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> The Origins of Sex: Cosmic Solution to Ancient Mistery, A study out of Caltech and NASA's Jet Propulsion Laboratory has used digital organisms to simulate life before sex and yielded a possible mechanism for instigating Earth's
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post Feb 01, 2009, 04:13 PM
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Comets and asteroids have been blamed for a lot of things before. Shaping Earth. Jumpstarting life. Wiping out dinosaurs. Even possibly altering human evolution.

But never sex.

Roughly 1 billion years after the first organisms romped in the hay, the origin of sex remains one of biology's greatest mysteries. Scientists can't say exactly why we do it, or what triggered those initial terrestrial flirtations. Before sex, life seemed to manage fine by employing asexual reproduction -- the cloning of offspring without the help of a partner.

Now a new study out of Caltech and NASA's Jet Propulsion Laboratory has used digital organisms to simulate life before sex and yielded a possible mechanism for instigating Earth's first courtship.

Intimacy never sounded so stressful.

Comet or asteroid impacts could have stressed asexual organisms enough to send them down the path of sexual reproduction after forcing a flurry of genetic mutations, the study shows. Heavy doses of radiation might also have done the trick.

While these potential catalysts for mutations are highly speculative, researchers Claus Wilke and Chris Adami announced Monday night that they have determined with certainty one possible way that organisms could have managed such a chaotic environment to their advantage in opening the original door to sexual liberation.

The key to this mutation management, Adami told SPACE.com, is the discovery that when things get rough, a population of organisms adapts to handling a few mutations, while also ensuring that many mutations will be self-destructive.

"Mutations can and do still occur," he said, "but they lead to dead organisms and therefore do not affect the future."

Before sex

Sex never should have happened, biologists often say.

Though the ultimate act of affection has been around longer than anyone can remember, it wasn't always so. On the early Earth, all organisms reproduced asexually.

Any gardener is familiar with how asexual production works. Underground runners can create multiple clones (not to mention destroy a good lawn). Potatoes give up an eye to create another potato. Bulbs divide. Cacti, exhibiting no creativity in this area but managing to foster progeny nonetheless, simply let pieces of themselves fall to the ground and hope for the best.

Some animals get in on the asexual act, too. Sponges and sea anemones produce little ones via buds. Flatworms, if cut in two, grow a new head on one of their severed ends and a new tail on the other.

These are handy and powerful ways to leave a legacy.

For one thing, there's no need for a partner -- no butting of horns, no beating of the chest, no late nights at the bar. Reproduction is virtually guaranteed. Also, when desirable traits evolve, they are not quickly diluted by evolution. Your offspring are just like you. Exact clones.

Sex, on the other hand, combines myriad mutations with each pairing of genes, and the process "can wash out the good and accumulate the bad," Adami says. Just ask any failed child of successful parents.

The age of sex

Despite all these advantages for asexual reproduction, somewhere along the evolutionary line sex became all the rage.

Thankfully so, for we humans owe our existence to that first melding of the genes. Asexual reproduction provides for a plodding style of evolution, relying solely on accidental mutations to effect change. It's an evolutionary slow train that might never have gotten around to delivering humans. It can also limit a population's ability to survive severe environmental change.

Sex, on the other hand, allows plants and animals to evolve quickly, because the gene pool mixes and the fitter survive.

Yet as any parent knows, sex is a rather inefficient way to make babies. Biologically speaking, the man spends nine months doing absolutely nothing productive while the woman does all the work (in some households, this problem is known to persist far longer).

So in an evolutionary sense, why would sex ever have become so popular? More to the point, why would any asexual organism have bothered to try out sex in the first place?

We're all mutants

Researchers have long known that mutations rewrite portions of an organism's genetic code. Some mutations can be good, in fact helping a species to thrive at the expense of others. But the effect can sometimes be deadly. Since sex involves two parents, there is twice the number of mutations to muck up the genetic scripts.

