In 2001, the initial sequence of the human genome cut the figure dramatically. The International Human Genome Sequencing Consortium put it at 30,000 while a rival group led by Craig Venter estimated the number at 26,000. In 2004, the final draft of the human genome reduced the figure even further to around 24,500 and in 2007 further analysis suggested that it was more like 20,500. And that’s where the figure has sat. Until now.