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The fact that genetic developments linked to higher intelligence have been dated to around the time of a sudden explosion in the making of more complex tools would appear to be more than a coincidence( 18 October, p 6 ). What was required in a tool? How and where it would be used? How it …

I have bipolar disorder. In the modern world, that is often very unhelpful, particularly during hypomanic episodes. However, in a hunter-gatherer society, I could see these episodes having an advantage. You could stay up all night to watch out for danger. Even the hallucinations that come with psychosis may have been seen as important to …

As your article states, it is very likely that will-o'-the-wisps are caused by the ignition of methane or phosphine when bubbles of these merge( 11 October, p 19 ). High-speed propellers and pumps are affected by cavitation when the blades are travelling so fast that bubbles of vapour appear and collapse very rapidly. This violent …

Robert Lawrence Khun's article on the landscape of consciousness certainly engaged my brain, so I came down on the side of thinking that is where my consciousness lies, therefore making it a biological problem( 25 October, p 36 ). But that still leaves a lot of questions to answer. When, at school in the 1960s, …

Coltan Scrivner is right that horror helps us "find meaning, connection and even growth in the face of our deepest fears". It is important that the hero escapes, as Odysseus (but not all his men) did from the Cyclops and the horrors of being locked in a dark place, ahead of being eaten. I once …

I don't recognise the profiling of horror film fans suggested by Scrivner. There is a missing category: the staple thrill of hoping – or at least trying to work out – which character survives the zombies, razor-sharp pendulums, or the end of life as we know it, rather than morbid curiosity. I'd put myself in …

The article by Jacklin Kwan on the number of fundamental constants there are (or should be) raises an important issue that cuts to the heart of physical theory: are constants genuine features of nature, or are they artefacts of our descriptive language? It seems to me that the answer lies not in counting constants, but …

David Flint is right that we need to remove carbon dioxide from the air in order to keep the world at a good temperature. The easiest way to do this, in my opinion, is to harvest biomass. The biomass can be stored as it is or transformed into another form, like charcoal, or even burned …

I cannot help feeling that making coffee with beans from civet "scat" was originally done for revenge, bullying or a joke. My guess is that a disliked manager, or annoying colleague, was given a cup as a joke or a dare, and surprisingly, really liked it( 1 November, p 17 ).

Eating leafy green vegetables reduces the body's dietary acid load, meaning it makes it more alkaline (18 October, p 33).