You are currently viewing the summary.
View Full TextLog in to view the full text
AAAS login provides access to Science for AAAS members, and access to other journals in the Science family to users who have purchased individual subscriptions.
More options
Download and print this article for your personal scholarly, research, and educational use.
Buy a single issue of Science for just $15 USD.
Summary
The new wealth of microbial genome sequences is threatening to overturn evolutionists' "tree of life." In the current tree, a universal common ancestor gave rise to the two microbial branches, the archaea and bacteria (which lack cell nuclei), and the archaea then gave rise to the eukarya (all organisms that have cell nuclei). But the new sequences show that genes don't evolve at the same rate or in the same way, so the evolutionary history inferred from one gene may be different from what another gene appears to show. Even more perplexing, some genomes have been found to contain a mix of DNAs from both the archaea and the bacteria. Many evolutionary biologists are coming to believe that these mosaics arose because genes hopped from branch to branch as early organisms either stole genes from their food or swapped DNA with their neighbors. If this gene swapping was extensive enough, the tree's "base" may turn out to be indecipherable: a network of branches that merge and split and merge again before sprouting the modern kingdoms.