Wilke and Adami created two different simple, computerized life forms that "share many characteristics with bacteria," then placed them in a stressful environment where the rate of mutations was high. By studying digital creatures, they were able to zip through many generations in a short time.

The scientists found a natural throttle to the number of mutations a population of asexual bacteria can handle. The throttle can be thought of as a conservation law. The law dictates that a population capable of adapting to the harmful effects of a few mutations cannot possibly handle a bunch of mutations. Past a critical limit, the accumulated mutations make gibberish out of the genetic code and the organisms die.

Conversely, the new law also shows that a population which can handle many mutations would be highly vulnerable to the first few. "In fact there are such organisms [today]," Adami said. "Sex could, however, never evolve" in such a population. The offspring would be too vulnerable to the initial flurry of mutations that would be written into its code, combined from two organisms.

The birth of sex

Now imagine simple organisms long ago that just happened to share genetic information in a loose and uncoordinated fashion. Such sharing goes on today without leading to reproduction.

If such a population of organisms were suddenly faced with the stress of high mutation rates, it would over the course of many generations develop a capacity to handle a few mutations. But by the new law, numerous mutations would be intolerable.

The effect of all this, Adami says, is that bad mutations would be weeded out of the population.

When multiple mutations are intolerable, bad mutations cannot accumulate, because each successive bad mutation has an increasingly deadly effect on an already weakened organism. Useful mutations, however, do not harm a population in these conditions, Adami said.

Put another way: "When multiple mutations are intolerable, bad mutations cannot accumulate, while the good ones still can."

This could pave the way for the benefits of sex to be enjoyed.

A theoretical door would be open to sexual freedom, and if a pair of organisms mutated enough to go behind that door, then their newfound ability to share beneficial mutations, via sex, would give them a Darwinian advantage over their asexual cousins in the highly stressful environment.

"You can imagine a path that leads from the uncorrelated exchange of genetic material to the completely orchestrated recombination process," he says, referring to the birth of sex.

Any number of catastrophes might have fueled a changed environment and a rate of high mutations, Adami explains. A cosmic impact could have altered Earth's atmosphere for millions of years, exposing the planet to high doses of radiation. Increased volcanic activity is another possible source.

But Adami stressed that these possibilities, while useful to consider, were not a part of the study and so remain highly speculative.

Not actually living organisms

Clifford W. Zeyl, who studies evolutionary genetics at Wake Forest University, called the work surprising and interesting, but added a further caution:

"Since the idea came from a study of digital organisms and not from any historical evidence that such stresses actually acted on living organisms, or that they would have had the effect of selecting for sex, I think it's highly speculative," Zeyl said.

Adami is confident that the computer experiment renders an accurate picture, and he suspects that if such a test could be carried out on real organisms (it can't, because it would take too long) similar results might be found.

"The digital organisms actually live in the memory of the computer, so all we do is set up the experiment and then observe," he said. He added that some biologists are skeptical of any research carried out using digital organisms, but says there is "no reason whatsoever" to think that the findings would not apply in real-life situations.

The study results are published in the July 22 issue of the Royal Society journal Proceedings: Biological Sciences B.

http://www.space.com/scienceastronomy/sola...sex_010710.html
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trojan_libido
post Feb 03, 2009, 03:57 AM
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Give a researcher a large cash sum and freedom to do whatever he desires, and he quickly uses the facilities computers for digital sex... I guess students never grow out of porn smile.gif

Its an interesting proposal, but its a computer simulation of what they think might have happened if and when certain events took place. Basically, I find it quite sketchy and home to major assumptions, a lot of it based on Darwins theory of evolution.

