With its deeply embedded roots, sturdy trunk and dense profusion of branches, the Tree of Life is a structure of nearly unfathomable complexity and beauty. While major strides have been made to establish the evolutionary hierarchy encompassing every living species, the project is still in its infancy.
At Arizona State University's Biodesign Institute, Sudhir Kumar has been filling in the Tree of Life by developing sophisticated methods and bioinformatics tools. His latest research, which appeared on the advance online edition of the Proceedings of the National Academy of Sciences will uniquely enable scientists to analyze very large datasests to set time to the multitude of branching points (nodes) on the tree, each representing a point of species divergence from a common ancestor. The new method differs significantly from currently used techniques and excels in providing results of equal or greater accuracy at speeds of 1000 times or faster.
For the proper study of evolutionary history, two components are key: the relationships between organisms (known as phylogeny) and their times of divergence. As Kumar explains, the powerful technique for estimating the time of divergence between species was initially realized over four decades ago, when the concept of molecular clocks was introduced. Initially the idea rested on the assumption that alterations in either the amino acid sequences of proteins or the nucleotide sequences of DNA between various species accumulate at a uniform rate over time and can be used to evaluate divergence times. The resulting phylogenetic structure is known as a "TimeTree," that is, a tree of life scaled to time.
Prior to the use of molecular clocks, morphological changes between species were the primary means of identifying divergence times. Since then, molecular clocks have proved a vital tool for evolutionary biologists, supplementing the fossil record and providing a powerful means to time t
|Contact: Richard Harth|
Arizona State University