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You report that there are around a billion dogs in the world, with up to 85 per cent free to interact with the environment to some degree as feral or street dogs ( 24 July, p 43 ). While your article imagines how dogs might fare in a future without us, a world without responsible …

You report that race-based adjustments to diagnostic criteria reflect bad science and should be abolished ( 17 July, p 16 ). Fair enough. But we also often read that this or that medical procedure hasn't been sufficiently validated because the clinical trials involved a limited cohort, for example mostly white people. We also sometimes read …

You report that fish addicted to methamphetamines that end up in Czech rivers may have a reduced survival rate. It may not be so ( 17 July, p 20 ). If both predators and prey are equally debilitated, then they will all still be on the same footing and the pollution may not make any …

In "Where's my robot car?", Jeff Hecht points out that self-driving cars that stop at every false alarm would cause gridlock ( 31 July, p 45 ). I would add that pedestrians could also learn that they won't need to wait to cross the road in front of fully autonomous vehicles that detect people. Cars …

As a postgraduate physics student 50 years ago, I was told by an AI expert that "we shall have machine translation licked in 10 years ". I think we are similarly over-optimistic about the imminent arrival of truly self-driving cars. One problem is software written for ideal conditions. I'll believe that self-driving cars have arrived …

Hecht's article omits one potential route to fully autonomous level 4 or 5 driving, namely fully interconnected traffic. If every vehicle, be it driving or stationary, would constantly transmit its actions and position to all vehicles around it, one could achieve a level of mass "awareness" that gets around the shortcomings of stand-alone sensors. Traffic …

You say countries with many partially vaccinated people and a lot of coronavirus infections (such as the UK) are breeding grounds for new variants of the SARS-CoV-2 virus that may evade antibodies ( 31 July, p 8 and Leader ). On the other hand, you say in your related Leader that lower-income countries will be …

Regarding your Leader, a balance must be struck between "the speediest possible end to the pandemic" and the long-term effects of lockdown restrictions on the mental and physical health of millions. I fail to see how the UK government could have reacted to delta any more safely than it did. The editor writes: If vaccinations …

Further to James Wong's look at claims that food is becoming less nutritious, there is reason to think this will occur ( 17 July, p 24 ). Higher levels of carbon dioxide increase plant growth, but as more carbon enters the plant it doesn't bring an increase in essential proteins and minerals, thus diluting the …

Regarding Luce Gilmore's comments on consciousness, the rejection of mystical vitalism doesn't exclude the possibility that consciousness only arises from certain living brains ( Letters, 24 July ). It may be that billions of diverse neurons, having trillions of varied and ever-changing connections carrying constantly modulating signals, bathed in a brew of ions, hormones, enzymes …