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If we exclude the panspermia hypothesis, then life on Earth, with key biomolecules utilising only one of two possible mirror-image – or chiral – forms, arose from random "experiments" in which prebiotic molecules became self-replicating and able to adapt ( 1 March, p 34 ). It seems unlikely that only a single instance survived to …

Assuming the chirality of life on Earth was randomly selected and locked in, the opposite chirality could have happened just as easily. We are now exploring other worlds and moons looking for life. What if we discover mirror bacteria on Saturn's moon Titan? Would it be safe to return samples to Earth? Would any hitchhiking …

The idea that artificial intelligence has no "clear use case" is, in my opinion, disconnected from the facts. Many may feel that AI usage has negative consequences, but there are plenty of stories of people using it in effective ways ( Leader, 15 February ). My younger colleagues avoid Google. They use ChatGPT or its …

Numerous peer-reviewed studies have validated the demographic origins of blue zones. The insights extracted from these longevity hotspots have created principles that have helped people live longer, healthier lives for a quarter-century. Claims to the contrary insult the science of demography and the people of blue zones, who are very proud of their culture of …

You report the view that rewilding and nature restoration in the UK and other European nations risks "offshoring" food and forestry production to places where biodiversity and the environment will suffer. Most rewilding in the UK takes place on land of very poor quality, often where farming has been uneconomic for decades and persists only …

In a way, the question "When did time begin?" is a non-question. Time is our manufactured, mental measuring stick, expressed as a word, to gauge and so compare motion. In this sense, it will have begun sometime after we started to use speech, between two other questions you posed: "When did Homo sapiens originate?" and …

Talk of how to cook the perfect boiled egg reminds me of trying to cook one in compost. My compost bin was insulated to accelerate decomposition, so got unusually hot. I buried a foil-wrapped egg about 20 centimetres deep in it and left it for 1 hour. The result was a hard-boiled yolk swimming in …

The wish, need or preference to pin down a precise official start date for the Anthropocene is curious. The boundary between the preceding epochs, the Pleistocene and Holocene, says Encyclopaedia Britannica , is "around 10,300 ± 200 years" ago. Perhaps it makes sense for the Anthropocene start date to remain uncertain, too ( 22 February, …

Could it be that the research on proclivity for dessert focuses too much on sugar? Most restaurants once offered savoury options for this course. That is now mostly just a cheeseboard. I don't think anyone had issues with having a savoury dessert, which indicates that sugar wasn't a factor ( 22 February, p 18 ).

I have two further possible explanations for the rise of ancient buildings with corners. I would have thought that it would be easier to construct a waterproof roof over a rectilinear structure than over a round one. Also, what about the ease of adding extensions to structures( 8 March, p 14 )?

I wonder whether the nocebo effect could affect life expectancy. If, for example, you believe your allotted span to be three score years and 10, will you tend to succumb by age 70( 22 February, p 38 )?

The cosmic dark ages weren't truly dark, as neutral hydrogen atoms absorb light only at some frequencies ( 22 February, p 32 ).