How does natural selection account for male pattern balding?
August 16, 2007 8:28 PM Subscribe
How does natural selection account for male pattern balding?
The women were already pregnant by the time the men started going bald and it basically didn't matter.
posted by 6550 at 8:36 PM on August 16, 2007
posted by 6550 at 8:36 PM on August 16, 2007
Balding males use less energy growing hair, and can thus put more into the care of their children and/or grandchildren.
posted by pompomtom at 8:41 PM on August 16, 2007 [1 favorite]
posted by pompomtom at 8:41 PM on August 16, 2007 [1 favorite]
It may not be natural selection, but sexual selection at work:
There is no consensus regarding the details of the evolution of baldness. Most theories regard it as resulting from sexual selection. A number of other primate species also experience hair loss following puberty, and some primate species clearly use an enlarged forehead, created both anatomically and through strategies such as frontal balding, to convey increased status and maturity.
One theory, advanced by Muscarella and Cunningham, suggests baldness evolved in males through sexual selection as an enhanced signal of aging and social maturity, whereby aggression and risk-taking decrease and nurturing behaviours increase.(1) This may have conveyed a male with enhanced social status but reduced physical threat, which could enhance ability to secure reproductive partners and raise offspring to adulthood.
In a study by Muscarella and Cunnhingham, males and females viewed 6 male models with different levels of facial hair (beard and moustache or clean) and cranial hair (full head of hair, receding and bald). Participants rated each combination on 32 adjectives related to social perceptions. Males with facial hair and those with bald or receding hair were rated as being older than those who were clean-shaven or had a full head of hair. Beards and a full head of hair were seen as being more aggressive and less socially mature, and baldness was associated with more social maturity.
Here's the abstract from that study:
Both male facial hair and male pattern baldness are genetically based, suggesting that they contributed to fitness. The multiple fitness model provides an evolutionary interpretation of the social perception of male pattern baldness and beardedness in terms of the multidimensional meaning of physical maturational stages. Male facial beardedness is associated with the sexual maturation stage and is hypothesized to signal aggressive dominance. Male pattern baldness, by contrast, is associated with the next stage of physical maturation, termed senescence. Pattern baldness may signal social maturity, a non-threatening form of dominance associated with wisdom and nurturance. We tested these hypotheses on social perceptions using manipulated male facial stimuli. We presented faces with three levels of cranial hair, including full, receding, and bald, and two levels of facial hair, beard with moustache and clean shaven. Consistent with the model, a decrease in the amount of cranial hair was associated with increased perceptions of social maturity, appeasement, and age, and decreased perceptions of attractiveness and aggressiveness. Targets with facial hair were perceived as more aggressive, less appeasing, less attractive, older, and lower on social maturity than clean shaven faces.
So maybe women tend to chase hairy, irresponsible and aggressive young guys, but settle down and raise kids with balding but stable and nurturing men, even though they find them less attractive than men with full heads of hair.
Or male baldness may be associated with another, yet identified trait that is being directly selected, and baldness survives as a tagalong.
posted by maudlin at 8:42 PM on August 16, 2007 [3 favorites]
There is no consensus regarding the details of the evolution of baldness. Most theories regard it as resulting from sexual selection. A number of other primate species also experience hair loss following puberty, and some primate species clearly use an enlarged forehead, created both anatomically and through strategies such as frontal balding, to convey increased status and maturity.
One theory, advanced by Muscarella and Cunningham, suggests baldness evolved in males through sexual selection as an enhanced signal of aging and social maturity, whereby aggression and risk-taking decrease and nurturing behaviours increase.(1) This may have conveyed a male with enhanced social status but reduced physical threat, which could enhance ability to secure reproductive partners and raise offspring to adulthood.
In a study by Muscarella and Cunnhingham, males and females viewed 6 male models with different levels of facial hair (beard and moustache or clean) and cranial hair (full head of hair, receding and bald). Participants rated each combination on 32 adjectives related to social perceptions. Males with facial hair and those with bald or receding hair were rated as being older than those who were clean-shaven or had a full head of hair. Beards and a full head of hair were seen as being more aggressive and less socially mature, and baldness was associated with more social maturity.
Here's the abstract from that study:
Both male facial hair and male pattern baldness are genetically based, suggesting that they contributed to fitness. The multiple fitness model provides an evolutionary interpretation of the social perception of male pattern baldness and beardedness in terms of the multidimensional meaning of physical maturational stages. Male facial beardedness is associated with the sexual maturation stage and is hypothesized to signal aggressive dominance. Male pattern baldness, by contrast, is associated with the next stage of physical maturation, termed senescence. Pattern baldness may signal social maturity, a non-threatening form of dominance associated with wisdom and nurturance. We tested these hypotheses on social perceptions using manipulated male facial stimuli. We presented faces with three levels of cranial hair, including full, receding, and bald, and two levels of facial hair, beard with moustache and clean shaven. Consistent with the model, a decrease in the amount of cranial hair was associated with increased perceptions of social maturity, appeasement, and age, and decreased perceptions of attractiveness and aggressiveness. Targets with facial hair were perceived as more aggressive, less appeasing, less attractive, older, and lower on social maturity than clean shaven faces.
So maybe women tend to chase hairy, irresponsible and aggressive young guys, but settle down and raise kids with balding but stable and nurturing men, even though they find them less attractive than men with full heads of hair.
Or male baldness may be associated with another, yet identified trait that is being directly selected, and baldness survives as a tagalong.
posted by maudlin at 8:42 PM on August 16, 2007 [3 favorites]
I think it also just may be a side effect of testosterone, so while men may be less attractive hair wise, the extra testosterone more than compensates in other ways that increase the likelihood that a man will reproduce.
posted by whoaali at 8:42 PM on August 16, 2007
posted by whoaali at 8:42 PM on August 16, 2007
Or on preview, maudlin is probably a lot closer to the mark.
posted by whoaali at 8:43 PM on August 16, 2007
posted by whoaali at 8:43 PM on August 16, 2007
Large Marge: my money would be on the fact that male pattern balding occurs at an age well after mating occurs, so it's not selected for or against.
