Do you have ideas, or do ideas have you? What exactly are ideas? Are they divine sparks of inspiration, the accidental by-products of our weird ape brains, neuronal fireworks displays that find meaning in our lives – or are they more than all these things?

One idea that I've spent the past three years of my life investigating is that ideas are, to a very real extent, 'alive' in their own right – surviving, reproducing, evolving, going extinct, just like living things.

It sounds a harmless proposition, but the implications are quite startling. If ideas are just like living things, then they are subject to Darwinian rules – inherently selfish entities, doing anything and everything they must to survive and propagate. And in this scenario, what are we? Little more than their hosts, their habitats? Vehicles to carry them from one parasitic generation to the next, coerced accomplices to their wild ambitions? If this idea has any substance at all, it will upset a lot of people.

It's not my idea, you understand. 'Meme theory', as it has been labelled, evolved in the minds of people including biologist Richard Dawkins, philosopher Daniel Dennett and psychologist Susan Blackmore, years before it entered mine. But at some point I, too, became infected and, in 2009, I decided to do what every good vehicle should do and take its passenger for a ride.

Like Darwin, I ventured abroad, into the cultural wilderness of America, to search out first-hand evidence that ideas are subject to natural selection. As I crossed the prairies, I classified the changing moustaches of farmers, plotted the evolution of the cowboy hat, dated American barns, and charted a taxonomy of tepees. In doing so, I found the evidence I needed to suggest that ideas do evolve just like the finches and tortoises that Darwin discovered in the Galapagos.

What's more, I found that viewing our world through 'meme goggles' is like suddenly spotting that vase in the optical illusion with the two faces. Your focus shifts from the human beings to the things in between – the countless living ideas that skip through our seven billion brains, each one competing for space in our cerebrums and the chance to procreate through our tongue and wrist movements. The mêlée of a new form of life is revealed. It's quite a view! Let me give you a few glimpses, with examples from my notebook.