Natural Selection or not?
January 10, 2019 6:12 AM   Subscribe

Nature loves beauty too Darwin believed that animals enjoy creating and appreciate beauty for beauty’s sakes. Now, scientists are revisiting the idea that beauty evolves not for survival, but for the eyes of all beholders.
posted by Yellow (30 comments total) 16 users marked this as a favorite
This is difficult to read. Prum sounds like he should know better. The author clearly doesn't. There are multiple, often non-mutually exclusive explanations for how 'ornamental' adaptations come to be favored. Cummings isn't making any arguments for beauty as a thing outside of evolution, just reaction to stimulus. The birds in the opening spiel can be easily explained by fisherarian runaway, memetic cultivation, and/or Dennet's supernormal stimulus. These aren't new or hard-to-understand ideas. Unless you're not interested in understanding them cause, like, wow...nature, man. Beauty. How does it work? Tide goes out, magnets come back in.
posted by es_de_bah at 6:37 AM on January 10 [8 favorites]

AHAHAHA IT IS MY THESIS. (Molly Cummings and Mike Ryan are actually both on my thesis committee.) My entire thesis is working out whether condition dependence--a common phenomenon used to argue that sexually selected traits have evolved in order to signal male quality--might actually make more sense as a byproduct of makes working out where to invest their energy as a function of their overall context.

I'm very excited by this piece.
posted by sciatrix at 6:42 AM on January 10 [15 favorites]

Er, to clarify, I'm excited by the public lens on work that is real close to mine. I actually agree that the article itself can be a little confusing, but to clarify: the research is probably suffering from the author blowing up claims; the "newness" of the work being emphasized here boils down to "how can we understand sexual selection as a process in its own right divorced from natural selection?"

The interesting thing as far as I go, and I would argue as far as Mike and Molly go, is the critique of the primacy of "good genes" or indicator trait models of sexual selection within both popular discussions and the literature. The alternative explanations you mention are both things that at least the UT Austin researchers I know are very well aware of and know aren't new; the interesting thing is the point that even a trait that might bear a cost might still yet be evolving for "neutral" (as opposed to natural-selection/survival-mediated) reasons.
posted by sciatrix at 6:51 AM on January 10 [8 favorites]

Agreed, sciatrix. And I'm sorry if I came off as crappy on the first post of the thread. Early morning grumpiness. But I hate the way people write about evolution sometimes. I understand the draw of focusing on beauty, but I feel like it glosses over the reality. God don't make no evolution makes junk. It's ok to like the junk. You like it because of evolution, and junk. Animals do to, because you're an animal.
posted by es_de_bah at 7:03 AM on January 10 [3 favorites]

What the hell are we paying these so called scientists for??
Of course beauty is involved in survival.
Given the choice of partner between an ugly one or a good looking one (all else being equal) every person I have ever known will choose the good looking one every time. It doesn't require years of expensive study to come to that conclusion.
Sexual attraction is part of natural selection, not a separate subject.
posted by Burn_IT at 7:15 AM on January 10

I mean, I totally agree! I get frustrated actually for a similar but different reason: it's like everyone insists that the beauty's gotta exist for a reason, that the most beautiful must survive better or be advertising that they're the best at fighting something off or fighting each other or or or.

And. Nah, man. Animals think stuff is eye-catching, too. That's the whole point of that supra-normal stimulus work in particular, or the stimulus tuning work on signals following perceptive sweet spots in signal receivers. I think that's the thesis of Mike's work right at the base of it: that sometimes, beauty is neutral or detrimental with respect to natural selection, and yet it survives anyway.
posted by sciatrix at 7:20 AM on January 10 [5 favorites]

Also, Burn_IT, if you want to debate me for my paycheck, you can feel free. Pistols references to the literature, dawn, guns arguments drawn. Double or nothing, to be adjudicated by our peers. I'll let judgement go to the Blue.

Double or nothing.
posted by sciatrix at 7:23 AM on January 10 [11 favorites]

Beauty exists as an essential aspect of the life-form's self-representation. Self-representation is how the life-form interprets the world that surrounds it and the life-force within it.
posted by No Robots at 8:06 AM on January 10

*munches popcorn*
posted by sixswitch at 8:35 AM on January 10 [2 favorites]

A duel? I put 10 Quatloos on Sciatrix.
posted by happyroach at 8:47 AM on January 10 [8 favorites]

Good luck with your thesis, Sciatrix!
I have questions, but I have to think about them a bit.
posted by mumimor at 8:59 AM on January 10 [2 favorites]

christopher alexander's work on beauty and wholeness in "the nature of order" would inform this debate
posted by paradise at 9:18 AM on January 10

What the hell are we paying these so called scientists for?? Of course beauty is involved in survival.

