Evolutionary advantage of X?

Dave!

Hey folks,

Thought it might be an interesting and useful idea to have a thread to speculate on and suggest explanations for particular traits or characteristics or anatomy.

For example, one might suggest that eyebrows on humans keep sweat from the eyes, so when fleeing from a predator or enemy, your vision is not adversely affected by your perspiration.

One that has been troubling me lately is laughter. What's the advantage of it? It's absolutely ubiquitous and has been in all cultures I am aware of, so I'd find it hard to imagine it doesn't have a good Darwinian explanation.

Cheers.

Hivemind187

Dave! wrote: »

Hey folks,

Thought it might be an interesting and useful idea to have a thread to speculate on and suggest explanations for particular traits or characteristics or anatomy.

For example, one might suggest that eyebrows on humans keep sweat from the eyes, so when fleeing from a predator or enemy, your vision is not adversely affected by your perspiration.

One that has been troubling me lately is laughter. What's the advantage of it? It's absolutely ubiquitous and has been in all cultures I am aware of, so I'd find it hard to imagine it doesn't have a good Darwinian explanation.

Cheers.

Also present in other primates (and some animal nuts will say that certain other mammals exhibit the vestages of "humour").

Likely this is something to do with familial bonding or the odd sensation of being put at ease by a smile (dolphins for example are perceived to be friendly because of an accident of the shape of their skull)

Nothingcompares

If we consider laughter to be a very obvious expression of happiness we can consider those that laugh to have the greater ability to convince others they were happy. This would in turn suggest the individual is content with regard to the fundamentals (food, water, shelter, health) and therefore a desirable mate.

laughter could also be seen as friendliness so you're less likely to be killed by a stranger if don't appear threatening.

Zillah

Laughter is a strange one though. Yes, you can laugh as a social bonding thing. But people can also laugh for all sorts of other reasons. We can laugh when we suddenly realise something we hadn't realised before, when we see an animal bump into a tree, when someone makes a reference to an event from our past. I have absolutely laughed my ass off without another person anywhere near.

The list is virtually endless, and often bizarre. The Greek philosopher Chrysippus laughed himself to death while watching a drunk donkey trying to eat figs. Go figure.

Dave!

Zillah wrote: »

The Greek philosopher Chrysippus laughed himself to death while watching a drunk donkey trying to eat figs.

Well that would be pretty f*cking funny tbh!

anti-venom

I think laughter has something to do with recognising patterns. If your brain recognises a surprising pattern it will reward you with an enjoyable sensation (laughter). Pattern recognition is fundamental to human cogniton and the evolution of laughter has encouraged us, as a species, to sharpen our cognitive skills.

That's why we don't find repeatedly hearing the same old jokes funny anymore. The surprise has gone and so there is little or no need for a reward for recognising it.

Dades

Apparently it's the best medicine.

Zombrex

Research has shown that laughter, particularly in other primates, doesn't have a whole lot to do with humor.

There has been some research that suggests that we have evolved laughter (possibly 1 million years before speech) as a method of putting others around us at ease. It appears to be a method to ease possible aggression from others.

This would explain why people tend to laugh or smile uncontrollably in nervous or tense situations (demonstrated in a scene from Full Metal Jacket where the Drill Sargent beats on of the cadets for sniggering at his shouts) particularly when they feel threatened by others.

Dave!

Any links to that research Wicky?

I find anti-venom's explanation quite intriguing too.

robindch

Zillah wrote: »

The Greek philosopher Chrysippus laughed himself to death while watching a drunk donkey trying to eat figs. Go figure.

Wikipedia claims that it was Chrysippus who fed the donkey the wine that plastered him, so perhaps he's the first case of indirect suicide by laughter? Can't think of a better way to go.

Anyhow, the 1974 documentary Animals are Beautiful People is worth watching for the scenes of monkeys, elephants and giraffes wobbling around the veldt pissed, and a few shots of them recovering the next morning.

I only narrowly missed doing a Chrysippus myself.

Zombrex

Dave! wrote: »

Any links to that research Wicky?

http://men.webmd.com/features/why-we-laugh

Dave!

