The fourth branch

Is there a new class of micro-organisms?
April 20, 2011
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 marine microbes each seem to show a branch (probably the same one) that doesn’t fit on the conventional tree of life. It’s possible that these genes might have been acquired from some unknown forms of virus (viruses are excluded from the tree). The more exciting alternative is that they flag up a new domain. If so, its inhabitants would so far seem to be rare—a minor anomaly (like the Basque language) which has persisted quietly for billions of years. But since we are ignorant of perhaps 99 per cent of species on the planet, who knows?

You and your robot companion

The EU is looking for big ideas. Really big ones. Its Future Emerging Technologies Flagship project offers to fund two scientific projects to the tune of €1bn each over the next ten years. These must be “ambitious large-scale, science-driven, visionary research initiatives that aim to achieve a scientific breakthrough, provid[ing] a strong and broad basis for future technological innovation and economic exploitation in a variety of areas, as well as novel benefits for society.” In other words, they’ve got to achieve a heck of a lot, and will have truckloads of money to do so.

Six of the applications—all of them highly collaborative, international and interdisciplinary—have now been selected for a year of pilot funding, starting in May. They range from the technical to the borders of science fiction.

One promises to develop graphene, the carbon material that won last year’s physics Nobel prize, into a practical fabric for information technologies. Another proposes to figure out how the brain truly works; a third will integrate information technology with medicine to realise the much-advertised “personalised medicine.”

But these things will all be pursued regardless of the Flagship scheme. More extraordinary, and therefore both more enticing and more risky, are two proposals to develop intelligent, sensitive artificial agents—characterised as Guardian Angels or Robot Companions—that will help us individually throughout our lives. The sixth proposal, which received the highest rating, is to develop massive computer simulation systems to model the entire “living Earth,” offering a “crisis observatory” that will forecast global problems ranging from wars to economic meltdowns to natural disasters—the latter now all too vivid. The two initiatives to receive full funding will be selected in mid-2012 for launch in 2013.