Well, excu-u-u-u-u-u-s-e me, but I know a lot of bald guys younger than me, AND I'm still mating with purpose, AND men tend to remain procreationally able into their 70s. So neener neener.
posted by unSane at 8:47 PM on August 16, 2007
Well, excu-u-u-u-u-u-s-e me, but I know a lot of bald guys younger than me, AND I'm still mating with purpose, AND men tend to remain procreationally able into their 70s. So neener neener.
posted by unSane at 8:47 PM on August 16, 2007
Umm, the Wikipedia entry gives some suggestions on current theory.
The page is disputed, so its also worth checking out some of the counter arguments. No straight answer to the question methinks.
posted by bramoire at 8:49 PM on August 16, 2007
The page is disputed, so its also worth checking out some of the counter arguments. No straight answer to the question methinks.
posted by bramoire at 8:49 PM on August 16, 2007
Natural selection is a long term thing. Maybe 50,000 years ago women didn't care if a man had a full head of hair when deciding whether to jump him.
posted by smackfu at 9:08 PM on August 16, 2007
posted by smackfu at 9:08 PM on August 16, 2007
San Francisco, CA (WFN) -- Humans have evolved incredibly since the dawn of time -- and we have color-blind, bald, left-handed and homosexual men to thank.
San Francisco surgeon Dr. Leonard Shlain figures that 8 percent of all men are either color blind, bald, left-handed or gay. Therefore, those traits must benefit the entire race -- or they would have died out by now.
For instance, color blind men have an advantage while hunting because they're less fooled by camouflage and left-handed male soldiers have an advantage over right-handers when fighting mano-a-mano.
Dr. Shlain thinks homosexuality probably evolved in hunting tribes to ensure that there would be more men to hunt for the food but wouldn't produce hungry offspring.
However, the doc admits he has yet to figure out the need for baldness since hair protects the brain against overheating.
Dr. Shlain is the author of a new book, "Sex, Time And Power" (Viking).
posted by Brian B. at 9:11 PM on August 16, 2007 [1 favorite]
San Francisco surgeon Dr. Leonard Shlain figures that 8 percent of all men are either color blind, bald, left-handed or gay. Therefore, those traits must benefit the entire race -- or they would have died out by now.
For instance, color blind men have an advantage while hunting because they're less fooled by camouflage and left-handed male soldiers have an advantage over right-handers when fighting mano-a-mano.
Dr. Shlain thinks homosexuality probably evolved in hunting tribes to ensure that there would be more men to hunt for the food but wouldn't produce hungry offspring.
However, the doc admits he has yet to figure out the need for baldness since hair protects the brain against overheating.
Dr. Shlain is the author of a new book, "Sex, Time And Power" (Viking).
posted by Brian B. at 9:11 PM on August 16, 2007 [1 favorite]
bramoire, the Wikipedia entry is discussing the Muscarella and Cunningham study I cited above. I looked at the counterarguments you've linked, but they haven't convinced me (yet) that M&C are wrong.
From the first link: I wanted to demonstrate how baldness was linked to insulin resistance, metabolic syndrome, diabetes, coronary artery disease and similar health problems. Sexual selection often works against individual fitness, so it's not surprising that a trait that may be favoured by sexual selection may also be associated with traits that threaten long-term survival. While I'm not absolutely wedded to M&C's theory, it's still viable if these diseases typically weaken or kill bald men who have already helped raise their offspring to adulthood. I'd also have to know how strong the association was: do 50% of bald men show a 50% increase in heart disease morbidity and mortality versus hairy men, or is the effect smaller, or larger? Merely saying that something is linked doesn't demonstrate that there is a strong correlation in the expected direction.
The second link features an argument from someone who deeply misunderstands evolution, thinks it must be purposeful, and that intermediate stages of the development of a trait offer no evolutionary advantage.
As I said, baldness may not be the product of sexual selection, or there may be something else directly selected for with baldness surviving merely by association. Anyone find any more intriguing studies?
posted by maudlin at 9:13 PM on August 16, 2007
From the first link: I wanted to demonstrate how baldness was linked to insulin resistance, metabolic syndrome, diabetes, coronary artery disease and similar health problems. Sexual selection often works against individual fitness, so it's not surprising that a trait that may be favoured by sexual selection may also be associated with traits that threaten long-term survival. While I'm not absolutely wedded to M&C's theory, it's still viable if these diseases typically weaken or kill bald men who have already helped raise their offspring to adulthood. I'd also have to know how strong the association was: do 50% of bald men show a 50% increase in heart disease morbidity and mortality versus hairy men, or is the effect smaller, or larger? Merely saying that something is linked doesn't demonstrate that there is a strong correlation in the expected direction.
The second link features an argument from someone who deeply misunderstands evolution, thinks it must be purposeful, and that intermediate stages of the development of a trait offer no evolutionary advantage.
As I said, baldness may not be the product of sexual selection, or there may be something else directly selected for with baldness surviving merely by association. Anyone find any more intriguing studies?
posted by maudlin at 9:13 PM on August 16, 2007
Why must everything be justified in terms of evolution and natural selection?
some shit just happens.
Well right. And there is a tendency for people to look at something and then try to figure out how it evolved, when in fact it's all guesswork and there is no way to ever know if any 'theory' is actually correct.
posted by delmoi at 9:18 PM on August 16, 2007
some shit just happens.
Well right. And there is a tendency for people to look at something and then try to figure out how it evolved, when in fact it's all guesswork and there is no way to ever know if any 'theory' is actually correct.
posted by delmoi at 9:18 PM on August 16, 2007
Just because today's youth-oriented culture finds baldness unattractive, does not mean that it was always so, or that it will remain so in the future. I'd suggest that people shouldn't use current cultural trends as a yardstick to measure what is being selected for in human males. No evidence has been presented to actually show a negative selection for bald men at all.
posted by Ironmouth at 9:46 PM on August 16, 2007 [3 favorites]
posted by Ironmouth at 9:46 PM on August 16, 2007 [3 favorites]
The women were already pregnant by the time the men started going bald and it basically didn't matter.
Totally.
posted by lain at 9:47 PM on August 16, 2007
Totally.
posted by lain at 9:47 PM on August 16, 2007
And...I don't think that baldness would make surviving into maturity and successfully mate any more difficult for a human.
posted by lain at 10:00 PM on August 16, 2007
posted by lain at 10:00 PM on August 16, 2007
There's a study which suggests that some traits that are specific to one sex can be passed along and not driven out by natural selection due to the fact that the gene is carried by a person whose sex isn't affected by it.
