Nutrition in human evolution

[Askur]

In most species we see a reduction in brain size the bigger the animal gets. In humans on the other hand, both the brain and our body have become bigger. In some articles it is claimed there is not much probability we could have evolved such a big brain by living on the savannah only. The fatty acids, like DHA and AA are the most imortant reasons that allowed our brain to become so big. And the only place to find enough of such fatty food is in the water. No, I'm not talking about the aquatic ape theory. You don't have to adapt to water to collect food at the shoreline occasionally. Some monkeys do the same thing in our modern times.
My question is; if they didn't get the fatty acids from the water, where would they find a sufficient source of this kind of food in the forest or on the savannah?

Another claim is that the size of the brain is inversely proportional with the gut, and because of this it would be impossible to us to evolve into the intelligent species we are today if we were pure vegetarians. Is this correct or just speculations? But of course, there is no doubt at all we are strongly adapted to comsume meat and animals as the true omnivore as we are, which is telling us a thing or two about our origin.

[Jois]

Why wouldn't the standard sources: "LA can be found in certain seed oils, while ALA is in dark green leafy vegetables, flaxseed oil, and linseed oil" have been adequate?  I have no idea what equivalents must have been present where early humans evolved or what insects, seeds, nuts, and plants might have been there that are no longer be available for testing today.

A Google search would give the list quoted above many times over.

Jois

[Askur]

The keyword is sufficient. Is there sufficient amounts of these fatty acids on the savannah or in the forest?
I have tried Google but most sources say it is the same pattern anywhere; when mammals grows the brain have problems to keep up with the growth.
So I was hoping might could get a opinion from an expert.

[Jois]

Here's an expert's opinion:

http://www.ajcn.org/cgi/content/full/72/6/1586

Jois

[Askur]

Some experts says one thing, other expersts says something else. Who shall we believe?

Other says:
"Why does size and velocity of growth matter? The reason is that the biosynthesis of AA
and DHA is relatively slow, and may not be able to keep pace with body growth in fast-
growing animals. Rats and mice desaturate and chain elongate the parent essential fatty
acids to produce larger amounts of AA and DHA than their precursors. Stepping up in
size from the guinea pig to the wild pig the impact of velocity of growth results in a
progressive decline in AA and DHA whilst the precursors linoleic and linolenic acids
become more dominant in liver lipids. Instead of DHA, the DPA is now the major
metabolite of α-linolenic acid.
So the faster an animal grows, the larger it becomes and the greater is the constraint of the biosynthesis of AA and DHA."

Katharine Milton is by the way working in the Division of Insect Biology, not with paleoanthropology.

But she has some points, even if I don't know how a paleoanthropologist will say to them.

Others of her comments is not so good.

"If humans in the African Rift Valley consistently utilized lacustrine resources, why the long period of stasis in human encephalization between 1800 and 600 thousand years BP?"

Well, why was the brain in the suborder Odontoceti or toothed whales stabile for so many years before it suddenly started to grow, even if they had lived in the ocean for millions of years already?
Because the evcolution of the echo localization made it  necessary to develop the brain further. Living in an environment which allowes growth of the brain is not enough, there has to be a need and a selective pressure present too.
The brain of our ancestors did not increase in size just because it was "cool", but because at some point it gave them an advantage. The evolution of language must have been a very important factor. Before this point there was no bigger need to have a much bigger brain.

"Another puzzle concerns the technologic explosion, a burst of creativity in anatomically modern humans that appears to have begun fairly abruptly in the Late Paleolithic period some 40 thousand years BP and involved the dramatic acceleration of cultural evolution. This technologic explosion was not accompanied by any increase in human brain size and thus some other factor, possibly the development of fully modern language, has been suggested to underlie it."

Restructure of the brain often assume a growth at the same time, but it is not always absolute essential.

"Elephants, for example, have brains that, over the course of their evolution, "were enlarged even beyond the extent expected for their large bodies."

Elephants are one of the animals we can say for sure evolved in water, or at least their ancestors. Yet they do have an impressive brain nad have also evolved on the savannah since then. But not as impressive as in humans.
Brain Weight as % of Body Weight:
human 2.10
African elephant 0.15

"The "aquatic foods argument" also offers no real explanation for why these foods stimulated human brain expansion. In this Lamarckian scenario, the quiescent brain appears to be waiting patiently for humans to discover aquatic foods and then, eureka, the brain is free to enlarge and modern humans result."

Lamarck meant that acquired characteristics are inherited. I don't see what this theory has to do with the subject.
If the brain got bigger because of the food, it means it couldn't start grow until there was a safe source of the right nutrition. It could also mean our ancestors were the right place at the right time.
If she truly believes scientists believe out brain got bigger and our mind evolved just because of the food alone she has probably misunderstood.

"Not only are the selective pressures involved in this scenario unspecified, no information is provided as to how these large-brained humans were then able to provide DHA and other brain-specific nutrients for themselves or their developing offspring once they moved away from lacustrine or shore-based environments."

The last part is a good point, but when it comes to the first part it is important to remember that lack of information at the present is not synonymous with an error.

