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You report on a study that says "peaceful" male bonobos may be more aggressive than male chimps. On behalf of the Australian branch of the organisation that has been the long-term sponsor of the Congolese trackers who follow, monitor and protect the bonobos referred to in the article, and having tracked and filmed these bonobos …

With reference to the gathering demographic problem of falling birth rates in many nations, I can see ramifications, such as the need to welcome young immigrants to places such as the UK, rather than trying to stop them, and a need to use robotics to fill labour gaps. Some countries may offer bonuses to families …

Andrew Scott is right about the need to promote ageing well over chasing greater longevity. I'm painfully aware that arthritis is a hindrance to successful ageing while at the same time viewed as inevitable for older people. Arthritis doesn't kill, it is just a gateway condition to things that do — dementia, cancer, stroke — …

As attempts over the past 20 years have demonstrated, carbon capture and storage is fraught with difficulty and unlikely to make a significant contribution in the future. A worthwhile alternative strategy in which citizens and various levels of government worldwide can participate is carbon sequestration through tree propagation 20 April, p 8 . In cities, …

Carbon capture and storage is a complete waste of time, money and effort. It can't work at the scale necessary to make any meaningful difference in the time available and consumes a lot of energy. We need to focus on what will make the greatest difference in the least time: a complete cessation of new …

Your list of key technologies for carbon capture and storage omits any mention of biochar. This is produced by pyrolysis of agricultural, forestry, garden or other organic waste materials in limited oxygen/air to produce something akin to charcoal. Most biochar is incorporated into soil, where it can lock carbon away for millennia. A recent report …

You report that "post-op infection is often due to skin-dwelling microbes". Surgeons try to prevent these infections by sterilising the skin before cutting into it, but nature abhors a vacuum and when most of the biome is killed you have no control over which organisms multiply to fill the (nearly) empty niche. Maybe it is …

Many years ago, in eastern Canada, I encountered numerous eastern garter snakes – the species in your report on a study that found they appear to recognise their own scent. Noam Miller, the researcher who found this ability, attributes it to the fact that garter snakes are social creatures, unlike ball pythons, which appear not …

The evidence that anxiety is rising in children is largely unequivocal. You describe several potential causal factors, including social media, interactions at school and socio-economic status 6 April, p 35 . Another possibility worth mentioning is the use in schools of low-intensity interventions to raise awareness of mental health. These are often given whether or …

You posit that advances in the ability of artificial intelligence to do pure maths may "herald machines that reason and think like humans". While I agree that this will contribute to the ability of AI to reason and gain general level intelligence, it doesn't necessarily mean they will ever think like us Leader, 13 April …