Letters archive

Aspects of economic anthropology are worthy of closer consideration in the debate on the decline of egalitarian groups (28 July, p 38) , in particular the differences in work and leisure time that exist between hunter-gatherer economies and systems like our own. Surviving hunter-gatherers like the !Kung have been found to spend an average of …

Your article on adding iron to patches of ocean to encourage plankton growth and so capture atmospheric carbon (21 July, p 15) , brought to mind a related method of increasing ocean fertility by the vertical mixing of waters. You recently suggested that whales may have played a part by stirring the sea when diving …

If a weakening, slowing polar jet stream is causing weather patterns to stall, leading to extreme weather (7 July, p 32) , imagine the disruption if it were to disappear altogether. Jet streams – high-speed winds in the upper atmosphere – occur at the meeting point of atmospheric "cells", large-scale circulations of air, such as …

I'm surprised that your exploration of facial expressions gave no proposed communicative function for a look of surprise (21 July, p 40) . It is a great clue to misunderstandings. If you say something routine to someone and they look surprised, that tells you instantly that something is wrong. You are very likely to correct …

Software linking known reaction paths to create an "internet of chemistry" has the potential to do more than give cheaper routes for chemical synthesis (28 July, p 6) . It could also improve the safety of large-scale chemical production. In many industrial reactions, the greatest hazard comes not from reagents or products, but from intermediates. …

Your look at von Economo neurons (VENs), found in larger-brained creatures and possibly linked to emotion, empathy and self-awareness in humans (21 July, p 32) , reminded me of the idea that in society there are functional psychopaths. Such people have varying degrees of empathy less than the societal norm. Is it possible that the …

Your story on enhanced rock weathering to remove carbon dioxide from the atmosphere (7 April, p 4) quoted some "back-of-the-envelope calculations" showing it would require 100 gigatonnes of the mineral olivine a year, spread 1 centimetre thick over 3.6 billion square kilometres of land. I am the architect of one such scheme and I beg …

Katrina Karkazis and Rebecca Jordan-Young call for an end to current sex-testing policies in international athletics and the Olympics (21 July, p 26) . I agree. Sex should not be the determining factor for eligibility to compete. Ability should. The current sex-centric mechanism for deciding how many competitions there are and selecting who can participate …

If a superior extraterrestrial intelligence arrived on Earth, as Anthony Wheeler suggests in his letter (21 July, p 30) , then presumably it would be intelligent enough to realise that the sheer number of humans, all consuming resources, causes problems. It therefore seems likely that these beings would do as we do when faced with …

I am disturbed by some of the language in your story on breeding albatrosses (21 July, p 16) . It has been known for decades that many pair-bonded bird species engage in extra-pair matings, and up to half the eggs of any brood may result from this. So it is unscientific to use such anthropomorphisms …

I would like to counter David Evans's letter (21 July, p 31) . He says only a truly clumsy person makes an injection hurt. I've had type 1 diabetes for four years and have yet to find a consistently pain-free spot to inject. I agree there is no need to fear needles, but there is …

In view of the need to capture carbon and your report on rice plants growing five times larger when given a microbiotic fungus (28 July, p 8) , what a temptation to use this on giant sequoia, even if it would be a long-term experiment.

• In our Editorial that commented on the Tax Justice Network's report of a staggering $21 trillion or more that has been stockpiled in tax havens (28 July, p 3) , we should have said that nearly half that sum involved fewer than 92,000 people, roughly the richest 0.001 per cent.