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You looked at a book discussing Neanderthals' extinction at a time when a separate species, Homo sapiens , moved into their areas. Both populations were distinct prior to interbreeding, and today a vestige of Neanderthal DNA remains in our species( 27 September, p 30 ). The current genetic mix we see in Homo sapiens today …

Rosemary Sharples feels that public transport doesn't go everywhere and doesn't allow for the user's choice of time, route or travel companions, and says the most flexible form of public transport, a taxi, is the most expensive. But look at Vienna, where public transport does indeed go everywhere and is very frequent, including late into …

The idea that our brains are always on the verge of disorder seems to me to have quite limited explanatory value. Criticality in the brain may describe seizure states well mathematically, but it doesn't explain them. If it also describes Alzheimer's disease, in which there is widespread and progressive loss of neuronal function, akin to …

I read your story "Quantum supremacy is here at last". Yes, I agree that the advances reported on build on ideas that have been explored for decades. But is quantum supremacy here yet? I think not. It is still beginning( 27 September, p 11 ).

In addition to improving recycling, Saabira Chaudhuri's call for standardised plastic packaging across brands for similar products could solve quite a problem for me, especially in strange stores. Very few products clearly tell you what they are for – the brand name outshines all such useful information. Standardised packaging would be a great help, along …

I was interested to read your article about the inaccuracies of AI search tools, headlined: "AI doesn't have all the answers". This could be contested – by the comedian Eric Morecambe, for example, who would probably argue: "No, it's giving the right answers. But not necessarily to the corresponding questions( 27 September, p 17 )."

My experience with large language models (LLMs) is that questions about technical systems, such as Windows 11, produce fairly good answers because the information comes from professionally produced documentation. Everything else is a mixed bag. The reason why is evident and not easily fixable. If LLMs are trained on unfiltered data from the web, then …

Your article on covid-19 vaccines' economic benefits lays out the stark disparity between the value that governments and businesses put on human lives (the lower estimated benefit of $5 trillion), and the value that individuals do ($38 trillion). No wonder so many of us feel that "society" doesn't value or care about us: these figures …

Paul Broady suggests plans to capture carbon from the air are a distraction, and we should focus on deep cuts in emissions. He is half right. We do urgently need to make deep and permanent emissions cuts and to keep cutting until we get as close to zero as we can. But this won't be …

Your article "Uncovering the ins and outs of belly buttons" must be wrong about the historical lack of study into the umbilicus: haven't millions of people been accused of contemplating their navel( 11 October, p 16 )?