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Adam Vaughan reports measures we could take to reduce greenhouse gas emissions from transport ( 30 March, p 23 ). As he says, they will not be enough. That's because one thing is missing: panic. Academics and policy wonks are still talking as if we are facing an ordinary problem, like stagnant productivity. We are …

I was interested to read about evolution by persistence and its connection to the Gaia hypothesis of a self-regulating planet ( 23 March, p 34 ). It got me thinking about a crucial part of the theory. Gaia doesn't care. There is a danger that some people reading the article will take comfort in the …

Isn't the most remarkable fact about the evolutionary process that, by means of the human brain on this planet, the "universe" is asking questions about its own existence?

You suggest that the absence of infant rabbit bones at Neanderthal sites means that rabbits were hunted individually rather than flushed from burrows ( 16 March, p 20 ). It is also possible that rabbits were raised in captivity and harvested only as adults. I am sure that the Neanderthals were smart enough to cotton …

While the article on functional disorders was enlightening ( 6 April, p 28 ), as a scientist I find myself uneasy at the idea that no physical cause can be found. Given that the brain is a physical object, anything that happens in the brain has a physical cause. It may be that functional symptoms …

No one who has had the misfortune to suffer from an invisible illness would use the word "think" so carelessly, as in saying that "we can think ourselves ill". We understand "thinking" to mean consciously having thoughts. People with functional disorders are at the mercy of some neurological dysfunction, which is a little more complicated …

Thank you for the feature on the possibility of selection by persistence ( 23 March, p 34 ). It is true that whenever a system, whether a saucepan of water on a flame or a planet orbiting a star, is agitated by a flux of energy, it is inevitable that structures will form ( 21 …

I am glad that the Gaia hypothesis is being revisited, as it can explain a lot. If the planet is seeking stability, human activities such as rising carbon dioxide levels and pollution of the oceans challenge this. As a result of climate change, we now have floods, fires and the spread of disease, all of …

Two questions come to mind on the use of cross-laminated timber (CLT) in buildings ( 16 March, p 33 ). Does it burn well? And do termites eat it? The editor writes: • Tests by the US Forest Service show CLT resisting fire and indeed blasts ( bit.ly/NS-CLT1 ). Early work suggests that it is …

Nick Blackstock reports seeing black leopards in Kenya in 1956 (Letters, 30 March ). I worked in that country during the early 1960s with Gurner van Someren, a member of a noted East African family of naturalists, who in the 1940s sought to prove that black leopards were a separate species. In his role as …