Y chromosome evolving faster than the rest of the genetic code? What will result?

@Joe Nation,

I'm learning already. Junk dna - so noncoding dna for which there is no obvious purpose. When I read this article that was my first thought. Because they didn't offer any purpose or outward manifestation- I thought that maybe that's because there weren't any.
But I wasn't aware of the definition of junk dna. It's sort of fascinating that (according to what I've read) it could be dna no longer needed at this juncture in our evolution, but being held in reserve for what traits may be needed in the future.
Fascinating!

2 Replies

@aidan,

Quote:

It's sort of fascinating that (according to what I've read) it could be dna no longer needed at this juncture in our evolution, but being held in reserve for what traits may be needed in the future.

Evolution doesn't work this way.

The term "held in reserve" needs a subject. Who is "holding" this dna in reserve? Does this imply that the organism is planning for the future? or is there some outside planner holding this dna in reserve?

What does it mean to say that dna that is "needed"? I don't need hazel eyes, and I certainly don't need to be bald-- yet this dna is undeniably present in my genes.

A big red flag should go off in your head whenever anthropomorphic terms are used to describe evolution. There is no master plan in evolution.

1 Reply

@aidan,

aidan wrote:

I'm learning already. Junk dna - so noncoding dna for which there is no obvious purpose. When I read this article that was my first thought. Because they didn't offer any purpose or outward manifestation- I thought that maybe that's because there weren't any.
But I wasn't aware of the definition of junk dna. It's sort of fascinating that (according to what I've read) it could be dna no longer needed at this juncture in our evolution, but being held in reserve for what traits may be needed in the future.
Fascinating!

There's actually no such thing as 'junk' DNA. Here's a light little article on it with links at the source -

http://www.smartplanet.com/technology/blog/rethinking-healthcare/god-dont-make-no-junk-dna/732/

Quote:

Some European scientists have recently abandoned the junk designation entirely, preferring to call for the study of the whole genome under the name hologenomics.

In just the last year we have found that “junk DNA” has a vital role to play in evolution, that proteins can “cut and paste” it into a form that actually does code, and now that its byproducts can help diagnose certain types of cancers.

Scientists have even seen how cod turned some junk DNA into a form of evolutionary antifreeze that allows the fish to survive in cold polar waters.

The same sorts of discoveries are being made with plants. So-called “junk” makes a genome more sturdy, and allows for rapid evolution of a species in reaction to stress.

We just didn't understand how it was used before.

Cycloptichorn

1 Reply

@Cycloptichorn,

Quote:

Some European scientists have recently abandoned the junk designation entirely, preferring to call for the study of the whole genome under the name hologenomics.

This is a name change... nothing else.

Evolution is a series of random mutations (emphasis on random). Some of these mutations are going to be beneficial, some are going to be bad and a whole lot of random mutations aren't going to do much of anything.

The argument here is that the more DNA you have sitting around doing nothing, the more likely it is that some random mutation will turn on some trait that (by pure luck) will help the animal survive.

Does this mean it isn't junk? (Perhaps the term 'junk' is an example of anthropomorphism I was saying should be avoided).

1 Reply

@aidan,

aidan wrote:

But then I thought, why would the semen be stored in an environment that could potentially produce more mutations?
Is there an evolutionary concept that would explain why that would be beneficial or necessary as opposed to garnering a net negative?

For some reason, sperm require a temperature environment which is slightly lower than normal human body temperature, that's why the testes are outside the primary body cavity. The fact that they are in an environment which has a higher probability of mutation is purely coincidental.

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@ebrown p,

Quote:

About 95% of the human genome has at one time been designated as "junk",[3] including most sequences within introns and most intergenic DNA. While much of this sequence may be an evolutionary artifact that serves no present-day purpose, some junk DNA may function in ways that are not currently understood. Moreover, the conservation of some junk DNA over many millions of years of evolution may imply an essential function.

I paraphrased what I read here when I said 'in reserve'- referring to the sentence where the author talked about the conservation of some junk DNA over many millions of years of evolution.
The host being the different people (not the same) who pass on and/or inherent that seemingly inactive or 'junk' dna. What I meant and how I interpreted this is that though there is no outward manifestation in one generation, the DNA is still present because the needs of future generations may be different and may require the changes or mutations that DNA may carry.
This was the other paragraph I'd read which addressed what Cyclo said. I just held onto the junk DNA title as I responded to Joe so he'd know that it was that part of his post I was responding to.