[Jois]

This Katherine Milton looks like she could be expert enough to discuss nutrition:

Dr. Katharine Milton
Dept. of Anthropology
University of California
Berkeley, CA 94720, USA
e-mail: kmilton@uclink4.berkeley.edu
KATHARINE MILTON is a professor of physical anthropology at the University of California in Berkeley. She received her Ph.D. in anthropology from New York University in 1977 and carried out two years of fieldwork in Panama as a post-doctoral fellow with the Smithsonian Institution. Her research focuses on the dietary ecology and digestive physiology of Primates, both humans and non-human, and has involved her in fieldwork with howler monkeys, woolly spider monkeys and chimpanzees as well as forest-based human societies in both the Brazilian Amazon and Papua New Guinea. She is the author of more than 60 publications and was recently elected to the American Academy of Arts and Sciences. Her publications on ecological practices of Amazonian groups include the following: Protein and carbohydrate resources of the Maku Indians of Northwestern Amazonia. American Anthropologist 86:7-27 (1984); Comparative aspects of diet in Amazonian Forest Dwellers. Philosophical Transactions of the Royal Society, Series B. 334: 253-263 (1991); Civilization and its Discontents. Natural History, March 1992, pp. 36-45 (1992).


Also follow references in both Milton's letter and the Cunnane letter - both published in nutrition journals rather than anthro or paleoanthro types. 

Jois

[richard01]

"The "aquatic foods argument" also offers no real explanation for why these foods stimulated human brain expansion. In this Lamarckian scenario, the quiescent brain appears to be waiting patiently for humans to discover aquatic foods and then, eureka, the brain is free to enlarge and modern humans result."

I am following this in detail, and have brought up the subject in paleoanthro - I am more than convinced aquatic foods are the answer to sudden 'brain-bursts' simply because DHA and AA are far more readily available in fish and other aquatic animals' flesh than they are terrestrial animals' - except their brains themselves.

There are several papers on fatty acids in fish, etc (and early fish catching) uploaded in recent days to the the paleoanthro group.

They include: Broadhurst et al - on DHA in fish diets
                      Kathlyn Stewart on fish at Olduvai

But here is one I am studying currently, that gives the 'current paradigm' version of sources of DHA in early hominids

Fatty Acid Composition and Energy Density
of Foods Available to African Hominids
Evolutionary Implications for Human Brain Development
Loren Cordain, Bruce A. Watkins, Neil J. Mann

Its in pdf format, so I can't directly find the source  immediately, but if you google some names, etc, you'll soon find it.

They basically end up saying that none of the available savannah foods provide DHA except ruminant brains, and that none supply much energy either, except bone marrow - therefore early man must have been an obligate tertiary scavenger for his staple foods long after the prime predator, large hyaenas, etc, left only such remains (brains and long bones), and they wandered the savannah looking for such delicacies.

They dismiss fish sources by a sole reference to recent fishing/foraging activity by the Ache of Paraguay.

They also say: "This dietary shift
from a predominantly plant based diet to one in which animal foods became increasingly important allowed for the relaxation of the selection pressures that had formerly constrained encephalization in Australopithecus species "

In other words, hominid brains were busting to get out, but were held back until they turned from eating up their greens to cracking left-over skulls.

This sounds less Lamarckian than Creationist.

It was presumably this very early intellectual initiative, a revolution from "eating, roots, shoots, and leaves", to a conscious change in diet, that led us to where we are today.

regards

Richard

[richard01]

I'm sorry if my last heavily sarcastic message killed this discussion on the vine.

There seem to be three key essentials that would allow the evolution of a larger human brain:

Energy: Aiello and Wheeler touched on this with the 'expensive tissue' theory, that posits the replacement of a large vegetarian gut with a smaller meat-eating one, and its balancing replacement with a larger brain - but without a lot more back-up material on exactly how it might have happened, this becomes a 'just-so' story. Plain energy is not enough, or we'd get more intelligent by eating more french fries.

Lipids: To make the structure of brains, you need certain essential fatty acids  (EFAs) amongst which DHA is very important. Enough to construct a brain cannot be made directly from vegetable foods, and not a lot more from animal flesh.

Therefore you need a 'burst' of extra input - most could come from fish, or ready-made from other animal brains - Cordain et al found that little could come from other recognised terrestrial sources than animal brains themselves - bone marrow has an insignificant amount. And they also posited that early humans could not have hunted or scavenged whole carcasses - they just got the left-over bits - brain and marrow.

But there's little of that about - various studies (Tappen et al, O'Connell et al ) suggest that you'd be lucky to scout across the savannah and find a usable carcass more often than once every 9-10 days - not enough to cause a 'brain burst'.

Of other terrestrial sources, insects turn out to have surprisingly large amounts of both protein and fatty acids, and foraging them (at the right time) is highly productive. Many Africans and SE Asians eat insects regularly nowadays, and there are surprisingly large figures for local trade (1600 tons of dried caterpillars every year from Botswana).

These might have (just) done the trick, but have not been much studied - you could imagine the headline:

"Man the Grub Hunter"

- not the sort of thing to attract research funding from wealthy ranchers, farmers, agrochemical industries, or anyone else, including respectable Christians who might have thought that Elijah, being sent to the desert to survive on locusts, was being punished, not being given a very good dietary alternative.

But the main source of DHA, etc is marine fish and shellfish.

Then, the third key factor is iodine. It's not such a problem nowadays, as most countries have mandated iodised salt as a compulsory diet supplement, but it was, especially in areas far from the initial dispersal of methyl iodide from the original manufacturers, marine sea plankton.

Inland Kenya, Tanzania, and most of Central Africa had, until recent salt iodisation policies, some of the severest iodine-deficiency problems on earth.

One of the symptoms of iodine-deficiency is cretinism - hardly the kind of milieu in which a 'super brain' could have evolved in an otherwise unremarkable ape.

regards

Richard