It's dangerously easy to say "oh yea, makes sense, natural selection happens by mating so if mates choose club wings, I get it. Obvious." But Prum's trying to go a step further, and test just how far out of balance and arbitrary the mate selection part can be from the direct do-not-die part of evolutionary fitness.
He proposes that we can differentiate between these two by considering that the club wings aren't actually indicators of higher direct fitness, because they hurt the ability to fly, even among females that have no need for such shenanagins. I'm not sure I totally agree with or grasp that, but at least it's an attempt to further understand and test the idea.
I'm frankly surprised by comments accusing a well established evolutionary biologist of severely misunderstanding natural selection. The author has spent his career, among other things, investigating mechanisms of evolution, and identifying and performing tests to assess their relative importance to a particular species (here's an example: http://prumlab.yale.edu/sites/default/files/prum_1997_phylog...).
You might consider whether your objections are addressed in his work not aimed at the lay population, and that your criticism really just amounts to "He wrote this at not exactly the right level of sophistication for me." Maybe that's true, but it's a pretty boring claim.
Some traits are shaped by sexual selection because of their deleterious effects. It's an honest signal: if you can survive despite having that crappy trait, you must be really robust!
You can't conceptualize that as a fitness hit, because of what fitness means in the context of evolutionary biology. But you had better be able to conceptualize it somehow, because it's interesting and important if true.
species die out because of maladaptive pressures. that doesn't contradict the theory of evolution and natural selection's role in it.
If we said 40 millions years ago - protowhales cannot run as fast because their mates really like the membranes between their legs this would still be technically true.
Most birds can fly because their parents could fly. The genes for flying stick around because so many other traits of birds have evolved to benefit or rely on the ability to fly. But that doesn't mean flying itself is some magical end goal. Flying is only useful for natural selection insasmuch as it grants the organism a better likelihood of reproducing.
Why would natural selection necessarily prefer birds that are ideally designed for flying in what we perceive as a graceful manner? In fact, we know that it doesn't. Ostriches, emus, and penguins can't fly, though their ancestors were able to. That is not evidence that they are evolutionary dead ends. The huge variety of penguin species that have evolved since the ancestor of penguins lost the ability to fly proves the opposite, in fact.
This bird clearly flies well enough to continue to survive. If the traits that work against it flying gracefully grant it more reproductive success than flying slightly better would, then natural selection will favor those traits.
Natural selection is often treated far too preciously. Sure, it took a genius in Darwin to identify and clearly describe the phenomenon, but the process itself is tautological. It comes down to, "the things that reproduce better reproduce better". This bird exists, therefore natural selection favored its traits. If we don't understand why, the failure is ours, not natural selection.
TFA has a weird definition for natural selection.
Evolution has no preferences and sexual selection is natural selection.
It's a matter of definition, I think. Darwin made a distinction between natural selection and sexual selection,
> Sexual selection was first proposed by Charles Darwin in The Origin of Species (1859) and developed in The Descent of Man and Selection in Relation to Sex (1871), as he felt that natural selection alone was unable to account for certain types of non-survival adaptations. https://en.wikipedia.org/wiki/Sexual_selection
So the distinction the article here makes is a reasonable one with a long history. But more recently, the terms are often defined as non-distinct,
> Factors that affect reproductive success are also important, including sexual selection (now often included in natural selection) https://en.wikipedia.org/wiki/Natural_selection
Traits need to be considered with the ones they compete against. It's impossible to judge the bird in isolation.
Since the 1930s, it's been well known that in some cases sexual selection will undermine natural selection. Very simply, if a male is liked by most females, then a female has an incentive to mate with that male, even if the female does not like that male, because then her male children will have a trait that most females like. This can lead to a feedback loop that then goes to far, with maladaptive consequences.
This is a well studied case:
-------------------
Fisherian runaway or runaway selection is a sexual selection mechanism proposed by the mathematical biologist Ronald Fisher in the early 20th century, to account for the evolution of exaggerated male ornamentation by persistent, directional female choice. An example is the colourful and elaborate peacock plumage compared to the relatively subdued peahen plumage; the costly ornaments, notably the bird's extremely long tail, appear to be incompatible with natural selection. Fisherian runaway can be postulated to include sexually dimorphic phenotypic traits such as behaviour expressed by either sex. Extreme and apparently maladaptive sexual dimorphism represented a paradox for evolutionary biologists from Charles Darwin's time up to the modern evolutionary synthesis. Darwin attempted to resolve the paradox by assuming genetic bases for both the preference and the ornament, and supposed an "aesthetic sense" in higher animals, leading to powerful selection of both characteristics in subsequent generations. Fisher developed the theory further by assuming genetic correlation between the preference and the ornament, that initially the ornament signalled greater potential fitness (the likelihood of leaving more descendants), so preference for the ornament had a selective advantage. Subsequently, if strong enough, female preference for exaggerated ornamentation in mate selection could be enough to undermine natural selection even when the ornament has become non-adaptive.[3] Over subsequent generations this could lead to runaway selection by positive feedback, and the speed with which the trait and the preference increase could (until counter-selection interferes) increase exponentially ("geometrically").
