Friday, June 7, 2013

New Algorithms Force Scientists to Revise the Tree of Life


When the British morphologist St. George Jackson Mivart published one of the first evolutionary trees in 1865, he had very little to go on. He built the tree — a delicately branching map of different primate species — using detailed analysis of the animals’ spinal columns. But a second tree, generated by comparing the animals’ limbs, predicted different relationships among the primates, highlighting a challenge in evolutionary biology that continues to this day.

Now, nearly 150 years later, scientists have vast amounts of data with which to build so-called phylogenetic trees, the modern version of Mivart’s structure. Advances in DNA sequencing technology and bioinformatics enable them to compare the sequence of hundreds of genes, sometimes entire genomes, among many different species, creating a tree of life more detailed than ever before.

But while the abundance of data has helped resolve some of the conflict surrounding parts of the evolutionary tree, it also presents new challenges. The current version of the tree of life is more like a contentious wiki page than a published book, with certain branches subject to frequent debate. Indeed, just as the spinal column and limbs created contrasting maps of primate evolution, scientists now know that different genes in the same organism can tell different stories.

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