Big brains evolved due to capacity for exercise

Aug 04, 2011

The relatively large size of the mammalian brain evolved due to a capacity for endurance exercise, researchers conclude in a recent study.

In the study published in the journal this month, anthropologists David A. Raichlen of the University of Arizona and Adam D. Gordon of the University at Albany conclude that the in mammals may have evolved in conjunction with increases in exercise capacity, rather than solely in response to natural selection for higher cognitive abilities.

Mammals have larger brains than non-mammalian animals of the same ; primates (apes, monkeys, humans, lemurs, and lorises) have larger brains than non-primate mammals of the same body size; and humans have larger brains than non-human primates of the same size. Anthropologists have long attempted to discern the reasons humans and other primates have relatively large brains compared to other animals species. The theories offered include the need for greater cognitive power to process visual information, and an increased capacity to manage complex social interactions in large groups.

Gordon said, "Brains are very energetically expensive to maintain, so most previous research has asked why certain species need big, expensive brains. We're asking a slightly different question: how do species grow and maintain expensive big brains in the first place?"

Earlier research in experimental settings had shown that endurance exercise boosts growth in some mammals. Controlling for associations with body size, the researchers examined the correlation between brain size and a metric known as the maximum metabolic rate (MMR), the measurement of the limit for aerobic exercise frequency and capacity. By collecting brain sizes and MMRs in mammals, they analyzed the relationship between body mass and the correlation of residual brain size to residual MMR. They found a significant correlation between maximum metabolic rate and brain size across a wide range of mammals.

"What we discovered," Gordon said, "is that across distantly related mammal species, those with relatively high capacities for endurance exercise have relatively large brains, while those with relatively low capacities for endurance exercise have relatively small brains. This suggests that the phenomenon observed in experimental lab settings may work on an evolutionary time scale as well."

The next step, the researchers say, is to test the brain-to-exercise relationship in primates, including humans, and determine the underlying mechanism for the brain's growth.

Explore further: How ferns adapted to one of Earth's newest and most extreme environments

More information: Relationship between Exercise Capacity and Brain Size in Mammals. PLoS ONE 6(6): e20601. doi:10.1371/journal.pone.0020601

Provided by University at Albany

5 /5 (4 votes)

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kevinrtrs
1.2 / 5 (20) Aug 04, 2011
The obvious questions that then arises is how are they going to show that capacity for endurance resulted in big brain size? Where did the capacity for endurance come from? Which is the cause and which is the effect? Did big brain size give rise to higher capacity for endurance because the bigger brain required the larger endurance?
Because no one was there to witness this assumed change, the result of the research will only be highly disputable since the researchers will not be able to make any kind of definitive statement.

A much better explanation for the correlation would be that the mammals were created with bigger brains and endurance in the first place. No evolution required.
Of course this more appropriate explanation has been ruled out a-priori by the philosophic decision to exclude a creator and so they are left to muddle about in a never-ending circle.
Squirrel
2.3 / 5 (3) Aug 04, 2011
The paper does not offer any adaptive link between endurance exercise and increased brain size only suggesting it might be mediated as a side effect of increased circulation of neurotrophic factors such as BDNF, IGF-1, and VEGF. It notes humans are an exception to this link: "When humans are included, the relationship between MMR and brain size residuals is no longer significant"
Ethelred
4.6 / 5 (10) Aug 04, 2011
A much better explanation for the correlation would be that the mammals were created with bigger brains and endurance in the first place.
If there was some evidence for Creation as opposed to the massive evidence for evolution that might be true. Since the evidence is that evolution is real, the Earth is old, and the Flood never occurred your idea is simply religion based on fantasy.

As usual.

Now do you have evidence that actually supports your beliefs? Especially your belief in the Great Flood despite the total lack of evidence for it.

Ethelred
Pkunk_
3 / 5 (5) Aug 04, 2011


A much better explanation for the correlation would be that the mammals were created with bigger brains and endurance in the first place. No evolution required.


In the end kevinrts comes right to the point - God created man.
Also , the scope is now widened to include all mammals. Note that the mouse , monkey , horse and ALL mammals were magically created in the same instant by the same benevolent god that that kevintrs so loves. Also note that kevinrts's god is better that the rest and you should worship only kevintrs's god , OR HE BE SMITE YOU.

Also according to kevintrs, there is no proof that man has evolved fro the apes , since they were created at the same time - "No evolution required."

While I believe god exists , he is probably more like the Greek gods , looking down upon us lower evolved beings .. Until one day we will evolve to the status of gods.
Mayor__Dooley
4.4 / 5 (7) Aug 04, 2011
Is god trolling not abuse? It is tediously pathetic and certainly intended to be insulting.

