The honest answer is “We don’t know.” Life is far too complicated to understand in general, let alone how it evolves. But it is clear that it has evolved, and is still evolving.
So what do we mean by evolve? Does the idea make any sense?
Yes it does, and it has three basic principles: (1) Variation: there is a variation among individuals in a population (2) Heredity: offspring resemble their parents (3) Differential reproduction: in a given environment, some forms produce more offspring than others.
I got the above from the New York Review, May 27: Not so natural selection by Richard Lewontin – which started me thinking about this.
But Darwin’s attempt to go beyond this is faulty – as anyone can easily see. The survival of the fittest, simply means that the fittest survive – and explains nothing.
I used to be struck by the amazing variety of plants I would see in my morning walk along a country road down here. It was clear to me, that plants wanted to change – and if those changes survived, new species resulted. In most cases, it was impossible to see what advantage these changes had. There was plenty of sun and rain, and no frost – so variety was all over the place. Even the insects seemed under control – although there is plenty of variation here too. Plenty of room for everything.
No doubt some plants had advantages over others, but they did not seen determined to ruthlessly eliminate the competition. One suspects Darwinism was appealing because of Social Darwinism – which made the Victorians of his day the ultimate species.