 In this case, the fragments were kept close together in a glassy state, akin to what happens when things are freeze-dried. The fossil chromosomes allowed researchers to assemble the genome of an extinct species for the very first time. In the process, they found 28 pairs of chromosomes, the same number and with the same structure as modern elephants. This made it possible to reveal a new secret from ancient history, which genes made the hair grow on woolly mammoths.