Once upon a time, a young Swedish scientist called Svante Pääbo couldn’t decide whether he wanted to study biochemistry or Egyptology. He opted to do both and extracted DNA from an Egyptian mummy. It was only a smidgeon of DNA, but a new science was born.

Pääbo, who won the Nobel Prize in Physiology or Medicine in 2022, published his work on the mummy in the journal Nature in 1985. This went hand in hand with rapidly improving technology to sequence the genetic ‘letters’ of DNA in bulk. In 1990 a consortium undertook to sequence the entire genome (that is, the full complement of DNA) of a human being within fifteen years. This was a big promise. The first genomes to be sequenced were those of viruses, which are very tiny. In 1996, scientists conquered the genome of brewer’s yeast, which consists of twelve million DNA ‘letters’. The human genome has around three billion. By 2001, the consortium had published the first draft of its sequencing of the human genome (it’s been improved a lot since), at a cost of $3 billion. The effort, not to mention the expense, was compared with the Apollo space programme to send people to the moon. Since then, the technology has improved so much that a human genome can be sequenced for $1,000.

Genomes of thousands of humans have now been sequenced, along with those of an enormous range of animals and plants, and many archaeological and fossil remains too. In 1997, Pääbo’s group sequenced DNA from the bones of a Neanderthal, our closest extinct relative. Now the genomes of many Neanderthals are