NOT having any family is tough. Often unappreciated and uncomfortably different, orphans have to fight to fit in and battle against the odds to realise their potential. Those who succeed, from Aristotle to Steve Jobs, sometimes change the world.
Who would have thought that our DNA plays host to a similar cast of foundlings? When biologists began sequencing genomes, they discovered that up to a third of genes in each species seemed to have no parents or family of any kind. Nevertheless, some of these “orphan genes” are high achievers, and a few even seem have played a part in the evolution of the human brain.
But where do they come from? With no obvious ancestry, it was as if these genes had appeared from nowhere, but that couldn’t be true. Everyone assumed that as we learned more, we would discover what had happened to their families. But we haven’t – quite the opposite, in fact.
Ever since we discovered genes, biologists have been pondering their origins. At the dawn of life, the very first genes must have been thrown up by chance. But life almost certainly began in an RNA world, so back then, genes weren’t just blueprints for making enzymes that guide chemical reactions – they themselves were the enzymes. If random processes threw up a piece of RNA that could help make more copies of itself, natural selection would have kicked in straight away.
As living cells evolved, though, things became much more complex. A gene became a piece of DNA coding for a protein. For a protein to be made, an RNA copy of the DNA has to