Cheers son!

Another one (stemming from the thread about breast feeding in AH :pac: ) -- would I be right in thinking that the sexual desire/lust for women's breasts is a "by-product" of the breast being our first source of nutrition? Makes sense to me. But if that's the case, why do women not have the same level of lust for other women's breasts?

Or do they? OMG HOT

fitz0

Wicknight wrote: »

Research has shown that laughter, particularly in other primates, doesn't have a whole lot to do with humor.

There has been some research that suggests that we have evolved laughter (possibly 1 million years before speech) as a method of putting others around us at ease. It appears to be a method to ease possible aggression from others.

This would explain why people tend to laugh or smile uncontrollably in nervous or tense situations (demonstrated in a scene from Full Metal Jacket where the Drill Sargent beats on of the cadets for sniggering at his shouts) particularly when they feel threatened by others.

Ive found that laughing in those sort of situations usually gets me a smack in the teeth.

Zombrex

Dave! wrote: »

Cheers son!

Another one (stemming from the thread about breast feeding in AH :pac: ) -- would I be right in thinking that the sexual desire/lust for women's breasts is a "by-product" of the breast being our first source of nutrition? Makes sense to me

My understand is that male lust for women's breasts evolved along with us as we started to stand up right. Women's breasts increased in size as they mimic the visual appearance of a woman's bottom, the two round "humps" (as Black Eyed Peas would say) and the crack in the middle. The bottom when we were primates would have been the main visual attraction but the roundness and shape changed as we moved from crawling around the African planes to standing and walking upright. The bottom still is a main source of visual attaction in other primates.

So basically a womans cleavage attracts men because it reminds them of a womans bottom, or what a womans bottom looks like when she is bending over :eek:

This would also explain the common male desire for ... ahem ... titty w**ks ... but I will need a letter from your parents before I explain that one to you children...

AtomicHorror

Dave! wrote: »

Cheers son!

Another one (stemming from the thread about breast feeding in AH :pac: ) -- would I be right in thinking that the sexual desire/lust for women's breasts is a "by-product" of the breast being our first source of nutrition? Makes sense to me. But if that's the case, why do women not have the same level of lust for other women's breasts?

Or do they? OMG HOT

They're a visual indicator of fertility. There's also a hypothesis out there that they encourage copulation from the front, which works better for humans than other positions in terms of conception. Plus they're like, hot.

Edit: Wick gets there ahead of me on the position bit.

Dave!

AtomicHorror wrote: »

Plus they're like, hot.

Is that a direct quote from the Origin of Species?

Cheers lads

robindch

AtomicHorror wrote: »

Plus they're like, hot.

If there are any researchers out there short a volunteer or two, please PM me -- I think I'd like to be involved with the pointy end of this.

All in the name of science, of course.

AtomicHorror

Dave! wrote: »

Is that a direct quote from the Origin of Species?

Yeah I'm pretty sure it's in there somewhere.

robindch wrote: »

If there are any researchers out there short a volunteer or two, please PM me -- I think I'd like to be involved with the pointy end of this.

All in the name of science, of course.

Oh for the days when science was a pervy old boys club. The ladies outnumber the gents in biology these days. Not that I'm complaining about that.

The Mad Hatter

Wicknight wrote: »

My understand is that male lust for women's breasts evolved along with us as we started to stand up right. Women's breasts increased in size as they mimic the visual appearance of a woman's bottom, the two round "humps" (as Black Eyed Peas would say) and the crack in the middle. The bottom when we were primates would have been the main visual attraction but the roundness and shape changed as we moved from crawling around the African planes to standing and walking upright. The bottom still is a main source of visual attaction in other primates.

So basically a womans cleavage attracts men because it reminds them of a womans bottom, or what a womans bottom looks like when she is bending over :eek:

This would also explain the common male desire for ... ahem ... titty w**ks ... but I will need a letter from your parents before I explain that one to you children...

Oh? I'd heard (I forget where) that that hypothesis had been discredited.

