Over the past four decades, researchers have come up with ways to run ever-more-sensitive DNA tests. In the most extreme of these, experts can reconstruct the entire genome using DNA fragments extracted from a single cell.
Similar tests allow scientists to study DNA from fossils dating back thousands of years. Over time, genetic material in fossils degrades until it becomes scarce. Yet scientists only need to rescue trace amounts for analysis.
“We can be down to 10 or 20 molecules,” said Brian Kemp, a geneticist at Washington State University, who regularly extracts DNA from tiny fish vertebrae more than 10,000 years old.