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Catherine Brahic asks whether we will soon use CRISPR to create children that are fitter by design, rather than by evolution, and if so whether we will have transcended the state of living things ( 30 June, p 36 ). If this comes about, surely it will be another step change in evolution, comparable to …

Brahic suggests that we may soon no longer fit NASA's criteria for life because we now use CRISPR editing techniques to modify our own genome and hence may no longer be subject to Darwinian evolution. But we have been modifying our genomes for as long as we have existed as a conscious species, simply by …

Clare Wilson reports doctors saying that you cannot replace their wealth of experience and "gut feeling" during consultations ( 7 July, p 25 ). But when discussion or examination of a patient isn't enough, doctors rightly send them for tests. We all dislike incursions into our expertise, but sometimes it can be more expert still …

Chester Peterson makes the point that not all the pasture land that livestock graze on can produce crops (Letters, 2 June ). Instead of using it for grazing, why not allow this land to be reclaimed by forest, or even afforest it, and let nature's carbon sink do its job?

You accompanied an article on the public acceptance of genetically modified food with a comment piece by Lesley Paterson in favour of scientists asking for public views on where to take GM food ( 7 July, p 23 ). This is superficially appealing, but problematic. Such consultations don't happen for most areas of science – …

I was interested to read about how the GM debate may turn into the gene-editing debate ( 7 July, p 22 ). Has anyone done any research asking people who are against gene-edited foods whether or not they are also against using gene editing in treatments for, say, cancer?

I am surprised Tom Kirkwood is so circumspect about the limits of human longevity ( 7 July, p 24 ). Most ideas about ageing explain how we age – mechanisms such as the shrinkage of telomeres at the ends of our chromosomes – not why we age, for example offering evolutionary reasons for an observed …

I was pleased by the unequivocal line you are taking concerning the possibility of a "no-deal" Brexit (Leader, 14 July ). The phrase "crash out" would be most appropriate. I hope you sustain this approach, as I fear that already we are being subtly primed by hard-liners to accept "no-deal" as a valid option. Now …

. Sam Wong reports a link between herpes infection and Alzheimer's disease ( 30 June, p 12 ). This made me wonder whether a vaccine could help prevent Alzheimer's. Immunisation against varicella zoster virus protects children and some others against chicken pox, and people over 60 against shingles. This virus is a member of the …

Tidal lagoons aren't an easy solution to our energy problems, as Hans van Haren correctly argues ( 23 June, p 24 ). Private industry has been trying to get the UK government and taxpayers to underwrite large-scale energy projects like these for years. We should instead spend the money putting solar hot water panels on …