Thread: Human evolution, big brains, meat and TB

Reference : New Scientist, 21 June, pages 28 and 29

The above reference is an opinion piece, and thus is not widely accepted scientifically. We are free to agree or disagree.

About 2 million years ago, pre-human brains began evolving for much greater size. About roughly the same time, meat became a much more important part of the diet. The authors say the meat stimulated the brain evolution. It appears that meat contains lots of the amino acid, tryptophan, which is scarce in vegan diets. It is a precursor for vitamin B3, nicotinamide, the absence of which causes the brain wasting disease, pellagra. So the theory presented is that more meat gave more vitamin B3 which would permit brain size growth.

I disagree with this. I do not think evolution works this way. My view is that brains evolved into larger size because larger brains gave a strong evolutionary advantage, not simply because they could, with more vitamin B3. There would be a relationship, of course, since larger brains would permit more effective hunting methods, including sophisticated social cooperation in the hunt.

The link to TB is that the authors claim the tuberculosis bacterium was once symbiotic. Apparently, it is the only bacterium which makes nicotinamide. Thus, when meat is in short supply, the TB bacterium helps fill the gap. The authors suggest there is a relationship between high meat diets and low incidence of TB, and of course, high TB incidence when meat in the diet falls. ( I would be more inclined to associate poverty and overcrowding with TB, which is associated with low meat diet). Apparently, high levels of nicotinamide actually work to kill TB bacteria.

So who is right? Is it low meat or poverty that causes TB? Is it high meat that causes brain evolution, or large brains that permit a high meat diet?

I'm inclined to disagree also. First of all, our closest relatives are chimps which do eat meat as against other apes like gorillas and orangutans which seem to be largely if not entirely vegetarian.

Is it high meat that causes brain evolution, or large brains that permit a high meat diet?

I don't see why it has to be an either or issue in the first place. My view is that it's better to be an omnivore in the first place because there's always something you can eat.

I have a bit of an inclination to the view that the really big step towards a much bigger, better brain came a bit later in the picture with the use of fire. Extracting more easily digestible nutrients from anything and everything you eat makes the whole metabolically expensive burden of having a big brain much more supportable.

I have to agree. I think they're not asking the right question. I would think the question would be: "why does the human brain require so much B3."

The same organ with the same essential abilities could probably be built from a number of other building blocks just as easily. There's no reason why that one in particular had to be the one that the human evolution chose. So why did it choose that one?

A parsimonious answer would be that, when the human brain was increasing in size, B3 was available and even plentiful, so evolution chose that as the most elegant building block.

Why was the human brain increasing in size? Well, because humans were starting to hunt as a means of getting food.

My personal speculation as to why the human brain grew is a combination of tool and weapon use, plus social cooperation. I feel that the one and only thing that really sets humans apart from every other species is the use of advanced technology. Advanced in this case defined as anything from chipping stone tools and upwards. Basic tool use and even construction is widespread in the animal world. But once advanced tool and weapon manufacture and use is required, a larger brain is, also.

Combine this with sophisticated social cooperation, based on language, and a big brain becomes essential.

and obviously sufficient food to feed a large brain - the need for a large brain may exist for all the reasons you've mentioned, but if the diet is insufficient to support the growth and maintenance of a large brain, then that need will have to go unfulfilled

i sometimes wonder whether that was the case with Homo floresiensis

Bipedalism, changes in the birth canal and adaptations of the human skull have been suggested as factors in the rapid evolution of brain size in our species. The following article from two years ago remains quite interesting to me. Bipedalism would have completely changed our perspective on the world, increasing our effectiveness as hunters and tool-makers and enabling us to broaden our nutritional base. I agree that our discovery of fire would have made nutritional energy more available to us as well, making it also a likely factor in the process of brain size increase.

A new analysis of the skull suggests that human brain evolution may have been shaped by changes in the female reproductive system that occurred when our ancestors stood upright.

At some point in evolution, our ancestors switched from walking on all four limbs to just two, and this transition to bipedalism led to what is referred to as the obstetric dilemma. The switch involved a major reconfiguration of the birth canal, which became significantly narrower because of a change in the structure of the pelvis. At around the same time, however, the brain had begun to expand.

One adaptation that evolved to work around the problem was the emergence of openings in the skull called fontanelles. The anterior fontanelle enables the two frontal bones of the skull to slide past each other, much like the tectonic plates that make up the Earth's crust. This compresses the head during birth, facilitating its passage through the birth canal. In humans, the anterior fontanelle remains open for the first few years of life, allowing for the massive increase in brain size, which occurs largely during early life. The opening gets gradually smaller as new bone is laid down, and is completely closed by about two years of age, at which time the frontal bones have fused to form a structure called the metopic suture. In chimpanzees and bononbos, by contrast, brain growth occurs mostly in the womb, and the anterior fontanelle is closed at around the time of birth.
When this growth pattern appeared is one of the many unanswered questions about human brain evolution. The new study, led by Dean Falk of Florida State University, sought to address this. Working in collaboration with researchers from the Anthropological Institute and Museum at the University of Zürich, Falk compared the skulls of humans, chimps and bonobos of various ages to the fossilized skull of the so-called Taung Child.