So if a woman is carrying the baldness gene, she won't go bald, and will thus not be selected against. That gene may also have advantageous selection benefits for females.
You can read more in this recent Newsweek article
posted by stovenator at 10:22 PM on August 16, 2007
So if a woman is carrying the baldness gene, she won't go bald, and will thus not be selected against. That gene may also have advantageous selection benefits for females.
You can read more in this recent Newsweek article
posted by stovenator at 10:22 PM on August 16, 2007
When we addressed PMS six weeks or so ago, people threw out some similar "evolutionary just-so-stories", while others noted that not every trait conferred a benefit w/r/t evolution. I especially liked grouse's first response in that respect.
I know several people have said the gist of that here, but I thought the other thread might also shed some light.
posted by SuperNova at 11:33 PM on August 16, 2007
I know several people have said the gist of that here, but I thought the other thread might also shed some light.
posted by SuperNova at 11:33 PM on August 16, 2007
I think more interesting than the discussion of why men aren't universally head-hairy (in reality probably the majority are, and of course some women will prefer baldness, allowing the genes to have some outlet to get passed on), is why women continue (for the most part) to be attracted to head-hairyness, a trait that seems to have limited physiological value. Restated differently, the story of evolution from apes has us losing more and more body hair, so what confuses me is why head hair remains at all.
posted by njgo at 11:54 PM on August 16, 2007
posted by njgo at 11:54 PM on August 16, 2007
Stovenator is right, I think.
The gene for baldness is located on the X chromosome, and appears to be recessive in females, so that a woman will only display male pattern baldness if she has two copies of it, and even then only if she has a sufficient level of dihydrotestosterone (a metabolite of testosterone, and the hormone that most efficiently-- by a wide margin-- activates the gene), which is rare.
This effectively means it can only be selected against when borne by a male.
Which brings us to the question posed by njgo: why would females find it unattractive? The answer seems to me to be supplied by the Wikipedia article on male pattern baldness:
Sex hormone binding globulin, which is responsible for binding testosterone and preventing its bioavailability and conversion to DHT, is typically lower in individuals with high DHT. SHBG is downregulated by insulin.
Increased levels of Insulin Growth Factor-1 (IGF-1) have been correlated to vertex balding [5]
High insulin levels seem the likely link between metabolic syndrome and baldness. Low levels of SHBG in men and non-pregnant women are also correlated with glucose intolerance and diabetes risk, though this correlation disappears during pregnancy.
In other words, male pattern baldness indicates that you are likely to become diabetic, and displays the extent to which you have progressed toward that endpoint, and presumably that you are a risk to pass this highly unfavorable tendency along to any children you might sire.
Not terribly appealing.
posted by jamjam at 1:28 AM on August 17, 2007
The gene for baldness is located on the X chromosome, and appears to be recessive in females, so that a woman will only display male pattern baldness if she has two copies of it, and even then only if she has a sufficient level of dihydrotestosterone (a metabolite of testosterone, and the hormone that most efficiently-- by a wide margin-- activates the gene), which is rare.
This effectively means it can only be selected against when borne by a male.
Which brings us to the question posed by njgo: why would females find it unattractive? The answer seems to me to be supplied by the Wikipedia article on male pattern baldness:
Sex hormone binding globulin, which is responsible for binding testosterone and preventing its bioavailability and conversion to DHT, is typically lower in individuals with high DHT. SHBG is downregulated by insulin.
Increased levels of Insulin Growth Factor-1 (IGF-1) have been correlated to vertex balding [5]
High insulin levels seem the likely link between metabolic syndrome and baldness. Low levels of SHBG in men and non-pregnant women are also correlated with glucose intolerance and diabetes risk, though this correlation disappears during pregnancy.
In other words, male pattern baldness indicates that you are likely to become diabetic, and displays the extent to which you have progressed toward that endpoint, and presumably that you are a risk to pass this highly unfavorable tendency along to any children you might sire.
Not terribly appealing.
posted by jamjam at 1:28 AM on August 17, 2007
Where does this "Women don't fancy bald men" consensus come from? (perhaps from the makers of Rogaine?)
Baldness can be a very attractive trait.
posted by tiny crocodile at 2:55 AM on August 17, 2007
Baldness can be a very attractive trait.
posted by tiny crocodile at 2:55 AM on August 17, 2007
Balding is SUCH a desirable trait that I had a big bald spot tattooed on the back of my head. It's extremely realistic and garners me endless compliments.
(Shalin's book has some interesting discussion of this and other 'non-adaptive' traits, but falls apart towards the end when he employs a literary device that just does not work in that genre of book. Otherwise, the content is interesting and it's the first thing I have read that addresses non-adaptive traits at all.)
posted by FauxScot at 5:03 AM on August 17, 2007
(Shalin's book has some interesting discussion of this and other 'non-adaptive' traits, but falls apart towards the end when he employs a literary device that just does not work in that genre of book. Otherwise, the content is interesting and it's the first thing I have read that addresses non-adaptive traits at all.)
posted by FauxScot at 5:03 AM on August 17, 2007
It is worth noting that the development of maturity-related physical characteristics are found throughout primates. In terms of sexual selection, obvious maturity is a good indicator of genetic fitness because a mature individual has survived for multiple seasons, managing to evade all of the dangers posed by food scarcity, social conflict, parasites and disease, and predators.
That said, in regards to human beings, trying to perform the kinds of experiments that have been used to confirm sexual selection hypotheses would be ethically problematic.
posted by KirkJobSluder at 5:21 AM on August 17, 2007
That said, in regards to human beings, trying to perform the kinds of experiments that have been used to confirm sexual selection hypotheses would be ethically problematic.
posted by KirkJobSluder at 5:21 AM on August 17, 2007
Thanks to SuperNova for pointing out my previous comment on a similar question.
Asking why natural selection accounts for some phenotypic trait is really begging the question, because you haven't established that it is responsible for the trait in the first place. Coming up with just-so stories to explain natural selection when you haven't shown this is like coming up with a detailed biochemical explanation of how maggots spontaneously arise from rotting meat—since maggots don't arise spontaneously, your explanation is useless.
Sexual selection is merely a subset of natural selection. If you think of it as being fundamentally different from other forms of natural selection, then you need to consider that fitness in this context just means success at reproduction.
