IACTA EST Staff Member

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    Unless the first link is in regards to the arxiv paper.

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    Heaven forbid you should get off your arse and do your own research into a hypothesis you know clearly know nothing about.
     
  15. iceaura Valued Senior Member

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    The heat stress hypothesis was never advanced to explain the entire growth of the human brain to its current state - it was advanced to explain the initial boost in size and capacity, the overcoming of the cost barrier that prevents, say, chimpanzees, from enjoying the incremental benefits of an incremental brain capacity boost.

    It has the attractive feature of not only providing an incremental benefit as Darwinian evolution normally requires (and cooking does not provide), but agreeing with much else we think is likely about the circumstances surrounding the sudden overdevelopment of the hominid brain that led from chimp-brained bipedal hominids to us: the loss of hair covering, the development of efficient distance running physiognomy, the transition to savanna environments and land meat consumption, the development of more sophisticated tools, and so forth.
     
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  16. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    No the links should be provided by person claiming they exist and refute the six links and one video (all from very high quality sources) I gave. I don't have any way to know which two articles you referred to, even I were willing to search.

    You clearly have nothing relevant to the discussion in your recent posts (1964 & 1962) which are only attacks on me - your unsupported claims that I "know nothing about it." I never claimed to know much - other than be aware of and quote what others highly regarded experts have said on the subject. With each of my 6 quotes in post 1751, there is of course the link, so you can read more. - I don't ask you to search for links and call you lazy for not doing so.
     
    Last edited by a moderator: Mar 10, 2015
  17. Trippy ALEA IACTA EST Staff Member

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    You've misrepresented what I said. What I suggested was that maybe while you're waiting for me to find the time to present the link or links to which I was referring, you could do some actual research into the hypothesis rather than simply dismissing it because you don't like it.

    Read for comprehension:
    I'm not in the position of having to refute anything when what I'm proposing is compatable with your six links.

    On the one hand,I've told you everything you need to know about one of them, on the other hand, you don't neccessarily need to refer to the two specific articles I was thinking of in order to do some background research into a hypothesis which to you is novel.

    It's not unsupported, you yourself go on to support it in your very next sentence, and it's entirely relevant, you're dismissing the hypothesis out of hand, without doing any background research on it, without understanding it, and without understanding the role your 'objections' play in it.

    Right, and here you are, attacking me because I didn't provide the links you wanted on your time frame and you're too lazy to do your own background research.

    News flash ass-hat.
    1. I don't live in your time zone.
    2. I work full time.
    3. I have a wife with a disability.
    4. I have two lovely children that I enjoy spending time with and prioritize over spoon-feeding people information they're too lazy to look for themselves.

    All of which I have mentioned at various times in the back-room.

    I provided you with the explanation as to why I wasn't in a position to provide you with the link you wanted right here in post #1961. Read for comprehension:
    Which, again, I have mentioned in the backroom - essentially 'prime time US', that time when the majority of the posters are on, co-incides with my working day.

    Now, it's 7.30am, typing this post has made me late for work, luckily, seeing as how I am at home, rather than at work - as I was yesterday when I posted on the matter, I have access to my bookmarks. Here is the arxic paper I was referring to:
    http://arxiv.org/abs/1312.5403

    I think the other article I saw was on my facebook feed, and the chances of me finding it again are negligible, but I also have an inkling that it may have been in reference to this paper, but I can't be sure.
     
  18. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Thanks. It is so short, I'll just quote it all for others to read:

    "Growth in brain volume is one of the most spectacular changes in the hominid lineage. The anthropological community agrees on that point. No consensus, however, has been reached on selection pressures contributing to that growth. In that respect Martin (1984) can be invoked. In his review of size relationships among primates he stated that despite the relationship between brain size, body size and feeding behavior no single interpretation could be provided that revealed the causality of such relationship.
    This paper deals with one specific aspect of hominid brain growth; the fact that for most of the hominid period, growth in brain volume was exponential in character. To the best of our knowledge, no attempt has been made to identify a selection mechanism that can facilitate just the exponential features of that growth (as distinct from any of its other characteristics). It is broadly accepted that the dynamics of this growth were peculiar. Growth was very fast, or even rapid in the evolutionary scale of time. The most profound evidence of that opinion was expressed by Haldane that this dramatic increase in brain size was the most rapid evolutionary change known to him. "

    I would assume that author of that arxiv post would know about the flood of literature in the two years prior to his article indicating that the discovery of cooking was what launched the sudden (he calls it exponential) growth in brain volume, yet he states:
    "To the best of our knowledge, no attempt has been made to identify a selection mechanism that can facilitate just the exponential features of that growth (as distinct from any of its other characteristics)."

    I guess the part now bold explains why he does not at least mention cooking, but I don't understand why it excludes cooking.
    Having cooked food in your new environment is a huge change, with very strong selection pressure. Those that don't like the new taste, get to keep their small brains and big guts needed to digest the raw mass they eat daily and have their genes eliminated from the gene pool, assuming taste preferences are at least weakly genetic determined.
    ---------
    As far as locating source of something read, that I have partially quoted, but forgot to give link as I almost always do, I find that just entering all I quoted into Google almost always works.
     
