# Some questions on evolution.
**URL:** https://boards.straightdope.com/t/some-questions-on-evolution/685403
**Category:** Factual Questions
**Created:** [April 5, 2014, 12:00pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403 "2014-04-05T12:00:57Z")
**Posts on this page:** 10
**Page:** 4
### Author:  [@Colibri](https://boards.straightdope.com/u/Colibri)
#### Post date: [April 8, 2014, 2:45pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403/61 "2014-04-08T14:45:42Z")
> [@Chronos](#):
>
> It’s possible that the development of our intelligence past a dog-like or chimp-like level was due to runaway sexual selection. In early hominids, being a little smarter than average might have directly resulted in survival advantage, so they might have favored potential mates who were a little smarter. But then, once that tendency becomes established, you start seeing individuals who favor smarter mates just because smarter mates are favored by other individuals. It’s a positive feedback loop. As it happens, it kept up until it got to the point where greater intelligence is again a direct advantage, but it could also, given slightly different circumstances or worse luck, gotten to a point where we were too overspecialized for intelligence, and died off due to a deficiency in other areas, before our intelligence got to the point where we could make up for those other deficiencies.
My own pet theory is that our intelligence is due to runaway selection, but not sexual selection per se. Human level intelligence is not necessary for survival, but it is necessary in order to compete with other humans. We evolved our intelligence through competition within bands, or between small bands, for access to resources and to mates. Those individuals who were better able to assess the motivations of other members of the group had an advantage over them. And such a “theory of mind” needs a rather complex mind to carry out.
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### Author:  [@Colibri](https://boards.straightdope.com/u/Colibri)
#### Post date: [April 8, 2014, 2:51pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403/62 "2014-04-08T14:51:11Z")
> [@you\_with\_the\_face](#):
>
> Without our powerful brains, we’d be pretty defenseless relative to other species. We’re not particularly strong or fast. We’re thin-skinned with small canine teeth and clawless fingers. We don’t even have fur to protect us from bugs.
>
> Intelligence is what gave our species a fighting chance for survival.
There are plenty of other species that are relatively defenseless that do just fine without intelligence. Why should we lose our defenses, and _then_ evolve intelligence to compensate for their loss? More likely we evolved intelligence first, and that allowed us to lose some of our defenses.
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### Author:  [@you\_with\_the\_face](https://boards.straightdope.com/u/you_with_the_face)
#### Post date: [April 8, 2014, 3:03pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403/63 "2014-04-08T15:03:12Z")
> [@Colibri](#):
>
> There are plenty of other species that are relatively defenseless that do just fine without intelligence. Why should we lose our defenses, and _then_ evolve intelligence to compensate for their loss? More likely we evolved intelligence first, and that allowed us to lose some of our defenses.
What is the environment like where such species are found? Perhaps they can afford to be defenseless (like early man was in my just-so-story) because their niche is stable and few threats abound.
What evolutionary pressure would “allow” us to lose some of our physical defenses without that loss hurting our competitiveness? For instance, strength? To be smart and strong seems like a winning combination to me; surely those with both traits would outcompete those with just one.
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### Author:  [@md2000](https://boards.straightdope.com/u/md2000)
#### Post date: [April 8, 2014, 3:03pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403/64 "2014-04-08T15:03:23Z")
My pet theory is based on the data that humans went through some sort of bottleneck about 70,000 years ago, where the source population for moder man was down to a few thousand individuals. I suspect some mutation or ecological bottleneck (or both) gave an advantage to higher intelligence - then those with the higher function brain advange spread and replaced all the less able versions of humanoids across the world.
yes, at a certain point brainpower is best used to outwit (or match) the tribe across the valley in competition for resources, so humans competed with themselves and produced better brains.
One theory is that language replaced flea-picking as the means of “grooming” and establishing heirachy among humans. In apes and chimps, the lesser picks fleas off the higher-ups as a sign of submission. The number of interactions that are possible in a day limits the size of a peaceful pack. With speech (specifically, gossip) one person could interact with multiple others, and the size of a pack with an established heirarchy could be significantly lager (say, a hundred instead of a dozen). Of course, the chief topic of gossip is who’s sleeping with whom (or more specifically, who’s _she_ sleeping with?) This topic helped a male to ensure he was not being cuckolded, an essential element of passing on his genes.
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### Author:  [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)
#### Post date: [April 8, 2014, 3:08pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403/65 "2014-04-08T15:08:57Z")
> [@Learjeff](#):
>
> In addition, the smartest creatures tend to be mammals, which have a rather different brain organization than birds and reptiles, with a wrinkled cerebral cortex. It seems to be that among mammals, intelligence is boosted by increasing the area (rather than the volume) of this cortex (leading to the wrinkles). Possibly, the accident that allowed this development did not happen in the dinosaur line, purely from chance.