Flamed Diving

I always laugh when I'm nervous. Anytime I'm having a serious quarrel with a g/f I start bursting my arse laughing. You should see the mayhem it causes!

Zombrex

The Mad Hatter wrote: »

Oh? I'd heard (I forget where) that that hypothesis had been discredited.

what, men don't like titty w**ks? :eek:

anti-venom

Wicknight wrote: »

what, men don't like titty w**ks? :eek:

It's not always practical, is it? Given some women's shapes you would need a six inch WIDE langer to make it work!

Zombrex

anti-venom wrote: »

It's not always practical, is it? Given some women's shapes you would need a six inch WIDE langer to make it work!

Your point? :cool:

anti-venom

Wicknight wrote: »

Your point? :cool:

It's not too shrouded a reference to small breasts and short range weaponry.

Dave!

Wicknight wrote: »

Your point? :cool:

So the legends are true?!?! :eek:

Galvasean

The Mad Hatter wrote: »

Oh? I'd heard (I forget where) that that hypothesis had been discredited.

Indeed. I taught the reason men went for big breasts is because it signifies an ability to lactate well, thereby increasing the chances of offspring surviving. This is at a subconscious level enticing for men. Same goes for wide hips, they signify an ease of passage for child birth.

Galvasean

Apparently, its all about symmetry.

http://news.nationalgeographic.com/news/2008/08/080818-body-symmetry.html

robindch

Gaviscon wrote: »

I taught the reason men went for big breasts is because it signifies an ability to lactate well, thereby increasing the chances of offspring surviving.

As above, this view seems to be false, though commonly held. I recall reading somewhere a couple of years back that human babies survive at a rate which is independent of the mother's breast size, leading one to suspect that this size is a sexual selection variable and has no survival-related value.

The Hottentots of South Africa's (kind-of) notwithstanding, I don't believe that increased hip/bum width has been shown conclusively to increase survival rates either.

Has anybody come across any, er, hands-on research in this area?

Zillah

I usually seize upon the idea that breasts are awesome because a good bountiful rack is likely to be able to feed my soon-to-be-conceived infant.

Of course this hypothesis goes without support, flopping around as I post.

pH

Apologies if I've nothing to add about the evolutionary basis of titty ****, however I've a question about sexual selection.

Given you accept peacock tails were formed by sexual selection, can sexual selection not explain anything with the answer "Just because females liked it"?

A secondary question is can sexual selection just explain features that are specific to one of the sexes, or can it explain features/traits that both males and females have in common?

Scofflaw

robindch wrote: »

As above, this view seems to be false, though commonly held. I recall reading somewhere a couple of years back that human babies survive at a rate which is independent of the mother's breast size, leading one to suspect that this size is a sexual selection variable and has no survival-related value.

The Hottentots of South Africa's (kind-of) notwithstanding, I don't believe that increased hip/bum width has been shown conclusively to increase survival rates either.

Has anybody come across any, er, hands-on research in this area?

I think it's more the case that the waist/hip ratio and perky breasts* are all indicators of youth and no prior children - thus, likely to be fertile, healthy, and not already committed elsewhere.

*it's not really size, although under a certain size might lead one to assume the girl in question is too young.

cordially,
Scofflaw

nozzferrahhtoo

There is no evolutionary reason for laughter. Its purely a conspiracy of the american corporate machine to make money.

Walt Disney - "Laughter is America's most important export."

Sorry..... Ive been working on the theory that its possible to make, and argue for, a conspiracy theory about just about ANYTHING.

AtomicHorror

nozzferrahhtoo wrote: »

There is no evolutionary reason for laughter. Its purely a conspiracy of the american corporate machine to make money.

Walt Disney - "Laughter is America's most important export."

Sorry..... Ive been working on the theory that its possible to make, and argue for, a conspiracy theory about just about ANYTHING.

Motive seems to be the stumbling block for most. I post on a science forum where there's a user who is convinced that NASA is deceiving the public about the existence of other planets. I've little doubt they could make a good stab at it, but I can't for the life of me imagine why they'd bother.

