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Bob Holmes assesses the environmental argument for giving up eating meat (17 July, p 28) , tacitly accepting the broad scientific consensus that current animal-farming techniques have unsustainable environmental impacts. However, it is not just meat that is implicated in such damage, but all products we derive from farmed animals. The Vegan Society has reviewed …

Like Tom Wakeford and Jackie Haq (26 June, p 26) , we were part of the group overseeing the preliminary dialogue between scientists and members of the public, discussing breakthroughs in synthetic biology with a view to gauging their response to the new technologies. We consider that during the dialogue, several scientists made statements about …

Clive Hamilton's article on the debate over geoengineering highlights a regrettable tendency for discussion of climate change to be polarised by political dogma (17 July, p 22) . Hamilton mentions as proponents of geoengineering right-wing think tanks opposed to fossil fuel cuts on political grounds. However, increasingly, reputable scientists are considering the effectiveness of geoengineering …

The lack of evidence of humans controlling fire 2 million years ago need not be a stumbling block to the hypothesis that the discovery of cooking at that time caused humans to evolve so differently from other primates (17 July, p 12) . It is possible that we ate cooked food for a long time …

Michael Brooks mentions the double-slit experiment, saying that as long as no one is watching, the photon exists in two places at once. When discussing Markus Arndt's application, which showed that a carbon-70 molecule can also go through two slits at once, he states that: "though these ball-shaped molecules aren't quite as substantial as cats, …

Stuart Clark suggests that, because the sun's output is reducing, the sun is shrinking (12 June, p 30) . Conditions on the sun's surface may not be allowing as much energy to escape as before, but there is no evidence to suggest that the sun is creating less energy below the surface. The sun may …

Helen Thomson describes how haphazard brainwaves may be behind some of the symptoms of schizophrenia (10 July, p 28) . Temporal lobe epilepsy is spread by abnormal waves of neural excitation, and is often associated with disorders of memory and attention. Could this open up new treatments for the condition?

You report that people with schizophrenia might benefit from spraying the "cuddle chemical" oxytocin up their noses (17 July, p 10) . What about a good old-fashioned cuddle? The production of synthetic oxytocin will probably be very profitable for some company or other, but who knows, there may be volunteers for the real thing.

• We claimed there are monkeys in Madagascar (24 July, p 10) . There are no native monkeys there, although there are plenty of prosimian primates. • The numbers of eggs displayed in the diagram accompanying our article on a vegetarian world were all too small by a factor of 1000 (17 July, p 28)