[dragonwriter]

> It's how evolution is supposed to work: a simple organism gets some random changes and becomes more complex.

Er, no, that's not how evolution is supposed to work.

There is nothing in evolutionary theory that indicates a necessary preference for increasing complexity.

If (and this is a premise outside the scope of evolution) life starts with the something very close to the simplest form which can be "alive", it is unsurprising and consistent with evolution for evolution to produce some forms which are much more complex, and for the average complexity to increase over time -- especially if its not constrained by an upper bound on viable complexity.

But you, for instance, start with a bag of zeroes, periodically randomly add or subtract 1 to each number in your bag and then throw out any that are less than zero, over time the highest number and the average number in your bag is going to increase -- the change process isn't biased, but the selection process is.

[stefantalpalaru]

The existence of a fitness function does not explain the increase in complexity. The most successful life forms on this planet are the unicellular ones. Why would the selection process favor anything else?

[dragonwriter]

> The existence of a fitness function does not explain the increase in complexity.

That would be an interesting rebuttal if I calimed that the existence of a fitness function explained the increase in complexity.

Since that's not what I said, it's just a non-sequitur.

What I said was that if you start with a collection of items all uniformly near one boundary and then vary the collection randomly rejecting things that fall outside of the boundary, both the maximum and mean distance from the boundary will increase over time, until and unless that behavior is constrained by a boundary on the other end.

(In the case of life, I'm talking about a strong, "outside of this you don't have anything that counts as life" boundary, not a fitness function in the evolutionary sense, which addresses the relative reproductive success among viable life forms.)