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In his article on how Â鶹´«Ã½ covered a proposed solution to the hole in the ozone layer in 1994, Simon Ings says concern about climate change was then the "preserve of a fringe few" (From the archives, 1 June ). Even in the 1980s, global warming was mainstream enough for my teenage friends and …

You describe eight wonders of the human brain ( 22 June, p 34 ). There is a ninth, without which the other eight would be trivial: our absolute dependency on the signs and symbols of language. Our internalisation of the world around us, substituting symbols for reality using rules adopted by each culture, has become …

James Mitchell Crow suggests that Australia can stay competitive only if the country becomes a hydrogen producer and exporter ( 8 June, p 20 ). But production of hydrogen by electrolysis requires large quantities of electricity and fresh water. Australia's sunshine and wide open spaces do have the potential to produce electricity from solar and …

I was interested to read your report on spiders that produce nutritious milk-like fluids, which said "milk secretion is exclusive to mammals" ( 8 December 2018, p 20 ). I work on pseudoscorpions, which, like spiders, are arachnids. They don't lay eggs but possess sophisticated reproductive strategies that involve embryos and larvae being attached to …

Paul Whiteley claims the reason for the anger of the gilets jaunes protesters in France was the "incompetent and arbitrary" imposition of fuel taxes by president Emmanuel Macron (Letters, 15 June ). I, too, hate taxes, but they will support progress against climate change, which is hardly a "nebulous concept". Fuel taxes have been shown …

Calls to replace politicians selected by the people with informed benevolent dictatorship (as in the Citizen Councils that Whiteley says Extinction Rebellion wants) have been made before by those with simple solutions to complex problems. The Russian Revolution comes to mind. The editor writes: Extinction Rebellion in fact demands a "citizens' assembly" that would make …

Bryn Glover says that because humanity has only a couple of decades to get its act in order, we need to pay much more attention to the short-term effects of methane emissions (Letters, 15 June ). We do have around 20 years to avoid reaching a tipping point that is followed by runaway climate change. …

Glover says tackling methane emissions should be a priority . Can a reader tell me if there is any possibility that methane released from melting permafrost could be harvested and used as an energy source? This would also unburden the atmosphere of a potent greenhouse gas.

Herman Pontzer writes that "even Socrates, not remembered as an athlete, bemoaned the lack of fitness among his students" ( 15 June, p 34 ). But Plato recorded in the Symposium that it was at the gymnasium that Alcibiades tried to seduce Socrates , saying: "he trained and wrestled with me". Being athletic, even if …

Hannah Critchlow's book The Science of Fate argues for the absence of free will ( 15 June, p 30 ). I presume that her genes, environment and circumstances made it inevitable that she would write a book. It would also be inevitable that such a book would deny the existence of free will, that I …