Doesn't change the fact that preferring those traits are ingrained in us due to thousands of years of evolution and aren't changing any time soon. Worry about what you have control over you'll be happier
This species is doomed by the chasing of this superficial attractiveness.
> ...the evolutionary mechanism behind this novelty is not adaptation by natural selection, in which only those who survive pass on their genes, allowing the species to become better adapted to its environment over time. Rather, it is sexual selection by mate choice...
In natural selection, it is only individuals which mate which pass on their genes -- surviving is no good if you don't mate! It is my understanding that sexual selection has been classed as a variety of natural selection. If the species sexually selects itself to a point of maladaption, it goes extinct -- just as if it was maladapted to its environment for any other reason. Notably, these birds are not there: they still seem to be okay.
> In the absence of direct costs to the choosers, the population will not be saved by natural selection. Because the cost is deferred, the whole population can ease further and further into maladaptive dysfunction, generation by generation.
This seems to be treating natural selection as a game of one round, or describing a situation where there is almost no capacity for variation in the species. But if it's really true, that the species is in a kind of dead-end, where the most successful mates are the most maladapted, and there is little capacity in the genome to remedy this situation -- as the females could develop a different standard of attraction, or the males some other method of attraction -- then the effect of natural selection would be to extinguish the species. This is, in some sense, how "progress" is made in natural selection -- as much by elimination as anything else. This leads us to:
> Instead of ensuring that organisms are on an inexorable path to self-improvement, mate choice can drive a species into what I call maladaptive decadence...
It has been said by many more well informed than I am, that there is something specious about an "inexorable path to self-improvement" with regards to animals. Animals become more adapted to their environment; but they don't become "better animals" since a change in the environment leads them to be worse adapted. The subtlety is that, traits may be gained, and then lost, and both were "better": to gain fur as the earth cooled, and to lose it again as the earth warmed.
And finally I must ask, where has the author shown the birds are maladapted? They fly awkwardly, sure -- but what difference does it make for them?
Through that lens, there's no counterintuitive behavior here, and natural selection isn't being undermined. It's an emergent polarization.
>The clumsy wings of males could be rationalized as a handicap that provides information about the birds’ condition or genetic quality.
Also known as an honest indicator of fitness.
>But the observation that female club-wings have also probably made themselves less capable fliers can only be described as decadent —
Why the "probably" there? Previously the author mentioned that the bones where hollow in the females, unlike the males. Maybe they can fly just fine!
>sexual selection leading to a decline in the capacity for survival.
Yeah but, the fact that they exist, shows that they have survived.
So natural selection.
The author of this article is an Evolutionary Biology researcher at Yale. It would be really weird if he severely misunderstood natural selection.
Yes, Virginia, "most biologists," who get their news from Nature and Cell, are sadly lagging behind laypeople who read the New York Times. Is it any wonder people have so little faith in scientists? I think science journalists have a responsibility to highlight the fallibility of scientists and the flaws of the scientific process, but it is not public-minded criticism to make your readers believe that the majority of scientists working in an area are too dense to understand something that an average person can understand from a newspaper article, or already did understand if they read a single pop science book about evolution in the last several decades. That's just pandering.
Now, we could make the same mistake and assume that we, who do not write science journalism, have noticed something about it that one of its most successful practitioners (published in the New York Times, after all) never has. Or we could assume he understands it better than we do and does this shit on purpose because he likes being published.
Sexual selection definitely produces some interesting effects, but it's still a form of natural selection. This article portrays it as the opposite. I think it's far easier to understand the outcomes of sexual selection if you realize that reproductive success is the only thing that matters. And the factors that influence reproductive success vary widely. It's important to not get eaten, die of disease, starve to death, or die young. But for organisms that reproduce sexually, it's even more important to be able to find a mate. An organism that lives twice as long but reproduces just once is far less successful than an organism that lives half as long but reproduces twenty times. The whole idea that sexual selection is somehow at odds with natural selection instead of just being one of many selection pressures, is deeply confused.
Well, I can't say concerning Ostriches etc but a common pattern in recently emerged islands is for birds to reach the island first. There not being any predators, some of the bird species evolve to being flightless. Once rats or other mammals reach these Islands, these species tend to become extinct. So naturally occurring "evolutionary dead-ends" are certainly possible (European sailors releasing rats and rabbits to the many islands they visited accelerated the process but it is still "inevitable" since mammals will to a given Island sooner or later).
Sure, one can define selection and fitness "internally" and thus whatever survives is "fittest" up to a given point. But it seems reasonable to take an external view and judge that certain evolution paths lead to the end of species. There's no reason abolish this kind of analysis just because one has honed the specific, technical meaning of these terms so that they aren't concerned with the question.
I believe most of the time you're right, the changes are random. However, at least one experiment has shown that species can pass adaptive traits to their offspring (called Lamarckian inheritance) [1]. The experiment is intriguing, in that it seems to hint something more is going on than the Darwinian inheritance model.
