Announcement

Collapse
No announcement yet.

Expensive Tissue Hypothesis and Klieber's law

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Expensive Tissue Hypothesis and Klieber's law

    Today I was reading the thread at http://www.marksdailyapple.com/forum...makes-us-human

    It contained link to an interesting blog by Dr Eades.
    http://www.proteinpower.com/drmike/l...arians-part-ii

    The ETH hypothesis is based on the Kleiber's law, which states that all animals with the same mass will have similar Metabolic rate. This means that Humans and Chimpanzees with same weight should have same metabolic rates. Humans have larger brains which is balanced by having a smaller and simpler GI Tract.
    The ETH hypothesis says that we evolved to have a bigger brain because we shifted to a larger meat diet, and this allowed us to have a simpler GI Tract which allowed our brain to grow, by using the extra available memory.

    This hypothesis fails if we look at the big cats which are true carnivores and have a very simple GI tract and also very small brains. But they do honor the Kleiber's law. Vegetarian primates have a bigger brain than the carnivorous big cats. This does not make sense.

    This means that the savings from the GI tract and the small brain are used somewhere. I think that the solution is Gluconeogenesis. It is very thermogenic, and wastes nearly 30% of the energy. This 30% waste will balance the savings from the GI Trace and the small brains.

    So how are humans able to get a bigger brain. The reason is that humans are not able to use much protein, we need to get our fuel from fat or carbs. Since our digestive system is simple so the carbs must also be simple to get digested and provide the required fuel. Using the two fuels is not very thermogenic and wastes little energy.

    Why did the big cats not develop big brains? Because the big cats need to increase the consumption of fat, which they did not have means to do. They don't have our unique hands that can use tools to get at the fat stored in bones and skulls. They also cant use the fats in fatty vegetables, because those require slightly more sophisticated digestive systems than theirs.

    Chimpanzees must have started using tools to get access to more fat from animals. But since they are not very good hunters I think that this would have been a very gradual process.
    The ETH article talks about two big jumps in the brain size. The second can be accounted for easily by control of Fire.

    The first is a bigger problem. For a big jump, there needs to be a single identifiable change in diets. It cannot be meat. The reason is that the skill of proto-humans would have increased slowly, with slow increase of fat and consequent slow increase of brain.

    I think there is a possible solution to this. How difficult it is to break a coconut? Is there any animal apart from humans that are able to eat it? A coconut is a plentiful resource of simple carbs and fat. The single event would be, the means and ability to break open a coconut. This might allow a big jump, but would constrain proto-humans to the tropics. When the brain grows sufficiently large then proto-humans would be very good hunters and would not be confined to the tropics and could move outside. The tropics are a poor place to find archeological evidence. The jump would be seen for the hunters that moved outside the tropics.

    Humans are also known to have originated in Africa which has plentiful coconuts on its beaches, and would provide the ideal place for humans to evolve. Coconuts are also very good for humans.

    Does anybody finds this hypothesis plausible?

  • #2
    I've read up on this, awhile back, and it's very interesting.

    As a total layman, I'd say your hypothesis is plausible.
    I began this Primal journey on December 30th, 2009 and in that time I've lost over 125 LBS.

    Comment


    • #3
      This badass is the coconut crab:


      He is so powerful he can actually claw a hole in a coconut husk and pry it open.

      As far as the first "leap" in brain size, scavenged meat (especially marrow) and tubers are among the explanations I have seen. Most tubers you have to cook, but there are a few that you can just pound the crap out of and soak.
      Give me liberty. Exploration of other options will be vigorously discouraged.

      Wondering something sciencey? Ask me in my Ask a Biochemist Thread

      Comment


      • #4
        @MG

        That crab is interesting. But it is too small to become that brainy ;-).

        I am not sure if scavanged meat would be a very consistent part of the diet. Tubers could be, but I am not sure if proto-humans were intelligent enough to do any complicated processing. I would think Tubers cooked on fire were definitely the reason for the second jump. It also must have caused the increase in AMY1 copies.

        Another thing I found that first tool use is possibly around 2.6Mya. This would coincide well with the first jump, and possibly those tools allowed proto-humans to break open the coconut.

        So the initial 2.5 mya was a slow increase in fatty meat consumption and brain size.
        Then tools became sophisticated enough to break open a coconut, and we have a jump.
        Then again slower increase till around 1 mya we gain control of fire and then another jump.
        After that the remaining growth.
        Then we learn agriculture, possible increase in brain, but we lose our bodies.
        I guess the agriculture did not cause damage to the brain, but only to the bodies.
        The damage to the brain is only very recent, with the lack of any nutrients due to consumption of fake food.
        Last edited by Anand Srivastava; 04-06-2010, 11:32 PM.

        Comment


        • #5
          Seems like crustaceans and shellfish would be another easy and reliable source of calories in the same regions where coconuts tend to grow. I do like your coconut theory, though. Are coconuts available year-round?
          Give me liberty. Exploration of other options will be vigorously discouraged.

