Phylogeny: Rewriting Evolution
Kevin Peterson maps out the standard phylogenetic tale for placental mammals. First, Peterson scratches a line leading to elephants, which branched away from the rest of the placentals around 90 million years ago. Then came dogs, followed by primates (including humans) and finally rodents — all within a frenetic 20 million years. This family tree is backed up by reams of genomic and morphological data, and is well accepted by the palaeontological community. Yet, says Peterson, the tree is all wrong.
A molecular palaeobiologist at nearby Dartmouth College, Peterson has been reshaping phylogenetic trees for the past few years, ever since he pioneered a technique that uses short molecules called microRNAs to work out evolutionary branchings. He has now sketched out a radically different diagram for mammals: one that aligns humans more closely with elephants than with rodents.