Robot companions may no longer be science fiction if the EU decides to fund a new project
The 20th-century biologist and atheist JBS Haldane once offered the dry observation that if God existed, he had an inordinate fondness for beetles. But God surely favours single-celled organisms more: beetles and humans share the same neighbourhood (“animals”) on the tree of life, while single-celled life forms have two of the three fundamental branches—bacteria and archaea—all to themselves. Bacteria and archaea are so alike that the latter were awarded their own branch only in the 1970s. Archaea have a different biochemistry from bacteria—their metabolism usually produces methane—and they are found everywhere, including the human gut.
Now, a team at the University of California, working with genomics pioneer Craig Venter, claims to have found hints of a fourth major branch in the tree, again populated only by single-celled organisms. These branches, called domains, are the most basic divisions in the Linnaean system of biological classification. We share our domain, the eukaryotes (distinguished by the way cells are structured), with plants, fungi and yet more monocellular species.
Like most things Venter is involved in, the work is controversial. But perhaps it is not half as controversial as his belief, expressed in a recent panel debate in Arizona, that all life on Earth might not have a common origin. “I think the tree of life is an artefact of some early scientific studies, which are not really holding up,” Venter said, to the alarm of fellow panellist Richard Dawkins.
Drop in the ocean
Despite the glee of creationists, there was nothing in Venter’s speculative remark that need undermine the case for Darwinian evolution. The claim of a fourth domain is backed by a little more evidence, but remains highly tentative. The data was gathered on a now famous round-the-world cruise that Venter took between 2003 and 2007 on his yacht, to collect genomic information about the host of unknown micro-organisms in the oceans. The techniques that he helped to develop allow the genes of different organisms to be quickly compared in order to identify evolutionary relationships between them. By looking at the same group of genes in two different organisms, one can deduce where in the tree of life they shared a common ancestor.
Using Venter’s data, the evolutionary biologist Jonathan Eisen, also at the University of California, discovered that two families of genes in these…