There are at least two possibilities here:

1. You, an armchair observer who (I assume) has no background in evolutionary biology, nor any prior familiarity with this specific area of research, have outsmarted professional specialists in the field.


2. You've misunderstood the ideas being discussed.
posted by escape from the potato planet at 10:31 AM on January 10 [8 favorites]

Now, scientists are revisiting the idea that beauty evolves not for survival, but for the eyes of all beholders.
I could quote not so natural selection in dog breeding where owners selectively breed for what they consider to be beauty.
posted by Burn_IT at 11:16 AM on January 10

I disagree with the assertion that the peacock's tail has no adaptative value.

If you look at a peacock in full display mode, you might notice that the tail feathers tend to curve forward from the center outward, giving the tail as a whole a pronounced dish shape, and that the peacock's head tends to be about where you might expect the focus of that dish shape to be considered as a reflective surface, giving the peacock a fairly good first approximation resemblance to a Direct TV satellite dish on two legs. I think it's quite likely that peacocks can use their tail feathers to focus and amplify sounds that would otherwise be completely inaudible.

In that context, the eyespots on the tail feathers can be seen as a mechanism to evoke a startle response in any predator that might be concealed in the bushes, for example, the sound of which would then be picked up and detected by the tail feather dish antenna arrangement.

And peacocks don't tend to maintain a static display, in videos I've seen, they pivot like scanning radar dishes, and also flex their tail feathers abruptly, producing an excursion which has reminded me of the excursions of big subwoofers in audio speakers, and which might be expected to generate a subsonic signal that could also produce a startle reaction.

And one of the traditional uses of peafowl is as watch-animals.
posted by jamjam at 11:19 AM on January 10 [1 favorite]

We need to be careful around the word 'belief'. Any belief can be held without regard for evidence. Then there's the difference between 'opinion' and 'informed opinion'.

Science has advanced in making accurate predictions because it has backed up hypotheses with observations ('evidence'). It has sometimes gone astray because those observations must often be interpreted.

Two scientists may look at the same observations and interpret them in different ways. IF one of the interpretations becomes 'gospel' for an orthodox majority ... its defenders may slip into conservative behaviors resembling those of revealed religion (belief).

That unfortunate human tendency may ... and has often ... held back science for decades or longer. (The delay of 'plate tectonics' for a half-century being one example.)

Darwin proposed a HYUUUUGE idea which is still being worked out a century-and-a-half later. It's unwise to stake a claim on what's 'correct' or 'right' or 'proven'.
posted by Twang at 11:37 AM on January 10 [1 favorite]

Oh, and when I went looking for any evidence that peacocks' tails might inspire trypophobia in some people, I found a (strangely doctored) video which also seems to show the effect of the erection of a peacock's tail on a flock of crows.
posted by jamjam at 11:50 AM on January 10

giving the peacock a fairly good first approximation resemblance to a Direct TV satellite dish

Have you considered the possibility that the peacocks are using their satellite dish-shaped tail feathers to actually tune in to Direct TV satellite broadcasts? If some animals are capable of appreciating beauty for the sake of beauty, perhaps they are also capable of appreciating American daytime TV? I mean obviously they didn't evolve those tails specifically to watch Direct TV, they would've adapted first for tuning in to some more primitive and ancient satellite broadcast, like Sputnik or whatever. It's just a theory.
posted by sfenders at 2:43 PM on January 10 [4 favorites]

The thing about evolution is that it is subject to probability. You have six million individuals and you sort them out according to the one with all the best traits and the fewest of the worst traits as #1 and the one with the biggest collection of the worst traits and fewest of the best traits as #6,000,000, and then you let them go into the real world.

