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Author Topic:   "Slanted" Eyes in Orientals
prophageus
Inactive Member


Message 1 of 97 (89367)
02-29-2004 3:43 AM


I have been searching Google and have found nothing, but I accidentally found this forum, so maybe someone knows.

Why do orientals have 'slanted' eyes?

What evolutionary purpose do they have?

Any extended info on this would be appreciated, I cannot find jack on Google. Thanks.


Replies to this message:
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Dr Jack
Member (Idle past 184 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 2 of 97 (89379)
02-29-2004 7:28 AM
Reply to: Message 1 by prophageus
02-29-2004 3:43 AM


Why do Caucasions not have 'slanted' eyes?

As far as I know there is no advantage to either eye structure, so it may just be historical accident.


This message is a reply to:
 Message 1 by prophageus, posted 02-29-2004 3:43 AM prophageus has responded

Replies to this message:
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prophageus
Inactive Member


Message 3 of 97 (89425)
02-29-2004 3:25 PM
Reply to: Message 2 by Dr Jack
02-29-2004 7:28 AM


Good point. Maybe. Although, it makes MORE sense evolutionwise to have wider eyes, because vision is one of our most important survival tools. Unless you live in a sandy area with sandstorms all the time. But.. as far as I know Asians did not start out in sandy areas and then spread. But, what do I know?
This message is a reply to:
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Coragyps
Member
Posts: 5377
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 4 of 97 (89430)
02-29-2004 4:13 PM
Reply to: Message 1 by prophageus
02-29-2004 3:43 AM


Hi, new person!

I agree, in the absence of any real data, with Mr Jack: it's likely just a variant with no Deep Evolutionary Significance (TM). You might try "epicanthal fold" in Google, if you're really interested - that's the real name of the eyelid structure that gives rise to "slanted eyes." I didn't see much in the first page or two there apart from definitions and ads from cosmetic surgeons, though.


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Phobos
Inactive Member


Message 5 of 97 (99466)
04-12-2004 4:17 PM
Reply to: Message 2 by Dr Jack
02-29-2004 7:28 AM


quote:

As far as I know there is no advantage to either eye structure, so it may just be historical accident.

e.g., sexual selection


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reddish
Inactive Member


Message 6 of 97 (100696)
04-18-2004 5:42 AM


Slanted eyes = sexy
Sex = reproduction

Natural selection works in weird ways. The slanted eyes are there for the same reason that men in general have relatively long and smooth members.


Replies to this message:
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RAZD
Member
Posts: 19759
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 6.4


Message 7 of 97 (100756)
04-18-2004 5:16 PM
Reply to: Message 6 by reddish
04-18-2004 5:42 AM


just don't confuse sexual selection with survival of the fittest

the scissortail flycatcher has a tail that makes it dangerous for survival and tests have shown that females will select for males with longer tails if they are available. sexual selection at odds with survival.

sexual selection could be the cause of the rapid growth of human brain capacity.


we are limited in our ability to understand
by our ability to understand

RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}


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Lammy
Member
Posts: 3607
From: Chicago
Joined: 03-29-2004
Member Rating: 2.0


Message 8 of 97 (100760)
04-18-2004 5:54 PM
Reply to: Message 1 by prophageus
02-29-2004 3:43 AM


Just so you know, traditionally, men with more slanted eyes than others are considered more powerful looking. Traditional art always portrayed Generals, Kings, and government officials to have really slanted eyes.

So, I guess it has something to do with cultural and sexual selection as well.

By the way, I'm east asian, if you haven't noticed from my avatar.

[This message has been edited by Lam, 04-19-2004]


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JustinC
Member (Idle past 2923 days)
Posts: 624
From: Pittsburgh, PA, USA
Joined: 07-21-2003


Message 9 of 97 (100789)
04-18-2004 10:49 PM


Natural and Sexual Selection
Is this dichotomy warrented? A lot of people think so (e.g. every author of every biology text book I've read), but I would say no. Most people would point out that the difference between natural selection and sexual selection is that in sexual selection, the fittest don't necessarily have reproductive success. But how do you define fitness apart from reproductive success? You can't.

That is why I like to speak of natural selection without using references like good, better, best ( or fit, fitter, fittest). I prefer the definition of: differential reproductive success of organisms due to inheritable traits. If this definition is used, I see no difference between sexual and natural selection.

Where am I wrong?

ps. I'm writing this during an Ecology cram session so my mind might not be working right.


