Letters archive

Clare Wilson reports a test of people's responses to the philosophical "trolley problem", now prominent as a way to probe opinions on who a self-driving car should save ( 19 May, p 14 ). There are reasons to be cautious about any interpretation of the results. As Wilson notes, a problem with this test – …

In recent years we have learned much about our close relationship with the Neanderthals ( 26 May, p 44 ). They looked and behaved so like us that we would not blink if we passed one in the street today. They created cave art and their hyoid bone would have allowed them to produce recognisable …

Please leave our haldi doodh alone. Diss it and the aunties will come for you. Love, India Dhenuka Ganesh responds to the suggestion that turmeric latte ( haldi doodh ) may not be all it's cracked up to be ( 16 June, p 35 ).

Alice Klein says Neanderthals and Denisovans seemingly did not develop the same level of intelligence as us ( 9 June, p 6 ). But Neanderthal brains were somewhat larger than those of Homo sapiens , and we are reminded in the same issue that there is a subtle relationship between brain size and intelligence ( …

Colin Barras discusses chimp evolution being shaped by sex with bonobos and describes them as "close relatives" ( 2 June, p 4 ). When I studied biology many years ago, I was taught that organisms belonged to the same species if, and only if, they could produce fertile offspring together. Horses can mate with donkeys, …

Clare Wilson discusses risks arising from screening for cervical cancer, and says it is caused by human papillomaviruses ( 2 June, p 20 ). Not all cervical cancer is caused by HPV. Vaccinations, as amazing as they are, will not eliminate it. Without those facts, women can't evaluate the risks of testing. Procedures done after …

Your leader article states that "it's time we stopped dismissing women's health problems", with the cervical cancer screening programme as example ( 2 June, p 3 ). Under the UK National Health Service women receive HPV immunisation, contraception, antenatal and postnatal care and cervical screening. They are also screened for breast cancer, osteoporosis and, in …

Peter Fairley discusses the possibility of 100 per cent renewable energy ( 9 June, p 26 ). This throws up at least a couple more considerations we will have to face in the future. What effects on animal and human biology will there be from long-range super-high-voltage direct current transmission from sites where green energy …

Surely it is not so much a question of whether we can get all our energy from renewable sources , but that we must. The only point to debate is how quickly. It seems likely to me that production of hydrogen fuel using electricity to split water will be a major part of this process. …

Your excellent article on water starts off by saying that if it behaved like a normal liquid and became denser as it cooled, lakes would freeze from the bottom up, killing all the fish ( 2 June, p 26 ). But freezing kills living things because water expands when it turns to ice and hence …

Timothy Revell discusses holding artificial intelligence to account and European Union citizens getting the right to an explanation of AI decisions ( 14 April, p 40 ). Should software not be able to say "I don't know"? I worked on an AI system for use during anaesthesia. We needed to detect one of two states: …

• In less of a tizzy: the pulsar B1957+20 rotates a mere 600 times per second ( 2 June, p 17 ).