Letters archive

Colin Barras reports analysis of Cheddar Man's 10,000-year-old DNA suggesting that he may have had dark skin and blue eyes ( 3 March, p 12 ). In Agricola , 8000 years later, the Roman historian Tacitus divides the inhabitants of Britain into three categories thus: "The reddish hair and large limbs of the Caledonians proclaim …

It is great that Wild Earth's bioreactor-grown dog food has a lower carbon footprint ( 24 March, p 12 ). But companies such as Beyond Meat in the US and Moving Mountains in the UK are using plants to biomimic meat. This causes much less climate change, among its other advantages. It ensures that all …

Your careers special highlights the dramatic challenge Brexit poses to the UK's ability to attract and retain top scientists and engineers from Europe ( 7 April, p 49 ). But what faces young people in the UK who are considering such fields? After a career in aerospace, I have been a " STEM ambassador " …

Timothy Revell discusses whether artificial intelligences should be required to explain their decisions ( 14 April, p 40 ). This seems reasonable until we apply the same rules to humans. When people have to make quick decisions in complex situations they confabulate, making up a plausible reason for a decision even when this has no …

I couldn't agree more with Paul Marks on the stupidity of "killer kettles" and other internet of things products ( 24 March, p 24 ). An example that particularly concerns me is the enthusiasm the UK government and energy companies have for installing "smart" meters. These are not smart at all – they can simply …

Mark Lynas says the genetically modified staple crops he is now advocating "have nothing to do with the corporate behemoths that are the usual targets of suspicion in the GM debate" ( 7 April, p 26 ). But is it possible for poor farmers to harvest seeds to be used the following year? If not, …

You quote Charles Denby saying that it takes 50 litres of water to grow enough hops to make a pint of beer ( 24 March, p 19 ). I am an avid home brewer and use about 200 grams of hops per 40-litre batch – nearly 3 grams per pint. A typical hop plant yields …

It was great to read that finally someone is thinking outside the box in the search for life ( 24 March, p 40 ). One simple and definitive test for life wasn't mentioned. Complex carbon compounds such as sugars and amino acids typically have two chemically identical forms, called enantiomers, that are mirror images of …

Tom Gauld's cartoon depicts a conversation: "Did you hear about Professor Larson's new theory? It's literally blowing people's minds." "I think you're misusing the word 'literally'." "Sadly, I'm not." (Letters, 20 January). Many of our heads were literally blown a few years ago when dictionaries began to include an additional definition for the word "literally" …

• In the satire Great Apes , the actors were of course playing apes not monkeys ( 7 April, p 48 ). • It was private investment in renewable energy in the developed countries that has halved since 2011 ( 14 April, p 25 ).