nineteenth century naturalist Charles Darwin
was the first to realise that all life is governed by this rule. He found
that creatures did indeed adapt though he didn't know how because, in
his time, people didn't know about genes.
It turns out that genes can change. They don't always make perfect copies
when a cell divides. Sometimes a mistake is made. This is called a mutation.
Most mistakes are disasters - the organism dies. Some are useful and give
the creature an advantage which allows it to have babies which are more
likely to be successful. But this process is entirely accidental. This
slow business of trying new body shapes and styles, some of which work
and some of which don't, has been going on for as long as life. Perhaps
you know about it. It's called evolution
- the survival of the fittest.