Tuesday, April 18, 2006

The y-chromosome

(This thought is based on my perfunctory knowledge of genes and genetics. I wish some knowledge had diffused into me through my roomie from the past. But it hasn't. So bear with me and correct me but dont refuse to question me.)

I wonder why men prefer younger women and women prefer elder men. The reasons can be speculated without much trouble and is strewn all over the internet: the younger the woman, the better her chances of begetting kids. Since men remain fertile (and possibly lusty) long past their prime, it is only reasonable that men choose younger women to maximize their chances of making as many children as possible. As for the woman, she wants a man that can bring that piece of dinosaur meat every night without fail, and teach her kids to throw the spear right. A strong, stable man seems like the right feller: likely to be the elder of two young men. The second point is less certain than the first. But it sure sounds plausible.

Now, during sex, the y-chromosome from a man becomes the y-chromosome of a boy. Assuming mutations occur at a constant rate, this implies that the y-chromosome in a boy at any given time in the history (and future) is bound to be more evolved than the corresponding chromosome in a girl. The next logical step is to find out what traits are influenced by the y-chromosome and wonder if they are more developed in a man than a woman. So I turn to google.

It turns out that people thought the y-chromosome was devoid of any genetic information. But recent work shows that it contains numerous genes related to sperm production and traits like body size and tooth development. I find it strange that a small chromosome of a man could be more evolved, logically, than its counterpart in a woman. Does this imply that traits like tooth development/body size are better/more suitable in men compared to women? The evidence upon a direct inspection remains inconclusive. I find the possibilities mind boggling but I have just consumed a glass of soy milk, and a good game of soccer in about to start in the pleasant warmth that seems to have finally found its way into new mexico. So, I will leave the rest of the thinking to you. :)

16 Comments:

Blogger Born a Libran said...

Okay, dude, here goes... I am shooting off my mouth here and I really dont know whether anything I say is true. All my momentary knowledge about the mammalian Y chromosome has come from the wikipedia, like 5 min ago...

Anyways, it seems like the Y-chromosome diverged from the X-chromosome and is losing quite a lot of the genes except those which are male sex specific. There are a few other genes but they are in the process of being eliminated. This is because X and Y-chromosome homologous recombinations (i.e., mixing parts of both chromosomes) are harmful and the rate of homologous recombination is proportional to parts of the chromosome which have matching base pairs. To eliminate this homologous recombination and as a result of the loss of homologous recombination, they are losing parts of the chromosome which are similar to each other. Now, on to the chromosome for boys versus girls.

Assuming that the important genes that have to evolve in boys is only the male sex-related ones, then it makes sense that they are evolving in the future. The girls have a second copy of the X chromosome (if I am not wrong) and that might be important for expression levels of the genes (how much protein or hormone is produced) in the cell in girls (so, I expect X chromosome genes to be important for some aspect of female well-being like female harmones or in general physical characteristics like body size/shape, etc.) Since Y chromosome was X-chromosome at some point of history, some of these grooming genes are just the last to be eliminated. I dont know what other logical reason I can give for the observation of what is present in Y-chromosome now.

Homologous recombination between X and Y chromosome is related to human evolution according to some studies but remains inconclusive and was not even mentioned in wikipedia. So I dont know what to say about that.

9:57 AM  
Blogger OtherHalf said...

Ah! Ha so now you touch upon a dear topic, the Y factor. The fact that i shied away from Biology and never once looked back means that there is not much i can contribute to the chromosome discussion but one point sure did catch my attention, "Why are younger women attracted to older men"?
A woman by her very nature is looking out for Mr Reliable, the Prince charming she can fall back on and a man is out there waiting to fulfill this need. Now when a man is older than a woman it sure is easy for a woman to look upto him and respect him as a man. Not that it is not possible when the age difference is in the negative but we are talking about how these things are eased with a positive difference.
I used to believe that sex had a role to play in this too, because procreation is but the most basic of our needs and desires and all are actions are driven by this one want. But though women may become less fertile with age, they may not necessarily become less lustier or that their sex drive wanes. I think this is a wrong belief nurtured over the years possibly owing to the fact that women were so less expressive when it comes to talking about their sexual desires even to "THE ONE" in their life, especially in a country like India.

1:43 AM  
Blogger littlecow said...

