The author fails to mention what is probably the largest downside to sex: an entire half of the population is completely unable to reproduce. The question "why do we have sex?" could be restated as "why do males exist?"
Unfortunately the answers to that question trouble some people so it's difficult to establish the truth. The simple answer comes down to the fact that a species has to find a balance between maintaining genetic diversity, which is important for resilience and adaptation, and maintaining a strong breeding population. Males are there to allow some really wacky variations to exist that just wouldn't be viable in females. It only takes a tiny handful of males to take part in reproduction, but it takes essentially all females (especially considering they are only 50% of the population to begin with).
I get what you're saying, but I think facts suggest that this isn't downside with significant impact. Populations seem to grow just fine in all sexually reproducing species as long as conditions are ok.
Even some of the poorest countries have very high fertility rates, as high as 6-7 births per female, so availability of women is not an issue.
> The simple answer comes down to the fact that a species has to find a balance between maintaining genetic diversity, which is important for resilience and adaptation, and maintaining a strong breeding population.
> the basic fact that males have more diverse expression
Not to be a jerk, but you guys are just throwing out this stuff without backing it up and it's not at all self-evident to me. How are males more diverse?
Kind of feels like a big reason why this stuff is touchy is cause we're just saying things without having evidence for it, so yeah, there's not a lot of common ground to discuss.
The Y chromosome only codes for 55 genes, while the X chromosome codes for 900 genes [1].
The Y chromosome self-evidently doesn't contain genes necessary for basic survival, because females don't have it.
Males have only one X chromosome.
Each cell in a human female has one X chromosome fully active and another one partially active [2], which means their phenotype, as far at it depends on the X chromosome, has lower variance because of partial averaging.
This isn’t about sex chromosomes, we have 1000’s of genes that are sex-biased this means that their expression is dependent on sex.
The level of bias isn’t even solely dependent on the gene in question but on much more complex mechanisms that are frankly not well understood for example in humans testicles and mammary glands have some of the highest levels of sex biased expression in of all tissues. Other tissues like brain, heart and muscles also have variance but to overall lower levels (higher brain tissue expression variance in males for example has been linked to higher likelihood of schizophrenia and other mental conditions).
Overall males it seems that there is a higher variances of sex biased gene expression in various tissues compared to females.
This means that it goes beyond we have a backup X chromosome and gene deactivation escape mechanisms.
Gene expression variance can explain why males might a higher overall variance in traits.
The existence of those mechanisms doesn't mean the increased variance from only one X chromosome disappears - for males to have equal variance the increase from just one X would have to be compensated somehow, which is probably impossible given how directly important X is - the needed information is gone.
What I’m saying is that genetic variance and gene expression variance aren’t the same thing.
In fact in males there is a phenomenon that is called feminization of gene expression where by removing sexual competition causes gene feminization in males causing the population to more favorably express female bias.
I can’t find the study now but similar results have been reported in humans especially in sperm and testicular tissue that begin experiencing gene expression feminization rather quickly in monogamous relationships.
Colour vision being the classic example of something preserved or enhanced in females due to coding on the X chromosome. This helps women, for the most part, completely avoid red-green colourblindness.
Coincidentally when searching to make sure I wasn't saying this the wrong way around, I was presented with this weird sexist propaganda[0] that only works because of the weird way people tend to think about these facts: you only acknowledge it if you can make it sound like women are better at everything and make no tradeoffs.
Greater male variance in humans has nothing to do with the article, or general discussion about the evolutionary benefits of sexual reproduction, because what's true of some categories of animal, like mammals, is not true of birds and other animals (whose sex chromosomes work differently -- female birds have greater variance, last I checked).
Currently on mobile so won't be able to post much.
To focus on one particular subset of this, recent research seems to indicate pretty conclusively that there is greater variability of (certain aspects of) intelligence among men than among women.
The reasons for this are poorly understood.
Is it genetic differences? Are boys and girls encouraged to investigate different things? Is it a limitation of our testing methods?
We aren't entirely sure yet so it's hard for people on either side to claim any complete understanding or provide a definitive answer.
Yeah, we should be able to discuss topics like this without pearl clutching and the only way to really do that is with actual facts supported by evidence.
I appreciate you providing that information, really.
Isn't it a common known fact that while average IQ is the same for males and females, male IQ varies more and hence there are more male idiots as well as more male geniuses?
I'm sure you can google the IQ variance stuff.
I'm also willing to bet the height distribution, libido, interest in hobbies, single-mindedness vary a lot more in males than in females.
Politically correctness aside, wouldn't it make perfect sense that the sex that produces more gametes in a day than whole countries of opposite sex in their entire lifetimes would be the sex with more variance in any kind of feature because the potential rewards for taking a genetic risk could also pay a lot more than for the other sex?
> Isn't it a common known fact that while average IQ is the same for males and females, male IQ varies more and hence there are more male idiots as well as more male geniuses?
I had heard this as a kid, but I haven’t seen anything to back it up recently that didn’t turn out to be wishful thinking by the author/reposter.