          Wondering something sciencey? Ask me in my Ask a Biochemist Thread

          Comment


          • #6
            yes, and by the loads. Each tree gives like more than 50 (upto 75) coconuts in a year. Are crustaceans and shellfish high in fat? Otherwise they would be good supporting food, but not really brain food.

            Comment


            • #7
              Some good mono and plenty of n-3 where they've got it. Some are much fattier than others. The larger they are, the more nutritious organs they have. Still, you're probably right that they're not an ideal primary calorie source. Most are 90+% protein.

              On a side note, how the hell does a single tree manage to get enough energy to produce that many energy-dense drupes? I mean, tropical sun notwithstanding, that's pretty impressive.
              Last edited by Molecular Grokologist; 04-07-2010, 12:02 AM.
              Give me liberty. Exploration of other options will be vigorously discouraged.

              Wondering something sciencey? Ask me in my Ask a Biochemist Thread

              Comment


              • #8
                Originally posted by Anand Srivastava View Post
                Humans are also known to have originated in Africa which has plentiful coconuts on its beaches, and would provide the ideal place for humans to evolve. Coconuts are also very good for humans.
                First of all - great question, one that is pondered hard amongst anthropologists.

                I belive the highest contributing factor to our species success was bi-pedalism and the ability to control fire, and cook our food. This opened up a vast treasure chest of available food both on land and shallow shores. I think marine fatty acids and protein contributed to our brain size, more than coconuts.

                http://www.news-medical.net/news/2006/02/19/16061.aspx

                http://www.psychologytoday.com/blog/...uman-evolution

                There is also the highly debated aquatic ape hypothesis.
                Last edited by Sungrazer; 04-07-2010, 05:04 AM. Reason: added another link
                Sometimes you need to be told the truth in order to be able to see it.

                My journal

                I see grain people...

                Exist in shadow, drifting away.

                Comment


                • #9
                  Very interesting thoughts from Anand and I'm glad to see MG on the case to discuss them.

                  Sungrazer mentions the Aquatic Ape Hypothesis, which I haven't seen discussed here, but would make an excellent topic both for Mark and for the forums. For those who may not know, it explains bipedalism (and several other odd adaptations of Homo, such as hairlessness, blubber, tears, voluntary breath control, etc.) as an adaptation to an environment that required lots of wading and occasional swimming. As an explanation for bipedalism, I've never found any other theory that came close in terms of parsimonious explanatory power. We could draw a lot of practical lifestyle conclusions from this hypothesis, assuming it is accurate...

                  Comment


                  • #10
                    Originally posted by Anand Srivastava View Post
                    The first is a bigger problem. For a big jump, there needs to be a single identifiable change in diets. It cannot be meat. The reason is that the skill of proto-humans would have increased slowly, with slow increase of fat and consequent slow increase of brain.
                    It could be meat related.

                    Improvements in hunting techniques could have quickly opened up access to more food. The development of any weapons such as spears, hand axes, cutting implements, bow and arrow, bola, etc. could account for a relatively sharp rise in meat availability.
                    The "Seven Deadly Sins"

                    Grains (wheat/rice/oats etc) . . . . . Dairy (milk/yogurt/butter/cheese etc) . . . . . Nightshades (peppers/tomato/eggplant etc)
                    Tubers (potato/arrowroot etc) . . . Modernly palatable (cashews/olives etc) . . . Refined foods (salt/sugars etc )
                    Legumes (soy/beans/peas etc)

                    Comment


                    • #11
                      Given that Neanderthal (although admittedly more sturdily built than early humans) managed to hunt by ambush, wrestling even large prey to the ground and clubbing it with sharpened rocks, Tarlach could be right. Even the smaller hominids could surely do the same to small game.
                      Give me liberty. Exploration of other options will be vigorously discouraged.

                      Wondering something sciencey? Ask me in my Ask a Biochemist Thread

                      Comment


                      • #12
                        Sorry was out on a vacation.

                        @Tarlach
                        I am not sure if we could call the tools you mentioned as really simple. Simple tools that we are talking about are stones that have been chipped away to make them slightly sharper. Proto-Humans managed to learn (or maybe developed the dexterity) that chipping away at stones could make them better tools by 2.5mya. Before that they were using much blunter tools.

                        I guess it is obvious that preceding 2.5mya proto-humans were relying on meat to increase the brain size. But my point is that protein is not the important factor, Fat is. Getting fat from meat will increase even with blunt tools. You don't need sharp tools to kill animals or to break their bones. Sharp tools don't increase animal hunting possibility, as much as dexterity and intelligence. I think to account for a jump we need something that provided a sharp increase in fat availability.

                        Extracting meat from a coconut is not possible without a sharp tool. This is what I believe happened 2.5mya, and provided a large increase in fat availability.

                        Comment


                        • #13
                          @MG

                          My only issue is with the jump. Why was there a jump? Animal fat can surely increase the brain size slowly, there is no contention over that. The contention is only on the jump. Animal fat cannot provide that.

                          Comment

                          Working...
                          X