@b-a-l: wo...wo... that was a lot of power-packed-ununderstandable stuff. but your point perhaps is that the interactions between the y-chromosome and the rest of the genes is unknown and hence the expression of genes in the y-chromosome as character traits might not be an indicator of the evolution of the y-chromosome itself. very correct.

@better1/2: Yes, indeed. But is it possible that her perception that an older man would be more reliable itself is flawed and occurs only because of the conditioning in the past (that you mention)? In this age where varied levels of intelligence and maturity are present in people (quite irrespective of age, I might add), why should this old practice be held forth?

Simplify. Isn't it true that the only requirements are that you should love the guy and the guy should love you in turn. That both parties agree and decide to live a happily ever after life? Why do we often mess up things by thinking along lines that are far too complicated? *the questions are as much for me, as they are for you! - of course, with the "guy" replaced by a "girl"*

9:24 AM  
Blogger littlecow said...

@saale: of course, man is looking for a reliable woman *in our times*. i fail to understand how a man looking for a reliable woman would contradict a woman looking for a reliable man, which is what i had said. thats one point. secondly, in the times when dinosaurs still roamed around earth (and never knew that speculators like you and i would arise on this dirty planet a few million sunrises later), it is unlikely that men were looking for women that would stick around with them for eternity. infact, scientists think (and i tend to listen) that men probably lived with as many women as they could - the process of natural selection working there - which means that they were specifically not looking for a woman that would advocate monogamy. (perhaps, men have not changed much over the years. afterall, what is a few hundred thousand years in the story of evolution?!)

so, there... there is nothing wrong with a woman looking for a man that can bring dino meats and there is no gender bias in that statement.

if it sates you any better, no, i am not a chauvinist. on that front, i am also an anti-feminist. equating a man to a woman is like saying, a kid will grow up just fine with a mother and a father - both of whom are male. its ridiculous and i find it comic. a male chauvist and a feminist look like two different extremes to me, and the right way is somewhere in between.

my logic is certainly not based on moonshines. period-ically, it does wax and wane. but no correlation to moonshines. mmm...hmmm... not at all. :)

6:34 PM  
Blogger Born a Libran said...

@lc: Dude, my point is the following. One should not see the y chromosome in isolation. At some stage, y chromosome was the same as x chromosome and they started diverging. As they diverged, y chromosome kept losing genes because they were already present in x chromosome and it is harmful to have common genes in both x anf y chromosomes. However, this process is still ongoing. As a result, some of the genes in x chromosome are still present in y chromosome. There are some genes which are important for males and is present and maintained in y chromosome and I think these genes should not be present in the x chromosome. So, in order to understand what genes in y chromsome are important for the male species over the female species it is important to only look for genes present in y chromosome which ARE NOT present in x chromosome. I dont expect the body size genes and those for tooth development to be exclusively in the y chromosome (though I might be wrong). I hope this was clearer.

6:38 AM  
Blogger littlecow said...

@saale: :) What can I say?!

@b-a-l: Got it this time around. Looking for y-specific character traits is the right thing to do.

8:15 AM  
Blogger littlecow said...

@saale: of course! if you hit the wilderness of new mexico, what else is there to do?! but i have to warn you that i have not taken to alcohol as much as i would have liked to (infact, i find drowning in an alcohol induced stupor to be utterly boring. how could you use up this already too short a life on alcohols? ;) )... as for your sarcasm, yes, it is very much welcomed in this blog and elsewhere, at the right times!

10:12 AM  
Blogger atma_tripta said...

At the outset, Iam not an expert on genetics. However, I think there is an important aspect to the whole issue..timing.
Typically, in animal kingdom, females make the mate selection just after they attain their reproductive age while the males have to compete with the best and they are successful a little later intime..when they are strong and have effectively dealt with the competition. Hence, the age factor may just be superfluos...just a evolution's way of males looking for females with maximum 'productive' life and the females looking for the 'best' care for their young under a (generally) stronger male.
And to think that we can beat ages of evolution with a hundred years of conditioning...:)
@

11:04 AM  
Blogger m. said...

ow. just some things that caught my eye.