> wouldn't it make perfect sense that the sex that produces more gametes in a day than whole countries of opposite sex in their entire lifetimes would be the sex with more variance in any kind of feature because the potential rewards for taking a genetic risk could also pay a lot more than for the other sex?
I don’t see why the number of gametes is relevant, as the average number of viable offspring is necessarily the same.
If you have a person with $2 billion dollars, and then 1000 people with $100,000, they have an average wealth of $2.1 million, but the average really fails to capture the dynamic.
This should hold for males, and I can see it making the number of gametes relevant. Historically, 80% of women and 40% of men have reproduced. In terms of reproduction, a woman could have maybe 20 children if they usually had twins or something. If a male wins big, like Genghis Khan, they might literally manage thousands.
I mean, it really doesn't seem like a stretch to see different selection pressures on males and the Y chromosome.
> In general, most researchers have failed to find greater variability in either sex in any area that is consistent across cultures and not confounded by social factors.
So it is saying we haven't been able to isolate the extent of the social impact. But this applies to so many things. Do we have research that shows that most people are heterosexual that is consistent across culture and not confounded by social factors? No, we don't. There have historically been cultures where the view on sexuality, what constitutes sex, and how sex is viewed are so different than we cannot say that our current split of people's orientation is based only on biology.
But, this sort of disclaimer is not being equally applied because it would apply all psychology and sociology research. We have a few examples of research that shows just how extreme the social impact can be, but we don't understand impact enough to account for it.
Is it good science if the standards research are held to are not consistent depending upon the topic?
> I don’t see why the number of gametes is relevant, as the average number of viable offspring is necessarily the same.
Biologically, there are usually a complex history of reasons for an exhibited trait. It's important to remember tha sperm carry either a Y OR X gene expression, which inherently leads to more variability.
So, the question implied by your casual comment is, what is the purpose of the multitude of sperm?
Is a multitude of sperm an evolutionary dead end (inefficiency)? Maybe, but there's no going back. The sperm faces quite a bit of natural resistance along it's fertilization journey. It's necessary, probably along the lines of the morphologically convoluted duck penises.
Is a multitude of sperm otherwise useful? Yes. It ensures a limit to the number of variations that can be passed on. If there are too many variations maybe the flagella will not be as efficient and loses to competition. -https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4242561/
Doss this directly contradict the idea of males having more variability? (posed by the previous paper). No. There are also environmental conditions (including seminal fluid involvement), temperature and the male/female bodies. Ovum are subjected to and less affected by environment than sperm, which likely is the source of greater variation overall. -https://jeb.biologists.org/content/218/1/107
There is also the nature of the disposability of sperm and the likelihood that there is less strict quality control, for a lack of better term, since competition solves inefficiencies on production quality. I could find nothing that indicates that this is a specific topic of study.
> So, the question implied by your casual comment is, what is the purpose of the multitude of sperm?
Rather, I am asking why to expect the number of gametes to be more relevant than the number of viable offspring when considering genetic diversity.
Exactly three of the $big_num of sperm my father’s body created led to offspring. Likewise exactly three of my mother’s eggs. Gamete_father >> Gamete_mother is true, but does not appear important in this specific regard.
I accept the other reasons you give for there being lots of sperm cells, but it’s answering a different question :)
Also the expression of neuro-diversity is usually more severe (do not have a linke for that one).
While we are at it, can we talk about the loop deformation, too?
Aka, evolution as a blind machinery, adapting humanity to the cycle of strife, by allowing neuro-diverse speacilizations to exist, which in turn try to propagate the circumstances they thrive in.
Thanks to science, we had a nice 90 years of surplus and plenty, basically bribing ourselves out of natures grasp. Now the whole messy affair returns with a vengance, and it will be interesting to see, if leviathan-cybernetics ( aka societal implants (cellphones, self-surveilance etc.)) can reign the forces of the old world in, were wishfull thinking and society regulation mechanisms (religions, rules, etc.)fail.
Most of the pictures of human females I see on the internet look the same. Young, nubile, thin, light-skinned, teased hair, painted like a clown, and where visible, completely devoid of body hair.
Perhaps observation bias is at play?
If you go to actual scientific literature, it's surprising how much everybody knows to be true is complete and utter billshut.
> Not to be a jerk, but you guys are just throwing out this stuff without backing it up and it's not at all self-evident to me.
Well as for "you guys", I don't know this guy, I'm just adding my two cents to this dollar. As for it being self-evident: of course it's not self-evident, that's why it's a matter for scientific research. Your answers will be found searching for literature, not impugning the motives of random strangers on Hacker News.
It really wasn't a knock at your motives and it wasn't personal. I just feel like if you are going to make statements and even go so far as to label them as fact, it is your job to back it up.
Unfortunately the answers to that question trouble some people so it's difficult to establish the truth. The simple answer comes down to the fact that a species has to find a balance between maintaining genetic diversity, which is important for resilience and adaptation, and maintaining a strong breeding population. Males are there to allow some really wacky variations to exist that just wouldn't be viable in females. It only takes a tiny handful of males to take part in reproduction, but it takes essentially all females (especially considering they are only 50% of the population to begin with).