Professor Eric Alm and recent graduate Lawrence David have created a sort of genomic fossil that shows that the collective genome of all life underwent an enormous expansion about 3 billion years ago, which they’re calling the Archean Expansion. Many of the new genes appearing in the Archean Expansion are oxygen related, and could be the first biological evidence of the Great Oxidation Event, the period in Earth’s history when oxygen became so plentiful that many anaerobic life forms may have become extinct. A report of this work appeared in Nature online Dec. 19. Read a news release.