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JustinC
Member (Idle past 2923 days)
Posts: 624
From: Pittsburgh, PA, USA
Joined: 07-21-2003


Message 10 of 97 (100790)
04-18-2004 10:49 PM


Natural and Sexual Selection
double

[This message has been edited by JustinCy, 04-18-2004]


    
Chiroptera
Member (Idle past 15 days)
Posts: 6531
From: Oklahoma
Joined: 09-28-2003


Message 11 of 97 (100798)
04-18-2004 11:40 PM
Reply to: Message 9 by JustinC
04-18-2004 10:49 PM


Re: Natural and Sexual Selection
Sexual selection is natural selection, true. But sexual selection can be given an unambiguous definition, namely when the selective force is the choice exerted by potential mates. If peahens chose peacocks with flashy tails over those with drab tails, then big, flashy tails is a result of sexual selection. But you are correct - it is still natural selection in that the reason males' tails are big and flashy is because males with flashy tails are more likely to produce offspring than males with drab tails.

Edited to add:

The difference is that in sexual selection the driving selective force is explicitly specified.

[This message has been edited by Chiroptera, 04-18-2004]


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RAZD
Member
Posts: 19759
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 6.4


Message 12 of 97 (100814)
04-19-2004 1:19 AM
Reply to: Message 11 by Chiroptera
04-18-2004 11:40 PM


Re: Natural and Sexual Selection
Problem here is Natural Selection is the bigger umbrella, and can be seen to include both survival selection and sexual selection, even though those two selection pressures can operate in opposing manners. A specimen that survives to advanced old age has strong surival selection advantage, but if the genes don't get passed on it doesn't matter. Likewise a sexual preference that ends up causing lower surival rates is not long for survival either.


we are limited in our ability to understand
by our ability to understand

RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}


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Replies to this message:
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Parsimonious_Razor
Inactive Member


Message 13 of 97 (100829)
04-19-2004 2:07 AM
Reply to: Message 12 by RAZD
04-19-2004 1:19 AM


Re: Natural and Sexual Selection
quote:
Likewise a sexual preference that ends up causing lower surival rates is not long for survival either.

I disagree with this. I think a lot of sexual selection decreases surivial, hell most of it might. It would only matter if the decrease in survival had a direct and significant effect on the ability to producve offspring. You also have the "sexy son" hypothesis going on which makes it very difficult to alter female preference once it is in full spring, add that to a red queen race I think you could concive of sexual selection that could destroy a species.

[This message has been edited by Parsimonious_Razor, 04-19-2004]


This message is a reply to:
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RAZD
Member
Posts: 19759
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 6.4


Message 14 of 97 (100896)
04-19-2004 9:58 AM
Reply to: Message 13 by Parsimonious_Razor
04-19-2004 2:07 AM


Re: Natural and Sexual Selection
The bias for sexual selection being disadvantageous could be the result of point of view: anything that we cannot explain any other way (ie no perceived benefit) is due to sexual selection. The long tails of the scissorbird that make it harder to fly, land, perch, and particularly slower on takeoff must be sexual selection views.

That sexual selection can cause a runaway mutation (Fisher, sexy son) and that it will test mate fitness due to high costs (can't fake, only the best look the best) is fairly obvious.

But how do you gauge selection for slanted eyes? Most of sexual selection might be unnoticed because it seems mundane most of the time. (Young) men tend to focus on aspects under their control for sexual selection (fitness, hardbody) while being in denial about other skills (verbal communication?) that may be more beneficial. And obviously if sexual selection was not a powerful part of human sexuality, hairstyle and make-up would be dead industries.

enjoy.


we are limited in our ability to understand
by our ability to understand

RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}


This message is a reply to:
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Replies to this message:
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Parsimonious_Razor
Inactive Member


Message 15 of 97 (100932)
04-19-2004 1:23 PM
Reply to: Message 14 by RAZD
04-19-2004 9:58 AM


Re: Natural and Sexual Selection
I am not arguing the power of sexual selection I have spent the last two semesters studying nothing but sexually selected traits. I don't think you can say that people just lump any trait we don't have a survival benefit for into sexual selection. There are some pretty standard ways to look for SS in action. Opposite sex preference for the trait, increased mating success for exaggerating the trait, decreased success for eliminating or decreasing the trait, ect.

Honest signaling by its very nature decreases the over all health of the organism. Itís costly and forces you to turn energy away from usually immune development and is a not a very efficient use of calories.

I doubt that slanted eyes falls under any framework for honest signaling. Though I haven't specifically studied it I can't see how they are a large and costly signal. I think you could almost just classify it as an arbitrary variation. All the classic facial signals that have been identified in research as honest signals (facial symmetry, estronization/testosteronization) are present in every group of people. There hasn't been a sudden selection pressure for say directional asymmetry for the eyes in some group. But there is an almost infinite variety in which faces can be organized and still adhere to the basic signaling of Homo Sap. Most people find traits that belong to individuals they are around a lot more attractive than traits of individuals they do not see often. But whatís interesting about this is that after living with another group for a period of time you will get the attractiveness switch so that you are finding the new traits more and more attractive (though most people still rank the traits of where they were born and raised as always slightly more attractive). In short I don't think its sexually selected, I think its just an arbitrary variation or perhaps a byproduct of some other adaptation working on a different level.


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