Resolving the Tree of Life

Scientists have long used physical traits to shed light on evolutionary relationships. Sometimes this has worked, like using lactation to group mammals. And, sometimes, it hasn’t: people once thought bats were featherless birds! Today, evolutionary biologists rely more heavily on molecular-based phylogenies to resolve relatedness. But, what they haven’t been able to do is address big picture questions about how observable traits (phenotypes) evolve across higher taxa.