A New Tree Of Life Allows A Closer Look At The Origin Of Species

[Guest guest]

A New Tree Of Life Allows A Closer Look At The Origin Of Species

http://www.medicalnewstoday.com/medicalnews.php?newsid=38826

In 1870 the German scientist Ernst Haeckel mapped the evolutionary

relationships of plants and animals in the first 'tree of life'.

Since then scientists have continuously redrawn and expanded the tree

adding microorganisms and using modern molecular data, yet, many

parts of the tree have remained unclear. Now a group at the European

Molecular Biology Laboratory (EMBL) in Heidelberg has developed a

computational method that resolves many of the open questions and

produced what is likely the most accurate tree ever. The study, which

appears in the current issue of the journal Science, gives some

intriguing insights into the origins of bacteria and the last common

universal ancestor of all life on earth today.

" DNA sequences of complete genomes provide us with a direct record of

evolution " , says Peer Bork, Associate Coordinator for Structural and

Computational Biology at EMBL, whose group carried out the

project. " For a long time the overwhelming amount of data (the human

genome alone contains enough information to fill 200 telephone books)

has made it very difficult to pinpoint the information needed for a

high-resolution map of evolution. But our study shows how this

challenge can be tackled by combining different computational methods

in an automated process. "

Bork's lab specialises in the computational analysis of genomes, and

recently they applied this expertise to the tree of life. Since all

organisms descend from the same ancestor, they share some common

genes. Francesca Ciccarelli and Tobias Doerks of Bork's group managed

to identify 31 genes with clear relatives in 191 organisms, ranging

from bacteria to humans, to reconstruct their relationships.

" Even using such genes, you might get the wrong answer, " says

Ciccarelli. " Organisms inherit most genes from their parents, but

over the course of evolution, a few have been obtained when organisms

swapped genes with their neighbours in a process called horizontal

gene transfer (HGT). Obviously, the latter class of genes does not

tell you anything about your ancestors. The trick was to identify and

exclude them from the analysis. "

" This procedure drastically reduced the 'noise' in the data, making

it possible to identify as yet unknown details of early evolution, "

says Tobias Doerks. " For example, we now know that the first

bacterium was probably a type called gram-positive and likely lived

at high temperatures †" suggesting that all life arose in hot

environments. "

The improved tree has also shed light on other research carried out

by the group. Bork and colleagues are participating in projects that

collect genetic material of unknown species en masse from

environments such as farm soil and ocean floor. " With the new high-

resolution tree in hand, it is now possible to classify genetic

material from this unexplored microbial world and further our

understanding of life on the planet. "