The sum of our parts
For each of the human traits discussed in your article “10 Mysteries of you” (8 August, p 28), the authors imply that if one explanation is correct, the others must be false.
In the real world, however, no one selective pressure acts on a trait in isolation. Rather, a multitude of collaborative, conflicting and sometimes shifting pressures are simultaneously at work within a population. It is the interaction of these selective pressures that ultimately determines the “shape” of any particular trait.
If we have difficulty finding a single convincing evolutionary explanation for a particular trait, like blushing or dreaming, it is almost certainly because that particular trait is the result of a selective compromise, as is the case with the persistence of the sickle-cell gene in populations where malaria is endemic.
Sometimes an observed trait can be a neutral side effect resulting from selective pressures acting on a completely different trait. There has been no selective pressure for belly buttons, but we all have one as a result of selective pressures that brought about the mammalian umbilical chord.
Caroline Williams summarises a number of putative reasons why we have pubic hair, but omits one.
In our evolutionary history, pubic hair played an essential part in the thermoregulation of heat-stressed hunter-gatherers. A sweat drop which falls to the ground is a sweat drop wasted. Ledges, warm emulsifying sebaceous secretions and sweat-trapping hair remnants (eyebrows, moustache, beard, chest hair and pubic hair) would have checked the downward progression of sweat drops and won time for evaporation. I expanded on this in 1993 in the Journal of Human Evolution (vol 25, p 417).
In order to understand nose-picking it is important to differentiate between dried nasal mucus and the stranded rhabditiform larvae of intestinal worms. Some of these lose their way during their migration through the body and end up in the nose (or even the ears). When this happens, we pick them out of the nose and have a choice: discard or swallow.
The presence of intestinal worms leads to raised levels of white blood cells called eosinophils, a sign of an active immune system. Whether this activity reflects the body’s attempt to repel parasites or the parasite’s grateful contribution to the health of the host isn’t important. It is a fact that the presence of worms improves our immune status.
So swallowing the strays is a way of ensuring that the immune system is maintained.
Hastings, East Sussex, UK
My 12-year-old son loves New 杏吧原创. This morning as we leafed through it together at breakfast I pointed out your article on what strange creatures humans are, thinking the item regarding nose-picking might be of particular interest to a 12-year-old: “There’s an article here discussing the things we don’t understand about humans… like why we pick our noses.”
He looked up from his cereal and gave me a gaze of zen-like clarity. “Because we can,” was his considered retort.
How lucky that we don’t have claws or hooves.
Warninglid, West Sussex, UK
Cough mixture
Bob Holmes warns us that the second wave of a pandemic flu outbreak tends to be worse than the first (8 August, p 40).
The most likely explanation for this increased severity is the near certainty that there will be a reassortment of genes between a mild pandemic strain of the virus and some nasty, rare type. An obvious candidate for this nasty type would be bird flu, but there are plenty of others out there, especially if the reassortment can be with virus types that do not currently infect human beings.
If 500 people a year get bird flu and 10 per cent of the population get swine flu, the chances that no one will catch both viruses at the same time are slim. Even if we incorporate the requirement that it must reassort in human infection, as it can in pigs and birds, then we must assume it will indeed happen.
This raises the question: why are we using Tamiflu on a mild virus? All this is likely to achieve is to drive resistance, just in time to make Tamiflu useless against something serious.
Bob Holmes’s reports of the research into potential broad-spectrum antiviral treatments led me to an interesting conjecture. If we are able to manufacture tailor-made antibodies to target cell components that are only exposed when a cell is infected by a virus, then it might also be possible to develop broad-spectrum vaccines, based on the same antigens.
Of course, thorough safety testing would be needed if trying to stimulate an immune response to “self” antigens. While a drug can be stopped, the effects of a vaccine are largely irreversible. Developing a vaccine might also be unattractive to pharmaceutical companies, since widespread immunity to viral diseases would lead to fewer people buying their antiviral drugs.
Fry panned?
