One area where comparison of genome sequences isn't all that relevant, says Moran, is the emerging science of transplanting organs and tissues from pigs to humans.

[The success of pig-human transplants] has very little to do with whether there's a two per cent or 20 per cent difference in the genome sequence — if those numbers actually meant anything anyway — the main barrier is caused by just one gene," says Moran.

That gene is called galactose-alpha-1,3,galactotransferase — gal-transferase for short . All mammals except humans and higher apes have a working version of gal-transferase, which coats cells with an antigen (a molecule that our immune system reacts to). This means if pig tissue is transplanted into humans our immune system will mount a drastic rejection response as our bodies detect the antigen and attack it.

Scientists have come up with a solution to stop tissue rejection: genetically modifying the pigs by eliminating the gal-transferase gene. A few more human genes are also added to the pigs to make the pig tissue even more acceptable to our immune system.