Brain Evolution

[DrmDoc]

Hello All,

 

Here are other comments I've posted elsewhere that some of you may want to explore. Again, I welcome your thoughts:

 

"This difference between cortical volume and interbrain size supports a distinction suggested by the relative factors effecting cortical evolution among species divergent from humanity. While researching brain evolution for a book I wrote a few years ago, it became clear to me that the cortical development among animals ancestral to humans might have been compelled by a disparity in their sensory acuity. In a nutshell, ancestral animals, akin to contemporary primates, may not have had the sensory acuity of the predators they likely encountered as the protection of their receding African rainforests surrendered to the perils of what may have been a rapidly expanding continental savannah. Consequently, our animal ancestors were probably compelled to reason beyond the limitation of their sensory to survive and compete against faster, stealthier, sensory superior animals.

 

Some believe that the differences in diet (as suggested by fossil teeth evidence) influenced the differences they discovered in brain size between primitive co-existent primate families. While some early primates may have been herbivores, some researchers believed that our ancestral primates began to eat meat and that this steady diet of protein enhanced their brain development. What these researchers failed to consider is the amount of reasoning and brainpower essential to procuring and maintaining a diet of meat compared to that required to obtain leaves, nuts, and roots. Essentially, when our ancestral primates began to eat meat, they had to reason how to compete with other, more skilled meat-eating animals to safely procure and maintain a source of sustenance that probably resisted being that source vigorously.

 

Foraging among the trees of what was once lush rainforests, early primates didn't need the degree of visual, olfactory, and auditory acuity required of animals living in the flat, open grasslands of early Africa. Emerging from a retreating forest to a predator fraught savannah, early primates were likely forced to adapt beyond their sensory limitations to survive. Without sensory capabilities comparable to their savannah contemporaries, the competition, danger, fluid and varying circumstances associated with obtaining meat probably compelled our primate ancestors' use of brainpower in ways not required by foraging. As we know, through contemporary brain study, sensory experience and learning stimulate brain growth and development. Rather than meat consumption itself, the mental demands associated with obtaining meat likely stimulated the larger brain developments we have found among the primates considered ancestral to humans. Consequently, our dependency on the sophisticated thought processes our primate ancestors evolved to survive distinguishes our larger cortical-to-interbrain size ratio over that of more sensory dependent animals—in my opinion."

[PhDwannabe]

it became clear to me that the cortical development among animals ancestral to humans might have been compelled by a disparity in their sensory acuity. In a nutshell, ancestral animals, akin to contemporary primates, may not have had the sensory acuity of the predators they likely encountered as the protection of their receding African rainforests surrendered to the perils of what may have been a rapidly expanding continental savannah. Consequently, our animal ancestors were probably compelled to reason beyond the limitation of their sensory to survive and compete against faster, stealthier, sensory superior animals.

 

You make one claim here, and then a variation on that claim. First, that the relative lack of sensory acuity (compared to other animals) among early primate ancestors compelled cortical growth on an evolutionary scale. Second, that relative lack of sensory acuity, as well as relative lack of speed, and relative lack of stealth compelled this growth. Is it sensory acuity, or is it all three? It's not particularly novel to suggest that h. sapiens occupy a niche in which a relatively high degree of cognitive skill, and relatively low degrees of physical strength or senses are used to make a living. To make more specific variations upon that claim requires some more evidence. To make it in general terms is largely to recite what's already well-known.

 

It also strikes me that this particular hypothesis:

 

the mental demands associated with obtaining meat likely stimulated the larger brain developments we have found among the primates considered ancestral to humans

 

is somewhat incomplete, given that brain-to-body mass ratio has steadily increased along the mammalian line since very early mammals during the mesozoic. Also, the rapid advances in encephalization during the history of the early hominids we're talking about occurred long before the technology associated with hunting had arrived. Thus, the "mental demands" of obtaining meat are really the mental demands of scavenging--a strategy not unlike what mammals had already been employing for millions of years. One would have to make a case that scavenging meat and scavenging vegetable matter are qualitatively dissimilar. In both cases, other scavengers must be fought off or outsmarted (though they generally gather in higher density in the case of meat). Extremely simple tools are used in both--early hominids no doubt used stones to break open large bones and extract marrow, but this is probably not terribly new. Primates of all kinds employ sticks and rocks to get at ants and termites, nuts, roots, and honey. Animals far "down the tree" from primates have been seen to exhibit tool use behavior as well.