The real world rolls a few dice and it just happens that the top 8,000 individuals by every possible measure are on the landmass where a human being with a pair of rubber boots comes wandering through and those 8,000 individuals are all mashed into a thin layer of slime on the rocks. Of course those black rubber come-ashores flatten 2.7 million individuals in total but by a coincidence it gets the entire top 8,000 possibly because they were in the most advantageous spot to get the most promising combination of sun, seawater and nutrients. But the highest ranking surviving 8,000 (and their mediocre 1 millions sisters) buy it because a tree falls down and they are in the shade of the trunk and don't get any sun any more, and so on with one random event after another until it is perfectly plausible that the 8,000 individuals who actually survive and reproduce all come from the bottom one-twelfth of the genetic lottery, random environmental hazards having cut unavoidable swaths through the population.

Not only does the Goddess use a set of polyhedral dice, which appear to the naked eye to be smooth spheres, to roll up the genetic lottery, but she uses a set with as many sides to roll up the environment those genetic conglomerations are meant to fit themselves to. The amount of numbers that need to be crunched is eye-wateringly large. So many factors means that luck is the biggest factor. Science requires scientific notation but quickly limits its studies to those that the human lifetime and scientific notation can handle.

Thus with evolution you can see multiple generations where fitness is not nearly as important as not-being-in-the-wrong-place-at-the-wrong-time. Look at the population of the US and tell me that Donald Trump is the pinnacle of human evolution, or it is just possible that the brightest, healthiest, strongest, most resilient, sanest (etc. etc.) person ever born in the US might have been born in a family that couldn't afford to send her to post secondary education and was too bright to sell her into debt bondage to overcome that handicap and is currently quietly working as a hairdresser.

I more question the definition of beauty than the possibility that beauty exists for its own sake. I think a peacock is gaudy and annoying, but a wren has the most interesting subtle plumage. I also like paintings of sad little children painted on velvet, with tears glued on out of a tiny bead of crystal plastic but the photograph of an emaciated dead human body will make me stare and cry that such at thing could be so lovely, so ephemeral, so meaningful, so incredibly crafted and so irrevocably transformed from what it was.

Beauty is so subjective I am bewildered at how anyone could say it exists for its own sake. It exists because it has a pattern that draws the attention, and creates an emotional resonance. The chimpanzee that took a long side trip to stand and stare and rejoice at a waterfall was (IMCO) undoubtedly experiencing that waterfall as beautiful. The ant at its feet, not documented by jane Goodall, was (IMCO) undoubtedly rejoicing in the iridescence and refraction of the droplet of water that had landed in the grass, while it had never not known the light and sound of the waterfall as invisible music of the spheres and never had any real awareness of it. Both ant and chimp instinctively seek water, which brings in the emotional hook, but both had the capacity to enjoy light and reflection and colour. Both critters miss a billion other achingly beautiful things that they can't perceive but which have also formed patterns and meaning if there were eyes to see it. It's the old tree-falls-in-the-wood question. Is there beauty if there is neither perception nor life? And I say yes because I am alive to make that judgement. All the things I am not seeing and can't see are so beautiful that the mere idea of them makes me want to sit down and hold my head in my hands and try to recover for a bit.
posted by Jane the Brown at 2:59 PM on January 10 [4 favorites]

eacock a fairly good first approximation resemblance to a Direct TV satellite dish

Have you considered the possibility that the peacocks are using their satellite dish-shaped tail feathers to actually tune in to Direct TV satellite broadcasts? If some animals are capable of appreciating beauty for the sake of beauty, perhaps they are also capable of appreciating American...

Have you considered how very very obvious that joke is, sfenders?
posted by jamjam at 4:38 PM on January 10

jamjam, those aren't crows. They'd be itty bitty. That's just how the end of peacock feathers look which don't have the "eye" feature.
posted by es_de_bah at 5:35 PM on January 10 [1 favorite]

I disagree with the assertion that the peacock's tail has no adaptative value.

Okay! As behaviorists, we can evaluate that possibility by doing some basic experiments. The first question we want to ask is where and in what context male peacocks are likely to raise their tails. If this is primarily an anti-predation issue, I would expect them to raise trains equally often when there are other peacocks around as when they are alone. If they are also using the tail to startle predators, I would expect to see trains raised more frequently in the presence of predators or alarm, not less. If there is no anti-predatory function, I would expect to see the trains raised primarily around other peacocks, when the birds have conspecifics to communicate with. And of course, we would need to work out why female peahens don't need this apparently adaptive anti-predator response.