San Francisco surgeon Dr. Leonard Shlain figures that 8 percent of all men are either color blind, bald, left-handed or gay. Therefore, those traits must benefit the entire race -- or they would have died out by now.
No, no, no! That sort of thinking is totally wrong. Evolution is full of surviving deleterious traits, such as through genetic hitchhiking or genetic drift. This is why you shouldn't get your evolutionary biology from surgeons any more than you would get surgery from an evolutionary biologist.
posted by grouse at 5:53 AM on August 17, 2007 [4 favorites]
Asking why natural selection accounts for some phenotypic trait is really begging the question, because you haven't established that it is responsible for the trait in the first place. Coming up with just-so stories to explain natural selection when you haven't shown this is like coming up with a detailed biochemical explanation of how maggots spontaneously arise from rotting meat—since maggots don't arise spontaneously, your explanation is useless.
Sexual selection is merely a subset of natural selection. If you think of it as being fundamentally different from other forms of natural selection, then you need to consider that fitness in this context just means success at reproduction.
San Francisco surgeon Dr. Leonard Shlain figures that 8 percent of all men are either color blind, bald, left-handed or gay. Therefore, those traits must benefit the entire race -- or they would have died out by now.
No, no, no! That sort of thinking is totally wrong. Evolution is full of surviving deleterious traits, such as through genetic hitchhiking or genetic drift. This is why you shouldn't get your evolutionary biology from surgeons any more than you would get surgery from an evolutionary biologist.
posted by grouse at 5:53 AM on August 17, 2007 [4 favorites]
The gene for baldness is carried by women. Therefore, it doesn't matter how well hirsute men do in the dating game, because the baldness is still passed on.
posted by orange swan at 6:03 AM on August 17, 2007
posted by orange swan at 6:03 AM on August 17, 2007
It could be that what provoke baldness in later life has other, more positive effects in earlier life, when humans usually reproduce.
Eunuchs, who have reduced hormone levels, rarely go bald. Those who benefit from testosterone during their reproductive age get baldness in exchange when they're older.
posted by stereo at 6:07 AM on August 17, 2007
Eunuchs, who have reduced hormone levels, rarely go bald. Those who benefit from testosterone during their reproductive age get baldness in exchange when they're older.
posted by stereo at 6:07 AM on August 17, 2007
A couple random points to throw out:
1. For most of the history of the human animal, people had a lifespan of about 30, and probably started reproducing when they were about 15. So it's entirely reasonable to say that men were passing along their MPB genes before they manifested MPB. Back then, a woman looking at potential mates probably couldn't even look at a guy's father to see if he had MPB and would have passed that along to his son.
Men with the MBP gene are having children before they manifest MPB in modern times as well, even though the average ages of fathers has gone up a lot.
2. One possibility I don't think I've seen mentioned yet is that MPB has no particular advantage of its own, but it is genetically tied to a seemingly unrelated trait that is beneficial (perhaps resistance to a disease or something like that).
posted by adamrice at 6:16 AM on August 17, 2007
1. For most of the history of the human animal, people had a lifespan of about 30, and probably started reproducing when they were about 15. So it's entirely reasonable to say that men were passing along their MPB genes before they manifested MPB. Back then, a woman looking at potential mates probably couldn't even look at a guy's father to see if he had MPB and would have passed that along to his son.
Men with the MBP gene are having children before they manifest MPB in modern times as well, even though the average ages of fathers has gone up a lot.
2. One possibility I don't think I've seen mentioned yet is that MPB has no particular advantage of its own, but it is genetically tied to a seemingly unrelated trait that is beneficial (perhaps resistance to a disease or something like that).
posted by adamrice at 6:16 AM on August 17, 2007
The gene for baldness is carried by women. Therefore, it doesn't matter how well hirsute men do in the dating game, because the baldness is still passed on.
I'm sorry, but that can't be right either. If that principle were true, then natural selection could not act on any phenotype that were only visible in one sex, unless the responsible gene was on a chromosome passed down by only one sex. That would mean that natural selection does not act on female traits expressed by nuclear genes, which would result in some seriously unfit women.
We can also do a thought experiment to disprove this. Say the allele for male pattern baldness were so deleterious that men with it could not reproduce at all. We'll also assume that every individual has so many offspring to eliminate the effects of variance. Let's start with a female carrier and a male without the allele (because otherwise he wouldn't be able to reproduce). They have four children, a male with each allele and a female with each allele. Only 1/3 of the reproducing organisms from this generation have the deleterious allele. Mate the females against the male, and the next generation only 1/7 of the reproducing organisms will have the deleterious allele. It will keep shrinking each population.
Now surely the effect is reduced, as if the gene prevented reproduction for any carrier, then it wouldn't have survived the parental generation. But natural selection can still act on sex-linked genes.
One possibility I don't think I've seen mentioned yet is that MPB has no particular advantage of its own, but it is genetically tied to a seemingly unrelated trait that is beneficial
That's what I meant when I referred to genetic hitchhiking.
posted by grouse at 6:37 AM on August 17, 2007
I'm sorry, but that can't be right either. If that principle were true, then natural selection could not act on any phenotype that were only visible in one sex, unless the responsible gene was on a chromosome passed down by only one sex. That would mean that natural selection does not act on female traits expressed by nuclear genes, which would result in some seriously unfit women.
We can also do a thought experiment to disprove this. Say the allele for male pattern baldness were so deleterious that men with it could not reproduce at all. We'll also assume that every individual has so many offspring to eliminate the effects of variance. Let's start with a female carrier and a male without the allele (because otherwise he wouldn't be able to reproduce). They have four children, a male with each allele and a female with each allele. Only 1/3 of the reproducing organisms from this generation have the deleterious allele. Mate the females against the male, and the next generation only 1/7 of the reproducing organisms will have the deleterious allele. It will keep shrinking each population.
Now surely the effect is reduced, as if the gene prevented reproduction for any carrier, then it wouldn't have survived the parental generation. But natural selection can still act on sex-linked genes.