Quote:

Some[who?] consider the "junk" label as something of a misnomer, but others[who?] consider it appropriate as junk is stored away for possible new uses, rather than thrown out; others prefer the term "noncoding DNA" (although junk DNA often includes transposons that encode proteins with no clear value to their host genome). About 80% of the bases in the human genome may be transcribed,[4] but transcription does not necessarily imply function.

Quote:

What does it mean to say that dna that is "needed"? I don't need hazel eyes, and I certainly don't need to be bald-- yet this dna is undeniably present in my genes.

Ah, but you do need pigment in your cornea (ideally). It needn't be hazel necessarily, but that's the specific mix you ended up with, due entirely to your ancestry.
You know, just as people who live in hot climates have darker pigment in their eyes, skin, and hair- which was a NEED thousands of years ago when people didn't have sunscreen or sunglasses.
Your people apparently didn't come where that protection was as great a need.

1 Reply

@ebrown p,

Quote:

The argument here is that the more DNA you have sitting around doing nothing, the more likely it is that some random mutation will turn on some trait that (by pure luck) will help the animal survive.

Hmm, to a certain extent; but there is also evidence that much of the so-called 'junk' DNA is simply inactive for reasons that we don't understand, and can be reactivated for further reasons we don't understand. It's not random.

Quote:

Does this mean it isn't junk? (Perhaps the term 'junk' is an example of anthropomorphism I was saying should be avoided).

Yup. Junk = worthless, this clearly is not.

Cycloptichorn

1 Reply

@Cycloptichorn,

Quote:

much of the so-called 'junk' DNA is simply inactive for reasons that we don't understand, and can be reactivated for further reasons we don't understand.

Cyclo,

My point is that DNA is purely a result of random mutations which are filtered by natural selection.

Are you suggesting there is something more then that?

The phrase "reasons that we don't understand" suggest some higher purpose to evolution. The very definition of "random" (as in "random mutation") means that there is no "reason" behind it.

You also are still using the verb "reactivated" in the passive tense. Who is doing the reactivating?

1 Reply

@ebrown p,

ebrown p wrote:

Quote:
much of the so-called 'junk' DNA is simply inactive for reasons that we don't understand, and can be reactivated for further reasons we don't understand.

Cyclo,

My point is that DNA is purely a result of random mutations which are filtered by natural selection.

Are you suggesting there is something more then that?

I don't believe that there is a 'guiding force,' but external conditions often cause DNA to act in certain ways, and we don't understand the vast majority of them.

Quote:

The phrase "reasons that we don't understand" suggest some higher purpose to evolution. The very definition of "random" (as in "random mutation") means that there is no "reason" behind it.

You also are still using the verb "reactivated" in the passive tense. Who is doing the reactivating?

The DNA 'reactivates' itself. There is no other guiding force.

I should say that I consider all terrestrial life to be nothing more than the expression of one single creature. The DNA is the life, in billions of different variations. We are simply a single expression of this. And we don't really understand how it works, our knowledge of DNA and genetic expression is in it's infancy.

Cycloptichorn

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@ebrown p,

Oh baby.

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@aidan,

Quote:

the DNA is still present because the needs of future generations may be different and may require the changes or mutations that DNA may carry.

This is simply wrong.

You are stating here that there is a reason for random mutations to progress a certain way. Random mutations by definition can't have a reason. Natural selection only selects for the organisms that right now can reproduce or not. There is no mechanism to select for future needs.

If you reword this is away that doesn't imply some mystical knowledge of the future-- say that sometimes, through serendipity, DNA that happens to have not changed over a long period of inactivity happens to be useful-- I would agree. I wouldn't reject out of hand the idea that we evolved with lots of extra DNA because it increases the chance that random lucky (in terms of survival) things might happen.

But, if a certain sequence of DNA with no physical manifestation survives a series of random mutations, it is pure blind luck.

Quote:

You know, just as people who live in hot climates have darker pigment in their eyes, skin, and hair- which was a NEED thousands of years ago when people didn't have sunscreen or sunglasses.

Sometime evolution progresses is a way that makes sense. Sometimes it doesn't. There are some genetic traits that survived just fine without any help to reproduction-- like male pattern baldness. There are some evolutionary traits that are harmful that still exist in a species.

It is a common mistake to put some mystical (almost divine) purpose to evolution.

Evolution is a set of random mutations which are filtered by natural selection. Random mutations are random- even natural selection often comes down to chance.

Sure, you can explain some human traits by exploring environment or culture or what have you. But a lot of it was just random... a few mutations different, or some primitive battle with a different outcome or a mudslide wiping out a village, and humans could be a lot different.

Humans have a hard time accepting random.

1 Reply

@ebrown p,

Quote:

There are some genetic traits that survived just fine without any help to reproduction-- like male pattern baldness.

