left behind...,

guardian |  As science progresses the upgrades that become available will increasingly widen the gap between rich and poor. Research on implantable devices called brain-computer interfaces (BCIs) are in trials to help disabled people move their defunct limbs or robotic prosthetics.

More advanced devices could link people's brains directly to the internet, giving them vast and faithful memory storage, and seamless access to information, even if that does include endless footage of cats in hats.

Work is ongoing into BCIs that connect many brains at once, allowing animals to cooperate by accessesing each others' brain power - work which raises deep questions about the future meaning of identity.

Genetic engineering will be more disruptive still. A new genome editing procedure called Crispr has given scientists their first real hope of making safe, precise changes to the human genome. They have already used it to correct cells with genetic faults that cause cataracts and cystic fibrosis. Similar therapies might allow improvements to human performance.

Western history has made many of today's researchers flinch at studies into the genetic basis of intelligence. But the Beijing Genomics Institute, the world's largest genomics research centre, has taken on the job . If the project bears fruit, it might drive attempts to boost human intelligence by genetically modifying embryos.

George Church, a geneticist at Harvard University, suggests another radical possibility. He has developed tools that can scramble the genetic code leaving it functional but unrecognisable to invading viruses. His first goal is to engineer a bacterium that is resistant to viral infection. But he does not dimiss the possibility of changing human DNA too – leading to a biologically new kind of human.

"In the 21st century, there is a real possibility of creating biological castes, with real biological differences between rich and poor," said Harari. "The end result could be speciation. We're used to being the only human species around, but there is no law of nature that says there can only be one species of human. With this kind of upgrading treatment we could have, in the not too distant future, more than one human species on Earth again."