In his third lecture, Richard Dawkins uses the metaphor of a tall mountain - Mount Improbable – to explain evolution. When we look at Mount Improbable, its peak seems insurmountable. We could never jump to the top by chance. But if we take a slow, gradual ascent around the outside, we are able to reach the summit. In the same way as a person climbing Mount Improbable would ascend by tiny steps, life on Earth has evolved through a series of small, gradual changes.
Some creatures have evolved to imitate their environment. In the insect world, leaf insects and thorn bugs protect themselves against predators by looking and behaving like leaves and rose thorns. Richard explores the idea that all creatures like these are the key, and nature is the lock. In the same way that a key exactly fits a lock, humans and animals alike have inherited improvements over time that enable us to ‘fit’ our environment. In a series of stages, we have all evolved to complement the natural world.
But if evolution has gone through intermediate stages, there must have been times when we were not a perfect fit. A leaf insect must have at one stage only half looked like a leaf, a thorn bug only half like a thorn. So how do organisms function when they’re only half a key? And how do they evolve their perfection?