Male baldness lets women know which males have more testosterone; it serves a purpose, in the same way that female characteristics do. It is only our social norms which have decided that baldness is a bad thing.

Cycloptichorn

2 Replies

@Cycloptichorn,

You are missing the point Cyclo.

It is a logical fallacy that everything that results from random mutations has a purpose. Things are random... sometimes there is a reason, but other times they are just because they happened that way.

Human brains are designed to look for meaning even when meaning isn't there (which explains why trying to understand a random process like evolution is so difficult).

I could bring up a million examples... from hemophilia to finger hair, you would be able to come up for a purpose for each. Of course, if by random chance humans had a tuft of thick hairs on their knees you would come up with a "reason" for that.

This says more about how your mind works then about the random process of evolution.

1 Reply

@ebrown p,

Quote:

You are missing the point Cyclo.

No I'm not. You picked an example which actually does serve a purpose.

Quote:

It is a logical fallacy that everything that results from random mutations has a purpose. Things are random... sometimes there is a reason, but other times they are just because they happened that way.

Good thing I didn't say that everything that results from random mutations has a purpose, then, isn't it? Please don't change my argument.

Cycloptichorn

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@Cycloptichorn,

I am skeptical, but fascinated, about this "male baldness" hypothesis.

Are you saying that bald men have more testosterone, or less?

Are you implying that bald men were ever more successful at mating then men with hair (not that I mind the idea)? The idea that this would favor older men (generally baldness starts at around 30) makes me more skeptical, considering that until the past few centuries, the prime mating age was between 14 - 20 (meaning baldness would happen too late to affect mating success).

1 Reply

@ebrown p,

Quote:

Are you saying that bald men have more testosterone, or less?

If I were to generalize, I'd say that bald men have more testosterone - as male pattern baldness and hair loss in menopausal women is attributed to lack of estrogen and an excess of testosterone.

Also, during the time that the prime mating age for women was between 14-20, during the time of arranged marriages- the prime marriage age (if not mating age) for men was older.

1 Reply

@aidan,

In sensu strictu, the Y chromosme is not evolving, as it is neither responding to a populational dynamic, nor an environmental change. The changes in the laundry list within the chromosome are just the more rapid inclusions of additional mutations. Mitochondrial DNA is inherited only through mommies. Women do pqss the mDNA on to both sones and daughters, only the daughters pass it on to future generations. Y chromosomes are just the opposite, wherein the Y chromosome is passed on only by the father , from father to son to son. Maternal inheritance is traceable in mDNA and paternal inheritance is traceable through the DNA of the Y chromosome.
The greatest historical diversity of Y DNA is seen in SubSaharan Africa, which supports a locus for a prehistoric "Adam" The interesting thing (as determined from studies) is that subsequent diversity in Y DNA begins to decrease several (geometric) times less in European and Asian YDNA than subSaharn YDNA. The apparent "increase in nat selection " for YDNA (if ya want to buy that), is the fact that women can only have so many offspring whereas men can impregnate as many partners as their interests allow. An example of the lower diversity in Asian populations has been traced to the wide ranging insemnation of women by Genghis Khan (and the subsequent sons-of -Khan who were the rulers of that area of Asia . The YDNA has been traceable for wide areas that , as has been suggested, reflect the wide range that Khan , and his libido, actually had affected.

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And now we find out what a lot of that formally unknown DNA is.....
fossil viruses. One of which enabled mammals to start making placentas.
http://www.nytimes.com/2010/01/12/science/12paleo.html?ref=science

Joe(what odd and wonderful thingies are viruses.)Nation

1 Reply

@Joe Nation,

Joe Nation wrote:

And now we find out what a lot of that formally unknown DNA is.....
fossil viruses. One of which enabled mammals to start making placentas.
http://www.nytimes.com/2010/01/12/science/12paleo.html?ref=science

Joe(what odd and wonderful thingies are viruses.)Nation

Interesting. So viruses add an additional chance for variation/mutation in the genome.

I wonder if viral activity on a global scale could be a contributing factor in some of the punctuated equilibria of evolution? If populations were suddenly exposed to a higher degree of mutation in their genome (due to increased viral activity) then natural selection would have more to work with.

1 Reply

@rosborne979,

Thats the substance of Lynn Margulis theory. Cept she called it the "capturing of genomes" from viri. Its quite common in the lower plants . Several fungi are related to bryozaons by one or two intercedant DNa stems from phages and viri. I always thought that she was on to something cause her data was impoeccable. Her only problem was that she carried her stuff a little too far into the realm of "Gaia"

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Y chromosome evolving faster than the rest of the genetic code? What will result?

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