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Kudos for a cogent article on a vital subject: competition vs cooperation and the individual vs the group. Nature requires both. Without competition, evolution can't operate. Without cooperation, it can't produce interesting results( 12 July, p 38 ). As suggested, when we ask if human nature is selfish or altruistic, we are asking the wrong …

Apart from the environmental destruction of the planet, perhaps the greatest tragedy for humanity is extreme and rising inequality. So it is essential to ask whether it can be alleviated or reversed by the falling birthrate highlighted in the book you review, After the Spike . Fewer children should allow greater opportunities for the best …

The book lamenting humanity's falling birthrate is off the mark. Instead of decrying this trend, economists should try to figure out how an economy can thrive without relying on unsustainable continual growth!

So "AI companies and tech analysts alike say the agentic AI revolution is just around the corner"( 12 July, p 34 ). That would be in the same way as commercial nuclear fusion, fully autonomous all-road cars, personal flying vehicles, paperless offices and world peace, then?

The creators of AI agents that will run our lives for us need a posh motto. I suggest: "Living? Our servants will do that for us." It is from the play Axël by French writer Auguste Villiers de l'Isle-Adam.

Agatha Windig is probably on to something with her observation that contact lenses stop the tears while chopping onions, but not that it involves the iris and pupil. A rigid gas-permeable lens would probably filter out the volatiles that the onions release, keeping them from irritating the surface of the eye, the cornea, which would …

I see that orcas, by offering what appear to be gifts for us, are experimenting on us, presumably to determine our intelligence and whether we are worth teaming up with (or maybe domesticating). I'd love to know their conclusions( 12 July, p 19 ).

I was fascinated by the report of fig trees that produce calcium oxalate, but the question is how this benefits them. Samburu County, Kenya, where they are native, is prone to bush fires( 12 July, p 15 ). Do we know if these fig species are more fire-resistant than other plants that don't produce calcium …

Howie Firth posed a superb scenario related to the question of whether we have free will: "If every action we make is predetermined by the laws of physics, then it is possible to imagine constructing a computer that could predict what I will do at a particular moment". He then suggests that, knowing its prediction, …

Devi Sridhar's take on public health initiatives as key to longer, more enjoyable lives, rather than individual striving, brought to mind an important project in south London. Guy's, King's and St Thomas' hospitals use any and all interactions with patients to look at their " vital five ": key burdens of disease that, if addressed, …

Carl-Friedrich Schleussner is at the International Institute for Applied System Analysis in Laxenburg, Austria ( 26 July, p 8 ) Influenza viruses have an RNA genome ( 12 July, p 16 ).