Really cool study: Discovery of site indicating that early hominids (1.95 mya) butchered and ate aquatic animals (fish, aquatic reptiles, hippos, crocs...) - this evidence seems to support the hypothesis that getting the nutrients from fish provided the nutrients that are needed to support larger brain growth. http://www.wired.com/wiredscience/2010/06/first-fish-diet/
So my questions/rant - I hope its coherent:
is there fossil evidence of the evolution of larger brains in areas where access to rivers and floodplains is limited (i.e. the 'brain food' diet is not present)? If so, then is there another explanation?
I wonder if there could sort of be a Lamarkian evolution here (I know, disproved, but...). If the mother has a greater ingestion of these proteins and lipids needed for a brain, it could be transferred to the fetus, right? So along with neotenic heterochrony (in this case when the stages of skull development are slowed, allowing more room for a brain to expand), there could be circumstantial (more nutrients) advantage that allows the brain to develop further (get larger)? I think the key is in the delayed fusing of the skull, which may have gotten later and later, extending into postnatal development, with the ingestion of the more enriched diet, that gave the brain space and nutrients to grow through generations. Lifestyle would have to change, need to have access to these nutrients in the infant development and early childhood, as well as during adulthood in order to feed the fetus. You would also need development of prolonged parental care of young since they would be born "earlier" in their developmental stage (bones are still soft, muscle coordination is slow, unlike say a newborn gazelle which can run within an hour of birth). But, and I'm not sure if this is circular or not, with a larger brain, adults may (I don't understand neuroscience so I'm not sure if larger really means better survival, but from the evolutionary standpoint, it probably has some correlation, otherwise it wouldn't have developed) have a better ability to think about their environment, survive in it by building better tools (need archaeological evidence for this) or using current tools in new ways (new game - such as aquatic animals!) and thus continue the nutrient flow to the next generation. I wonder how much genetics is even involved. I mean, you would need the heterochrony thing, right? But once you have that, then what? 1.95 mya, hominids were structurally very similar to modern humans, they walked upright, with the s-shaped spine, the arched, flat, inlined feet, the alterations to the pelvis and femoral head, the dexterous hands, etc. The main differences are in stature (which may have been largely environmentally induced, such as adaptations to high elevated areas - barrel chested and blood cabable of carrying more oxygen, skin colour in different areas of sun exposure, which we see today) (stature can also be affected by diet - better diet in youth leads to taller adults - from more modern observations) and of course the head. The head changed a lot. Some of it still fits within environmental influence such as the stength of the jaw muscles (eating softer foods with less need for grinding, such as fish, means that mucles of the jaw are not used as much - this is a developmental thing - experiments down with gorillas where muscles were weakened in youth so huge crest on top of the skull didn't develop and the muscle attachment for the jaw muscles was lower on the skull). Then the teeth, the size of (the molars getting smaller, the canines looking more like incisors, the incisors getting larger (actually, I can't remember if they do get larger or only in relation to the decrease in molars, should look that up)). This could be related to selective pressure of the diet (less grinding) and the use of tools to do the rough cutting. There is again that heterochrony, paedomorphosis, thing going on too, since the jaw doesn't grow as much in relation to the skull. But the main thing too look at is the change in the skull region, the height of the forehead, the rounding and vaulting. And that is why brain development is the intriguing question, the skull is the main difference between modern humans (us) and the hominids of 1.95 million years ago (along with everything that came with an enlarged brain and the ongoing cultural revolution).
I'm currently reading Panda's Thumb by Stephen J. Gould. In a couple of the essays he writes about the 19th century obsession to determine differences between races by measuring the size of the skull. This was an attempt to confirm the prejudice (one I and Gould and most people today do not hold) that European white men (specifically men) were the most intelligent, most logical, and most cultured due to larger skulls and subsequently larger brains. However, evidence (as far as I understand it, its probably a bit more complicated ) has shown that the skull size does not indicate any differences in intelligence. (So there is a lot more that you can talk about in terms of the scientists of the time and the racism, and not to belittle the issues, but I'm going to go a different way with this thought.) Gould also mentioned in this essay, if I remember correctly, that skull size and brain size does not say anything about intelligence, that these measurements were abandoned when IQ tests began to be the basic tool to measure intelligence (again some racism in this issue that I won't get into). What I wonder though, is this assumption that skull/brain size = more intelligent. From my limited understanding of nueroscience, I think that intelligence is more about the inter-connectivity of certain parts of the brain, the way the brain folds and the speed of the neurons interacting, and not necessarily size. For example, if you look at a bird, they have tiny brain to body size ratios, but some species can solve puzzles and interact with humans to portray needs and sometimes feelings (african greys are the reference here). We also have primate examples with sign language in gorillas and chimpanzees who can communicate with humans. But, goes the argument, they have smaller brains and they don't do this in nature (first, I'm not sure entirely if we, as humans and scientists, have any idea how animals communicate because many certainly have the potential to learn how to communicate with humans in human based languages, second, there is evidence of animals solving problems without being taught by humans in labs and also creatively solving things in the wild). This is especially intriguing when you look at their diets, fruits, nuts, mites for the primates with occasional meat (but not in the same amount as described is needed for larger brains). So I guess what I'm getting at is, there seems to be this impression that larger brains was the key to becoming 'intelligent' (the definition of intelligent probably needs to be more concise here, but I think using the general term still gets the idea across). Sure, this new study linking diet and possible brain development is important, but we don't even know really what's going on in the brain, because getting larger is one thing (and the only thing we have fossil evidence for), but being better insulated due to nutrients and thus faster, or being folded in new weird ways leading to new pathways, we just don't know anything about. I have heard that you can kinda get an impression of the brain on the inside of the skull. I'm sure they are already doing this, but maybe looking at the surface of the brain engraved on the bone would be a better indicator of whether the brain is developing into something more like us. (Pointing out a problem in this, fossils generally don't preserve the inside of the skull, simply due to how fossils are formed - you would need the actual bone for this, or get really lucky with a fossil, so in addition to being lucky enough to find this, you would also need to be able to interpret it...) Anyway, I don't really have a solution to the brain development delema, but I think that we should be careful about assigning enlargement with intelligence. And if you know more, please let me know, since I obviously don't know everything about brains.
So, diet probably did have a great effect, but the details are wuzzie.
"There isn't a sharp line dividing humans from the rest of the animal kingdom. It's a very wuzzie line. It's a very wuzzie line, and it's getting wuzzier all the time" - Jane Goodall (as in www.symphonyofscience.com).
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