 

 

Although, the biggest thing going on here is: could you share some of the anthropological literature which drew you to these conclusions?

[DrmDoc]

It seems you only know one mode—attack!

 

it became clear to me that the cortical development among animals ancestral to humans might have been compelled by a disparity in their sensory acuity. In a nutshell, ancestral animals, akin to contemporary primates, may not have had the sensory acuity of the predators they likely encountered as the protection of their receding African rainforests surrendered to the perils of what may have been a rapidly expanding continental savannah. Consequently, our animal ancestors were probably compelled to reason beyond the limitation of their sensory to survive and compete against faster, stealthier, sensory superior animals.

You make one claim here, and then a variation on that claim. First, that the relative lack of sensory acuity (compared to other animals) among early primate ancestors compelled cortical growth on an evolutionary scale. Second, that relative lack of sensory acuity, as well as relative lack of speed, and relative lack of stealth compelled this growth. Is it sensory acuity, or is it all three? It's not particularly novel to suggest that h. sapiens occupy a niche in which a relatively high degree of cognitive skill, and relatively low degrees of physical strength or senses are used to make a living. To make more specific variations upon that claim requires some more evidence. To make it in general terms is largely to recite what's already well-known.

 

If I may simplify, in research some have suggested that larger brain size among ancestral primates may have occurred as that ancestry moved from a herbivorous diet to meat consumption. The idea is that the increase in protein consumption, associated with a carnivorous diet, may have led to this growth. My position, on that issue only, is that there could have been factors more compelling than dietary intake. In describing those factors, I suggested how certain sensory and physical disadvantages might have led to behaviors that could have resulted in increased brain size and development. In support, I briefly described how such disadvantages might have required reasoning capabilities and, by extension, brain power beyond those of competitors adapted to sensing, stalking, and capturing source of sustenance adapted to avoiding same. With a bit of patience and cordial inquiry from respondents, I would have further explored how experience has proven the most compelling factor in sustained brain growth. Brain studies of domesticated animals, for example, have shown as much as a thirty-five percent reduction of growth in their visual cortices relative to non-domesticated species. Presumably—given the unstable diet of non-domesticated animals compared to those in domestication—this size variance arises from the limited visual experiences of domesticated animals relative to the rich and varied experiences of wild animals.

 

 

It also strikes me that this particular hypothesis:

 

the mental demands associated with obtaining meat likely stimulated the larger brain developments we have found among the primates considered ancestral to humans

is somewhat incomplete, given that brain-to-body mass ratio has steadily increased along the mammalian line since very early mammals during the mesozoic. Also, the rapid advances in encephalization during the history of the early hominids we're talking about occurred long before the technology associated with hunting had arrived. Thus, the "mental demands" of obtaining meat are really the mental demands of scavenging--a strategy not unlike what mammals had already been employing for millions of years.

 

One would have to make a case that scavenging meat and scavenging vegetable matter are qualitatively dissimilar.

 

Indeed, what one group of savannah mammal have adapted to do after "millions of years" is not reflective of what others were required to learn and do over a few hundred or thousand of years. Evolution obviously selected for certain groups of primates with mental capabilities exceeding their sensory and physical limitations.

 

 

In both cases, other scavengers must be fought off or outsmarted (though they generally gather in higher density in the case of meat).

 

Given your obvious erudition, I am astounded by this comparison between plant and meat savaging.

 

 

Extremely simple tools are used in both--early hominids no doubt used stones to break open large bones and extract marrow, but this is probably not terribly new. Primates of all kinds employ sticks and rocks to get at ants and termites, nuts, roots, and honey. Animals far "down the tree" from primates have been seen to exhibit tool use behavior as well.

 

 

This is not about the development of tools but rather the changes in brain development likely compelled by dramatically altered survival conditions and demands.

 

Although, the biggest thing going on here is: could you share some of the anthropological literature which drew you to these conclusions?

 

My conclusion are rooted in what contemporary brain studies suggest about compelling factors in its growth and development. If you are sincerely interested in those, then we can explore a few.

Edited August 17, 2010 by DrmDoc

[PhDwannabe]

My conclusion are rooted in what contemporary brain studies suggest about compelling factors in its growth and development. If you are sincerely interested in those, then we can explore a few.

 

Throw 'em down, Doc! What're you waiting for?

