We can look at the genomes of things alive today. They can be measured and compared, from these comparisons we can make educated guesses of what the genome of t

We can look at the genomes of things alive today. They can be measured and compared, from these comparisons we can make educated guesses of what the genome of the long gone last common ancestor of closely related species might have looked like. With theories of "molecular clocks" (rates of ambient mutations) we can make guesses at how much time is needed to explain different amounts of change in genomes. Here getting actual data from an ancient source beyond being interesting in its own right for rino lovers around the globe provides a reality check on the processes used for phylogenetic inferences across the tree of life