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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 …

Your collection of articles on reality was informative ( 1 February, p 39 ). Most provocative was Alison George reporting Donald Hoffman's claim that nothing we perceive resembles reality and we are "born with a virtual reality headset on". He says evolution gave us this to simplify things so we had "what we need to …

I am amazed that some Wikipedia editors deem female scientists to be "not notable enough for inclusion" ( 8 February, p 46 ). Many characters from anime films have their own pages, even supporting characters.

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 …

Michael Marshall reports on fears that a conference on scientific reproducibility has a hidden agenda to create doubt about climate change and hence support the fossil fuel industry ( 1 February, p 11 ). If so, its organisers are fighting a rearguard action to try to delay their retreat. Wind and solar is now less …

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 …

There is obviously some question about how the earliest settlers crossed seaways en route to northern Australia ( 25 January, p 38 ). In the 1950s, I was a surveyor in Papua. Coastal peoples there made large dugout canoes and joined three of them together to form lakatois well before European settlement. These canoes were …

• The chart in the online version of our article on stress shows negative effects of stress that people experienced over their lifetimes ( bit.ly/NS-stress ). • None of the substances found in commercial xylene is especially toxic, but they may be precursors of toxic chemicals ( 25 January, p 11 ).

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 …