Letters archive

You report artificial intelligence's ability to predict dangerous tipping points in complex systems, such as stock markets. Will it predict and tell us when it is going to take over and unleash our own weapons on us, or create new viruses leading to the extinction of most human life( 3 August, p 18 )?

When it comes to ice melt changing currents in the Atlantic Ocean that help keep northern Europe relatively mild, there is another factor at work beyond rising temperatures. Wildfires in North America are burning at ever-increasing rates. Much of the ash and soot is deposited on the Greenland ice sheet, changing its albedo and vastly …

Hands-on experiments to understand Neanderthal food preparation reminded me of my time working with a class of reluctant 14 and 15-year-olds. We were studying early "man", including flint tools. I acquired some large flint nodules and the students could try making simple tools – harder than it looked – then use them in various ways …

It seems premature to say that the downsides of anti-ageing therapies are a price worth paying. If they include a population explosion that turns out to be the last straw for an already overburdened planet, I suspect that the people alive at that time would disagree ( Leader, 6 July ).

In the UK, around 60 per cent of 6-year-olds are moderately to strenuously active for an hour a day, but that drops as they age – by 2.5 minutes per day each year ( 27 July, p 42 ). A helium II ion involves the removal of a single electron ( 3 August, p 36 …

Christa Lesté-Lasserre discusses the furore over a horse being whipped while training for dressage events, but doesn't address the major concern: why make a horse dance to order? If animals are unwelcome in circuses, why make a horse dance carrying a rider and call it a sport? Why "train" a horse to jump a very …

Alex Wilkins reports that a slight curve on the surface of a rock helps it make the biggest splash. I am of a generation that received corporal punishment. It was well known that the more charitable disciplinarians used an absolutely flat instrument. We, the recipients, could feel the reason suggested in the research: the flat …

With reference to childhood exercise, an additional factor struck me. As a child in a car-less household, I was frequently presented with a purse and a shopping bag and told to run and fetch whatever was needed from the local shops, thus clocking up both aerobic and weight-bearing benefits. My own children, however, just pop …

You report that butchered bones hint at earlier human arrival in South America. But could the butchered glyptodont, which has been dated to the last glacial maximum period, have become frozen after death, like a Siberian mammoth, and likewise thawed thousands of years later and been butchered then( 27 July, p 18 )?

You speak of doping in sports as an unfair advantage. I agree. But a few pages later in the same issue ( p 11 ) you report that a Google AI has achieved a silver medal score in a human mathematics competition ( Leader, 3 August ). Considering that a computer uses much more energy …