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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 …

Thank you for Raihan Alam and Tage Rai's excellent article on how society punishes people. The Mendota Juvenile Treatment Center study showed that offenders who received counselling did far better than those who didn't. The science shows that kindness leads to a better outcome for all concerned( 18 October, p 19 ).

Throughout humankind's history, we have had to get used to taking high risks simply in order to eat. If it didn't take risks, the tribe starved. Humanity has evolved to live with risks as a part of normal life. So the idea that criminals are deterred by the fairly low risk of being caught and …

On the main subject of untethering punishment from profit, I think the easiest way to remove any perception of authorities fining people in order to fill financial holes would be to fine them and burn the money. Then the criminal would be punished but the punisher wouldn't profit.

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 …

I read with concern that research scientists have developed a stronger, tougher plastic. Why? Plastics contribute massively to greenhouse gas emissions, pollute the oceans and kill wildlife. We should be phasing out plastics, not inventing more( 4 October, p 12 ).

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 …

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 ).