One possibility I don't think I've seen mentioned yet is that MPB has no particular advantage of its own, but it is genetically tied to a seemingly unrelated trait that is beneficial
That's what I meant when I referred to genetic hitchhiking.
posted by grouse at 6:37 AM on August 17, 2007
There may be one or more genes associated with MPB that are carried only by women, but the literature suggests that the genetic link may be more complicated:
Male pattern balding is a common androgen-dependent trait. The frequency of balding in the population increases with age but not all men develop balding even in old age. It is well-known that balding tends to run in families but the nature of the underlying genetic predisposition and the mode of inheritance are unknown. In this study we examined scalp hair status across a wide age range in 572 men and took family histories of balding in first degree male relatives. The results confirmed that there is an increased frequency of balding in the fathers of young bald men and a high relative risk of balding in young subjects with a balding father but these effects declined with increasing subject age. In contrast, there was a pronounced increase in the frequency of non-balding in the fathers of non-bald elderly subjects and an increased relative risk of non-balding in elderly subjects with a non-bald father, which were not evident in younger subjects. Analysis of the frequencies of balding and non-balding in the brothers of balding and non-balding elderly men, categorised by paternal hair status, failed to show that either balding or non-balding is due to the action of a single gene. Nevertheless, our results indicate that there is a genetic influence on balding in young men and on non-balding in elderly men. It is possible that the same genes are responsible for determining predisposition to balding and to non-balding but, at this stage, we cannot assume that this is necessarily the case. Genetic analysis of balding in young men is complicated by the fact that the destiny of hair status in non-bald siblings is unknown. This difficulty is partly overcome by studying non-balding in elderly men where balding and non-balding in similarly aged siblings are more fully expressed, which may make this age group a better target for future studies in this field.
Note that this study apparently didn't look for MPB in the family history of closely related women, so it's still possible that the average guy's maternal ancestors are a better predictor of MPB than his paternal ancestors.
On preview: adamrice, I mentioned that MPB might be a trait surviving because it's associated with another trait that is directly being selected.
And as delmoi said, we can spin any number of plausible stories, but in this case, at least, there are no solid answers. There may never be a good answer. But there are some highly plausible explanations for such issues as the survival of sickle cell anemia, where sickle cell trait (not full blown sickle cell disease) is selected for in areas with endemic malaria, so I wouldn't discount all attempts to discover why a given trait may survive in a population.
Back to the M&C study: it's possible that the women's expressed preferences for bald men could make MPB somewhat more prevalent than it would be otherwise, but preferences could vary across sub-populations or across time, or preferences could be irrelevant if most women have chosen the fathers of their children by the time MPB becomes evident. (But I disagree with adamrice about the life expectancy of 30 being a factor. That number is one of several thrown out there for mean life expectancy at birth, and is so low because of the historical high rates of infant mortality. Many of our ancestors who survived to adulthood grew to be very old, indeed.)
posted by maudlin at 6:42 AM on August 17, 2007
Male pattern balding is a common androgen-dependent trait. The frequency of balding in the population increases with age but not all men develop balding even in old age. It is well-known that balding tends to run in families but the nature of the underlying genetic predisposition and the mode of inheritance are unknown. In this study we examined scalp hair status across a wide age range in 572 men and took family histories of balding in first degree male relatives. The results confirmed that there is an increased frequency of balding in the fathers of young bald men and a high relative risk of balding in young subjects with a balding father but these effects declined with increasing subject age. In contrast, there was a pronounced increase in the frequency of non-balding in the fathers of non-bald elderly subjects and an increased relative risk of non-balding in elderly subjects with a non-bald father, which were not evident in younger subjects. Analysis of the frequencies of balding and non-balding in the brothers of balding and non-balding elderly men, categorised by paternal hair status, failed to show that either balding or non-balding is due to the action of a single gene. Nevertheless, our results indicate that there is a genetic influence on balding in young men and on non-balding in elderly men. It is possible that the same genes are responsible for determining predisposition to balding and to non-balding but, at this stage, we cannot assume that this is necessarily the case. Genetic analysis of balding in young men is complicated by the fact that the destiny of hair status in non-bald siblings is unknown. This difficulty is partly overcome by studying non-balding in elderly men where balding and non-balding in similarly aged siblings are more fully expressed, which may make this age group a better target for future studies in this field.
Note that this study apparently didn't look for MPB in the family history of closely related women, so it's still possible that the average guy's maternal ancestors are a better predictor of MPB than his paternal ancestors.
On preview: adamrice, I mentioned that MPB might be a trait surviving because it's associated with another trait that is directly being selected.
And as delmoi said, we can spin any number of plausible stories, but in this case, at least, there are no solid answers. There may never be a good answer. But there are some highly plausible explanations for such issues as the survival of sickle cell anemia, where sickle cell trait (not full blown sickle cell disease) is selected for in areas with endemic malaria, so I wouldn't discount all attempts to discover why a given trait may survive in a population.
Back to the M&C study: it's possible that the women's expressed preferences for bald men could make MPB somewhat more prevalent than it would be otherwise, but preferences could vary across sub-populations or across time, or preferences could be irrelevant if most women have chosen the fathers of their children by the time MPB becomes evident. (But I disagree with adamrice about the life expectancy of 30 being a factor. That number is one of several thrown out there for mean life expectancy at birth, and is so low because of the historical high rates of infant mortality. Many of our ancestors who survived to adulthood grew to be very old, indeed.)
posted by maudlin at 6:42 AM on August 17, 2007
OK, my opinion of "very old" may not be considered all that trustworthy by Frankie Valli fans.
This Wikipedia article, citing the 1961 Britannica, is the best quick reference I can find. Note that the Upper Paleolithic life expectancy at birth of 33 is accompanied by an estimate of an additional 39 years at age 15, making the mean life expectancy for a teenager 54 years total, a point at which MPB should be evident if it's going to happen at all. But most of the figures in that table are for life expectancy at birth, which can be misleading when you're trying to figure out how many people made it to their 50s or 60s (which is not really old, I swear!) Anyway, figuring out past life expectancy is a lot trickier than many people think.
posted by maudlin at 6:51 AM on August 17, 2007
This Wikipedia article, citing the 1961 Britannica, is the best quick reference I can find. Note that the Upper Paleolithic life expectancy at birth of 33 is accompanied by an estimate of an additional 39 years at age 15, making the mean life expectancy for a teenager 54 years total, a point at which MPB should be evident if it's going to happen at all. But most of the figures in that table are for life expectancy at birth, which can be misleading when you're trying to figure out how many people made it to their 50s or 60s (which is not really old, I swear!) Anyway, figuring out past life expectancy is a lot trickier than many people think.
posted by maudlin at 6:51 AM on August 17, 2007
Ha. I love the fact that a MALE sign of aging would be given a positive spin by the evolutionary biologists and their lay enthusiasts here. Seems to be more an indication of currently reigning gender norms than anything else. I seriously doubt that anyone would try to characterize female signs of aging (wrinkles, sagging, whatever) as positively selected.
posted by footnote at 6:56 AM on August 17, 2007 [1 favorite]
posted by footnote at 6:56 AM on August 17, 2007 [1 favorite]
I love the fact that a MALE sign of aging would be given a positive spin by the evolutionary biologists and their lay enthusiasts here.
