Letters archive

Speaking to Richard Webb, Sean Carroll wonders whether bacteria have decision-making power or agency ( 15 February, p 34 ). Arguably, the earliest known "decision-making" in the burgeoning tree of life occurs with chemotaxis: single-celled life forms propelling themselves in response to a chemical stimulus, for example towards sources of nutrients. Webb later quotes researcher …

Average human body temperature has fallen in the US since the 1860s, reports Michael Marshall ( 18 January, p 13 ). Julie Parsonnet, one of the team that analysed data from more than 677,000 measurements, says the most likely explanation is that immune systems have become less active because we get fewer infections, leading to …

Alain William proposes a unit of environmental impact, the Thunberg (Letters, 1 February ). Though designed to achieve desirable outcomes, this seems to have much of the charm of China's Social Credit System ( 17 October 2015, p 22 ). Likewise, Stewart Reddaway suggests that passenger aircraft should limit the number of premium seats (also …

Fred Pearce says large areas of tropical forest promote more rainfall than previously thought ( 2 November 2019, p 40 ). I recall that clouds contain tiny organisms. Trees emit complex chemicals – could these be the feedstock for aerial bacteria? It might be that what the trees emit not only feeds such bacteria, but …

I am impressed and intrigued by the skill of your picture desk in selecting eye-catching images: this is nicely demonstrated by the one printed with your article on mobile phone data and mental health ( 1 February, p 12 ). It shows a person on their phone in front of a vehicle bearing the National …

Jessica Hamzelou addresses the ethical dilemmas around beings with a mix of human and other genes, their grade of humanity and how we treat them ( 22 February, p 18 ). These quandaries extend to the disposal of, for example, pig-human tissue. If such tissue isn't deemed "substantially human", then what disposal mechanisms should be …

You discuss the prospect of lab-made shrimp, saying it would be an improvement over shrimp farming and that aquaculture has sustainability problems (Leader, 22 February ). Aquaculture aligns with the majority of the 17 United Nations' Sustainable Development Goals . It is highly resource-efficient, especially compared with terrestrial animal production. It makes a significant socio-economic …

Your article on the invention of the alphabet was fascinating ( 8 February, p 34 ). I suggest a further possible reason for its delayed uptake. For scribes, intellectuals and government officials, knowledge of hieroglyphs assisted them in maintaining their positions of power and influence in society. They would rightly fear and oppose the promotion …

Will Kemp says that when he was a vegan and working as a builder's labourer, his main source of calcium was sesame seed paste (Letters, 15 February ). He may well have ingested small quantities of cement, concrete and plaster. Could these, in fact, have been his main sources of calcium?

Donna Lu discusses the possibility that we are denizens of a computer simulation ( 1 February, p 42 ). We know that humans run simulations for distinct purposes, such as to build skills and to try to forecast phenomena. So why would "our" simulation world be run? Could we be an experiment designed to learn …