1. feminism does not hold the view that women are equal to men. that IS one opinion yes, but theres a lot more to it, based on the idea that women are unique. there are some aspects of the feminine that dont have a masculine counterpart, so if we look at women only as "the other sex" its an incomplete and inaccurate pov that doesnt do justice to anyone. and heck: men are no gold standard by which to gauge the other genders :D

2. taste this thought: this is part of the nonmainstream evolutionary theory sourcing right back to good ole Darwin himself. clitoral responses shape evolution. so if the y chromosome contains information about yada yada, it could simply be a kindly gesture of "dude, here: evidently women like this. follow these guidelines". which makes the male the passive element, attempting to please the female. quite an inversion of power structures dont you think?

3. there are still some absolutely unique features that women possess that men do not: such as higher pain tolerance thresholds, emotional resilience, presence of the egg even before puberty (yes, there are already eggs present - the man only produces his sperms after puberty), plus cet par, women live longer than men. so the conclusion about male bodily superiority is questionable.

evolution is a very very conditioned field of science. if you really want to dig up the interesting stuff, check out darwins own writing or geoffrey millers. darwin never said survival of the fittest was the only law - he was the earliest (in the west) to raise the issue of sexual selection. that examines issues like why so much brain power and reserves are "wasted" on core non-survival characterestics like wit or artistic expression, which nevertheless play a large role in sexual selection.

7:18 PM  
Blogger Selma Mirza said...

when two grown ups talk, baccha-log should learn to shut up. excellent conversation there, between bornalibran and littlecow.

society prefers a man to be bigger in everyway. in age, height, finance, 'caste' and so on. any relationship going against the norms is frowned upon. and i think old men (not older) prefer young women because they are plain horny-ol-men.

Did you read about Dr Strangelove? I just read about him on Kush Tandon's squarespace. Now Dr Strangelove is one twisted guy!

I will be back later with a non-rambling comment! [Puts gun in holster and walks off Terminator Style.]

7:19 PM  
Blogger Born a Libran said...

@M: I dont know too much about the evolution of multicellular organisms (and hence, all the stuff about sex, et. al.)... Hence, I can not appreciate what you had written in its entirety... However, would like to add Stephen Jay Gould's books to the list of books you suggest... I am more into understanding molecular evolution and I am quite a fan of Carl Woese's work on the same...

11:36 AM  
Blogger littlecow said...

I will get back to all of you in a couple of days. For now, let me spend my trainquil evening without venturing into arguments and anti-feminist bashing (m. - take note and equip yourself!) :)

@saale: I apologize for the delay in the fireworks. If you have the patience, you can enjoy the spectacle when it unfolds! :)

I know... I know... its all unnecessary hype and war-mongering. But what is life without some spice?

6:54 PM  
Blogger ligne said...

@bala : looks like this a very popular post.. I was reading it this morning and trying to figure out why you thought the y chromosome was getting propogated more..
there might be some justice to the statement..but dont really see it :)

8:18 PM  
Blogger mimosa pudica said...

Quick googling pointed me to another interesting article on a related matter.
It seems as if y-chromosome is losing genes since it doesn't have a partner to fix the errors in the mutation (like x). If it continues Y may become (E)X forever. Another theory is that Y is sneaking up and creating palindromes within itself to save the good genes.
Read more at
http://www.npr.org/templates/story/story.php?storyId=4225769

However, all of this is inconclusive.. so continue with sun,soymilk,soccer or whatever it is you do until proven otherwise

2:55 PM  
Blogger littlecow said...

Ok, I am ordering my responses in some logical sequence to spar with all the questions. So, dont take any offence - I love you all equally less.

@ligne: An older man marries a younger woman and they make babies. Now, the y-chromosome has been in circulation longer and hence, the probability of mutation is higher. Now, for the next generation, you dont have to consider anything else. The logic in the first question will apply again. Think, think! Therefore, the y-chromosome is more evolved. ps: I wrote it in a moment of inspiration and it took me a while to retrack my own logic! :)

@atma_tripta: See my response above. The y-chromosome being more evolved still stands (within the confines of my logic, that has crumbled in the past under continued attack by the stronger Force)

@evenstar: Dr. Strangelove is a very interesting movie. I was completely zapped out after I saw it for the first time (last year) and even now, I keep thinking about it. Twisted and strange. But makes one think. And on the balance sheet, thats what matters, isn't it? On another note, going by the photo on your profile, should you not put your sword in its sheath and walk away - Zorro style?

@saale: No, I am no masochist. Perhaps, that is a good reason to keep out of the anti-feminist controversy?! Afterall, why bother when years of observation has taught us that men will eventually surrender under the pretext of that four letter word (Ahem... pervert... I meant Love!)