"The evolutionary biologists" have done no such thing. As far as I know, I'm the only evolutionary biologist here and I have repeatedly pointed out the lack of evidence that male pattern baldness today is due to adaptive selection.
The authors of the paper maudlin refers to are not biologists, but psychologists. The assumptions of their discipline have repeatedly been attacked by evolutionary biologists.
posted by grouse at 7:30 AM on August 17, 2007
"The evolutionary biologists" have done no such thing. As far as I know, I'm the only evolutionary biologist here and I have repeatedly pointed out the lack of evidence that male pattern baldness today is due to adaptive selection.
The authors of the paper maudlin refers to are not biologists, but psychologists. The assumptions of their discipline have repeatedly been attacked by evolutionary biologists.
posted by grouse at 7:30 AM on August 17, 2007
@footnote- my sense is that MPB is not a sign of aging, but rather a genetic trait that sometimes/often appears late in life (Different from other non-MBP balding). This is as opposed to the characteristics you mentioned (sagging, wrinkles) which are not genetically dictated, but results of longevity. Such traits will basically arise after reproduction-age, and so be basically irrelevant in the mating game/genetic evolution story.
Hopefully a more science-savvy person can correct me if I'm off-base on this
posted by prophetsearcher at 7:35 AM on August 17, 2007 [1 favorite]
Hopefully a more science-savvy person can correct me if I'm off-base on this
posted by prophetsearcher at 7:35 AM on August 17, 2007 [1 favorite]
thanks for the clarification grouse! makes me even more convinced it's spin based on gender norms.
posted by footnote at 7:42 AM on August 17, 2007
posted by footnote at 7:42 AM on August 17, 2007
Evolution by natural selection doesn't mean that there's a good reason for every trait that survives. It just means there hasn't been enough selection against the trait (through the organisms expressing it dying before they can reproduce, whether by dying young or by not successfully finding mates and having young that survive to reproduce themselves) for it to die out.
We're a young species and haven't changed much from earlier humans that didn't live to what we now call middle-age. So there's little reason to expect a trait related to age to have been selected for.
posted by Zed_Lopez at 10:27 AM on August 17, 2007 [1 favorite]
We're a young species and haven't changed much from earlier humans that didn't live to what we now call middle-age. So there's little reason to expect a trait related to age to have been selected for.
posted by Zed_Lopez at 10:27 AM on August 17, 2007 [1 favorite]
Balding like gray hair is a sign of age and naturally occurs late in life. In many males it can be premature to give a false indication of wisdom and maturity. In religion monks often shave or partially shave their heads presumable in part to appear older and wiser.
Silverback gorillas use graying as a sign of maturity. People often go gray before they are really old, but often the graying mostly happens in highly visible areas - temples, beard, chest hair while less normally visible hair such as pubic hair retains it color.
posted by MonkeySaltedNuts at 11:25 AM on August 17, 2007
Silverback gorillas use graying as a sign of maturity. People often go gray before they are really old, but often the graying mostly happens in highly visible areas - temples, beard, chest hair while less normally visible hair such as pubic hair retains it color.
posted by MonkeySaltedNuts at 11:25 AM on August 17, 2007
I think there is a very interesting larger picture here.
Male pattern baldness (in this hypothetical view) is a genetically determined trait which is not very deleterious in itself, but points to another genetically determined trait which is quite deleterious.
The deleterious trait occurs in both males and females, but the indicator trait is only seen in males.
By choosing to avoid bearing children of men who have male pattern baldness (the end result of finding it unattractive), an individual woman improves her odds of having healthy immediate offspring, and gives herself an improved chance of having a dramatically more sexually attractive grandson.
When females in a given population tend to choose not to mate with males who display the indicator trait, male pattern baldness in this case, that has the effect of reducing the incidence of the much more unfavorable trait in the next generation below what it would have been if the indicator trait did not exist.
posted by jamjam at 1:18 PM on August 17, 2007
Male pattern baldness (in this hypothetical view) is a genetically determined trait which is not very deleterious in itself, but points to another genetically determined trait which is quite deleterious.
The deleterious trait occurs in both males and females, but the indicator trait is only seen in males.
By choosing to avoid bearing children of men who have male pattern baldness (the end result of finding it unattractive), an individual woman improves her odds of having healthy immediate offspring, and gives herself an improved chance of having a dramatically more sexually attractive grandson.
When females in a given population tend to choose not to mate with males who display the indicator trait, male pattern baldness in this case, that has the effect of reducing the incidence of the much more unfavorable trait in the next generation below what it would have been if the indicator trait did not exist.
posted by jamjam at 1:18 PM on August 17, 2007
Ach... Can't seem to find it now that I'm looking for it, but my (bald) father sent me a link to a study that correlated MPB with higher testosterone levels. As he's such a shag that his shirts don't touch his skin, I'm willing to entertain the theory.
posted by klangklangston at 1:58 PM on August 17, 2007
posted by klangklangston at 1:58 PM on August 17, 2007
Best answer: I think there is a very interesting larger picture here.
The larger picture is that there's no evidence that natural selection has anything to do with male pattern baldness.
Furthermore, you keep positing in your explanations that women find baldness unattractive. But many women do not find baldness unattractive. Of those that do there is no evidence that they are doing so due to genetic programming rather than cultural influence.
posted by grouse at 2:13 PM on August 17, 2007
The larger picture is that there's no evidence that natural selection has anything to do with male pattern baldness.
Furthermore, you keep positing in your explanations that women find baldness unattractive. But many women do not find baldness unattractive. Of those that do there is no evidence that they are doing so due to genetic programming rather than cultural influence.
posted by grouse at 2:13 PM on August 17, 2007
Furthermore, you keep positing in your explanations that women find baldness unattractive.
