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Digital Life and Evolution
mrivorey writes "Discover Magazine has a story about The Digital Evolution Lab at Michigan State University. Scientists there have created virus-like computer programs that replicate, mutate randomly, and compete with each other... in other words, they evolve. Among such feats as learning to add and compare numbers, these digital life forms also once avoided scientists attempts at "killing" them, by playing dead.
You can download the project yourself from SourceForge." We first mentioned this in early 2003, but it appears to have developed a good deal since then.
Dan Simmons included this idea in his Hyperion book series, where evolving digital life spead into the "infosphere" and became artifically intelligent. Later it tried to exploit the human race and wipe out large portions of it. People who download the project beware!
Philosophy.
I wonder how long until the first virus based on this code is released?
I'd like to see this run as a distributed computing project, as a sort of race to achieve measurable consciousnessness among the organisms.
Art Schools Dietzilla
I think this built-in inefficiency is to control the population, no?
No.
At no point will evolution favor inefficiency for inefficiency's sake. There is always an ulterior, efficient motive. In the case of sex, it's forced genetic diversity. One possible scenario for its promulgation could have been a cyclical death-scenario for some manner of simple organism (say, a recurring chemical change in a lake due to a hot spring or toxic runoff) wherein the asexual descendants (a.k.a. clones) would be successful and dominate for long periods but die off in vast waves whenever the environment changed drastically and rapidly. Those that developed sex and its subsequent genetic diversity had a greater chance of fostering enough differing offspring that at least some of their descendants made it through the local cataclysm.
Regardless, it's certainly not an inherent "inefficiency".
It would make sense to introduce sex or its analogue to any life-imitating algorithm, as the implications for the evolution of "mix, match and reward" permutations are many, complex and certainly worthy of further analysis.
That was the old thought. For years now, scientists have been doubting that theory. The work with the digital life has shown that, while it confers more genetic variety, it also allows more genetic damage to collect.
Sexually reproducing organisms do not do any better under most simulation conditions.
Recent studies of giardia have shown that this ancient organism has the genes for sexual reproduction. Apparently, sexual reproduction conferred some powerful advantage, given how early it developed in the history of life. But if this is so, why does giardia not actually use sexual reproduction? The genes are there - they have just never been seen to be activated. In all the conditions so far observed, giardia reproduces asexually. If the advantage of sexual reproduction is so great, why did giardia give it up?
Enquiring minds, etc.
This sig seemed like a good idea at the time....
While the "digital life" models may be helpful in visualising what's going on in real life, and in devising experiments to test real life with, the digital environment is about as artificial as it gets.
That said, what the models are showing is that sexual reproduction accumulates changes faster, but does not change the quality of what accumulates. The next step will be to tweak the models even further from reality in order to see them accumulate more advantages than handicaps. Otherwise the results are too depressing.
In analogue life (ironic that digital life should be an analogue of analogue life), genuinely advantageous mutations are collectors items - or would be.
Got time? Spend some of it coding or testing
An additional benefit with large organisms (or rather, organisms with brains) is that they can also actively play a part in the gene selection process by evaluating potential mates in an intelligent and decidedly non-random way. Usually (but not always) there is some reasonably rational basis for the selection that ties in with suitability to survival (and more importantly rejecting mates that are poorly suited to survival), so we see with many animals that females will choose the strongest males to mate with, and ignore weaker males or those that appear to have defects. Similar thing when males choose females, although other criteria may be used, usually these are linked to child bearing and raising capabilities.
Weaver birds as an example are notoriously picky about choosing males that are good at building nests - obviously important for successful reproduction.
Intelligent organisms are thus active participants in the evolutionary process - they/we guide it. Each species collectively makes these unintended decisions every time an individual chooses a mate about which "direction" they would like the species to go.
Asexual reproduction doesn't provide an organism the opportunity to make intelligent decisions about the genetic material of its offspring.
There is an interesting book on this topic called "The Mating Mind : How sexual choice shaped the evolution of human nature". It's interesting that sometimes a characteristic may be chosen not out of suitability to survival, but purely out of a kind of "cultural" preference that develops. E.g. Orangotans at some point in their past must have decided they like to be that particular shade of orange. We may "culturally" decide that blondes are hot, thereby "guiding" our species towards becoming increasingly blonde (although that is unlikely to happen, it's just an example).
