Letters archive

Large-scale DNA sequencing will undoubtedly shake up our picture of the tree of life (26 March, p 16) . As your article reported, it has already led to the identification of new species and the reclassification of some known ones, and may now have resulted in the discovery of a whole new domain. Sequencing removes …

Redefining cruelty in terms of the more measurable concept of zero empathy, as put forward by Simon Baron-Cohen in his interview with Liz Else (9 April, p 32) , raises intriguing possibilities. An autistic boy who places a plastic bag over his mother's head so that he does not have to see her eyes, or …

Simon Singh rightly draws attention to proposed reforms to English libel law (2 April, p 26) . One of the difficulties for legislators is that legislation can be double-edged, and the law cannot generally distinguish between good and bad claimants. Imagine a scientist who has been vocal in publicising her findings that a new drug …

Writing on the role of financial incentives to change behaviour (9 April, p 40) , Nic Fleming notes that the outcomes are often counter-intuitive. In the academic year 2004-05 I, along with colleagues, ran a randomised controlled trial evaluating the use of financial incentives to encourage adult learners to attend literacy classes ( Oxford Review …

Your otherwise informative "Instant expert" article about new technologies for carbon capture (2 April) missed some important numbers. For instance, how much is each technology likely, when mature, to add to the cost of a unit of electricity? And how does that compare with wind and solar? If we decide we need to cut emissions …

Michael Brooks mentions the prevalence of 12 and 60 in ancient systems of numbers (26 March, p 43) and ascribes this to the Babylonians having 12 signs of the zodiac and considering 60 to be an auspicious number. But I understand that it originated somewhere in the ancient Middle East, possibly in the Sumerian city …

The cover story on novel ways of treating disorders of the brain (9 April, p 35) stated that "until recently the only treatments available... were drugs or surgery", and these disorders were implied to include depression. This is a common and damaging misconception. There are other, well-researched treatments for depression, including cognitive behavioural therapy. According …

The trinity of theism, non-theism and strong atheism by which Jonathan Lanman classifies religious belief and non-belief (26 March, p 38) seems a good description of affluent western Judaeo-Christian society. But what about the rest of the planet? What conclusions about the origins of belief or non-belief can be drawn when viewed from the perspective …

Cirrus-like cloud (2 April, p 16) that originates as aircraft contrails can be expected to have two effects: trapping heat from the ground, and reflecting solar energy back into space. It would help if the model described evaluated the net global warming effect. London, UK The editor writes: Ulrike Burkhardt, whose results we reported, says …

I personally believe that chickens are not much more intelligent than broccoli, but as my wife keeps chickens and believes they are intelligent I thought she might enjoy the article "How to confuse a newborn chick" (26 March, p 22) . Her immediate response was that the minority of chicks drawn to the impossible Escher-like …

Your article says some free energy harnessed by wind farms will be lost as heat, affecting Earth's energy balance (2 April, p 8) . But isn't all wind energy eventually converted to heat, whether we catch it or not? If it weren't for windmills, that heat would be generated in forests, mountain slopes and everywhere …

• Luke Premo, who we quoted in our article on the fate of the Neanderthals (9 April, p 11) , is at Washington State University .