Creationism deserves no A or O.
PaulRC
2 / 5 (1) Aug 04, 2011
man and wolves are the two animals that evolved to hunt via endurance. this has been well established. so, why is this paper focusing on primates, when a animal model with nearly as exceptional endurance capability (wolves) is not a primate, and does not have as large a brain? this research seems busted by just this one data point.
Dug
1.2 / 5 (5) Aug 04, 2011
Clearly if endurance was pushing brain size and intelligence, bushmen and other groups that are still active hunters would be among the smartest of humans - and it would be reflected in their technical advances. Instead we have the stero-types of the intellectually slow athlete and nerdish couch potatoes. I suspect there are few variables unaccounted for in this very lose theory.
Isaacsname
3 / 5 (2) Aug 04, 2011
" What do we want !? "

" BraaaaaIiIiIiIiinssss "

" When do we want 'em !? "

" BraaaaaiiiiIiIiIiIinnnsss "

Glad I'm a conehead.
Djincss
1 / 5 (2) Aug 04, 2011
They try to make some link between the higher energy consumption of the brain and the capacity of the body to produce lots of energy, and yes these things all need lets say good blood supply, and more mytohondria to convert the energy, but really even if there is some correlation it does not answer the question about the bigger brain, the animals with the highest metabolic rate and capable of endurance are the small one, birds have the highest MMR, and they are not the one with the biggest brain , also the dogs that are more fast and capable of running a lot have small heads and brains comparatively, so there are so much exceptions that there is no rule at all about these things.
After all what I get from the article is that they say the big brain is affordable only for species that have the right metabolism for it, and bigger brain must indicate faster metabolism, but really it is not like that, brain produce the energy it need by itself, it only needs glucose.
Djincss
3 / 5 (2) Aug 04, 2011
But the connection here is that the animals with bigger brain needs more energy, so they are more active to search for it, and the brain pay off the energy it needs by more interaction with the environment, and the body is doing the interaction.
cyberCMDR
not rated yet Aug 04, 2011
I agree that they have only shown correlation and not causation. Given the energy required to support a big brain, a capability to provide that level of energy is needed. This level of reserves could also support strenuous physical activity.
Not sure if this relates to the apparent correlation between effective intelligence and the level of activity (or lack thereof) of many Americans these days. "Mens sana in corpore sano" (a sound mind in a healthy body).
gwrede
1.7 / 5 (3) Aug 05, 2011
Big brains evolved due to capacity for exercise
Well, then sleigh dogs and horses should be intellectual giants.
Doschx
5 / 5 (2) Aug 05, 2011
Big brains evolved due to capacity for exercise
Well, then sleigh dogs and horses should be intellectual giants.

Maybe they are, they HAVE somehow convinced our race to support and nurture most of their own. Except when food gets short and then we eat them, which may be some roundabout analog of the feudal class system...
macsglen
not rated yet Aug 07, 2011
Bushwah.
Humans are downright puny compared to most other vertebrates.
If there's any correlation between brain size and endurance exercise, it's that we with the bigger brains don't HAVE to do as much exercise!
Ethelred
3.7 / 5 (3) Aug 07, 2011
Humans are downright puny compared to most other vertebrates
Not on endurance for mammals. Very few mammals are even close. Wolves, horses sometimes, pronghorns and they are running from wolves and I bet horses had to do a lot that as well.

The key for human endurance is heat tolerance more than heart and lungs. That may be why the study found that humans didn't fit in well with the rest of the experiment.

There is a misconception, engendered by the usual idiot headline, that the study was about the CAUSE of larger brains.

Brains are very energetically expensive to maintain, so most previous research has asked why certain species need big, expensive brains. We're asking a slightly different question: how do species grow and maintain expensive big brains in the first place?
They are NOT claiming endurance is a cause of big brains. It ALLOWS big brains. In other words whatever drove the evolution of large brains may have had a secondary effect on endurance.

Ethelred
aroc91
not rated yet Aug 07, 2011
man and wolves are the two animals that evolved to hunt via endurance. this has been well established. so, why is this paper focusing on primates, when a animal model with nearly as exceptional endurance capability (wolves) is not a primate, and does not have as large a brain? this research seems busted by just this one data point.


It mentioned that the same phenomena applies to all mammals. Read the second paragraph again, first sentence.
Ethelred
3 / 5 (2) Aug 08, 2011
This is mostly to explain the first half of my previous post.

From the paper not the article:
Because human brain size relative to body size is greater than six standard deviations higher than the other mammals included in this study (see below), we performed an analysis first on nonhuman mammals, and then performed a second analysis including humans.


When humans are included, the relationship between MMR and brain size residuals is no longer significant in analyses of both raw data and PIC (rraw = 0.29, praw = 0.13; rPIC = 0.21, pPIC = 0.29), due primarily to the strong leverage of the human brain mass residual in the analysis of the raw data, and of the residual brain mass contrast between humans and Rodentia in the PIC analysis.


More
Ethelred
3 / 5 (2) Aug 08, 2011
Using equations for the full raw (non-phylogenetically controlled) data sample to calculate residuals of the humans from the mammalian regression lines, human MMR is slightly larger than that expected for their body size (residual is 0.03 standard deviations greater than expected), while human brain size is considerably larger than expected (residual is 6.36 standard deviations greater than expected).


And finally this bit from the conclusion:
Despite the human exception, it is clear that across nonhuman mammals, increased exercise capacity is associated with increased brain size.
I am suggesting the human heat tolerance may be a significant factor as that is a major key in our endurance. Also large brains produce a lot of heat and humans have some rather unique adaptations to cool and fuel the brain.

Ethelred