Darwin wondered whether the finches might have shared a common ancestor from mainland South America-whether all of life might have evolved through a process of “descent with modification”-and he drew a rudimentary tree in his private notebook, beneath the words “I think.” The tree showed how a single ancestral population could branch into many species, each with its own evolutionary path. In 1837, a taxonomist in London told Charles Darwin that the finches he had shot and carelessly lumped together in the Galápagos Islands were, in fact, many different species. “Everything in biology has a history, and we can show this history as a bifurcating tree,” she said.īirds are the most diverse vertebrates on land, and they have always been central to ideas about the natural world. The amount of data and computing power required for this mission is almost unfathomable, but the final product should be as simple in principle as the diagram Stiller had assembled as a child. Then, in 2017, she moved to the University of Copenhagen and joined B10K, a scientific collaboration that aims to sequence the genome of every bird species-more than ten thousand in all-and to reveal their connections in a comprehensive tree. Years later, as a graduate student in biology, Stiller worked on an evolutionary tree for seahorses and their relatives, using DNA to understand the ancestry of different species.

“I wonder if this experience of reconstructing a family tree primed me to appreciate trees and the powerful insights they hold,” Stiller told me in a recent e-mail. Sons killed fathers uncles kidnapped nieces siblings fell in love. As lineages became clear, so did family dramas. Frustrated, she wrote each name on a card and started to arrange children beneath parents on a desk in her bedroom. She often lost track of their relationships, however-their feuds, trysts, and betrayals-as she flipped among the entries. When Josefin Stiller was growing up in Berlin, she loved reading about Greek gods in an encyclopedia of mythology.

Tree of life