All of this is separate from whether or not the tail has a negative survival value, I should add: do peacocks with longer trains tend to be predated more than peacocks with shorter trains? Often this kind of thing is assumed rather than tested in sexually selected species: the thinking goes, this trait is really elaborated and obvious so it must be costly. Much of the time, studying the costs of these traits on survival itself reveals that they aren't as energetically expensive as you might think. Not always--I know of several systems, including Mike's own tungara frogs, where the cost to signaling with a lot of effort such that females prefer the signal is that... well, bats prefer it, too. But enough of the time that it is always worth checking before assuming a trait is costly.

Here's a discussion about observed peacock displays: note that peacocks do not begin displaying until the breeding season approaches and then display more frequently in "courtship grounds" where many other birds are displaying. This suggests that predator detection is probably unlikely, as there is no reason to suspect that predation increases during the breeding season.

This is a pretty good review on what we know about peacock signaling. I don't agree with all of its conclusions, but I will note that the only described study of predation on peacocks found a negative relationship with the number of eyespots--the trait that local female peahens seem to be evaluating males for--and the likelihood of any given individual having been eaten by a fox. Small study sample, but that's explicitly the opposite of the predictions of handicap models or other sexual selection models that posit that beauty is expensive. So, incidentally, is the finding that those long trains don't hinder the peacock's efficiency at walking in any way.

Come to think of it, my friend's got a small flock of feral peacocks--two peacocks, two peahens, and one as-yet unsexed peachick--living in her neighborhood. I should see if she'll let me observe the Flower-Eating Asshole from her back window sometime, or at least count the two peacock's eyespots and see which has more and who has the longer tail. Then we'll see who goes missing first!

All that being said, you're right to notice the role of noise in peacock courtship--it turns out that they aren't just observing each other, they're listening through (of all places) their crests. Listening might not quite be the right word--this is in the infrasound, lower-frequency than humans can hear--but they seem to have adapted their crests in order to better perceive the low-frequency airflow/air pressure of the displays, including the shaking of the feathers in train-rattling displays.

Note also that peacocks are known to be a lekking species, meaning that all the male peacocks who intend to mate will eke out display territories in the same area and raise their tails at once. Then they'll either stand

Because I've seen the researchers give a talk on it and the tiny peacock eye cameras were incredibly cute, I should mention that we do have a study on what the peacocks themselves (and the peahens) are looking at during the breeding season. (I'm still really impressed by this work, because it can be really hard working out exactly what females are attending to and in what modalities when you're studying these kinds of systems. What's beautiful: sound, smell, sight? And what exactly within those senses delights a prairie vole, or a peacock, or a pipefish?)

In that context, the eyespots on the tail feathers can be seen as a mechanism to evoke a startle response in any predator that might be concealed in the bushes, for example,

Fun fact: this is exactly how the eyespots work for the peacock butterfly, whose wings really do evoke a startle response in predators (in this case, chickens). Chickens who have see a peacock butterfly's display increase their vigilance and produce more alarm calls! And peacock butterflies with their wings painted over are much more likely to be snarfed up by a great tit.
posted by sciatrix at 5:52 PM on January 10 [13 favorites]

damn sciatrix, you just took this thread from lackluster to best of metafilter.
posted by es_de_bah at 6:49 PM on January 10 [1 favorite]

I am having fun! Please someone else talk later or I'll just hopefully stare at the screen to see if someone else has posted.

This kind of thing is one of the reasons I get so het up about this, though: folks take one look at a peacock and say firmly to themselves "oh of course that trait must be costly and expensive; obviously." But not enough people bother to check.
posted by sciatrix at 7:52 PM on January 10 [2 favorites]

I liked the article. I guess if you already follow this field the way it goes over 30-year-old (or older) arguments might seem boringly obvious, but I think it's just aimed at an audience who needs to have a bit of the history explained.

This part is a pretty clear brief explanation of Fisher's theory, which might help address some of the confusion in this thread:
At first, Fisher argued, females might evolve preferences for certain valueless traits, like bright plumage, that just happened to correspond with health and vigor. Their children would tend to inherit the genes underlying both their mother’s preference and their father’s trait. Over time, this genetic correlation would reach a tipping point, creating a runaway cycle that would greatly exaggerate both preference and trait, glorifying beauty at the expense of the male’s survival. In the early 1980s, the American evolutionary biologists Russell Lande and Mark Kirkpatrick gave Fisher’s theory a formal mathematical girding, demonstrating quantitatively that runaway sexual selection could happen in nature and that the ornaments involved could be completely arbitrary, conveying no useful information whatsoever.
So once sex A starts to choose sex B on the basis of a particular trait, like a long tail (and there could be all kinds of reasons why long tails are attractive), B will tend to evolve longer tails. And the environment that the species reproduces in now includes A's preference for long tails, whatever the other reasons for having a long or short tail might be.