Putative cures and preventatives for male pattern baldness are large enterprises over much of the world, grouse, and have been for some time. The pitches for these products are almost always implicitly or explicitly put in terms of improving or maintaining sexual attractiveness to women.
This alone constitutes very strong evidence that male pattern baldness tends to reduce a man's attractiveness to women, and everything I know from my own personal experience is consonant with this.
Therefore, it is by far the most reasonable presupposition upon which to base an argument.
That you are apparently unwilling or unable to see this very plainly visible evidence ought to be taken into account by anyone who is wondering how much weight to give your views, in my opinion.
posted by jamjam at 2:43 PM on August 17, 2007
Putative cures and preventatives for male pattern baldness are large enterprises over much of the world, grouse, and have been for some time. The pitches for these products are almost always implicitly or explicitly put in terms of improving or maintaining sexual attractiveness to women.
This alone constitutes very strong evidence that male pattern baldness tends to reduce a man's attractiveness to women, and everything I know from my own personal experience is consonant with this.
Therefore, it is by far the most reasonable presupposition upon which to base an argument.
That you are apparently unwilling or unable to see this very plainly visible evidence ought to be taken into account by anyone who is wondering how much weight to give your views, in my opinion.
posted by jamjam at 2:43 PM on August 17, 2007
"This alone constitutes very strong evidence that male pattern baldness tends to reduce a man's attractiveness to women, and everything I know from my own personal experience is consonant with this."
No, it doesn't. It constitutes very strong evidence that men are insecure about their hair, especially vis a vis women.
posted by klangklangston at 3:20 PM on August 17, 2007
No, it doesn't. It constitutes very strong evidence that men are insecure about their hair, especially vis a vis women.
posted by klangklangston at 3:20 PM on August 17, 2007
That you are apparently unwilling or unable to see this very plainly visible evidence ought to be taken into account by anyone who is wondering how much weight to give your views, in my opinion.
I would have hoped that the years I have worked on developing methods for identifying natural selection in humans and my peer-reviewed articles in the scientific literature would be taken into account more than my unwillingness to consider facile arguments regarding the sale of hair loss products during a period that is inconsequential in human evolution. But maybe I expect too much.
I said that many women do not find baldness unattractive. And the study maudlin refers to finds that women consider bald men to have traits other than attractiveness which are desirable. But of course, many women also do find baldness unattractive.
But even if almost every woman today found baldness unattractive (which is untrue) it wouldn't matter that much. Considering the marked variation in ideals of human attractiveness over different cultures and history, it is dangerous to extrapolate to evolutionary timescales. Keep in mind that the most recent time period in which selection has been observed in humans so far is about 7,000 years and that is exceptional.
Even beyond all that, even if you had a time machine and could use it to determine that bald men have been considered unattractive for millions of years, you still would need to find evidence that this aspect of phenotype alone induced selective pressure on human evolution such that it was reduced but not eliminated.
Some people here are suggesting just-so stories about how baldness's maladaptiveness influenced human evolution while others suggest just-so stories about how it is actually cryptically adaptive. This alone underscores the point I keep trying to make: you need to find the evidence that selection on a trait meaningfully affected evolution, and in which direction before starting to explain how.
posted by grouse at 3:52 PM on August 17, 2007 [2 favorites]
I would have hoped that the years I have worked on developing methods for identifying natural selection in humans and my peer-reviewed articles in the scientific literature would be taken into account more than my unwillingness to consider facile arguments regarding the sale of hair loss products during a period that is inconsequential in human evolution. But maybe I expect too much.
I said that many women do not find baldness unattractive. And the study maudlin refers to finds that women consider bald men to have traits other than attractiveness which are desirable. But of course, many women also do find baldness unattractive.
But even if almost every woman today found baldness unattractive (which is untrue) it wouldn't matter that much. Considering the marked variation in ideals of human attractiveness over different cultures and history, it is dangerous to extrapolate to evolutionary timescales. Keep in mind that the most recent time period in which selection has been observed in humans so far is about 7,000 years and that is exceptional.
Even beyond all that, even if you had a time machine and could use it to determine that bald men have been considered unattractive for millions of years, you still would need to find evidence that this aspect of phenotype alone induced selective pressure on human evolution such that it was reduced but not eliminated.
Some people here are suggesting just-so stories about how baldness's maladaptiveness influenced human evolution while others suggest just-so stories about how it is actually cryptically adaptive. This alone underscores the point I keep trying to make: you need to find the evidence that selection on a trait meaningfully affected evolution, and in which direction before starting to explain how.
posted by grouse at 3:52 PM on August 17, 2007 [2 favorites]
I said that many women do not find baldness unattractive. And the study maudlin refers to finds that women consider bald men to have traits other than attractiveness which are desirable. But of course, many women also do find baldness unattractive.
This statement would be perfectly true if, say, 10 million women (sexually mature females) found baldness in men attractive, and the other ~1.49 billion found it unattractive, all other things being equal (this necessary proviso would seem to limit the relevance of the study to which maudlin refers to the present argument, if I may rely on your statement here of its findings, by the way).
If your claim is that male pattern baldness has mainly a positive or a neutral impact upon a man's attractiveness to potential female mates, all other things being equal, or that we do not at present have enough information to form a reasonable opinion as to what MPBs impact on attractiveness might be at this moment and in the relatively recent past, please feel free to come right out and say so rather than continuing to use such ambiguous language; if you agree that on the whole, the impact on a man's attractiveness is negative, I would appreciate knowing that, as well.
Considering the marked variation in ideals of human attractiveness over different cultures and history, it is dangerous to extrapolate to evolutionary timescales.
I believe this to be true; however, in the case of body fat in women, for example, we have good evidence of marked swings in preferences. I know of no such evidence of swings in the case of male pattern baldness. In the absence of such evidence, and given the apparent bias against it in the periods for which we do have evidence, in a range of societies, if extrapolation to evolutionary timescales is to be made, I think it is most reasonable to cautiously assume that it has been unattractive, especially since we see from parallels with other primates, that MPB was probably at least present.
Keep in mind that the most recent time period in which selection has been observed in humans so far is about 7,000 years and that is exceptional.