[Ringer]

Hypotheses on why our brains developed the way they did range from interesting to nonsensical. The only ones I have ever heard that I could see as being truthful, at least in part, are:

1.) Social animals have a larger body:brain ratio, we as a species developed a very intricate social hierarchy that helped our brains develop. (the exception being the orangutan)

 

2.) Hunting animals usually tend to have " "

 

3.) The development of fire led us to start cooking and that helped shift our metabolism from breaking down food to using it to developing cortical processes.

 

 

Those, IMO, are the only ones that actually have a strong stance. The reason PhDwannabe attacks your stance is because they aren't strong stances. Anywhere you make a claim you have to be ready for attacks and should be prepared to defend your position.

 

Also, if you are going to make the same claims that PhD and I are going to be the only ones in the discussion you might as well stay with one thread since they pretty much discuss the same thing

Edited August 18, 2010 by Ringer

[ewmon]

IMO, rain forests require more senses for survival, and the Vietnam War (and other wars) proved it. Thick vegetation limits sunlight, causes sunlight to create moving visual patterns, and limits visual range. Survival depends upon increased visual, aural and olfactory perception and processing. Soldiers were unaware of enemies hiding in the vegetation who were close enough to reach out and touch them.

 

The US tried to develop people sniffers. Some were high-tech E63 Manpack Personnel Detector to detect their entry into possible ambush sites and to detect enemies in tunnels, and the airborne XM3 airborne personnel detectors which detected the odor of human sweat. Another device was a jar of bedbugs with a microphone inside, and the operator would listen through headphones to how the bugs reacted to air pumped through the jar. The jungle conditions of the Vietnam War also resulted the wide-spread use of infrared vision devices.

 

Soldiers are much, much happier in open country, away from the nerve-wracking close quarters of the forests (of any type). Sentries (both modern military and distant ancestral) posted in trees, on hills, etc can see for miles. If anything, our ancestors’ migration onto the open plains alleviated the need to obtain and process so much sensory information, and that this brain power, developed for the rain forests, could be used for other purposes.

Edited August 18, 2010 by ewmon

[Ringer]

But tropical areas like that aren't very hospitable to us as a species nor are they useful for social structures. Orangutans live in tropical areas and they are one of the very few non-social great apes with "higher" cognitive abilities. That hints at a social structure that broke down due to pressures arising in their environment.

[DrmDoc]

Forgive my lengthy absence from our little discussion:

 

 

Throw 'em down, Doc! What're you waiting for?

Contemporary brain studies suggest how enriched environmental experiences are compelling factors in brain growth and development (e.g., Uylings, H. B. M. "Development of the Human Cortex and the Concept of 'Critical' or 'Sensitive' Periods." Language Learning, Jun2006 Supplement, Vol. 56, p59-90, 32p, and Perry, B. D. "Childhood Experiences and the Expression of Genetic Potential: What Childhood Neglect Tells Us about Nature and Nurture." Brain and Mind, 2002, Vol. 3, p79-100.). In Uylings's article, for example, he describe how "Global neglect (i.e., minimal exposure to language, touch, and social interaction during the first 5 years of life) leads to a permanently smaller head circumference, smaller brain size…." However, Uylings goes on to say, "This does not mean that the brain cannot change further in adulthood; for example, environmental enrichment remains capable of challenging the brain, even in adulthood." Further studies in experience-dependent neural plasticity support Uylings's conclusions on how experience influence brain development (e.g., Kleim, Jeffrey A.; Jones, Theresa A.. "Principles of Experience-Dependent Neural Plasticity: Implications for Rehabilitation After Brain Damage." Journal of Speech, Language & Hearing Research, Feb2008, Vol. 51 Issue 1, pS225-S239, 15p, and Holtmaat, Anthony; Wilbrecht, Linda; Knott, Graham W.; Welker, Egbert; Svoboda, Karel. "Experience-dependent and cell-type-specific spine growth in the neocortex." Nature, 6/22/2006, Vol. 441 Issue 7096, p979-983, 5p.) Opposite of nutrition, my position is that experiences related to the more rigorous effort of sustaining a meat diet led to our animal ancestry's meteoric (IMO) brain growth and cognitive development above competing species. Clearly, given our ancestry's likely competitors, foraging among trees is not the same as savaging for meat. Maintaining a meat diet likely, as it does among contemporary animals, demanded a level of cunning, cooperation, and ingenuity exceeding that of more acclimated animals as our primate ancestry migrated from forest to savannah.