But it doesn't stop there! The environment that A reproduces in now includes their own B children being subject to the long-tail preference of other As. So even if really long tails turn out to be bad for other reasons (they attract predators, or whatever), there is still a benefit for A to choose Bs with long tails, and for Bs to have really long tails.

Then there is evolutionary pressure on As to produce A children who themselves prefer Bs with really long tails, because this will help them have attractive B grandchildren. And so on, even if the conditions under which long tails were ever beneficial cease to exist... and until the tails get really, really long and too many of the Bs get eaten.

(And at the same time there will be countless other factors interfering with this process - something the article gets into right at the end.)
posted by A Thousand Baited Hooks at 9:28 PM on January 10 [1 favorite]

sciatrix, most of your links to papers lead to a university library login page. I'm interested to read up on this over the weekend, so if you get a chance to fix the links (or give citation details so we can hunt them down ourselves) I'd be very grateful!

(I'm a biologist but never studied evolution in much depth -- and no animal behaviour at all -- so I'm really enjoying following the conversation. Thanks, all.)
posted by metaBugs at 6:04 AM on January 11 [1 favorite]

whoops, my bad! I was a bit distracted and must have forgot to strip out my automatically-added proxy settings. Tell you what...

Here's the citations for every link in my previous comment, with links to PDFs that should be open access for everyone--where I haven't seen a link via Google Scholar and the paper isn't published in an open-access format, I've gone ahead and uploaded a public access copy on my own cloud host. Wonderfully, many of them were open-access to begin with, which makes me feel all warm and fuzzy inside.

Harikrishnan, S., Vasudevan, K., & Sivakumar, K. (2010). Behavior of Indian peafowl Pavo cristatus Linn. 1758 during the mating period in a natural population. The Open Ornithology Journal, 3, 13-19.

Gadagkar, R. (2003). Is the peacock merely beautiful or also honest? Current Science - Bangalore, 85(7), 1012-1020. Note: this one also has an interesting discussion towards the end, with the author lamenting that so little of the research on a quintessentially Indian bird has been done by Indian biologists even when it can be done relatively cheaply.

Thavarajah, N. K., Tickle, P. G., Nudds, R. L., & Codd, J. R. (2016). The peacock train does not handicap cursorial locomotor performance. Scientific Reports, 6, 36512.

Kane, S. A., Beveren, D. V., & Dakin, R. (2018). Biomechanics of the peafowl’s crest reveals frequencies tuned to social displays. PLOS ONE, 13(11), e0207247.

The "incredibly cute" link goes to a National Geographic publication that should be free to everyone already. Peacock Surprise: What Females Like in a Male.

Yorzinski, J. L., Patricelli, G. L., Bykau, S., & Platt, M. L. (2017). Selective attention in peacocks during assessment of rival males. Journal of Experimental Biology, 220(6), 1146-1153.

Yorzinski, J. L., Patricelli, G. L., Babcock, J. S., Pearson, J. M., & Platt, M. L. (2013). Through their eyes: selective attention in peahens during courtship. Journal of Experimental Biology, 216(16), 3035-3046.

Olofsson, M., Løvlie, H., Tibblin, J., Jakobsson, S., & Wiklund, C. (2012). Eyespot display in the peacock butterfly triggers antipredator behaviors in naïve adult fowl. Behavioral Ecology, 24(1), 305-310.

Vallin, A., Jakobsson, S., Lind, J., & Wiklund, C. (2005). Prey survival by predator intimidation: an experimental study of peacock butterfly defence against blue tits. Proceedings of the Royal Society of London B: Biological Sciences, 272(1569), 1203-1207. (Note that I was wrong when I commented about great tits previously--I would have been thinking of a different paper I was also looking at, which did focus on great tits and whether they were more or less likely to attempt to eat peacock butterfly wings if they had or did not have eyespots. Here's that one:

Kodandaramaiah, U., Vallin, A., & Wiklund, C. (2009). Fixed eyespot display in a butterfly thwarts attacking birds. Animal Behaviour, 77(6), 1415-1419.)

posted by sciatrix at 11:32 AM on January 11 [7 favorites]

It's my understanding that as far as contemporary evolutionary theory is concerned, the null hypothesis is neutral selection, meaning that anything adaptive or detrimental is the thing to be demonstrated. And this means that any statement to the effect that if X exists in nature it is an adaptation can be considered false by default until actual demonstration.
posted by Pyrogenesis at 8:30 AM on January 12

That is a correct understanding, but one that is sometimes--particularly with respect to traits assumed to be detrimental--honored more in the breach than in the observance. This is especially true in species that do not have an active tradition of study by multiple lab groups, which includes both peacocks and my own study organism.