[1] http://newsroom.cumc.columbia.edu/blog/2014/07/17/effects-of...
It's Aristotelian biology.
After all, no real visible phenotype is truly based on a single gene, but rather the dynamic interplay of hundreds of gene products over the course of the organism's development.
Yes.
> evolution selects at multiple levels
That's just another way of saying that evolution selects for reproductive fitness with respect to a particular environment. If a gene is part of an organism, then the other genes in that organism are part of that gene's environment.
The aggregation of genes into organisms is itself an evolutionary adaptation (as is the aggregation of organisms into more complex organisms like eukaryotic cells and multi-cellular creatures). This aggregation provides reproductive fitness by enforcing a certain level of cooperation among the aggregated genes (see https://en.wikipedia.org/wiki/The_Evolution_of_Cooperation). But this is not the fundamental mechanism of evolution, and every now an then a gene "defects" and does what is best for it at the time. Cancer is an example of this.
Naively expecting "better" organisms to win fails to explain why these birds are evolving progressively "worse".
But if you go down and look at genes which handicap the male while triggering some silly attractiveness glitch in females versus genes that don't, it becomes clear that as long as the handicap isn't too strong, the former genes may easily win.
I think that's a point for the GCVOE this time.
It's my understanding that gene-centered view is the main view among evolutionary biologists.
Multi-level adaptation seems to have fallen under lack of evidence. Evidence from nature, mathematical theory, and evolutionary simulations seem to back up selfish gene theory. There are still people like David Sloan Wilson who work on it.
Well, sexual selection is distinguishable, because it's not about the environment or other species, but about interactions between sexes. I mean, consider ducks. How does the penis-vagina arms race have any relevance to overall fitness? Indeed, it seems more like a bug in the sexual reproduction app.
But on the other hand, human consciousness and language are arguably products of sexual selection. And they have increased fitness. So maybe it's most useful to consider sexual selection as just another source of variation, grist for the mill of natural selection overall.
But hell if you are wrong about the general trend ;)
edit:
Really what TFA did is it just falsified some extremely naive and humanly-subjective interpretation of the slogan "survival of the fittest", without bothering to mention that this interpretation had already been known to be defective years ago and there are subtler alternatives which don't have this problem.
> Even the peafowl has a longer tail than she needs.
Surely he means peahen, the female peafowl (of which the male peacock has the extraordinarily long tail.)
> that doesn't make any sense
If you look at the criticism leveled against this theory you will find that many of them have been addressed by the proponents of the theory, in many cases very successfully. Many things can be said about this theory but your claim strikes me as highly unqualified.
You're SOL on your height, but your muscle mass is quite malleable with pretty low effort. I work out for two hours a week, one hour on Saturday (upper body), one hour on Sunday (lower body and core). I don't look like an nfl linebacker, but it gets me to the athletic end of the dork spectrum at least. I'm betting you can find two hours a week to spare. If it doesn't take, you might have low testosterone, which is easily fixed medically (by taking testosterone, ie anabolic steroids... kind of extreme, and for the record, I don't take them myself, but if you actually have low t it seems somewhat reasonable to me.). Even if you don't want to work out, I don't think being short and skinny is a huge barrier to getting girls. Many of my friends fit this description and haven't had trouble. If that describes you, you may have other problems. If you've left unsaid that you're overweight, that's a lot harder to fix than muscle mass. Probably worth one good attempt to slim down, it works for some people, but doesn't for a lot of others. You may have to live with it.
Which brings me to... social skills. They really are skills. It comes naturally to a lot of people, but if it's unnatural for you, you CAN get better if you try. It takes a lot of effort, but if it's important to you, put some real effort (and time) into it.
Females are not as irrational in their preference for tall muscular men as you seem to think. Tall men make more money on average. So do good looking men. Why? There's two sides to any business: making shit and selling shit. I'm guessing you're good at the making part. Selling is just as important. People like to be around attractive people. Sucks for the non-beautiful, but just a fact of life. But you know what? They also like to be around funny, confident, and friendly people. And you can do something about that.
More height means you have more cells that could potentially become cancerous.
Wow, no shit:
http://www.wcrf.org/int/blog/articles/2015/09/why-taller-peo...
Not exactly the mechanism you proposed, but still...
By the way, a large majority of humans in the United States marry and even among the ones who don't marry a vast majority of them have dated. A large majority of people in the United States are not tall and muscular, we come in all shapes and sizes.
You may find this shocking but Women aren't uniform brainless sheep. Women come in all forms with all sorts of different things they find attractive. For example, I don't find muscles especially attractive and tallness does absolutely nothing for me. My husband is overweight and I don't mind a bit, doesn't distract from his attractiveness to me. Some women are even attracted to other women.
(Hint: it actually might be you since 99% of society can somehow manage to get a date)
Looking at japan, that number seems overestimated. That might be your personal experience, but because of survivorship bias - you'd be less likely to meet antisocial shut ins etc.
But I do know that I stressed out about shit like this in high school, then figured out that if you treat women like people and ask them out, some percentage of them will say yes.