In a sidebar to her article on gorillas, Stephanie Pain tells us of the disastrous repercussions for these primates of cellphone production: “If you must have a new [cellphone], then recycle the old one to reduce demand for coltan… Illegal mining of coltan ore is partly responsible for the plummeting number of eastern lowland gorillas in the Democratic Republic of the Congo” (25 July, p 34).
Stephen Fry appears in his interview, some weeks later, to know of the gorillas’ dire situation: “Take the example of the mountain gorillas. There are only a few hundred of them left” (15 August, p 24). Yet he also tells us that: “I have never seen a smartphone that I haven’t bought. I have cupboards and cupboards of them.”
With friends like these, who needs enemies?
From Arthur Mitzman
Bravo for Stephen Fry’s reasons for concern with the disappearance of fish species. He finds their loss “terrifying” because his “nephews and nieces, and great-nephews and nieces” may never be able to eat a fish and see them only in aquaria.
Fry’s empathy with future generations constitutes an answer and an implicit rebuke to those who hold views like Tom Dixon, who asks in his letter in the same issue: “If climate change does not affect me personally, materially and directly, within the limited window of my remaining years, why should I care?” (15 August, p 22)
Perhaps Dixon has no children, grandchildren, nephews or nieces.
Amsterdam, The Netherlands
Tuna meltdown
In his article on tuna stocks, James Joseph provides good figures for their status, correctly highlighting bluefin tuna as being of greatest concern (1 August, p 22). He goes on to say that three tuna stocks are at risk, one is recovering, one is slightly at risk and another may recover.
As conservation initiatives are difficult and slow to implement, let alone enforce, I am unclear about how he reached the conclusion that “it’s OK to continue eating tuna”. It would also have been worth mentioning in the article the various methods of fishing that affect levels of by-catch 鈥� the mortality of fish other than those species intended for the catch 鈥� as well as the potential for harming other animals.
As supermarket consumers, we should think carefully about whether we need to buy tuna, as well as other fish, or whether it is better to leave them in the sea for communities such as those in west Africa who have no other protein source. Their future rests on our lifestyle choices.
We still have a chance to prevent other species suffering the same exploitation as bluefin tuna. Rather than waiting until all the stocks are overexploited, we must slow down now.
Fringe benefit
Andrew Stiller complains that your editors and contributors are harming New 杏吧原创‘s reputation by taking cold fusion seriously (8 August, p 24). I have to defend your approach.
Cold fusion may be on the fringe of science and it may be extremely unlikely ever to work at all, let alone as a viable power source, but the activities of those who still think it has a future are of interest to many, myself included.
Sometimes original and useful science comes from people who started out on the fringes. It is always possible that those investigating cold fusion might discover something else interesting or useful.
Just as theatre is not degraded by the , but enhanced by it, New 杏吧原创 actually enhances its reputation by its willingness to report on fringe science.
Myriad minutiae
Although like John Cooke I am proud to be a pedant (8 August, p 25), I have no problem with James Dyson’s use of the phrase “quantum leap” (11 July, p 20) to imply a large progressive step.
The novel aspect of a quantum of energy, when the concept was introduced to physics just over a century ago, was its indivisibility, rather than its intrinsic size. Thus a quantum leap is one which must be accomplished in a single step, rather than as a series of intermediate steps.
It is typically sudden or abrupt, and may well also be large.
Beyond belief
I would like to believe that you weren’t intentionally ironic when you illustrated George Marshall’s “Are you a believer?” article on climate change with an ostrich with its head in a planet of sand (25 July, p 24).
This aspersion on the bird’s survival skills has been well publicised as being false, yet it is still widely promulgated 鈥� even in scientific magazines. Who’d believe it?
For the record
鈥� Nearly two years ago, in an article on early human migrations (27 October 2007, p 36), we mislabelled the Wally’s Beach archaeological site as being in the US, when its position on our map correctly shows it to be north of the border in Canada.
鈥� Serguei Komissarov, whose calculations on gamma-ray bursts we reported (15 August, p 13), is at the University of Leeds, UK.
鈥� E. O. Wilson proposed the Encyclopedia of Life project in 2003, not as we reported (22 August, p 23), and its financial backers are promising $30 million not $50 million.