Sometimes, when you are working with limited time and limited known resources on an interesting organism, you make some assumptions because you don't have the financial support to go back to basics and verify that your assumptions are or are not true. If the assumptions seem especially obvious, fewer and fewer people are motivated to test to see if they are correct or not. And then you wind up with awkward situations when someone does get around to testing and finds out that costliness is less common than assumed.

Measuring fitness in general, in the sense of measuring the total number of successful offspring achieved by individuals with given traits in a wild context, is really hard. We have a few systems where it can be done, mostly as a consequence of multi-decade projects devoted to obsessively tracking every individual in a given population and also paternity testing all of them and measuring them for the trait of interest. It is hard work and it is generally not "sexy" work, at least to start with, and those projects are expensive and particularly hard to start in a risky funding climate.

So a lot of people sort of... guess what's likely to be true and hope that it's enough to keep their labs going while they figure out enough non-intuitive and interesting findings to carve out some breathing space for the research program.
posted by sciatrix at 9:04 AM on January 12 [3 favorites]

Prum's work is fantastic, if for no other reason than, as sciatrix alludes to, he is discarding some assumptions that evolutionary biologists make as a matter of course, as a consequence of how precious little time we have and how very little is known about how any of this works at all.

Neutral selection is sort of the basic assumption now for molecular evolution, but it were not always so. And, it really mostly applies to DNA and proteins; not to morphological or behavioral phenomenon.

I study these guys (Treehoppers) because they have a fascinating dorsal structure absent in their closest relatives. They look like little aliens. The work I'm doing is molecular, trying to see how gene expression has changed in the treehopper lineage to build that dorsal structure--and that work has nothing at all to do with whether or not the trait is adaptive. But *everyone* who's ever worked on treehoppers assumes that it must be adaptive, probably to evade predators by crypsis, warning, or mimicry. However, no one has *ever* done that work. The inference that it's predator evasion works like this:

1) No sexual dimorphism, so it's unlikely to be a sexually selected trait
2) Sometimes they're very hard for humans to see; humans are good visual predators, so it follows that they're likely to be hard for other visual predators (hunting spiders, birds) to see
3) There are several species that exhibit myrmecomorphy (ant mimicry) which is a very common strategy in arthropod evolution and has been well characterized in other species [Or anyway, they look like ants to humans, so they probably are ant mimics]
4) There's a large amount of variation in helmet shape and size and coloration that happened in a relatively short amount of evolutionary time, and that's one of the hallmarks of adaptive radiation

and, unfortunately,

5) I mean, COME ON, JUST LOOK at it, that MUST be adaptive

However, in the early 20th century, prior to the Modern Synthesis, there was a strong contingent of evolutionary biologists who supported the hypothesis of orthogenesis, which means a kind of evolution that is progressive, which each generation being more intense than the last. They weren't talking about some kind of run-away selection, where the fitness benefits of a trait are so huge that they outweigh the detriments, they were talking about there being an internal force that caused, say, beetle horns to get bigger and bigger *unless* there was some purifying selection against large horns. Treehoppers were one of the most often pointed to candidates for orthogenesis.

I mean, look at this guy: Bocydium globulare, photo by Piotr Naskrecki. wtf is that helmet even for? How can that be adaptive?

Here in the early 21st century we benefit intellectually quite a lot from the work that others have done to demonstrate the adaptive significance of a variety of incredibly bizarre morphologies AND behaviors-- but that means that, in the absence of real empirical data, we tend to intuit that things are adaptive until proved otherwise. (And usually give an aside about how of course a naively adaptationist program is undesirable.) And so we do draw a lot of inferences about how or why a trait may be adaptive, but we hold those inferences tentatively, knowing that in the absence of empirical work, it's just a good guess.
posted by Made of Star Stuff at 8:35 AM on January 13 [5 favorites]

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