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Chelsea Whyte reports that in only seven species of mammal do females exhibit leadership ( 29 September, p 8 ). Leadership is a difficult concept to apply to animals, and indeed different definitions seem to be applied in each of the seven species cited. I cannot offhand think of any species of large long-lived social …

I feel safer with the pilot having the same outcome as me! @wotsapnin isn't quite ready for the driverless aircraft of the future ( 6 October, p 42 ) .

Economics is "not an exact science, after all", says Pascal Boyer ( 22 September, p 40 ). Economics is not a science at all. Where's the largely agreed body of prior knowledge? Where are the experiments capable of falsifying? Where – crucially – are the advances made by disproving previous theories? How come the same …

I am not sure why Steve Swift is having trouble with his electricity tariff timings ( Letters, 29 September ). He says his meter takes its timing from the mains frequency; I understood that most Economy 7 meters switch tariffs as a result of a signal broadcast on BBC Radio 4 longwave. I remember working …

I read your article about biological materials inspiring attempts to produce metals incorporating layers, or gradients in their composition or structure, in order to combine hardness and toughness ( 29 September, p 40 ). Surely there is a long history of layering steel or iron to make weapons such as swords – with a hard, …

Thank you for Chelsea Whyte's article on milk alternatives ( 22 September, p 22 ). It is high time that the question about the ecological and health impact of "alt-milks" is addressed in more detail – please write more! The perceived benefits and harms of these "milks" have been left to marketing and the fashions …

As a biologist and a space science enthusiast, I strongly object to Robert Zubrin's push for immediate human exploration of Mars ( 8 September, p 22 ). As humanity is witnessing on almost a daily basis, robotics and machine intelligence are opening vast swathes of knowledge and new fields of space enquiry. The huge amount …

Enid Smith reports that her self-sufficiency is thwarted because she can't find a washing machine that doesn't use a cold water fill, which is heated with expensive electricity ( Letters, 8 September ). She should try using cold water washing detergent — we've been using it for years!

Cixin Liu postulates that highly civilised aliens would be as incomprehensible to us as we are to ants ( 8 September, p 42 ). Could this be the solution to Fermi's paradox, "Where is everyone?" Answer: they're already here.

• The data artist with whom Hannah Redler-Hawes co-curated the LMAO exhibition is Julie Freeman ( 29 September, p 44 ). • Estimates of the number killed by Allied bombing raids on Germany in 1939-45 are in the hundreds of thousands ( 6 October, p 16 ).