February 10, 2009
Crunching the Data for the Tree of Life
By CARL ZIMMER
Michael Sanderson is worried. Dr. Sanderson, a biologist at the University of Arizona, is
part of an effort to figure out how all the estimated 500,000 species of plants are related
to one another. For years now the researchers have sequenced DNA from thousands of
species from jungles, tundras and museum drawers. They have used supercomputers to
crunch the genetic data and have gleaned clues to how today’s diversity of baobabs,
dandelions, mosses and other plants evolved over the past 450 million years. The pace of
their progress gives Dr. Sanderson hope that they will draw the entire evolutionary tree of
plants within the next few years. “It’s within striking distance,” Dr. Sanderson said.
There’s just one problem. “We have no way to visualize such a tree at the moment,” he
said. If they tried, they would end up with a blurry, inscrutable thicket. “It would be
ironic,” Dr. Sanderson said. “We’d be saying, ‘We’ve built it, but we can’t show it to
Ever since Charles Darwin first sketched a spindly sapling in 1837, biologists have relied
on evolutionary trees to understand the history of life. Today biologists draw
evolutionary trees to help them track the emergence of new diseases, identify species at
risk of extinction, and trace the history of disease-related genes in the human genome.
Within the next few decades, biologists may figure out how the millions of species on
Earth are related to one another. But for people to actually see that tree of life, the tree
itself will have to evolve.
Biologists have responded to the problem by enlisting the help of computer scientists and
software designers from companies like Google and Adobe to find a new way of looking
at evolution. Their goal is to create a program that allows scientists and nonscientists
alike to fly through evolutionary trees.
“Just like Google Earth changed the way people look at geography, a sophisticated tree of
life browser could really change the way we look at the life around us,” said Mark W.
Westneat, the director of the Biodiversity Synthesis Center at the Field Museum in
Darwin drew the first evolutionary tree when he was 28. He had recently returned to
England from his five-year voyage around the world aboard the Beagle, and his theory of
evolution was still in an embryonic state. It occurred to him that evolution could explain
the similarities and differences between species. The descendants of an ancestral species
might have evolved into different forms, splitting into separate lineages “like the
branching of a great tree from a single stem,” as he would later write in “On the Origin of