I remember once from undergrad the saying '"obvious" is the most dangerous word in mathematics.' Seeing how something could be true is dramatically different from identifying and defending that it is true.
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.
I agree. I'm inclined to think the concepts are more subtle, not less.
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.
What I've understood is that if the change that's detrimental is compensated for by other attributes that do connote fitness this can be an evolutionarily stable strategy. That is, if the the bird is able to survive even with the club wings that is in fact an indication of relative fitness and the club wings can be selected for. Though I've only heard this theory in reference to things like bulking/attractive plumage that itself connotes some kind of fitness. For example, those birds with crazy long tails are arguably less able to hunt or whatever but the ones that do hunt effectively cause the female to think: wow so attractive! And he can manage to provide.
it seems to me like the article is more about elucidating beauty as a mechanism of decadence than an attempt to upend natural selection as a core component of the theory of evolution. the article basically says that beauty (however defined for a given species) can be both a selective and maladaptive pressure, where conventionally it's thought of only as a selective pressure.
species die out because of maladaptive pressures. that doesn't contradict the theory of evolution and natural selection's role in it.
Yeah but his whole thesis in thus article is based on the assumption that efficient flight is important for the survival of this species.
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.
I will just echo the other posts here that the author of this article or his sources severely misunderstand natural selection and the special case of sexual selection. The most important thing to understand about evolution is that natural selection can only work with the existing traits of an organism, the current environment in which the organism exists, and what random changes happen. Furthermore, every change in the phenotype of an organism has a number of sometimes disparate impacts on its likelihood of reproductive success within its own environment. Given all of that, we should _expect_ to see seeming contradictions like this example.
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.
Ostriches, emus, and penguins can't fly, though their ancestors were able to. That is not evidence that they are evolutionary dead ends.
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.
> The most important thing to understand about evolution is that natural selection can only work with the existing traits of an organism, the current environment in which the organism exists, and what random changes happen.
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.
The puzzlement over the apparent reproductive disadvantages of wing-singing is simply a reflection of a misunderstanding of how evolution works. Evolution does not select for the reproductive fitness of species, it selects for the reproductive fitness of genes. And it does not select for the absolute fitness of genes, but rather for their fitness relative to competing alleles with respect to a particular environment. The genes for wing-singing are better at reproducing themselves in an environment where manakins already exist than the genes for alternative strategies for finding mates. That this might hurt the reproductive fitness of the other genes that go into making club-wing manakins matters not at all to the wing-singing genes. Genes don't think these things through. Genes don't think at all. Some genes build things that think, and some of those things that think end up being puzzled by the behavior of genes, including the very genes that built them.
You're describing this viewpoint: https://en.wikipedia.org/wiki/Gene-centered_view_of_evolutio...
however I don't think it's really an accepted (in terms of evidence) theory that explains all evolution. I think most biologists think that evolution selects at multiple levels (although likely the underlying processes are much more complex than just that).
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.
> But 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 which individuals pass on their genes only if they’re chosen as mates.
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,
Agreed. This is more akin to evolution being stuck in a suboptimal (and perhaps a dead-end) local minima - but it is still natural selection as more pleasing features = survival on an individual scale.
Evolution happens because of natural selection. It is the narrative of natural selection and does not always have a happy ending. The subtitle of the article is just plain wrong. Of course natural selection explains "the too sexy birds", it just can't predict how long the evolutionary span will be.
The title suggests "Fisherian runaway" but the article does not.
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").
Interesting findings, but really nothing here new about the evolutionary biology. This is just another example of Zahavian adaptations, aka handicap principle, "which explains the evolution of characteristics, behaviors or structures that appear contrary to the principles of Darwinian evolution in that they appear to reduce fitness and endanger individual organisms. Evolved by sexual selection, these act as signals of the status of the organism, functioning to e. g. attract mates."
The title reminds me of a species we're all familiar with where the females are adopting increasingly high standards for mates based in obsolete evolutionary preferences which have no applicability to fitness in the current environment, and where the skills relevant to survival in the current environment are ironically often seen as unattractive by the females, and males who cultivate these skills often don't have the time to develop the portions of the aforementioned obsolete traits that are trainable.
and guys prefer women with large breasts and wide hips, both unnecessary due to baby formula and C-Sections.
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
The human females find sense of humor attractive. That requires development of big brain. Think how shitty big brain is - it soaks up nutrition, takes insane amounts of protein to develop, makes the infant helpless for 12 years, diverts resources from muscle mass and bone, makes easier death during childbirth and permanently diminishes the ability of the mother to gather food.
This species is doomed by the chasing of this superficial attractiveness.
It's interesting to consider this article in light of the fact that the most ubiquitous and successful bird species are all drab and without much sexual dimorphism (crows, sparrows, gulls)
There are some things that seem odd about this author's terminology.
> ...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?
I see something in common between those birds and the modern western females. We will see soon how well nice look can compete with artificial intelligence for survival.
kevinalexbrown|8 years ago
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.
mbateman|8 years ago
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.
flippyhead|8 years ago
clairity|8 years ago
species die out because of maladaptive pressures. that doesn't contradict the theory of evolution and natural selection's role in it.
panzer_wyrm|8 years ago
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.
skywhopper|8 years ago
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.
lapsock|8 years ago
The author of this article is an Evolutionary Biology researcher at Yale. It would be really weird if he severely misunderstood natural selection.
joe_the_user|8 years ago
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.
ccallebs|8 years ago
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...
JacksonGariety|8 years ago
It's Aristotelian biology.
unknown|8 years ago
[deleted]
lisper|8 years ago
dekhn|8 years ago
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.
h0l0cube|8 years ago
bad_user|8 years ago
TFA has a weird definition for natural selection.
Evolution has no preferences and sexual selection is natural selection.
azakai|8 years ago
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
foglerek|8 years ago
devnull255|8 years ago
lkrubner|8 years ago
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").
https://en.wikipedia.org/wiki/Fisherian_runaway
sewercake|8 years ago
dekhn|8 years ago
zethraeus|8 years ago
mudil|8 years ago
https://en.m.wikipedia.org/wiki/Amotz_Zahavi
shaq_hammer|8 years ago
cmahler7|8 years ago
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
nerdponx|8 years ago
panzer_wyrm|8 years ago
This species is doomed by the chasing of this superficial attractiveness.
make3|8 years ago
flamedoge|8 years ago
jdpigeon|8 years ago
solidsnack9000|8 years ago
> ...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?
zethraeus|8 years ago
Through that lens, there's no counterintuitive behavior here, and natural selection isn't being undermined. It's an emergent polarization.
Jean-Philipe|8 years ago
antiquark|8 years ago
>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.
avodonosov|8 years ago
c3534l|8 years ago
So natural selection.
erikb|8 years ago
fangSchweeeee|8 years ago
[deleted]
education2020|8 years ago
[deleted]
paul343|8 years ago
[deleted]
denois|8 years ago