Evolution as Hill Climbing

John Holland proposed the idea of organisms as agents that perpetually seek high ground in a fitness landscape. Once at the top of a hill the species gets stuck. To get unstuck, a mutant agent takes a random leap off of the hill. It then begins climbing a new hill.

Here's a screen shot of a fitness landscape:

Each patch has an altitude attribute and is initialized as follows:

to init-patch
set altitude 12 * sin(18 * pxcor) * cos(18 * pycor)
set pcolor scale-color green altitude -12 12
end

The higher the altitude, the lighter the shade of green.

Turtles use the uphill and jump procedures to move.