Leigh Van Valen at the University of Chicago devised this analogy to explain several puzzles in biology. It is named after a character in the story ‘Through the looking glass and what Alice found there’, by Lewis Carroll. As the Queen explained to Alice, puzzled by why the Queen was always running fast but getting nowhere, it took all the running she could do just to keep in the same place.
The hypothesis called Red Queen is used to explain the evolution together of predators and their prey, and of parasites and their hosts. A more difficult question is the evolution of sex, when reproduction without sex is twice as productive as when only females actually produce offspring. Parasites and hosts are a simpler example, such as the Plasmodium species of microscopic single celled animals causing malaria in their human host.
Plasmodium parasites reproduce both asexually to expand their numbers vastly during infection, but also they reproduce sexually when being transmitted by mosquitoes. This enables them to produce offspring unlike their parents through the genetic mixing of sex; similarly humans. This constant generation of variation creates the potential for some offspring of plasmodia to be slightly better at surviving against the defences of humans. Such offspring will be positively selected by this evolutionary pressure.
These defences are immunological: antibodies and anti-parasitic white cells of blood. Likewise these defences will vary in offspring and those offspring that are better at countering the new advantage of the plasmodia will survive and continue to spread that genetic trait. So the race continues, without end. The balance swings back and forth – tiny advantage to Plasmodium followed by tiny advantage to humans.
But why do some parasites sometimes kill their hosts, as does Plasmodium, whilst others just take a little blood and cause much irritation as do fleas? When a child dies of an infection from Plasmodium falciparum it is because the blood stage of the parasite has lodged in the child’s brain, clogging the fine capillaries carrying oxygen and energy. The plasmodia inside the red cells of blood make the red cells sticky so they adhere to the inner walls of the capillaries. The usual explanation of this is that the parasite is evading the immune system of the child in these foci of infection away from destruction in the spleen. The human death, if it occurs, is a side effect of no advantage to the parasite, which will die with its host.
Another explanation has been proposed by Allan Saul, of the Queensland Institute of Medical Research. He points out the reproduction of Plasmodium falciparum by asexual means is to fast that it should result in total destruction of the blood before it could enter its sexual phase of reproduction. That phase is necessary for the Plasmodium to complete its life cycle in the mosquito. Saul proposed that the Plasmodium actually regulate their own reproductive rate so that they can maintain a long term infection in humans and thereby increase the probability of onward transmission.
The plasmodia possibly do this by acting as a multicellular organism, in which development is achieved as much by regulated cell death, or apoptosis, as by cell growth. Failure of such regulation in ordinary multicellular organisms leads to cancerous growth. The parasite protein out on the surface of the red cells is highly reactive with antibody and this leads to many infected red cells being caught and killed by the spleen, so regulating the numbers of the parasites to a stable level. The stickiness of the protein may be just a secondary effect.
Maybe.
See: Saul, A. 1999. The role of variant surface antigens on Malaria-infected red blood cells. Parasitology Today, 15, 455-457.
For more on the Red Queen Effect try Matt Ridley's 'The Red Queen', Penguin Books, 1993; specially chapter 3 on The Power of Parasites.
Don’t be daft — of course science is useful! The wheel, the bicyle, cars, airplanes, computers, lasers, antibiotics, vaccines, anaesthetics: what a cornucopia science and technology have brought us. Well, maybe; but the question was about scientists, not technologists. What is the difference you might ask; very reasonably since so often the two words are used as if synonymous.
They do not mean the same and the difference is very important. Scientists set out to discover how the natural world works — why does the Moon keep going round the Earth without falling down and crashing on us? Because it is moving so fast. Then why does it not fly off into outer space? Because of gravity. What is that? Ah — well, we are still working on gravity. Isaac Newton formulated his universal law of gravitation long ago and it it remains good enough for engineers to design a robot to land next to a chosen crater on the Moon. Albert Einstein’s general theory of relativity explained much more about gravity, but there remain anomalies and numerous propositions to explain them.
The engineer making a robot uses a wide and deep knowledge of physics in its design and the objective for the time being is to discover more about the nature of the Moon rather than bring back something utilitarian like precious new minerals. So scientists become technologists when they need to make instruments to get data. But an engineer seeking to improve the profitability of a automobile factory sets out to invent robotic assemblers and welders, not to discover a new law of economics.
This all seems obvious, but a closer look reveals hidden difficulties about how these endeavours should be funded. Sending robots to the Moon costs a lot of taxpayer’s money. So, again, are scientists any use? Not much, seems the argument made by some commentators who trace numerous technological advances from their early days, through to acceptance by consumers, followed by incremental improvement after improvement, until civilized life seems impossible without them. The electric light, telephone, automobile and computer are classic examples. An obvious demand from people for a more immediate and flexible means of communicating with other over long distances led from running messengers to horse drawn postal services, to semaphores and finally the electric telegraph which soon led the way to the singular and dramatic invention of the telephone. All done by technologists, in a demand-side operation. Perhaps there was some help from those chemists and physicists who wanted to know the nature of electricity. The strange thing is that many of those scientists could think of nothing to do with electricity that satisified any demand, other than their own curiosity. The discovery of the laws of electricity was offered to the world as a supply-side gift.
This becomes a complex debate about how the big differences between science and technology influence the proper use of public and private funds and how our lives can be improved by making better decisions on this. (For more, the web is little direct use. Try starting with Terence Kealy on 'Sex, science & profits: how people evolved to make money' published in 2008 by Vintage Boks, London, for a lively polemic in favour of inventors. Comroe J.H. & Dripps R.D. provide formal and detailed information on the benefits of basic research in Scientific basis for support of biomedical science, published in Science, 1976, vol 192, pgs 105-111.)
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Apr/04 - Test article
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