What does it mean to be human? Julian Baggini meets with scientists who aspire to take evolution into their own hands

MANY dystopian writers have imagined worlds in which a singular "human nature" has bifurcated or splintered into a plurality of human natures. They have portrayed societies in which the genetically modified rise above their inferior, natural cousins ("Gattaca"); or different castes of human are selectively bred for accomplishing different tasks ("Brave New World"). In some cases humans from working and middle classes evolve over millennia into two different species ("The Time Machine"), or they experience a reality that is entirely virtual ("The Matrix").

These dystopias are readily imaginable only because at some level it is obvious that human nature is malleable. There is no reason in principle why creatures like ourselves might not become radically different over time. Until recently, such mutations were simply abstract possibilities, limited to the power of gods, sorcerers and novelists. But lately we have begun to consider the possibility that technology might change us more in a generation or two than evolution has done over millions of years.

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