Challenging Mainstream Thought About Beauty’s Big Hand in Evolution

https://www.nytimes.com/2017/05/29/science/evolution-of-beauty-richard-prum-darwin-sexual-selection.html

by Thevet • 9 years ago

19 13 9 years ago

I think about this when I see wild turkeys in the area during early spring. The males fan their tail feathers and display their bright colors.

From a mate selection standpoint, the healthy ones have a full set of feathers that are brightly colored. Older and less healthy ones are missing feathers, or the colors are dull.

I think what we see in nature is a situation where what began as a selectable trait sometimes carries on evolving, i.e., becoming ever more colorful or pronounced, simply because it was easier to notice and measure, and at the same time, did not become a negative to survivability. If the female is attracted to the intense colors of males, and two perfectly healthy males are standing next to each other, but one is a little more saturated in color, she may select him solely for that reason.

trhway2• 9 years ago

There is a range of studies on various birds showing correlation between higher intensity/contrast of male feather colors and higher testosterone levels. For example:

https://www.sciencedaily.com/releases/2008/06/080602121302.h...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3187837/

or http://elitetrack.com/blogs-details-2765/

"Researchers may have discovered how the bright plumage of male birds evolved as a sign of health and vigor to potential mates. Testosterone, which weakens the immune system, increases the circulation of immunity-enhancing pigments called carotenoids, they find. Healthy birds let the pigment collect in the skin to flaunt their vitality.

[/] The bright coloration of some birds is a classic example of an animal advertising its high quality to potential mates. Carotenoids are the pigment in red, orange and yellow skin (and carrots), but they are also powerful antioxidants that boost the immune system. Only healthy male birds can afford to maintain a costly display of color by diverting resources away from the immune system, the theory goes. The male must therefore have good genes, and that's why a flashy male attracts mates.

In the mating game testosterone plays a similar role to carotenoids. The hormone makes male birds strut and croon but weakens their immune systems, and researchers knew that variations in testosterone levels between birds and seasons tend to match up with variations in the brightness of colors. "

onychomys• 9 years ago

I like how in one paragraph, Prum is espousing an adaptive basis for homosexuality and in the very next one talks about how maybe not everything is selected on. Maybe he has good reasons for thinking that homosexuality is adaptive that have been covered up with the author's "For a full account, you need to read the book", but given how bogus the overwhelmingly vast majority of evopsych is, I'd kind of doubt it.

EGreg4• 9 years ago

In fact, true homosexuality (no heterosexual coupling) would lead to lower fitness. Only humans and domesticated sheep have it. Probably because of relaxed evolutionary pressures on both, where fitness began to be less relevant.

Analemma_• 9 years ago

You are assuming quite a lot of facts not in evidence here.

trhway2• 9 years ago

Probably because of relaxed evolutionary pressures on both, where fitness began to be less relevant.

probably you don't understand evolution and natural selection.

true homosexuality (no heterosexual coupling) would lead to lower fitness.

i can speculate the opposite - given that homosexuality seems to be highly correlated (i'm stereotyping here, yet lets suppose that it is statistically true for the sake of argument) with creativity and noncomformal thinking and behavior, we can see how in the today's society where those traits are more and more fetching a premium it may result in higher fitness.

FullMtlAlcoholc• 9 years ago

Selection via environmental fitness is one of the least significant evolutionary pressures.

EGreg4• 9 years ago

Enough just-so stories! I have been mostly saying this part for the last several years:

But one particular aspect of his argument is his distress at the idea that almost all evolutionary change is assumed to be adaptive, contributing to fitness. In other words, if a fish is blue, it must be blue for a reason. The color must help it escape predators or sneak up on prey, or be otherwise useful in some way. Beauty, therefore, must be adaptive, or a sign of underlying qualities that are adaptive. Pick a behavior or an ornament or a physical trait, and it is useful until proven otherwise.

That’s backward, says Dr. Prum. Take beauty. Since animals have aesthetic preferences and make choices, beauty will inevitably appear. “Beauty happens,” as he puts it, and it should be taken as nonadaptive until proven otherwise.

rarec• 9 years ago

Optimising for sexual selection is an adaptive trait as far as fitness goes. Why is beauty then non-adaptive?

grinnbearit• 9 years ago

Aesthetic preferences exist for a reason, they've also been selected for and would often correlate with health indicators.

In the end reproductive success is all that's selected for, even at the expense of the host for the gene, like in the case of the peacock where their long tail makes them easy prey but also makes them easier to identify for a peahen.

olliej• 9 years ago

One thing my wife learned and told me (she’s a biologist so actual science vs my CS background :) ) was actually fairly interesting and is apparently widely considered true among evolutionary biologists:

If you are male of you are likely to carry genes from your father that produce a similar appearance to him. You will /also/ carry genes from your mother that prefer your appearance (your mother choose your father based on appearance). If you are female offspring you will inherit those same genes but won’t express the male appearance ones. You will still pass them on to your offspring.

So you end up with a cycle where offspring look like/prefer the appearance of their parents, and will forward variants of those genes on to their own offspring.

This is effectively a feedback loop that will carry on until limited by some other factor - eg if your tail is too long you may end up dying too quickly to mate, if it gets too small you may not be able to fly at all (some of the old pigeon breeds studied by Darwin are hilarious).

This means that the selection for beauty does not necessarily mean that there’s an awareness of fitness being proxied by beauty.

Once she had labouriously explained it to me it seemed really obvious.

* note I used male/female etc for ease of typing - there are a few species where the role of being attractive is reversed

Challenging Mainstream Thought About Beauty’s Big Hand in Evolution

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