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Reader Gerald Legg asks why the wreck of Ernest Shackleton's ship Endurance, found at the bottom of the Weddell Sea in Antarctica, looks so good ( Letters, 16 November ). There are several reasons. The cold water temperatures (-1.8°C; 28°F), total darkness, low oxygen and lack of sedimentation, together with the ship's strong wooden construction, …

Your article "The Botanic Age" gives welcome space to the subject of pre-Stone Age advances. It would seem important to also mention the Bamboo Age. Bamboo is nature's fast growing construction material and it can be modified to make anything from a knife to a source of ignition, cooking pot or twisted thread. It is …

As a hobby willow-basket maker, I have often observed that no tools are required. A sharp knife is useful, but not necessary. Likewise, textiles and grass-fibre baskets require no tools to create. The notion that early humans or prehumans waited for stone tools to be invented before developing other technologies is absurd. Our ancestors were …

On the issue of whether grief motivates a pet dog to bite the face of a dead owner, I have seen a few human bodies that have been partly eaten by animals. I suspect most target the face because it isn't clothed and there are easy routes to the soft interior, such as eyes, ears, …

The prospect that half the world will have myopia by 2050 might be good news for opticians, but is alarming for the rest of us. The fact that encouraging children to spend more time outdoors helps avoid myopia adds to the list of benefits of doing so, reinforcing the need not to shackle them to …

I favour the idea, one of several raised, that exposure to wide open space outdoors is what reduces myopia rates in children, rather than light exposure. Indoors the eye can only look as far as the walls, while outdoors it needs to deal with vistas of hundreds of metres, if not kilometres. Without this, is …

Missing from the item about experiments in which researchers used monkeys to predict US election outcomes was the fact that they strapped them into restraint chairs for hours. Those who defend animal experiments claim that animals are only used for important research questions and when there is no alternative, but what was described is case-in-point …

I was glad to read Kelly and Zack Weinersmith's debunking of Elon Musk's idea of million-strong colonies on Mars. If people insist on living in hostile places either in domes or underground, the world has numerous deserts where they could establish themselves, with any problems concerning temperature, pressure, radiation or communication with the rest of …

On the idea that insects hold the answer to the dilemma of how best to feed farmed fish, peer-reviewed research I recently coauthored, along with industry statements, casts doubt on the ability of insects to compete economically with fishmeal made from wild-caught fish ( Letters, 16 November ). If insects don't compete with fishmeal, obviously …

Neuroscience progresses through rigorous empirical measures of neural anatomy, circuitry and chemistry; studies of relationships to behaviour; and comparisons among species. Where is there added value from nebulous and simplistic abstractions such as Markov blankets and the free-energy principle( 19 October, p 32 )? These ideas came primarily from philosophy rather than hard science. Their …