@mimosa pudica: I do hope that the spate that befalls many a man (that of being an Ex) does not befall the gene that makes us unique. Thanks for the succint summary - my collective knowledge about the y-chromosome just doubled.

8:50 PM  
Blogger littlecow said...

@m.: Thank you for the long and thoughtful comment. I needed a shot of endorphin to kill my pain. ;)

>1. feminism does not hold the view that women are equal to men. that IS one opinion yes, but theres a lot more to it, based on the idea that women >are unique. there are some aspects of the feminine that dont have a masculine counterpart, so if we look at women only as "the other sex" its an >incomplete and inaccurate pov that doesnt do justice to anyone. and heck: men are no gold standard by which to gauge the other genders :D

You see, after reading your comment, I wanted to applaud. In a moments inspiration (and clearly swayed by your first point), I tried clapping with just one hand. Sadly, there was no sound. Can my right hand clap because i love it far more than the left? Nope. Can it clap because it is far more skilled than my left? Nope. Not at all. Females are unique. Yes. And that is really why we men like them. But men and women are packaged together as one deal - like Shiva and Shakthi packaged into one. So, feminists who walk around saying females are unique should also acknowledge by the strength of whatever arguments they put forth that men are also unique. And that these two unique creatures can never survive separately. (And now, dont get me started on the artificial insemination and no-need-for-men line of argument. It is plain ridiculous - propogation without love is like love without a heart. It is a possibility but it sucks!) :)

>2. taste this thought: this is part of the nonmainstream evolutionary theory sourcing right back to good ole Darwin himself. clitoral responses >shape evolution. so if the y chromosome contains information about yada yada, it could simply be a kindly gesture of "dude, here: evidently women >like this. follow these guidelines". which makes the male the passive element, attempting to please the female. quite an inversion of power >structures dont you think?

This argument holds true only under the assumption that a woman has direct control over clitoral responses. Consider this: A woman's hormones are running amok. Her clitoral responses, as you wish to call it, is looking around for being... err... responded to. Only if the man of her choice is willing to satisfy her, would her clitoral responses shape evolution - as then, the man with traits that she likes gets a better chance of having his genes carried forth. But then, she has competition. There is another woman looking for the same good man. What does the man do? He chooses the woman he likes better. So, the sexual tryst in our example is clearly not an unbalanced power game where one sex has the ability to completely vanquish another's preference. Thus, the male is not the passive element. And neither is the female. Both parties make the call together (no pun intended)

>3. there are still some absolutely unique features that women possess that men do not: such as higher pain tolerance thresholds, emotional >resilience, presence of the egg even before puberty (yes, there are already eggs present - the man only produces his sperms after puberty), plus >cet par, women live longer than men. so the conclusion about male bodily superiority is questionable.

My claim was NOT one of bodily superiority. It was one of a possible larger body size. Unless you live in a place which I have not visited before, you would not dispute this. On an average, a male is larger than a female.

The presence of an egg before puberty is news! Is that really true?!

>evolution is a very very conditioned field of science. if you really want to dig up the interesting stuff, check out darwins own writing or >geoffrey millers. darwin never said survival of the fittest was the only law - he was the earliest (in the west) to raise the issue of sexual >selection. that examines issues like why so much brain power and reserves are "wasted" on core non-survival characterestics like wit or artistic >expression, which nevertheless play a large role in sexual selection.

Yes, and there was this guy by name Wallace who was a co-proponent of the theory of evolution (as acknowledged by Darwin himself - my source is the discussion in the book Phantoms in the Brain). But Wallace differed from Darwin (who tended to attribute everything to sexual selection) and said core non-survival traits were not the effect of evolution itself but the result of "culture" which made us unique in the animal kingdom. Now, what is the relevance of this piece of trivia for our argument? None. It is just a few electrons carelessly tossed to the other side of the planet (?) That said, I woudl heartily prefer hearing/reading the essence of their arguments rather than a dozen archaic books on evolution. Perhaps, you could make this as a post on your blog?

In conclusion, the points you have raised are good, and it is one of those comments that makes the me think, wonder and learn a few new bytes along the way. Thank you!

Need I write the disclaimer that the sarcasms used in this response were merely of the friendly variety?

9:21 PM  

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