This reminds me of the "Progranisms" project I saw over on the Gentoo Linux forums:
i ght-progranism.html
r anism-neilh.c r anism-neilh-condensed.c
http://forums.gentoo.org/viewtopic-t-255505-highl
http://www.progranism.com/
Basically some guy put together an executable which makes a few (mutated) copies of itself when it runs, then executes those copies after a short delay. The idea is that executables might evolve which show interesting behaviors.
You can download his source code here:
http://www.progranism.com/junk/progranism-2.3.1.c
Because I like doing strange things, I made a variant of the program which mutates the source code and recompiles it (mutating until it gets something compilable), rather than mutating the executable directly:
http://www.its.caltech.edu/~neilh/progranism/prog
http://www.its.caltech.edu/~neilh/progranism/prog
http://www.its.caltech.edu/~neilh/progranism/ (some cleanup and maintenance scripts)
Unfortunately, it's stuck in a pretty steep local minima -- it makes some trivial mutations, but nothing major. One interesting possibility would be to have it search your hard drive for other executables and source files, and try to "mate" with those.
Another scary possibility would be to have viruses/worms with non-trivial evolution capabilities. That'd be a pretty nasty outbreak to try to control.
Finally, a rather neat-looking project is AI.Planet, which is trying to create an 3D evolving ecosystem/world of intelligent "organisms." Framsticks, a 3D life simulation project, is also pretty cool.
Simple definition usually is that if two organisms can't produce viable, fertile offspring then they're of different species.
Even in sexual organisms, this definition of species has some problems. You can easily have organism A that can breed with B, and B can breed with C, but A and C are incompatable. How do your divide up the species lines in this case?
In general, when a new species forms, each organism has to have others it can mate with, or else they would just die out without any offspring. The speciation process is a gradual one, and so, theoretically, there is probably a path you could follow between any two sexual organisms where any pair on the path could theoretically mate.
In Avida, for simplicity, we determine species by testing each orgasnism against the species of its parent. If it can cross-over at most points with the prototype of that species, it is marked as being part of that same species. If it cannot, we create a new species for it where it is the prototype. Not an ideal method, but it works in most cases (and we rarely need to resort to the species concept).
What's fun, is that this even works for asexual organisms. We can force all possible crossovers (in isolation of course -- this never feeds back into the system) to see if they would have any ability to mate if they has been sexual.
Dr. Charles Ofria
Director, MSU Digital Evolution Lab
I guess one nice thing about open source software is that even those who disagree with you can help you. :)
From the article:
When the Avida team published their first results on the evolution of complexity in 2003, they were inundated with e-mails from creationists. Their work hit a nerve in the antievolution movement and hit it hard. A popular claim of creationists is that life shows signs of intelligent design, especially in its complexity. They argue that complex things could never have evolved, because they don't work unless all their parts are in place. But as Adami points out, if creationists were right, then Avida wouldn't be able to produce complex digital organisms. A digital organism may use 19 or more simple routines in order to carry out the equals operation. If you delete any of the routines, it can't do the job. "What we show is that there are irreducibly complex things and they can evolve," says Adami.
The Avida team makes their software freely available on the Internet, and creationists have downloaded it over and over again in hopes of finding a fatal flaw. While they've uncovered a few minor glitches, Ofria says they have yet to find anything serious. "We literally have an army of thousands of unpaid bug testers," he says. "What more could you want?"
If the advantage of sexual reproduction is so great, why did giardia give it up?
Because they're an intestinal parasite and don't need it?
We can consistently see that asexual reproduction is popular among simple life and sexual reproduction is popular among complex life. This post in this thread gives a possible reason why. Is it that unreasonable to suspect that the more complex a lifeform is, the more benefit sexual reproduction confers? And if we are to take this suspicion seriously, then why would it be surprising that computer simulated models-- which by their very essence are simple-- would fail to demonstrate this benefit? And why would it be surprising that an organism that at one time used sexual reproduction would revert to exclusive use of asexual reproduction after settling into a very simple evolutionary niche, as giardia has?
I do not really see anything in your post that contradicts the purported advantages of sexual reproduction.
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