>
> (Meanwhile, there are birds with much more intelligence than we’d guess, based on this oversimplistic “intelligence is proportional to area” hypothesis. For many years, scientists assume birds couldn’t be smart for this reason, and they turned out to be wrong for certain birds like parrots.)
As I understand it, mammals like us perform the brain functions associated with intelligence on the surface of the brain; which is why as a rule the bigger surface area a mammal brain has, the smarter the mammal is. Birds on the other hand perform those same functions using clusters of neurons scattered throughout the mass of the brain, which both means that surface area doesn’t have anything to do with their intelligence, and appears to get greater intelligence from a given amount of brain mass.
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### Author:  [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)
#### Post date: [April 8, 2014, 3:11pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403/66 "2014-04-08T15:11:43Z")
> [@you\_with\_the\_face](#):
>
> To be smart and strong seems like a winning combination to me; surely those with both traits would outcompete those with just one.
Big brains and big muscles are both very energy hungry. A really smart, really strong creature would starve before a creature that is _just_ strong or _just_ smart would.
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### Author:  [@you\_with\_the\_face](https://boards.straightdope.com/u/you_with_the_face)
#### Post date: [April 8, 2014, 3:22pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403/67 "2014-04-08T15:22:40Z")
> [@Der\_Trihs](#):
>
> Big brains and big muscles are both very energy hungry. A really smart, really strong creature would starve before a creature that is _just_ strong or _just_ smart would.
You don’t need big muscles to be strong, though. Chimpazees are naturally much stronger than we are, for example, but it’s not because they have more or bigger muscle fibers.
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### Author:  [@Colibri](https://boards.straightdope.com/u/Colibri)
#### Post date: [April 8, 2014, 3:26pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403/68 "2014-04-08T15:26:10Z")
> [@you\_with\_the\_face](#):
>
> What is the environment like where such species are found? Perhaps they can afford to be defenseless (like early man was in my just-so-story) because their niche is stable and few threats abound.
Tapirs for example aren’t particularly fast, and have no real weapons. They inhabit tropical forests today, but in the past also lived in temperate forests.
Early man certainly didn’t live in a stable niche with few threats.
> [@](#):
>
> What evolutionary pressure would “allow” us to lose some of our physical defenses without that loss hurting our competitiveness? For instance, strength? To be smart and strong seems like a winning combination to me; surely those with both traits would outcompete those with just one.
Actually, we are not only big-brained compared to our immediate ancestors, we are also much larger and stronger. But with regard to those ancestors, there’s a general evolutionary principle that you can’t optimize everything at the same time. Brain tissue is extremely energy demanding. Increasing brain size might mean less energy was available to put into muscle mass. (However, later on increased intelligence would have improved our ability to obtain high-energy meat that could allow both further increase in both brain and body size.
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### Author:  [@Colibri](https://boards.straightdope.com/u/Colibri)
#### Post date: [April 8, 2014, 3:28pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403/69 "2014-04-08T15:28:54Z")
> [@you\_with\_the\_face](#):
>
> You don’t need big muscles to be strong, though. Chimpazees are naturally much stronger than we are, for example, but it’s not because they have more or bigger muscle fibers.
Chimps have greater arm strength than we do because of differing muscle insertions on the bones. Our muscle arrangement allows us to throw accurately, something that chimps can’t do. And that ability contributes to our ability to defend ourselves.
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### Author:  [@md2000](https://boards.straightdope.com/u/md2000)
#### Post date: [April 8, 2014, 4:35pm UTC](https://boards.straightdope.com/t/some-questions-on-evolution/685403/70 "2014-04-08T16:35:20Z")
> [@Der\_Trihs](#):
>
> Big brains and big muscles are both very energy hungry. A really smart, really strong creature would starve before a creature that is _just_ strong or _just_ smart would.
This is the thing about evolution. There are good tmes and bad times. Characteristics that are an advantage in good times can be a disadvantage in bad times.
If there’s little food to be had, a smart person might hide food from a srong person. Smart and strong, however, will starve faster. Depending on the circumstance of the food shortage, the winner will either be smart, or strong, or a bit (but not a lot) of both.
this is the same with big (or strong) vs small. If small is smart, they will quickly realize that sharing with a bigger, greedier individual puts them at a disadvantage. The brains for collaboration may be a better advantage than size.
So eventualy evolution produces the optimum combination of characteristics for all circumstances.
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