Are you referring to lactose tolerance? Many plausible arguments are now being made for strong selection by the black death in Europe and by smallpox in the Americas much more recently, but as I said in my first post to this thread, I think diabetes type II and metabolic syndrome are driving the bias against MPB. Animal studies tend to indicate diabetes is and has been a problem all across the mammals. I also think we are observing many strong selections in human populations right now. For example, sub-Saharan Africans are currently being selected for resistance to the AIDS virus.
I would have hoped that the years I have worked on developing methods for identifying natural selection in humans and my peer-reviewed articles in the scientific literature would be taken into account more than my unwillingness to consider facile arguments regarding the sale of hair loss products during a period that is inconsequential in human evolution. But maybe I expect too much.
If you expect to prevail by the weight of your authority rather than the cogency of your arguments, you do indeed expect too much.
posted by jamjam at 6:42 PM on August 17, 2007
This statement would be perfectly true if, say, 10 million women (sexually mature females) found baldness in men attractive, and the other ~1.49 billion found it unattractive, all other things being equal (this necessary proviso would seem to limit the relevance of the study to which maudlin refers to the present argument, if I may rely on your statement here of its findings, by the way).
If your claim is that male pattern baldness has mainly a positive or a neutral impact upon a man's attractiveness to potential female mates, all other things being equal, or that we do not at present have enough information to form a reasonable opinion as to what MPBs impact on attractiveness might be at this moment and in the relatively recent past, please feel free to come right out and say so rather than continuing to use such ambiguous language; if you agree that on the whole, the impact on a man's attractiveness is negative, I would appreciate knowing that, as well.
Considering the marked variation in ideals of human attractiveness over different cultures and history, it is dangerous to extrapolate to evolutionary timescales.
I believe this to be true; however, in the case of body fat in women, for example, we have good evidence of marked swings in preferences. I know of no such evidence of swings in the case of male pattern baldness. In the absence of such evidence, and given the apparent bias against it in the periods for which we do have evidence, in a range of societies, if extrapolation to evolutionary timescales is to be made, I think it is most reasonable to cautiously assume that it has been unattractive, especially since we see from parallels with other primates, that MPB was probably at least present.
Keep in mind that the most recent time period in which selection has been observed in humans so far is about 7,000 years and that is exceptional.
Are you referring to lactose tolerance? Many plausible arguments are now being made for strong selection by the black death in Europe and by smallpox in the Americas much more recently, but as I said in my first post to this thread, I think diabetes type II and metabolic syndrome are driving the bias against MPB. Animal studies tend to indicate diabetes is and has been a problem all across the mammals. I also think we are observing many strong selections in human populations right now. For example, sub-Saharan Africans are currently being selected for resistance to the AIDS virus.
I would have hoped that the years I have worked on developing methods for identifying natural selection in humans and my peer-reviewed articles in the scientific literature would be taken into account more than my unwillingness to consider facile arguments regarding the sale of hair loss products during a period that is inconsequential in human evolution. But maybe I expect too much.
If you expect to prevail by the weight of your authority rather than the cogency of your arguments, you do indeed expect too much.
posted by jamjam at 6:42 PM on August 17, 2007
"If you expect to prevail by the weight of your authority rather than the cogency of your arguments, you do indeed expect too much."
It's a shame, then, that you prevail on neither.
posted by klangklangston at 7:03 PM on August 17, 2007
It's a shame, then, that you prevail on neither.
posted by klangklangston at 7:03 PM on August 17, 2007
jamjam: My claim is that there is no evidence that sexual selection for or against male pattern baldness has had a significant influence on human evolution. I hope that is unambiguous enough.
Are you referring to lactose tolerance?
Yes.
Many plausible arguments are now being made for strong selection by the black death in Europe and by smallpox in the Americas much more recently
Those arguments were made before the availability of genome-wide data on human polymorphisms. Now that we have the data, it is not consistent with positive selection.
If you expect to prevail by the weight of your authority rather than the cogency of your arguments, you do indeed expect too much.
I'm less interested in arguments and more in science. Science relies first on data, and the arguments come only afterwards. Especially when it comes to evolution people are too interested in making "plausible arguments" to explain phenomena that have not been observed. You need to get the data, and then you can start explaining.
But if you're going to question my credibility because I don't agree with your hair loss product argument, you're damn right I'm going to bring out my credentials. If you think they are irrelevant, you can ignore them.
posted by grouse at 7:41 PM on August 17, 2007
Are you referring to lactose tolerance?
Yes.
Many plausible arguments are now being made for strong selection by the black death in Europe and by smallpox in the Americas much more recently
Those arguments were made before the availability of genome-wide data on human polymorphisms. Now that we have the data, it is not consistent with positive selection.
If you expect to prevail by the weight of your authority rather than the cogency of your arguments, you do indeed expect too much.
I'm less interested in arguments and more in science. Science relies first on data, and the arguments come only afterwards. Especially when it comes to evolution people are too interested in making "plausible arguments" to explain phenomena that have not been observed. You need to get the data, and then you can start explaining.
But if you're going to question my credibility because I don't agree with your hair loss product argument, you're damn right I'm going to bring out my credentials. If you think they are irrelevant, you can ignore them.
posted by grouse at 7:41 PM on August 17, 2007
Grouse has got it. For example, fatness was hot in women and men in old times because it said you were rich enough to eat as much as you wanted. That's how we have rubenesque women figures in painting.
Grouse is looking for scientific evidence. He sees this question as a scientific one. Frankly, the best answer for the question is scientific and he is right in pointing out that there are no evolutionary studies regarding baldness. Most of the psych studies are done on young females who sign up for the experiments as a requirement of taking Psych 101 in college.
The other people are asking a simpler question--"How come chicks don't dig bald dudes but there are still bald dudes around?"
The answer probably is that bald dudes are dug.
posted by Ironmouth at 8:32 AM on August 18, 2007
Grouse is looking for scientific evidence. He sees this question as a scientific one. Frankly, the best answer for the question is scientific and he is right in pointing out that there are no evolutionary studies regarding baldness. Most of the psych studies are done on young females who sign up for the experiments as a requirement of taking Psych 101 in college.
The other people are asking a simpler question--"How come chicks don't dig bald dudes but there are still bald dudes around?"
The answer probably is that bald dudes are dug.
posted by Ironmouth at 8:32 AM on August 18, 2007
This thread is closed to new comments.
posted by Large Marge at 8:35 PM on August 16, 2007