Taung Child was found in 1924 in a limestone quarry near Taung, South Africa, and was the first Australopithecine specimen to be discovered. It belonged to an infant of three to four years of age, and is estimated to be approximately 2.5 million years old. The skull is incomplete, including the face, jaw and teeth, but it contains a complete cast of the brain case, which formed naturally from minerals that were deposited inside it and then solidified. "Most of Taung child's brain case is no longer present, but you see all kinds of interesting structures in the endocast, like the imprints of the cortical convolutions," says study co-author Christoph Zollikofer. "We looked at the imprints of the sutures. These features are very well preserved, and have been known about for 50 years, but nobody paid attention to them."
In 1990, researchers from Washington University Medical School published a three-dimensional CT scan of the Taung Child endocast, and Falk subsequently reconstructed it again using more advanced computer technology. Comparison of this more recent reconstruction with scans of other species now reveal that the skull of Taung Child has a small, triangle-shaped remnant of the anterior fontanelle.
This suggests that Taung Child had a partially fused metopic suture at the time of death and, therefore, that the pattern of brain development in this Australopithecine species was similar to that of anatomically modern humans. Delayed fusion of the metopic suture indicates that fast brain growth in the period following birth came before the emergence of Homo, the genus that evolved from Australopithecines and eventually gave rise to our own species, Homo sapiens.

Bipedalism, birth and brain evolution | Mo Costandi | Science | theguardian.com

I have nothing of consequence to add to this most interesting and informative thread.. Thanks..
~ and some time for some reading.. much.. ~ great subject..

Scheherazade

While bipedalism is, no doubt, an important factor in human evolution, its impact on brain size is problematic. Ardipithecus, 6 million years ago, showed all the signs of being upright in stance and thus bipedal, and its brain was less than a modern chimp. Australopithecus​ was definitely bipedal 3 million years ago, and its brain was no bigger than that of a chimp. Only about 2 million years ago, after 4 million years of bipedalism, did the brain start evolving to great size.

I am conflicted by all that speculation about "what caused what". We know that Natural Selection functions by survivability and ability to generate off-spring.

IMO, everything (the entire environment) was responsible for the emergence of human ability for abstract thought. Lest we forget, some of our ancestors did NOT survive!. Lack of vitamins?

The most plausible explanation I have read is a genetic mutation which fused two genes into a single more complex genetic code, perhaps stimulating the growth of certain neural networks such as the mirror neural network in the brain.

All great apes apart from man have 24 pairs of chromosomes. There is therefore a hypothesis that the common ancestor of all great apes had 24 pairs of chromosomes and that the fusion of two of the ancestor's chromosomes created chromosome 2 in humans. The evidence for this hypothesis is very strong

Chromosome fusion

As I understand it, a secondary contributing factor is the shrinking of facial (chewing) muscle mass, allowing more room for expansion of the brain as well as increased folding of the tissue, thereby exponentially increasing our processing power.

The first vertebrates appeared over 500 million years ago (Mya), during the Cambrian period, and may have resembled the modern hagfish in form.[31] Sharks appeared about 450 Mya, amphibians about 400 Mya, reptiles about 350 Mya, and mammals about 200 Mya. No modern species should be described as more "primitive" than others, strictly speaking, since each has an equally long evolutionary history—but the brains of modern hagfishes, lampreys, sharks, amphibians, reptiles, and mammals show a gradient of size and complexity that roughly follows the evolutionary sequence. All of these brains contain the same set of basic anatomical components, but many are rudimentary in the hagfish, whereas in mammals the foremost part (the telencephalon) is greatly elaborated and expanded.[32]

Brain - Wikipedia, the free encyclopedia

Some noncoding DNA sequences play structural roles in chromosomes. Telomeres and centromeres typically contain few genes, but are important for the function and stability of chromosomes.[58][92] An abundant form of noncoding DNA in humans are pseudogenes, which are copies of genes that have been disabled by mutation.[93] These sequences are usually just molecular fossils, although they can occasionally serve as raw genetic material for the creation of new genes through the process of gene duplication and divergence.[94

DNA - Wikipedia, the free encyclopedia

Yes, the last paragraph of the link I posted also makes mention of ...

