Bots and Simulations > Tips and Tricks

NO MORE OVERFLOW

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Botsareus:
I did it more then once , the difference is very little but my first bot with mutating rates does better.

shvarz:
Yes, I am reading this.  But it is not an easy question, it will depend on many things and needs some serios statistical analysis and so on.  BTW, the way graphs are working now, it is impossible to see any long-term trends.

  Right now I am evolving a bot that can hunt for moving low-anundance food in sims with high friction.  I am over 25 million cycles now and beleive me that the evolved bots are much better than the one I started with.  I actually tried to put them against each other and the parent gets its brains knocked out.

I don't know for sure, cause Bots does not give details on his sims, but my impression is that he sets mutation rate too high.  The result is that he gets two effects combined: "Mueller's ratchet" and "error catastrophie" - both lead to decrease in fitness over time and the "mutating bot" will lose.

Numsgil:
Hey Schvarz, since you're our resident mutation expert (seeing as how you run them longer then most others) you should write up a short article on what settings to use, what you should expect to see, how to sort through the bots you get, etc.  Would be really interesting.

Also, what is Mueller's ratchet and error catastrophe?  I think I understand what you mean but I'd be interested in finding out for sure.

AZPaul:
Mueller's ratchet. Ahh, yes. Within most asexually reproducing species the buildup of diliterious genes will, eventually crash the population, even to extinction. Some corollaries in small inbred sexual populations as well...like Arkansas.

May I make one observation? Picky, I know, but do let's keep things straight.

"Evolution" does not happen to individuals. It happens to populations. It is the basis of speciel events and an individual does not constitute a species. Populations do. Individuals suffer mutations which add (maybe) to genetic variation within the population which leads to adaption (maybe) to changing environments. No individual evolves.  

Mutations may or may not be in the "individuals" best interest. Mutations are random events that have whatever effect they have and the individual suffers or prospers accordingly.

Mutations [you]are[/you] in the best interests of the "population." Individuals with dilitarious mutations (usually) do not survive to reproduce, thus, for a population over many generations, survived mutations add considerable genetic variation to the gene pool.

When the inevitable environmental change occurs, the more genetically varied the population the better the chance that some combination of available alleles (ex-mutations now ubiquitous within the population) will produce individuals better able to cope (fitter) in the changing environment. Or maybe not.

As for Bot's desire for a faster rate of mutation rates:

Keep in mind that in a simulator like DB the mutation rate, and the rate of mutation rates, is synonymous with overall evolutionary time. One way to simulate great lengths of time is to have a high rate of mutations and a high rate of change in those rates. The other side of the simulation, to make this time scale accurate, must be a very short individual life span.  

Since beneficial mutations, and allele variability, are slow to work through even a subset of a population, the higher the mutation rate the higher the generation "turnover" must be to weed out the bad (but lucky, since it may have been, by fluke, passed on to one generation) mutation and make the good alleles more frequent in the population.

In the absence of this, Shvarz has got it right. Not enough generations for natural selection to work, you end up with bad genes everywhere, very quickly. Back to brother Mueller and his silver ratchet. Or was that Maxwell and his silver hammer? Can't remember.

Numsgil:
Ah, see they don't teach this kind of thing in Bio 101.  I always knew we were playing with very specific cases with mutations.

One thing Paul, what do you mean by generational turnover?  I agree that speeding up mutations means that you need a way to speed up the removal of deleterious mutations from the population.

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