Researcher argues that sex reduces genetic variation

Jul 07, 2011

Biology textbooks maintain that the main function of sex is to promote genetic diversity. But Henry Heng, Ph.D., associate professor in WSU's Center for Molecular Medicine and Genetics, says that's not the case.

Heng and fellow researcher Root Gorelick, Ph.D., associate professor at Carleton University in Canada, propose that although diversity may result from a combination of genes, the primary function of sex is not about promoting diversity. Rather, it's about keeping the genome context – an organism's complete collection of genes arranged by chromosome composition and topology – as unchanged as possible, thereby maintaining a species' identity. This surprising analysis has been published as a cover article in a recent issue of the journal Evolution.

"If sex was merely for increasing diversity, it would not have evolved in the first place," said Heng. This is because asexual reproduction – in which only one parent is needed to procreate – leads to higher rates of genetic diversity than sex.

For nearly 130 years, traditional perceptions hold that asexual reproduction generates clone-like offspring and sexual reproduction leads to more diverse offspring. "In reality, however, the relationship is quite the opposite," said Heng.

And not only does asexual reproduction lead to higher rates of , it also is two times more efficient than sexual reproduction.

In fact, two billion years ago in Earth's biosphere, life relied exclusively on asexual reproduction, and every organism was capable of bearing young without costly competition to mate. With asexual species' faster and more efficient mode of reproduction, the origin and maintenance of sex – not exactly the fittest means of reproduction – puzzles scientists, who for decades have been asking, Why has sex evolved and survived?

Although many scientists have offered answers to this question, most have focused on the benefit of mixing or purifying genes. But by taking the genome theory into account, Heng's findings may have dethroned the queen of problems in evolutionary biology.

According to Heng, the hidden advantage has over is that it constrains macroevolution – evolution at the genome level – to allow a species' identity to survive. In other words, it prevents "Species A" from morphing into "Species B." Meanwhile, it also allows for microevolution – evolution at the gene level – to allow members of the to adapt to the environment.

Considering their observations and those of paleontologists, population geneticists and ecologists cited in the article, Heng and Gorelick argue that new research should focus on the genome, not just the individual , because the genome serves as both the genetic information unit and selection package for evolution.

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gwrede
3 / 5 (2) Jul 07, 2011
I'm ashamed that I did not figure this out years ago. All the facts were there, and it always disturbed me how sexual reproduction caused "more diversity". I'so glad I read this.
breadhead
1 / 5 (4) Jul 10, 2011
Perhaps homosexuals will evolve the ability to reproduce asexually, otherwise, how shall they propogate?
What force drives the idea of, "keeping the genome context"? Is there some cosmic intelligence involved in your evolution myth? Here I was led to the idea that random chance brought about life, the universe, and all that exists.
FrankHerbert
0.7 / 5 (48) Jul 10, 2011
Perhaps homosexuals will evolve the ability to reproduce asexually, otherwise, how shall they propogate?


I'm pretty sure we're only a few years off from this but not asexually.

Say for example 2 women want to have a child related to both. All you would really need is a donor sperm cell for the genetic material from one of the mother's eggs. If they wanted a male they could borrow a Y chromosome from a male relative. Obviously one would have to decide to carry the child.

For 2 men it would require a donor egg cell and a surrogate mother. I'd be shocked if this couldn't be done with current technology; however, I'd also be shocked to find it had been tried already.

It's really only a matter of time, most of which will probably be spent squabbling over moral aspects not the technology itself.
Ethelred
5 / 5 (1) Jul 18, 2011
said Heng. This is because asexual reproduction in which only one parent is needed to procreate leads to higher rates of genetic diversity than sex.
Bullshit. The guy is thinking of individuals. Sex isn't about individuals. It is about an extended organism. The ENTIRE species can be seen as a single organism adapting over time, spreading the risk, evolving new mechanisms of coping. If it was about staying the same then it would not have evolved. Evolution is NOT staying the same so evolving to stay the same is pretty much contradictory.

asexual reproduction lead to higher rates of genetic diversity,
I am curious as to where the evidence to support this bizarre claim exists. Mono-clonal species not only have low diversity what diversity that is there is an illusion since EACH line of descent is completely separated from the other lines and thus they are no longer a species.>>
Ethelred
5 / 5 (1) Jul 18, 2011
Why has sex evolved and survived?
Because it has survival value and not changing is anti-survival since the environment keeps changing.

most have focused on the benefit of mixing or purifying genes.
Sometimes I wonder if I am the only one gets it. Other times I wonder if I am full of crap. But the idea I wrote above seems to fit the evidence. Sexual species are extended organisms. No longer a single line of descent but a network that can change over time. The difficulty of understanding this is likely due to us THINKING as individuals and thus having difficulty in seeing the whole species as a network organism. It might be that the model of computer networks had to exist first before it could be understood.

In other words, it prevents "Species A" from morphing into "Species B."
Utter horseshit. It ALLOWS the species to morph instead going extinct. There is no survival value in remaining the same as the world changes around the species.

Ethelred
breadhead
1 / 5 (1) Jul 25, 2011
Do you really want someone to answer you Ethelred?

Frank, your process requires intelligence. Are you saying that evolution requires that? So without intervention - all natural selection processes, explain the asexual conversion please.
FrankHerbert
0.9 / 5 (50) Jul 25, 2011
The process I outlined wasn't evolution you moron. It's as much evolution as a doctor setting a broken leg is evolution. It would be a medical procedure using largely extant procedures.

