An international team of scientists described the first-ever sequencing of a complete human genome – the set of instructions to build and sustain a human being – in research published Thursday in the journal Science. The previous effort, was incomplete because DNA sequencing technologies of the day weren’t able to read certain parts of it. Even after updates, it was missing about 8% of the genome.

“Some of the genes that make us uniquely human were actually in this ‘dark matter of the genome’ and they were totally missed,” said Evan Eichler, a University of Washington researcher who participated in the current effort and the original Human Genome Project. “It took 20-plus years, but we finally got it done.”