Last week, however, Evan Eichler and colleagues reported that a gene known to be involved in development of the cerebral cortex was duplicated multiple times, and that this occurred exclusively in humans. They also estimate that these duplications took place between two and three million years ago, so it is tempting to speculate that they are somehow linked to the changes that may have occurred as a result of bipedalism.

Seafood has been argued as the original fuel behind the growth of the human brain, because, apart from containing vitamin B3, it also has high contents of PUFA's and most crucially Iodine, which are scarse in terrestrial meats. The argument is, that without these brain-specific micronutrients, we couldn't have grown a big brain. It should be somewhat easy to discern if e.g. Homo erectus as the first hominin with 1000cc brain had a diet including significant ammounts of seafood. To my knowledge, such studies haven't been made yet.

And that's as much as I should say about that.

Originally Posted by CEngelbrecht

Seafood has been argued as the original fuel behind the growth of the human brain, because, apart from containing vitamin B3, it also has high contents of PUFA's and most crucially Iodine, which are scarse in terrestrial meats. The argument is, that without these brain-specific micronutrients, we couldn't have grown a big brain. It should be somewhat easy to discern if e.g. Homo erectus as the first hominin with 1000cc brain had a diet including significant ammounts of seafood. To my knowledge, such studies haven't been made yet.

And that's as much as I should say about that.

I may be able to add some additional info to that.

I am conflicted about the proposition that diet was responsible for mental evolution of the hominid. Humans seem to thrive almost everywhere on a great variety of foods. However, there is speculation that shifting from vegetable diet to meat and fish may have caused the jaw muscles to lose bulk, thereby making room for a growing and developing brain.

This little tid-bit seems to support not only the dietary benefits of living near the sea, but also may have given rise to specialized tool making and a dependable route to the north.

Coastal dwelling also may have been one of the most efficient ways of migration from Africa into Southern Europe and spreading from there.

a) Abundance of food along the coastline and beaches.
b) Easy travel and trailmarking.
c) Absence of large predators along brackish coastal waters.
d) Development of special prying tools for shell fish, spears for larger fish

We do know that some of the oldest habitats were formed close to the sea. Actually a remarkable change of lifestyle for developing intelligence, which added an enormous amount of communal knowledge, as compared to small individual families living in the forest surrounded by threats from every direction, having little mental stimulation or mental challenges.

Primitive humans who inhabited the coast of South Africa 165,000 years ago and lived on a diet rich in shellfish could be the original ancestors of everyone alive today, a study suggests.

First humans 'lived at southern tip of Africa' - Science - News - The Independent

If you're looking for another angle, there's an interesting divergence that some of the protohumans took toward night vision.

Neanderthal brains focused on vision and movement leaving less room for social networking -- ScienceDaily

Neanderthals, in particular, had exceptionally big eyes compared to a modern human. Their brain was actually bigger than a modern human also, but it is suggested in the link above that most of it was devoted to the larger eyes, and bulkier body of the Neanderthals.

Now consider what might happen if a neanderthal with big eyes and a big visual cortex mates with some other protohuman with smaller eyes and a small visual cortex. It's not too unlikely that the offspring could be so fortunate as to inherit it's eyes from one parent, and its visual cortex from the other. So now it has a visual cortex that is larger than what its body needs.

The visual cortex allows us to dream, and drives our imagination. It allows us to imagine things. We're essentially creating images and then viewing them in our heads. It would be interesting to wonder if perhaps our development of an excessively powerful visual cortex were in fact an accident. It would mean that our additional brain space grew for a reason other than endowing us with intellect, but then ended up endowing us with intellect and making itself useful after all. (Much like how our hands grew in order to enable us to climb, but later found a use in tool manipulation.)

Of course, not all humans actually have any neanderthal DNA - so it might have occurred earlier on with some other big eyed species.

Is it just a null hypothesis, that Neanderthals couldn't have been smarter than us? I mean, with that bigger brain of theirs on roughly the same size body? Do we just completely rule out that possibility?

Neanderthals could easily have been smarter than us. So what? It did not save them. It is like being the class genius, only to see the sports jock with a low forehead get the girl. Other factors could have made the difference. Like, for instance, the fact that humans have a shoulder joint that permits us to throw stone tipped spears with force and precision. Neanderthals could not.

They say that among those ol' cave paintings from France and Spain, it's the oldest ones that are artistically the best and most naturalistic. This is the last known region inhabited by pure Neanderthals, and the oldest artwork are from around their last era. For all we know, Neanderthals could've made the oldest and best, and Cro Magnons were just lousy copycats.

How does it feel to the dumber hominin, Homo sapiens? That there might be an upper limit to our intellectual capacity. 'Cause it sure ain't the smartest among us spreading their genes the most. Quite the contrary. Mel Gibson has fathered eight children.

