From ”What Mad Pursuit”:
The second criticism is that we may not yet know all the gadgetry that has been evolved to make natural selection work more efficiently. There may still be surprises for us in the tricks that are used to make for smoother and more rapid evolution. Sex is probably an example of such mechanism, and there may, for all we know, be other as yet undiscovered. Selfish DNA -the large amounts of DNA in our chromosomes with no obvious function- may turn out to be part of another. It is entirely possible that this selfish DNA may play an essential role in the rapid evolution of some of the complex genetic control mechanisms essential for higher organisms
Francis Crick, 1988.