I am not an enthusiast for diversity of opinion where facts are concerned. - Richard Dawkins

They are in you and me; they created us, body and mind; and their preservation is the ultimate rationale for our existence. They have come a long way, those replicators. Now they go by the name of genes, and we are their survival machines.

Molecular evidense suggests that our common ancestor with the chimpanzees lived, in Africa, between 5 and 7 million years ago, say half a million generations ago. This is not long by evolutionary standards.

Orb webs in real life do their business largely in two dimensions. If the mesh is too coarse, flies pass straight through. If the mesh is too fine, rival spiders will achieve nearly the same result at less cost in silk, and will therefore leave behind more progeny to carry on their economically more prudent genes. Natural selection finds the efficient compromise.