A final way to measure biodiversity is by studying the genes of species. Geneticists have made enormous advances in the past few decades, and they can work wonders. For example, it is possible to tell whether one population of a species has been interbreeding with another population over the past ten thousand years, just by taking a few blood samples and studying the genes in the blood cells.

A final note about biodiversity: no matter now you measure it, it is declining very, very rapidly today. Scientists believe that species are now going extinct as fast or faster than when the dinosaurs disappeared—and that was one of the most massive extinction episodes the earth has ever seen.”