Sir

Your Editorial 'Who are we?' (Nature 453, 563; 2008) warns that research into the human microbiome should not be oversold until medical promise is established. Fads, hype and false promises have no place in any research, but neither should we bias debate by suppressing reasonable extrapolation.

We were led to believe, wrongly, that genome sequences would open our eyes and we would understand — but that did not reduce the value of those sequences in the slightest. They are more valuable than expected precisely because we did not understand them as expected. Research showing us that we do not comprehend what seems to be obvious can be important. Unfortunately, it is the most difficult to conceive, justify, fund and publish because, until we do, we think its premises are wrong.

Decisions on whether to fund particular projects are not scientific decisions. They are social decisions, and may therefore be over-influenced by hype. Research funding must compete with other funding needs, and research hype is up against the hype of military spending, spiralling oil costs and the latest celebrity exploits. Waiting for medical benefits to be proven before funding basic research would mean that basic research would never be funded.

Medicine is founded on germ theory, physiology, hygiene and antibiotics. Yet there are profound gaps in our understanding of those interactions. Health conditions common in the developed world (obesity, diabetes, allergies, asthma, heart, vascular and inflammatory diseases) remain rare to non-existent in the rural undeveloped world, despite the lack of potential treatment. The 'hygiene hypothesis' tries to explain these differences, but so far no protective agent has been found. If the microbiome project can eventually deliver such an agent, or agents, and stop even a fraction of the health decline associated with economic development, the effects will still be profound.

The analogy of the microbiome with rainforest biodiversity is apt. We should exhaustively sample and understand the diversity of both in the wild before the 'clear cutting' of modern agriculture and hygiene practices irreversibly destroys them both.

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