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Anna Machin's research on the effect of pregnancy on fathers is welcome ( 24 March, p 37 ). The West lets down fathers in more ways than one, and I think changing this is key to changing other inequalities. Current pay inequality is a reflection of societies' stereotyping of women as the predominant childcarer. If …

I was thrilled to read about Machin's work on fatherhood . When I became a father more than 40 years ago I found very little information; I was the one to be supportive. End of story. As a newly qualified vet, I spent a lot of time working out my feelings by pulling calves out …

You report that the influence of the father on a child increases when she or he is around 24 months old. In my experience, this is initiated by the child: "Daddy do it" for almost everything. My late wife Mollie and I figured that this was nature's way of freeing her up to have the …

I think I trust them more than the homicidal maniacs in charge at the moment Steffi Thompson is unimpressed by calls for artificial intelligences to explain themselves to the rest of us ( 14 April, p 40 )

Colin Barras reports analysis of Cheddar Man's 10,000-year-old DNA suggesting that he may have had dark skin and blue eyes ( 3 March, p 12 ). In Agricola , 8000 years later, the Roman historian Tacitus divides the inhabitants of Britain into three categories thus: "The reddish hair and large limbs of the Caledonians proclaim …

Theresa Jones suggests there may be a connection between migraine and low blood sugar (Letters, 3 March ). I find this especially interesting in light of a 2016 study by Janice Pogoda and others that found an inverse correlation between migraine occurrence and dietary sodium intake ( 20 August 2016, p 12 ). It strikes …

It is great that Wild Earth's bioreactor-grown dog food has a lower carbon footprint ( 24 March, p 12 ). But companies such as Beyond Meat in the US and Moving Mountains in the UK are using plants to biomimic meat. This causes much less climate change, among its other advantages. It ensures that all …

• Whiffy! It would be more precise to say that volatile compounds from household items like your deodorant and shampoo are one of the biggest sources of air pollution in Western cities ( 24 February, p 23 ).

Your careers special highlights the dramatic challenge Brexit poses to the UK's ability to attract and retain top scientists and engineers from Europe ( 7 April, p 49 ). But what faces young people in the UK who are considering such fields? After a career in aerospace, I have been a " STEM ambassador " …

You quote Charles Denby saying that it takes 50 litres of water to grow enough hops to make a pint of beer ( 24 March, p 19 ). I am an avid home brewer and use about 200 grams of hops per 40-litre batch – nearly 3 grams per pint. A typical hop plant yields …