Originally Posted by CEngelbrecht

They say that among those ol' cave paintings from France and Spain, it's the oldest ones that are artistically the best and most naturalistic. This is the last known region inhabited by pure Neanderthals, and the oldest artwork are from around their last era. For all we know, Neanderthals could've made the oldest and best, and Cro Magnons were just lousy copycats.

How does it feel to the dumber hominin, Homo sapiens? That there might be an upper limit to our intellectual capacity. 'Cause it sure ain't the smartest among us spreading their genes the most. Quite the contrary. Mel Gibson has fathered eight children.

Genetic diversity IS intelligent from the perspective of survival of the species, though. Remember that intelligence and even strength is not favored over adaptability and fertility by nature. Intelligence should lead to adaptability but only if the individual is capable of critical thinking, which is not always the case.

Who knows? Maybe the Neanderthals were the ones who realized the world was starting to get overpopulated in their time, and wanted to save the environment by having fewer children. And so they voluntarily reproduced less, leaving Cromagnons to continue freely overpopulating (because they didn't want to tell them not to.)

Maybe the Neanderthals decided that "peace is the way", and their dumber cromagnon cousins didn't agree.

But if brain size automatically dictates intelligence, then I would expect Elephants to be much smarter than humans, and evidence of that has yet to emerge. That they communicate is an established fact. Apparently they use low range sound frequencies below the level of human hearing.

Mystery of elephant infrasounds revealed -- ScienceDaily

But they don't build sophisticated tools, despite having that trunk available to use for a basic grasping mechanism.

One theory that seems to not be mentioned for larger brain size on this thread is the Machiavellian Intelligence Theory. It has been said that one of the things that species with the highest intelligence have in common are complex social environments. When we live in a social world, we tend to have rank structures within the societies. We see this with many baboons for instance where every baboon has a very specific ranking among the group and act certain ways to baboons that are above and below their own ranking. To compute these types of abstract arbitrary ideas needs certain parts of the brain to be emphasized.

Here is a link that briefly describes it better than me lol: philosophyofsocialcognition / Machiavellian intelligence theory

Originally Posted by kojax

Who knows? Maybe the Neanderthals were the ones who realized the world was starting to get overpopulated in their time, and wanted to save the environment by having fewer children. And so they voluntarily reproduced less, leaving Cromagnons to continue freely overpopulating (because they didn't want to tell them not to.)

Maybe the Neanderthals decided that "peace is the way", and their dumber cromagnon cousins didn't agree.

But if brain size automatically dictates intelligence, then I would expect Elephants to be much smarter than humans, and evidence of that has yet to emerge. That they communicate is an established fact. Apparently they use low range sound frequencies below the level of human hearing.

Mystery of elephant infrasounds revealed -- ScienceDaily

I recall reading that in large animals such as whales and elephants, a large portion of the brain is used to regulate the physical size and adjustment to specific submarine environments.. After all whales (as well as elephants) are nomadic and encounter a range of natural conditions, where they must remain functional.

But they don't build sophisticated tools, despite having that trunk available to use for a basic grasping mechanism.

Seems to me that elephants or whales have little use for tools. If they want to eat the little offshoots on high branches, they just knock the tree down. Their sheer size and strength does not require a lot of sophistication.

OTOH the cuttlefish has a very large brain for its size, which it needs as it is very vulnerable. This is how it learned to shape-shift to hide and later use that same skill as a hunting tool.

But even as a brain is large with large folds, I always assumed it was the number of folds in the brain structure that creates a greater volume without a need to increase skull capacity. More or less on the principle that miniturazation allows for more powerful computers without increasing their size.

What I do find very interesting is that most animals with large, well developed brains display "empathy". probably as a result of a longer learnng curve requiring longer attention and care.

Whales adopting an injured dolphin, elephants stopping by graveyard to pay their respects, a silverback gorilla protecting a small human child (which had fallen in the gorilla compound) from the curiosity of the more aggressive younger males, or an orangutan saving a duckling from drowning. https://www.youtube.com/watch?v=yZL5hesWpWM

For those who have not yet seen it, I hope I can remind people to watch and be moved by these little glimpses of compassion. https://www.youtube.com/watch?v=3zfgFfC5kOs

There are differences in the way brains are organized too. All that stuff about different areas that specialize in different functions.
One of the differences between Neanderthals and Moderns was how they used resources. Moderns would return to a salmon run at the right location and the right time to exploit it.
Neanderthals might have returned to the stream but they didn't seem to realize that timing mattered and were only able to exploit a salmon run by chance.

What I am getting at is is that while their brains might not have been structured in a way that allowed them to understand time in the same way this does not mean they were less smart, just not smart about the same things.