Now I'm not denying evolution here, but species development to its environment has never been witnessed. Individual mutations have, especially in fruit flies, but things such as the possible virgin birth and cloning ability of komodo dragons shows theres more variation than we think in sexual reproduction...

http://www.sciam.com/article.cfm?id=strang...t-true-komodo-d
QUOTE
Indonesian dragons can breed without the benefit of masculine companionship. Last week, researchers reported in Nature that the only two sexually mature female Komodo dragons in all of Europe laid viable eggs without insemination from a male. One Komodo, named Flora, lives at the Chester Zoo in England and has never been kept with a male; yet a few months ago she laid a clutch of 11 eggs, eight of which seem to be developing normally and may hatch as soon as January. Earlier this year, a now deceased female named Sungai from the London Zoo laid a clutch of 22 eggs, four of which yielded normal male dragons--even though Sungai hadn't had a date in two and a half years.

Some reptiles can hold onto sperm for several years, so initially researchers considered that Sungai's eggs had a father. But genetic analysis ruled that out, unless the father were somehow genetically identical to her. (Sungai did later mate with a male and laid a normally fertilized clutch, so don't think she died a virgin.)

These "virgin births" raised eyebrows because this asexual method of reproduction, called parthenogenesis, is rare among vertebrates: only about 70 backboned species can do it (that's about 0.1 percent of all vertebrates). Biologists have known that some lizards can engage in parthenogenesis, but nonetheless seeing it among Komodo dragons surprised zookeepers.

Despite having only a mother, the offspring are not clones. That's because an unfertilized egg has only half the genes of the mother. The sperm is supposed to provide the other half. In parthenogenesis, the mother's half-set of chromosomes doubles up to generate the full complement. Hence, the offspring derives all its genes from the mother, but they are not a duplicate of her genome.

Komodos have a curious twist in their sex determination as well. Although we think of females being XX (that is, having two X chromosomes) and males as being XY, it's the other way around in these giant monitor lizards. Two identical sex chromosomes make a male Komodo, and two different ones make a female. Biologists label the Komodo's sex chromosomes as W and Z, so ZZ makes a male and WZ makes a female. Birds, some insects and a few other lizard species also rely on this sex-determination system. (Embryos of some reptiles--notably crocodiles and turtles--don't have any sex chromosomes; rather, the incubation temperature dictates their gender.)

In Komodo females, each egg contains either a W or a Z. Parthenogenesis hence leads to embryos that are either WW or ZZ. Eggs that consist of WW material are not viable and die off (just as YY is not a viable combination); in contrast, ZZ does work. So all the Komodo hatchlings have been and will be male (ZZ).
Now thats a self-protecting system of reproduction! Female finds male = mixed children. Female can't fine male = all male children.
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post Feb 03, 2009, 05:44 AM
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QUOTE(trojan_libido @ Feb 03, 2009, 03:57 AM) *

species development to its environment has never been witnessed.

So, what do you call the HIV virus' mutation in response to drug treatment?
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post Feb 03, 2009, 05:56 AM
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QUOTE(code buttons @ Feb 03, 2009, 01:44 PM) *

QUOTE(trojan_libido @ Feb 03, 2009, 03:57 AM) *

species development to its environment has never been witnessed.

So, what do you call the HIV virus' mutation in response to drug treatment?
Depends upon how you define species development, but I would be careful in my definition with respect to this statement, as the whole of Darwinian evolution could be said to be species development in response to the environment. Then we come on to the meaning of 'witnessed'. Well the evidence is the fossil record largely, but there are many modern examples of rapid change, not least the evolution of the Peppered Moth that changed from white to black in response to environmental pollution and then back again after the various clean air acts.
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post Feb 03, 2009, 07:54 AM
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Thats not what intelligent design says!
http://www.evolutionnews.org/2009/02/evolu...ees_scient.html

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post Feb 03, 2009, 08:52 PM
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QUOTE(Phi @ Feb 03, 2009, 03:54 PM) *
Yerrr, such as this statement:

I doubt anyone, Dawkins included, would generally recommend sweeping aside all intuition to accommodate leaps of imagination, particularly when the intuition is your own and the leap is not. If Darwinism really is plausible, it must instead be the case that Darwin leapt to something of substance—something that really explains how, contrary to our intuitions, the remarkable gadgets we see in biology can be chalked up to mindless inevitability. What exactly is this explanation? It needs to be compelling, whatever it is, since the intuition we’re being asked to abandon is so tied to real-world experience—the very stuff of science.

