Letters archive

Peter Neumann is right to qualify the threat posed by jihadis returning from Syria; their motives are quite distinct from those who attempt terrorist activity within the UK (5 July, p 24) . However, all such jihadis have one very significant impact on return: their credibility among their peers is hugely increased. The effect of …

To establish how many people could benefit from a wheat-free diet, and why (12 July, p 28) it seems that much more work needs to be done. For the time being, science can't support or refute the proposition that a significant number of people could benefit from such a diet, but as a matter of …

Michael Slezak explores Australia's ambitions for turning its northern tropical land into a new food bowl (12 July, p 6) . Concerns have rightly been raised about diverting rivers and building dams to irrigate the land, and the environmental impact of these interventions, not to mention the permanent changes this would entail for the indigenous …

Richard Layard and David Clark rightly point to the good that has been done in the UK by the Improving Access to Psychological Therapies (IAPT) initiative (12 July, p 24) , but this only tells half the story. Cognitive Behavioural Therapy (CBT) and similar therapies currently available through the National Health Service (NHS) simply aren't …

You reported the US Supreme Court's decision that some companies can refuse to provide employees with healthcare plans that offer free birth control. It's important to note that "closely held corporations" are not restricted to just small or family-owned businesses (5 July, p 6) . According to the Internal Revenue Service, a closely held corporation …

I was concerned to read the diatribe against Japanese knotweed (5 July, p 38) . While not wishing to defend some of knotweed's thuggish habits, your article was in my view both biased and unscientific. To describe it as having the "biodiversity value of concrete" is absurd. It is in fact a valuable nectar source …

You describe a technique to use genetically tweaked red blood cells to deliver drugs that would otherwise break down after a few hours in circulation (5 July, p 14) . What is unclear is why this should be so. If the drugs in question decay so quickly, this would surely not change, given that the …

• For small-molecule drugs, excretion via the kidneys is the most common path of "decay". If such drugs were attached to red blood cells, they would not be filtered out by the kidneys and so would persist for longer in the body. For drugs in the form of antibodies and other proteins, removal via the …

Nick Bostrom repeats the central transhumanist fallacy that there exists a mechanical shortcut to superior intelligence (5 July, p 26) . He claims three such shortcuts; via speed, collectivity and quality. All three are guaranteed to fail. Fast processing does not guarantee superior intelligence. A fool given a million subjective years to write a program …

In common with many others, Bostrom assumes that top of the agenda for a superior artificial intelligence (AI) would be creating ever more capable successors without limit. The cynic in me suggests that a sufficiently smart AI might, unlike us, be wise enough not to create its own replacement. Of course, an AI so intelligent …

If Toby Pereira thinks xenon and argon are used by athletes as inert gases to simulate altitude training, he might wonder why nitrogen, a vastly cheaper alternative, is not used instead (12 July, p 26) . In fact, these noble gases are believed to have a biological effect related to the production of the performance-enhancing …

Your article on searching for the origins of life in billion-year-old water samples was interesting (5 July, p 8) , but the statement that "as far as the team could tell, the water contained no trace of life" is suspect. One thing we should have learned from the search for life on other worlds – …

When I saw the picture of the newly designed FireFly rocket, I couldn't help thinking that I'd seen it before (12 July, p 5) . Indeed I had. It was permanently ingrained on my memory way back in the 1960s when, as an impressionable young boy, I was completely besotted with anything to do with …

• The designer of the Hong Kong subway's AI system is Andy Chun (5 July, p 17) . • A lack of Curiosity: the Mars lander pictured in our book review was not the titular spacecraft (5 July, p 45).