    Last edited by a moderator: Mar 10, 2015
  19. Quantum Quack Life's a tease... Valued Senior Member

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    uhm... do you need a big brain before you start to cook or after?
     
  20. Trippy ALEA IACTA EST Staff Member

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    It's nine pages - you quoted the abstract.
     
  21. zgmc Registered Senior Member

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    From the link provided it was not clear to me either that there was more to the paper. Do you have to download the pdf?
     
  22. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Short answer is "After" as human size brain is impossible without cooking most of your food - not my opinion but stated in some of the 6 references in post 1751and implied by all that I gave; However, like most "short answers" that is not fully correct.

    Cooking proceeded brain growth, as it only takes a few generation to become common practice in any give society but significant average brain mass increase takes thousands of generations. It is not a which "chicken or egg" came first probelm, but more of a "co-development" process like flower/ bee co-development.

    The quite immediate benefit of cooking be coming common practice in any tribe, etc. is many more babies surviving to produce more. - Why the population of the "hairless ape" exploded much more rapidly than the brain grew. I don't have data on the pre-cooking population of the hairless ape (and not even sure it was hairless, before its surface to volume ratio at least doubled.) Black hair all over the body helps with the cooling problem under the hot sun. I.e. a large part of the solar energy is absorbed in hair which may be more than a cm from the body and has huge surface to volume ratio for dumping large part of that heat to the air. The fact that humans still have hair, curly and black, is from Africa, is more evidence that the human brain is close to the thermal limit - need that hair to avoid over heating if you live on the African pains.*

    As the brain is with all parts relatively close to each other (for faster signal transfer and less mass of "wires" - the axons or "white matter") it is crudely speaking "sphere like" not Hot Dog like in shape. That is the worst shape for cooling the brain and it is the first to die / fail at least/ when one has a high fever for days. This is even reflected in our language, when we say: "He is feverous / incoherent/ does not know what he is saying." etc. Because of it bad shape from a cooling point of view, there is a thermal limit on how big the brain can become without an "auxiliary cooling system" -

    Don't laugh. The biggest brained creatures that live on the hot African plains do have an "auxiliary cooling system" I.e. African elephants have huge ears to help cool their brains, which have an even worse surface to volume ratio than man's brain has. The Indian elephant is not subjected to as intense a heat stress, so get by with smaller, but still very large ears. Elephants don't cook their food, so need to eat most of the day and spend a great deal of energy doing that, chewing up small twigs, etc. and also have huge guts - I think their food takes more than a week o pass thur it and that their digestive system, including the vast amount of skin and muscle supporting it, makes up half their weight! Maintaining a big brain without cooking is a "full time job."

    * Also important to note is that humans were not /are not/ the only African animals that lived on the hot African plains; But are the only one that was able to have small gut relative to its body size** AND evolve bodies with only a tiny fraction of the body covered by hair. - The MUST be some unique feature that humans ONLY developed to permit this - you can guess what I think that is.

    ** "Only" is not completely true - a few African plains animals evolved very high speed running ability and needed not to have to lug around a big gut to achieve that and eat high caloric food (meat). For example, the cheetah can for brief periods run nearly 100 times faster than man can but man with club can catch and kill a cheetah as he can run after it and force it into heat prostration.
     
    Last edited by a moderator: Mar 11, 2015
  23. iceaura Valued Senior Member

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    That is not possible - that is, there is no incremental gain in cookery skills from an incremental gain in brain size from chimp, as far as anyone has ever noticed. Chimps cannot control fire, even. There is a chicken and egg problem. You need a much bigger brain than a chimp has, with more sophisticated social as well as technical potential, to enable cooking.

    A chimp mother spends a fairly long time - hours, spread over different days, sometimes - teaching her daughter how to fish termites with a twig. This is a two step tool forming operation and one step technique with an immediate reward - termites within seconds. Her sons often don't learn even that.

    As in most of the remarkably common glib explanations for human evolution, this begs the question. You need a large boost in brain capacity from chimp, to have any such "common practices in any tribe".

    The human brain has enough thermal safety margin and extra cooling capacity under ordinary circumstances to permit indefinite periods of long distance running in full sunlight at an ambient temperature of more than 90F. That is its limit - one of the highest in the endothermic world.

    It gains this capacity via:

    a couple of remarkable cooling systems, including a large and readily available expanse of hairless skin well supplied with variable blood flow it can use as a heat dump - much as elephants use their ears;

    and having been equipped with redundant capacity, despite the large expense of maintaining it, which prevents local and temporary failures from bringing down the system as a whole.

    But your emphasis on the vulnerability of neural circuitry, in general and in any organism, to overheating, is the key point. That's where redundant circuitry in early hominids is hypothesized to have been of incremental benefit, as initially required.
     
    Last edited: Mar 11, 2015
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