Real-world experience is the very stuff of science? What like quarks, and black holes, and amoeboid white cells infiltrating our tissues to fight disease, and organisms too small to see with the naked eye (some still invisible with a light microscope) determining every aspect of our lives (from disease to biorecycling), and special relativity, and Hubble deep space galaxies, and .............? Eh?
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post Feb 03, 2009, 08:59 PM
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That site's off to a good start, I'm sure:

[Editor's Note: Douglas Axe is actually a molecular biologist, not a microbiologist. And it’s been pointed out that the quote I used from Axe’s piece that describes the Darwinian story as requiring 400 million years had a context — the supposed evolution of a proto-insect into a wide variety of insect life forms. However, the way I presented it makes it sound like the whole of Darwinian evolution was only supposed to require 400 million years, which wasn’t what Axe was saying.]
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post Feb 04, 2009, 12:02 AM
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Well I believe the real process of evolution doesnt stop at our bodies boundaries, so I'm generally with everyone on that. What I'm saying is they're attempting to make simulated biology, and thats where assumptions must be made!
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post Feb 04, 2009, 09:12 AM
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I wonder if anyone takes that seriously?
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post Feb 04, 2009, 10:59 AM
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QUOTE(Phi @ Feb 03, 2009, 03:54 PM) *
Your link provided this link:

http://biologicinstitute.org/2009/02/01/bo...r-2009/#more-40

One of my Facebook friend's friend retorted:

That website is, indeed, full of gibberish. For a start, the author seems to be totally unaware of the non-linear regulatory effects of genes on other genes, and of the existence of genes which control whole patterns of expression (like homeobox genes). He's also purposefully ignoring, apparently, any kind of mutation effect other than point mutation. Since we know that cross-over, gene reduplication and gene insertion by viruses (for example) are equally significant causes of genetic change, his entire argument is moot. (Plus, of course, his argument ignores the successful use of genetic algorithms to search space, and, in, for example, Tom Ray's Tierra experiment, evolve in the absence of "artificial" fitness functions. It's like saying that nuclear fission can't possibly produce power, in the 1950s, standing by Hiroshima.) mad.gif

ps, my friend's friend is a mathematician.
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post Feb 04, 2009, 11:02 AM
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I guess I can stop worrying now about the possible evolution of multiply resistant staph bacteria!
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post Feb 04, 2009, 11:04 AM
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QUOTE(Rick @ Feb 04, 2009, 07:02 PM) *

I guess I can stop worrying now about the possible evolution of multiply resistant staph bacteria!
Exactly the opposite! I wish we could stop worrying about the multiplication of creationists!
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post Feb 04, 2009, 11:32 AM
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These anti-darwinians seem to studiously ignore so many obvious things. How do they do it? I guess being nuts helps. So if we didn't evolve from simpler life forms, then how did we get here? To say that the flying spaghetti monster created us in present form isn't quite satisfying, is it?
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post Feb 04, 2009, 11:52 AM
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QUOTE(Rick @ Feb 04, 2009, 11:32 AM) *

These anti-darwinians seem to studiously ignore so many obvious things. How do they do it? I guess being nuts helps. So if we didn't evolve from simpler life forms, then how did we get here? To say that the flying spaghetti monster created us in present form isn't quite satisfying, is it?

They seem to forget that they were once a single cell with a wagging tale themselves.
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post Feb 05, 2009, 12:14 AM
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Dogmatic religious farmers always stump me. If they don't believe in evolution, they have to ignore the effects of selective breeding. Its hard to ignore the effects of selective breeding!

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post Feb 05, 2009, 12:20 AM
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wow, are there more?
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post Feb 05, 2009, 12:26 AM
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ahh, here's belgian blue

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post Feb 05, 2009, 12:28 AM
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