Sex: do we really need it?

Australian Broadcasting Corporation Science ^ | Tuesday, 8 July 2003 | Wilson da Silva in Melbourne

[I_dmc]

Sex: do we really need it?

Wilson da Silva in Melbourne

ABC Science Online

 

 

Birds do it, bees do it, humans do it - but nobody knows why sex evolved at all, the world congress of genetics heard in Melbourne today.

"The evolution of sex has presented a paradox to evolutionary biology for over a century," said Associate Professor Sally Otto, an evolutionary biologist at the University of British Columbia in Vancouver, to delegates attending the 19th International Congress of Genetics.

"It's known there are a lot of costs to reproducing sexually. Why make sons and males, if you could just produce females that were able to reproduce by themselves? That's a division of resources into two sexes that seems unnecessary," she said.

Not only does this seem to waste resources, the whole process is prone to failure. There's the risk of not finding a mate, and the risk of getting a disease during mating. There's also a more subtle risk: if an individual reaches reproduction age and finds a mate, it is a successful genotype - a tried and true model of a species. But then that individual mixes their genotype with a mate, with no guarantee that the mixture is going to be any better.

[r9etb]

But if you have a successful mutation in a male, that success can be passed on to a much larger number of females.

You're pre-supposing the existence of males. But how you get males and females that can mate and produce fertile male/female offspring? Where does the mating behavior come from?

[XJarhead]

You're pre-supposing the existence of males. But how you get males and females that can mate and produce fertile male/female offspring? Where does the mating behavior come from?

No, I'm not. The shift from parthogenis to male/female offspring is the mutation that occured. You get a tiny sense that shifts like that are possible when you see people born as hermaphrodites. Hermaphrodites obviously can't engage in partAnd because it was such a successful mutation, it became the dominant pattern for advanced life.

The article basically makes the same point later on. Sex is the most efficient means for improving a species, so its pretty inevitable that such a mutation eventually would arise and become dominant.

[I_dmc]

Yes, mutations. That's why I posted this after reading it. I got to wondering. What effect will the changes in our culture, welfare state, etc, have on our collective genetics?

[The Shrew]

You can live for years without sex. I am living proof.

You call that a life?

;-)

TS

[Ohioan]

To understand the lunacy of Feminism:

The Feminist Absurdity.

William Flax

[Ichneumon]

I cannot believe a person with those academic credentials could ask such a stupid question.

Neither can I, especially when the many genetic/evolutionary advantages of sexual reproduction have been well known for *decades*.

I suspect this article is yet another example of a depressingly common trend: A reporter who understands too little about a scientific story to accurately present it, but doesn't let that stop them from trying to make their report more "dramatic" by playing up humdrum ongoing research as a "mystery" or a "revolution" of some sort.

In this article, it's the "mystery" of how "no one knows" why sex exists but the adventurous scientists are hot on the trail like Sherlock Holmes...

[manic4organic]

What's this "we" sh*t? I need it!

[Ichneumon]

If that's the case, then how did sex evolve in the first place? That's the paradox, see?

No paradox, actually.

Sexual reproduction can easily evolve in a number of ways, including the following sequence:

1. Start with single-cell organisms which reproduce by splitting, like most bacteria.

2. At some point one of the organisms stumbles upon a way to insert its DNA into other similar organisms, thus reproducing by "proxy" like a cuckoo bird which lays its eggs in other birds' nests. The evolutionary advantage to this should be obvious. And many microorganisms do this even today.

3. Eventually there's a whole host of its (direct and indirect) offspring around, all forcibly "impregnating" each other and cross-sharing DNA.

4. Since this is a valuable trait-sharing method, over time the species refines the process so that each individual is specialized at both "donating" DNA and being "receptive" to DNA from others. At this point there is true sexual reproduction taking place, even though there are no separate "males" and "females" -- all individuals are effectively hermaphrodites.

5. Later (and this can take place at either the single-cell stage, or a zillion generations later after the species has become hermaphroditic multi-celled creatures, like say earthworms), a mutant arises which has lost the ability to donate DNA, and becomes the first exclusively "female" organism in a population of hermaphrodites. No problem, it can still reproduce by receiving DNA from the hermaphrodites, even if it can't donate any DNA to others. It, and its female offspring, will still prosper and interbreed with the rest of the "male+female" population. Or perhaps a "male" arises first by losing the "receptive to DNA" structure -- same argument either way, it can still reproduce by donating DNA to others.

6. If females arise first, there's evolutionary pressure for at least some of the remaining hermaphrodites to specialize in impregnating the female form of the species. Over time they're likely to specialize so much that they become "males only". Or vice versa for the rise of a female type if males first arose in the population. Eventually hermaphroditic forms can fade away entirely, leaving nothing but "pure males" and "pure females" as the two dimorphic forms of the same species.

[Yeti]

But how you get males and females that can mate and produce fertile male/female offspring? Where does the mating behavior come from?

A long series of much smaller mutations, each of which was sustainable and/or advantageous to the organism(s) that posessed it.

[Nick Danger]

I cannot believe a person with those academic credentials could ask such a stupid question. The genetic variation and natural selection argument seemingly cuts that to ribbons.

That ought to cut both ways, though. One of the Great Mysteries, it seems to me, is why mitochondria have never developed an adaptation that attacks or interferes with arriving sperm that carry a Y chromosome.

If I'm a mitochondrium, and I'm in the egg waiting for a sperm to come along, it is in my interest to kill any Y-bearing spermatozoa. The only way my genes get any farther than one more generation of humans is if this egg I'm in gets fertilized with an 'X'.

If this adaptation had ever arisen, it would be noticable in maybe 50 or 100 generations. We would see 60-40 or even 70-30 ratios of female to male babies being born. This would be a highly successful adaptation for the mitochrondria. Can you think of any reason why this could not happen?

[VOA]

Speaking of evolving...

and think...parents are paying this droid to teach their kids about the birds
and the bees (so to speak)...

[Petruchio]

Sex: do we really need it?

Yes

[sit-rep]

bttt...

[sit-rep]

Looks Sexy in a flightsuit . . . Looks Silly in a french maid outfit

Ummmmm....may I be so bold as to suggest getting some sun on your time off? Any female would look good in a maid outfit, especially if she is fit enough to be in a flightsuit!

JMHO...

[Petruchio]

Click on my name.

Look at the picture.

Then re-think your post.

FRegards

[Calvin Locke]

Noooo! My ex blamed me for her weight gain since I would bring home Dove bars now & then. She told me how she "hated" me for trying to please her.

Go figure.

Scratch that. I don't need trial lawyers coming after me....

[usadave]

Sex: do we really need it?

Aside from when we have sex in order to procreate, our sexual needs are more psychological than physical.

[austinTparty]

More whining from ugly women who had issues with wardaddy.

;^)

[blackbirdphleps]

For the life of me I can't think of a single animal on earth that doesn't need a partner to reproduce. Off the top of my head. I know there are a few out there but there must not be many that are beyond single cells.

Did she skip the childhood stage that drives parents crazy???
Any parent out there know the WHY? Stage that all children go through.
Her question makes me wonder what planet she was raised on.
Cause any child who has a pet that a parent doesn't get fixed will find a way reproduce.

Sex: do we really need it?

YES!!!!!
I can't think of any other animals besides humans that not only mate to reproduce but cause it's enjoyable.

Doctor's even tell a pregeant woman to do IT in the last stage cause the sperm has benifical properties to helping making a deliver easier.