How do we get complexity?

Like a safecracker, evolution cheats by solving complex problems one step at a time. To open this combination lock by guessing the complete combination is very hard (chance of guessing combination is 1 in 10,000,000,000). But, we can crack each wheel in turn. On average it will take five spins to get one wheel, so 50 random trials will find the right combination.

How to evolve an eye

Despite not being perfect (see previous slides), the eye is still an amazing organ. How can we explain its evolution by blind natural selection? Darwin appealed to the existence of a range of plausible intermediate eyes in nature:

How to evolve an eye in 2000 easy steps!

• Shape of the eye changes at random by no more than 1%
• Selection retains only those changes that improved the optical performance of the eye (ability to resolve objects)
• 2000 steps would generate a vertebrate eye
• For realistic values of heritability and strength of selection, this would take 400,000 generations
• If one generation = one year then an eye takes less than half a million years to evolve