Bots and Simulations > Evolution and Internet Sharing Sims

On Evolution and Population Decline

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JossiRossi:
I'm working on a new zerobot sim. I had a 200 hour one recently but it ran so long that my bots began to lose all their DNA due to random deletions, I just wasn't lucky enough to get virus shots bumping up the DNA lengths as I did in a lost zerobot sim I had going a while back. That's always a disappointing thing, but it can happen where you spend a long time waiting for a zerobot sim to take off and it kind of just fizzles.

Also with zerobots getting the initial settings right is a REAL pain.

Numsgil:
For zerobot sims, make sure once you have a replicator that your mutation rates are low enough.  That early in their evolution selective pressure is more like a sneeze than a hurricane.  You have to be extremely careful not to overpower it.

EricL:

--- Quote from: Moonfisher ---I prefer oscilating mutations rates, with something like 100-200 cycles of strong mutation and 2000 with low mutations... that gives you a chance for more radical changes with good room for natural selection...
--- End quote ---
IMHO, mutation rate oscilation is counter productive.  Peaks of high mutation rate are almost as bad in my opinion as a sustained high mutation rate. It's like trying to evolve in an evironment prone to solar flares.  There is little bots can do to adapt to it and all it really does is destroy good DNA.  

Mutations are nearly almost always a bad thing.  The probability of a benifical mutation is maybe 1 in a million or similar.  When that rare event happens, you want that mutation to fixate in the population.  That takes time.  If the mutation rate is too high, whether it is constant or periodic, you run the significant risk of destorying that benificial mutation before it can fixate in the population.

Bascically, you want the mutation rate to be high enough that you have some diversity (but not total diversity - having some significant percentage of bots be identical is a good thing - a benificial mutation may be fixating...) within the population for selection to operate on and no higher.

shvarz:

--- Quote ---IMHO, mutation rate oscilation is counter productive. Peaks of high mutation rate are almost as bad in my opinion as a sustained high mutation rate.
--- End quote ---

I second that.

One way to help somewhat alleviate the problem of high mutation rate breaking all good DNA is to create a large "cache" of bots using a local teleporter. If the periods of high mutation rate are infrequent and short, then they would mutate only those bots currently in the sim. Teleporting bots back from the cache allows population to recover any good DNA that may have been broken. But, as Eric pointed out, beneficial mutations need time to spread through population and they need deterministic population behavior. You have to have large population sizes and a lot of time under stable environmental conditions.

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