In a way, sequencing DNA is very simple: There's a molecule, you look at it, and you write down what you find. You'd think it would be easy—and, for any one letter in the sequence, it is. The problem ...

The world's oldest DNA comes from a 2.4 million-year-old ecosystem in Greenland. Will scientists eventually sequence even older DNA? When you purchase through links on our site, we may earn an ...