Same goes for the "atheist conspiracy" currently peddling the lie that is Evolution :pac:

Zillah

AtomicHorror wrote: »

Same goes for the "atheist conspiracy" currently peddling the lie that is Evolution :pac:

We're in service to the devil, duh.

AtomicHorror

Zillah wrote: »

We're in service to the devil, duh.

Is that why I like heavy metal music and games of chance so much?

JC 2K3

The Female Orgasm.

Why?

Zillah

I hear that encouraging mammals to have sex is good for the continuation of their genetic code.

anti-venom

JC 2K3 wrote: »

The Female Orgasm.

Why?

At least you didn't ask, 'the female orgasm, How?';)

AtomicHorror

JC 2K3 wrote: »

The Female Orgasm.

Why?

Reward? Reward sensations are very commonly employed by our brains to encourage behaviour that is in line with survival and reproduction.

failsafe

anti-venom wrote: »

It's not always practical, is it? Given some women's shapes you would need a six inch WIDE langer to make it work!

And thus began the titty w*nk/penis girth evolutionary arms race.

pH wrote:

Given you accept peacock tails were formed by sexual selection, can sexual selection not explain anything with the answer "Just because females liked it"?

pH, that isn't my understanding of the sexual selection explanation. Something other than sexual selection usually kicks something like that off. IIRC it was Dawkins in the selfish gene that explained it something like this (as a possible scenario):
* Many male peacocks were fit enough to last to reproduction age
* If one or two had colourful marking it made them more susceptible to predators
* Therefore, a peacock with colourful markings/feathers who made it to reproductive age must have had kick ass genes to overcome such a big handicap
* Therefore females who were attracted to this handicap ensured that they were passing strong, 'cream of the crop' genes on to their offspring
* This was different to other attractions, as it wasn't something males could fake, i.e. they could grow bones that look like big muscles etc. but they couldn't "fake" being obvious to a predator
* After x amount of generations, females who are attracted to this have the "fittest" offspring, and gradually the "gene for" being attracted to bright feathers becomes widespread in the population. This has 2 further effects (which can spiral) which is what is often referred to as sexual selection:
1. Males without big feathers get laid less and less, and so the gene for feathers becomes more prevalent amongst men
2. Females who aren't attracted to bright colours/feathers produce sons without them, who in turn have a tough time impressing the vast majority of ladies, so they don't make daughters that are unattracted to feathers. So in the interest of having grandkids it does the females well to be attracted to bright feathers.
* This is then free to spiral once it reaches a critical mass because of 1 & 2 above, even though it may not confer an obvious "survival advantage".

Another analogy is to imagine a woman who looks at two men running a 100m sprint towards her (i.e. to reproductive age). If they both arrive at the finish at the same time (survive to reproductive age) but one has a big bag of coal on his back (colourful feathers) then she'd do well to pick him as the "fittest", as he can't really have fooled her about his speed.

This could be similar for breasts (I don't know) in the way that one poster earlier said. It was an advantage for men to be attracted to roundness in females (which led to being attracted to good baby makin' behinds) but once we stood upright females evolved nicer (:D) looking breasts before males lost the attraction to that shape. I'm sure, however, plenty of advantages, such as some mentioned above, must have been present for it to continue to confer advantage.

Incidentally, since we're on the topic (of naughty bits), I think it was Dawkins too who talked about the size difference in a man's erect and non-erect penis, and for the same reason. In an evolutionary sense, getting an erection can be a hard thing to do (pun fully intended). For example, some monkeys just have bones there to do the hard work (sorry, I'll stop now). Like a peacock's feathers, an erection proves something about a man's fitness, strong blood flow, lack of disease/heart problems etc. And, like the feathers, having a range of size demonstrates that "it's all natural" so that females can discern the real mccoy from the fakers. Again it's all men going out of their way to prove their fitness to females, as they get better and better at catching out tricks.

Goduznt Xzst

Evolutionary advantage of.... head hair

Why do we still have head hair when the majority of the rest of our body grows very small amounts of it. Is it a product of sexual selection? Or does it serve some evolutionary need?

