Why do we care what we are made of?
Colin Barras reminds us that our 30 trillion human cells are outnumbered by 39 trillion microbes 鈥� a more accurate representation than Thomas Luckey’s that microbes outnumber human cells 10 to one (13 April, p 28). But over 80 per cent of the human cells that make up our bodies are erythrocytes, also known as red blood cells. These contain no nucleus or organelles, they are simply packed with haemoglobin, the molecule that transports oxygen and carbon dioxide to and from our tissues. Some might say that they are not true cells at all.
But why would anyone care about the ratio of human to non-human cells in our bodies? Consider how many DNA-filled human cells, carrying our genes and presumably contributing to our sense of self, are replicating in our bodies compared with non-human cells: just under 7 per cent. In the end, does it matter?
How air pollution may cause teen psychosis (1)
You report a study by Helen Fisher and others linking air pollution from vehicle exhausts with teenage psychosis (6 April, p 25). You say that it isn’t clear how air pollution might be linked to psychotic experiences. The children studied were born in 1994 and 1995. The fuel additive tetraethyl lead was banned in the UK from 2000. So the children may have had between four and six years’ exposure to lead, which is known to affect the brain. Areas that now have high levels of nitrogen oxides would then have had high levels of lead pollution.
How air pollution may cause teen psychosis (2)
Adam Vaughan is right to note that the correlation between exposure to air pollution and teenage psychosis isn’t proof of causation. One smoking gun, though, is that air pollution is consistently worst in areas where poverty is concentrated, with all the social and psychological stresses it entails.
It is extraordinary that the study found that 30 per cent of teens surveyed reported at least one psychotic episode.
The editor writes:
鈥� We didn’t mention that the researchers did control for poverty. They had no data on lead.
Working hours and mental health
While discussing the effects of cutting work hours, Michael Le Page quotes a study by Huong Dinh at the Australian National University showing that men with unpaid care commitments could manage about 30 per cent more working hours than women with such duties, without experiencing a decline in their mental health (13 April, p 20). Such a dramatic disparity surely warrants much closer examination.
Were the 8000 participants randomly selected? Were they 50 per cent male and 50 per cent female? Could the difference be attributable to men being less comfortable discussing their mental health than women? What constituted an unpaid care commitment? There is a big difference between buying groceries and caring for an elderly relative, for example. The type of paid employment and levels of status and remuneration could also have a significant effect on employees’ ability to sustain mental health.
Le Page pointed out that to make assumptions about working hours based on male needs is detrimental to women’s interests. It is arguably also detrimental to the cause of gender equality to report differences in possible working hours without a more nuanced analysis.
My relation to religion is different as a woman
Harvey Whitehouse reviews evidence on religion’s role in human civilisation (6 April, p 36). But he makes no attempt to distinguish between the differing social needs of women and men. Formal religions are staffed by a ruling elite of men who, I believe, have a fundamental goal of regulating women’s sexuality.
Get to Proxima Centauri one small step at a time
Gilead Amit reports plans to send gram-scale craft to Proxima Centauri (13 April, p 32). Expecting that these could get a signal back to us is fantasy. The amount of power a 1-gram payload could generate can’t be more than a few watts. For comparison, the New Horizons spacecraft uses a 15-watt transmitter to reach us from Pluto.
Plans to get to Proxima Centauri should be incremental. Start with more modest lasers, and much bigger payloads and solar sails. Then work on improving each of the various components.
It isn't the people who need to be forced
A study investigated what people are willing to do voluntarily to reduce their carbon footprints, and concluded “not enough” (6 April, p 8). I think people would be happy to do far more if everyone had to do so. It is our leaders who need to be forced to make the necessary laws.
Social engineering to change travel and diet (1)
Adam Vaughan notes that the European Academies’ Science Advisory Council urges the European Union to change its stance on transport, which is that curbing mobility is not an option (30 March, p 23). Social engineering has given us the transport situation that we have now: they built it, and we use it. But social engineering can bring change. It has often been demonstrated that reducing road capacity reduces the amount of travel. There is no forced curb on people’s mobility.
Individuals then decide for themselves how they will change their activities. Most opt to vary their route or travel at a different time. Some go to greater lengths, including changing their travel mode or domicile.
Social engineering to change travel and diet (2)
Vaughan suggests caps on personal travel to reduce carbon emissions. But if capped travel could be traded, a rich person could buy travel from poorer people who were happy to accept a market price for it. This would be equivalent to a fuel tax that raised the cost to that price and whose proceeds were distributed evenly. A tax would make everybody happier than the cap method.
Social engineering to change travel and diet (3)
Taxing meat to cut consumption is curious: many of us are already taxed in order to make it cheaper. The only step needed is for governments to stop subsidising meat and dairy. Doing so absorbs , which itself comprises 40 per cent of the EU budget. Subsidies are also high in the US.
Smart street lights should set street speeds
Sam Edge suggests fitting street lights with motion sensors to save energy (Letters, 16 March). I would go further and provide a rolling corridor of light in rural areas. It would move along ahead of a moving vehicle.
This might have the added benefit of “nudging” compliance with the speed limit if the light wave were limited to it.
Meetings with famous primates and cultures
Your article on chimpanzees losing culture brought back memories (16 March, p 16). I took an elective course in anthropology as a freshman at the University of Illinois in early 1961, but I had no real interest in the field.
One day, our professor came in with a burly gentleman, who he introduced as the anthropologist Louis Leakey, who was travelling to California to announce a major discovery by a student named Jane Goodall. We were astonished as he showed us Goodall’s photos of chimpanzees using branches to catch termites and ants 鈥� clearly demolishing what we had learned in class a few weeks earlier, which was that humans are the only species to use tools.
If chimpanzees are losing their culture, the idea that they may eventually lose their tool-using skills is very sad.
Woman sniffs dog and observes its epilepsy
I am not at all surprised that Am茅lie Catala and her colleagues find that dogs can smell when someone has had an epileptic seizure. The reason for this is that I can smell when my dog has had one (6 April, p 19). My dog’s seizures are generally well controlled by medication, but if he has even a small one, even in the middle of the night, I know because of the telltale smell: an acrid pong like no other. It seems to come from his saliva. Since becoming a dog owner, I have realised that the human sense of smell is better than we realise.
For the record 鈥� 11 May 2019
鈥� The sculpture of human figures in the intertidal zone is by Antony Gormley (20 April, p 34).
鈥� Rhoetosaurus brownie may sound delicious, but the name of the giant dinosaur is Rhoetosaurus brownei (27 April, p 9).
鈥� Galactic brain: Breakthrough Starshot plans to go no further than our closest neighbouring star (13 April, p 32).
鈥� The average UK female scientist or engineer now earns 22 per cent less than the average male colleague (30 March, p 45).
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