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In drawing a distinction between risk as it relates to skiing and GM food production, Tudge asks: "Where is the exhilaration in GM soya?". Could I suggest that making inroads into world hunger and protecting the environment and society from toxic pesticides might provide the answer to this question?

DNA evidence that humans contain no genetic material derived from Neanderthals seems to be being taken as evidence that the two species never came into contact (17 May, p 14) . Such conclusions, though, betray an unspoken assumption that the two species were capable of interbreeding successfully. As far as I am aware there is …

Your article about the Pierre Auger Observatory contains an inaccuracy of which your readers should be aware (17 May, p 9) . At present, just over 2 per cent of the Southern Observatory has been constructed and is operating as a prototype instrument, not 10 per cent as you suggest. We expect to have 10 …

Paul Wesson may be correct in saying that Mach's principle is not incorporated in the equations of general relativity (17 May, p 30) . However, a strong connection between the distant universe and rotating bodies is implied. In Chapter 23 of his popular exposition Relativity, Einstein shows nicely how space-time is far from Euclidean when …

I was fascinated by the article explaining how a gecko can stick to a surface, supporting its own weight with only one toe (17 May, p 15) . What I would like to know is how the gecko is able to stick or release each foot at will as it moves across a surface. Why …

It is by no means obvious that the world is facing an epidemic of chronic illnesses induced by diet. The supposed links between diet and conditions such as cancer and respiratory disease are not strong. There is still great uncertainty about the causes of such diseases. Brundtland claims that changes in diet would generate positive …

It was unfair of Brian Spratt to dismiss the report of the European Committee on Radiation Risk (ECRR) as merely some anti-nuclear platform (17 May, p 24) . The Royal Society's own evidence on depleted uranium is arguably irrelevant since DU particles are entirely novel and cannot be equated with uranium ore dust. There are …

Colin Tudge asserts that scientific discoveries such as penicillin would have been given the green light under the precautionary principle (17 May, p 23) . However, this is accepted with hindsight. Yes, drugs such as penicillin would, were the benefits known in advance, be blindly accepted. However, in an era where mass media can spread …

The director-general of the World Health Organization, Gro Harlem Brundtland, claims "the world is facing an epidemic of chronic illnesses" and that "most of the damage could be prevented through simple changes in diet, by being more active and by not smoking" (3 May, p 23) . But 30 years of trials contradict her. For …