The Mad Hatter

Goduznt Xzst wrote: »

Evolutionary advantage of.... head hair

Why do we still have head hair when the majority of the rest of our body grows very small amounts of it. Is it a product of sexual selection? Or does it serve some evolutionary need?

Keeps us warm? We started wearing clothes on the rest of our bodies, but hats much later.

I dunno, this is a complete guess.

Zillah

A huge amount of heat is lost through the head. I presume keeping hair there serves a purpose for heat maintenance.

Goduznt Xzst

Yeah but the hair on our heads also grows indefinitely? What is the purpose of this? natural matting of the hair to form dread locks to provide more insulation?

But humans have not required thick body hair for a long time, if the reasoning for it is for protection from the sun or protection from cold then why do tribes that live under tree cover in warm environs still have head hair?

Is it a case that the bald gene just isn't passed on and that mates will sexually select someone with head hair over someone who's bald? Maybe it is subconsciously viewed as a result of sickness or old age and therefore the mate would not be the best suited at being an effective mate?

Dave!

On the topic of hair -- humans have alot of hair around the genital area, as well as under the arms. From what I understand, sperm production is increased when the testicles are cooler, so pubic hair can't be for keeping the balls warm can it? Then what of armpit hair?

I was thinking that perhaps it reduces friction in the areas. The armpits and groin are probably the areas that have the most movement/friction. I'd be curious to see if the temperature of the groin is on average higher or lower in someone with alot of pubic hair.

As for the head... I'd be inclined to think that it's for heat retention in the brain. Dunno if the evidence supports that though.

anti-venom

Goduznt Xzst wrote: »

Is it a case that the bald gene just isn't passed on and that mates will sexually select someone with head hair over someone who's bald? Maybe it is subconsciously viewed as a result of sickness or old age and therefore the mate would not be the best suited at being an effective mate?

I read somewhere recently that the opposite may be true. Baldness in males may have evolved as a display signal of seniority, virility and dominance thus indicating his suitability as a partner.

failsafe

I don't think reward is a good enough explanation for this. If you look at the alternative, that having sex "feels real good", that would be substantial to reward females enough for reproduction, without needing a climax.

Also, I read that the numbers don't quite support the reward theory. Female orgasm rarely happens through sex alone, and so 'in the wild' where most sex is just a quickie with no foreplay, so the orgasm would not be frequent enough to be the reward for reproduction. If you think about it anecdotally, considering our evolutionary past, both our cultural history before the sexual revolution and the rise of feminism, and considering our animal past, I find it hard to believe all our male ancestors were all Romeos enough to make the female orgasm a regular factor in reproductive success!

The best theory I've heard of is the "happy bonus". It's generally understood that men have nipples, because when we're wee foetuses in the womb, nipples are formed before we differentiate into either a boy or a girl, and so men have nipples because women need them. In much the same way, that naughty bit of sensitive flesh between our legs develops in both girl and boy foetuses in the same way. It then either becomes an out-y in a boy or an in-y in a girl (running between the clitoris and the g-spot). In the same (but opposite) way as nipples, an orgasm is needed by men as ejaculation needs to be a timed event. A good feeling won't suffice for reproductive success; it will provide reward for reproduction, but a climax is needed for the timed, optimal release of sperm. Because of this, women get a climax as a "happy bonus". The female orgasm probably isn't strong/frequent enough to be "selected for", but it has enough positives not to be selected against.

anti-venom

You've been reading your Gould, right Failsafe?:)

failsafe

I've been listening to a podcast of someone explaining Gould! (I'm a slow reader! )

I think I heard that the name of the book was "the case of the female orgasm" is that Gould?

anti-venom

The Case of the Female Orgasm is by Elizabeth A Lloyd. Not that I knew it offhand; I had to google the title. Looks like it might be an interesting read though.

failsafe

Oh, I thought the podcast said that the "happy bonus" was from that book, but I know I heard the name Gould in there too!

The podcast is Evolution 101, if you're interested. It's very very good. Nice 10 min episodes on discussions like this thread. Search for it in itunes or check out his website at http://www.drzach.net/