I'm confused as to what point you are trying to make. Are you trying to say evolution is false because it wouldn't lead to homosexuals or are you saying its false because homosexuals haven't evolved the ability to reproduce? The latter is total nonsense and the former is a studied subject.
FrankHerbert
0.7 / 5 (48) Jul 25, 2011
"Homosexual behaviour has been observed in hundreds of species, from bison to penguins. It is still not clear to what extent homosexuality in humans or other animals is genetic (rather than, say, due to hormonal extremes during embryonic development), but there are many mechanisms that could explain why gene variants linked to homosexuality are maintained in a population.

A common assumption is that homosexuality means not having children, but this is not necessarily true, especially in cultures other than our own. Until it became acceptable for same-sex couples to live together in western countries, many homosexual people had partners of the opposite sex. In some traditional societies, various forms of non-exclusive homosexuality were common."

http://www.newsci...ity.html
FrankHerbert
0.7 / 5 (48) Jul 25, 2011
explain the asexual conversion please.


Are you trying to claim sex couldn't have evolved? Your point is not really clear at all. If this is the case:

"The most primitive form of sex may have been one organism with damaged DNA replicating an undamaged strand from a similar organism in order to repair itself."

"Another theory is that sexual reproduction originated from selfish parasitic genetic elements that exchange genetic material (that is: copies of their own genome) for their transmission and propagation. In some organisms, sexual reproduction has been shown to enhance the spread of parasitic genetic elements (e.g.: yeast, filamentous fungi)."

"A third theory is that sex evolved as a form of cannibalism. One primitive organism ate another one, but rather than completely digesting it, some of the 'eaten' organism's DNA was incorporated into the 'eater' organism."

http://en.wikiped...oduction
Ethelred
5 / 5 (1) Jul 26, 2011
Do you really want someone to answer you Ethelred?
If I had there would have been a question. But I was sort looking for INTELLIGENT comments. I was commenting on the article. I think the idea in the article is idiotic. It is the sort of thing that someone with no understanding of the goal of life would write. Life does have a goal. Continuity. Not stasis, which the article has the scientist appearing to think as the goal, for that leads to extinction. Only by changing can any lifeform continue to exist.

Frank, your process requires intelligence.
Frank was talking about technologically assisted reproduction and thus yes it must have an intelligence involved.

Are you saying that evolution requires that?
No he wasn't talking about evolution thus he did not make that claim. Frank is not brain dead so he isn't going to much a such a silly claim without having first incurred serious brain damage.

But thank you for bumping the thread.

Ethelred
Ethelred
5 / 5 (1) Jul 26, 2011
A third theory is that sex evolved as a form of cannibalism. One primitive organism ate another one,
This sort of thing is how I think gene exchange might have evolved from in bacteria. I don't see it happening in eurchariotes as the structure is a bit complex for that. The mitochondria that are in all euchariotes most likely came from that but after the evolution of a cell nucleus I just see that as unlikely to occur again.

My thinking on this is purely aimed at sexually reproducing species not bacteria. It looks to me that early eukariotes were cloning species like amoeba still are. I think that early on there was only one DNA strand rather than a pair. The pairs likely occurred first by a failed split leaving one cell with two identical or nearly identical strands instead of one. Which allows for redundancy AND change. Life must have gone on for a long time without sexual reproduction as change seems to have been very slow in multicellular organisms.>>
Ethelred
5 / 5 (1) Jul 26, 2011
Mostly there are no signs of specialized cells, just a bunch of cells that stuck together. Much like fungi still do and they are mostly if not entirely monoclonal organisms.

That sort of reproduction means each line of descent is independent of even the closest of relatives. A new and useful gene can only be handed down a single line and cannot be handed off to relatives. Evolution in that case would work the pretty much the way the antievolutioist like to think it does. Slowly, slowly, with any flaw wiping out a line of descent often even after DNA pairing developed.

But an organism that exchanges DNA ACROSS lines of descent no longer is just a single line. It becomes a network. And it isn't a bunch of individuals networking. It is a SINGLE organism spread across the individual instantiations of the organism. Killing one individual instantiation does not kill off the networked organism.>>
Ethelred
5 / 5 (1) Jul 26, 2011
Mostly there are no signs of specialized cells, just a bunch of cells that stuck together. Much like fungi still do and they are mostly if not entirely monoclonal organisms.

That sort of reproduction means each line of descent is independent of even the closest of relatives. A new and useful gene can only be handed down a single line and cannot be handed off to relatives. Evolution in that case would work the pretty much the way the antievolutioist like to think it does. Slowly, slowly, with any flaw wiping out a line of descent often even after DNA pairing developed.

But an organism that exchanges DNA ACROSS lines of descent no longer is just a single line. It becomes a network. And it isn't a bunch of individuals networking. It is a SINGLE organism spread across the individual instantiations of the organism. Killing one individual instantiation does not kill off the networked organism.>>
Ethelred
5 / 5 (1) Jul 26, 2011
The hard part is the initial process of exchanging a DNA strand, and I am a bit fuzzy on how it might have occurred. I suspect it only occurred once. And all sexually reproducing life is descended from that one species with both plants and animals coming into existence after the development of sex.

Ethelred