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Chris Baraniuk says that a machine learning system can now examine photos and detect fakes ( 26 May, p 10 ). It shouldn't be too long, then, before someone invents an algorithm that trains itself to repeatedly tweak a false image to avoid detection by the algorithm that spots fakes.

You often have cause to bewail the absence of reasoned thinking by governments (as in your Leader of 9 June, p 3 ). Traditionally, people have accepted this absence with amused tolerance. But there are many reasons why unreason is a bad thing, not the least the intolerance and viciousness arising from bigotry and superstition. …

Susan Johnston says cattle fed on pasture "must have a lower carbon footprint" (Letters, 2 June ). In fact, pasture-raised animals emit far more methane than those fed grain, and methane dominates other aspects of their carbon footprint. Weight for weight, it has 105 times the warming impact of carbon dioxide during the 20 years …

As a strict non-participant in social media, I can observe objectively the effect it has on those who are addicted to it (I use those words advisedly). I read Jonathan Sullivan's review of Margaret Roberts's book on China's system of "porous censorship" ( 2 June, p 42 ) from that outsider point of view. It …

Do bowhead whales produce two sounds simultaneously through the manipulation of overtones as practised by throat-singers, John Velonis asks (Letters, 2 June ). I compared sonograms I made of normal singing and throat-singing in humans with one of bowhead whales . In normal singing, all the harmonics rise and fall in unison. In throat-singing, the …

David Grimstead mentions "Forrester's Ferric Food", an early 20th-century tonic which may actually have been good for you, and asks whether it sounds like the leghaemoglobin now used in some veggie burgers (Letters, 26 May ). Well, no (unless Forrester was quietly using tonnes of bean roots rather than pressing fruits as advertised). Legumes are …

Â鶹´«Ã½ drops weekly though my letterbox in its own printed plastic bag. You have recently run excellent articles highlighting the problem of recycling this type of plastic ( 19 May, p 25 ). So might you consider delivering in a paper envelope? Bath and North East Somerset Council efficiently recycle any paper we leave …

Robert Craig describes the problems of including practical work in science teaching in England, and expresses concern that pupils are missing out on an important part of their education (Letters, 19 May ). Isaac Newton was brought up on a manor farm where he would have seen carpenters and blacksmiths at work. As a boy …

Sam Wong's article "Female bonobos have midwife skills" was heart-warming ( 26 May, p 12 ). But I was surprised by the statement that "there is evidence that for most of the history of our species, death in childbirth was less common than it is now", which contradicts everything else I've read on the subject …

• Several drugs have passed trials and been approved for use in treating dementia by the US Food and Drug Administration, though none are cures ( 9 June, p 13 ). • We meant to say that we are now seeing some very old stars as they were at about 300 million years old, in …