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Thank you for your seven steps to save the planet ( 8 December 2018, p 31 ). I would have found it even more useful if it had contained a list of the barriers to achieving each step and how we might overcome them. Barriers to killing oil, gas and coal, for a start, include …

Weird: ignore the young's need for education but take blood to keep us old folk alive Rosie Evans avoids mentioning vampires in response to a plan to use young people's blood to treat Parkinson's ( 5 January, p 6 )

Olive Heffernan says that leaders such as President Macron of France need to find some backbone, confronted with climate change and the ' gilets jaunes ' opposition to his tax rises ( 15 December 2018, p 26 ). But why did Macron start by taxing the transport that the least well-off depend on? Surely it …

Your piece on the handprints of the prehistoric artists of Gargas and Cosquer caves offered several possible explanations for the missing digits ( 8 December 2018, p 16 ). None of these reflected my experience when teaching young schoolchildren to paint their own cave animals. While painting with their right hand, several children held a …

Michael Marshall discusses hypotheses on absent fingers in Stone Age cave art. Perhaps there is a simpler explanation. The ubiquitous practice of flint-knapping would have resulted in many injured and infected fingers. Rather than risk blood poisoning or gangrene, those with severely damaged digits could have amputated them with a newly knapped tool. So before …

Chelsea Whyte weighs up the pros and cons of meal kits ( 8 December 2018, p 22 ). She does not mention one quite significant drawback: the transport costs of getting these kits to people's houses. Presumably most are delivered in small or medium, diesel-fuelled vans. Many of these will be nearly empty, especially when …

Alice Klein highlights a study suggesting little difference between the environmental footprints of washable and disposable nappies ( 24 November 2018, p 22 ). I suspect this underestimated the average journey of a washable nappy and the commitment of those who use them. In the 1960s, my mother used terry nappies with my brother and …

Douglas Heaven reports that a prototype aeroplane using electroaerodynamic propulsion flew for 12 seconds, the same as the Wright brothers achieved with their maiden flight ( 24 November 2018, p 7 ). It is a historical fact that the Wright brothers flew their bird-like monoplane on 17 December 1903. But many believe that New Zealander …

Alice Klein and Chelsea Whyte say that switching Christmas lights to static rather than flashing mode uses less power ( 1 December 2018, p 22 ). This is true of incandescent lights, which draw high "inrush" current when the filaments are cold and have low resistance. But LED lights have no comparable phenomenon. Their energy …

• When inhibitory cells were implanted into epileptic rats and then turned off, these rats had nearly as many seizures as those with no implants ( 22/29 December 2018, p 8 ). • It is rolling resistance in tyres that accounts for between 5 and 30 per cent of vehicles' fuel consumption ( 8 December …