
Challenging Mainstream Thought About Beauty’s Big Hand in Evolution - Thevet
https://www.nytimes.com/2017/05/29/science/evolution-of-beauty-richard-prum-darwin-sexual-selection.html
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11thEarlOfMar
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.

~~~
trhway
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.sciencedaily.com/releases/2008/06/080602121302.htm)

or

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3187837/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3187837/)

or [http://elitetrack.com/blogs-details-2765/](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. "

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onychomys
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.

~~~
EGreg
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.

~~~
trhway
>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.

~~~
EGreg
You can speculate this, but explain why only humans and domesticated sheep
have been observed to practice homosexual behavior with no heterosexual
coupling.

[http://www.bbc.com/earth/story/20150206-are-there-any-
homose...](http://www.bbc.com/earth/story/20150206-are-there-any-homosexual-
animals)

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olliej
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

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

