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Debora MacKenzie reports work suggesting that the gum disease bacterium Por'phyromonas gingivalis is behind a range of diseases. ( 10 August, p 42 ) When I was growing up in the 1950s, many believed that decayed teeth served as “septic foci”, spreading disease throughout the body. I remember several advertisements for toothpastes and mouthwashes that …

After reading your recent article on the Gaia hypothesis, I wondered whether anyone had considered that the human species may be a solution to one of the biggest threats facing Gaia ( 10 August, p 13 ). It seems that humans have just the right amounts of aggression and intelligence to create things that could …

The news from Olafur Eliasson that Little Sun lamps increase the homework efficiency of girls in households without electricity by 80 per cent isn't inspiring: it's a sad story about the unequal expectations for boys and girls ( 13 July, p 28 ). I support the health and safety and climate justifications for replacing oil …

Clare Wilson does a good job revealing the pitfalls of most studies looking at diets ( 13 July, p 32 ). She could also have mentioned the emerging discoveries of the health effects of the composition of our microbiome – the organisms in our gut and on our skin, for example. Perhaps knowledge of how …

Wilson correctly points out the limitations and inconsistencies of observational studies based on questionnaires, and the inability to perform randomised controlled studies of diet and health. She concludes that the problem is serious enough that we should be sceptical of all dietary advice. But there are studies that examine health differences in geographical populations with …

Debora MacKenzie reports that infection with Porphyromonas gingivalis, a bacterium involved in gum disease, may cause a variety of serious diseases ( 10 August, p 42 ). I have heard that having all one's teeth extracted was a not uncommon 21st birthday present in parts of England until the middle of the 20th century. It …

Assuming that people who have no teeth at all wouldn't be troubled by plaque-dwelling bacteria, I wonder whether any correlation has been sought between toothlessness and the prevalence of the diseases identified by MacKenzie . The editor writes: These bacteria can get into your bloodstream just by chewing, so even having all your teeth pulled …

Donald Hoffman claims to have used the theory of evolution by natural selection to discover that what we perceive isn't objective reality, but an interface with it ( 3 August, p 34 ). He says evolution itself may be just an interface projection of deeper dynamics stemming from a network of conscious agents. But such …

In her excellent article, Leah Crane mentions that the atmosphere of Venus “inexplicably rotates 60 times faster than the solid planet” ( 22 June, p 42 ). We first learned of this implausible phenomenon in the 1960s when Desmond King-Hele discovered that Earth's atmosphere rotates up to 50 per cent faster about 370 kilometres up …

From Simon French, Totnes, Devon, UK I very much enjoyed the quantity of wrasse in one issue ( 20 July, p 17 , p 19 and p 34 ). Your report of a new purple species of fairy wrasse was followed two pages later by bluehead wrasse changing sex. Then, you quoted string theorist Timm …