Cui bono?

Addiction as interspecies manipulation.



Randall Munroe is not making this process up. Consider the single-celled amoeba-like parasite responsible for toxoplasmosis:

Toxoplasma gondii is known to remove rodents’ innate fear of cats. …. The microbe is a single-celled pathogen that infects most types of mammal and bird, causing a disease called toxoplasmosis. But its effects on rodents are unique; most flee cat odour, but infected ones are mildly attracted to it. This is thought to be an evolutionary adaptation to help the parasite complete its life cycle: toxoplasma can sexually reproduce only in the cat gut, and for it to get there, the pathogen’s rodent host must be eaten.

The mechanism offers an attractive take on human addictions to certain plant alkaloids. From the point of view of an opium poppy, coca shrub, or cannabis plant, its human commensals – Afghan peasants, Colombian drug smugglers and Californian advocates for marijuana legalisation – are all just useful idiots, unwitting allies in increasing its reproductive chances in the tangled bank of life.

You think plants don’t have the nous to follow toxoplasma? Consider this brilliantly successful innovation, a device to manipulate a huge range of animals into spreading pollen more efficiently than wind:


Magnolia flower, an early example (up to 95 myr BP).

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Any reader attending Mark’s cannabis policy summit at NYU on April 17-18 should feel free to reuse this. I’m not going. Bunch of speciesists if you ask me.

Author: James Wimberley

James Wimberley (b. 1946, an Englishman raised in the Channel Islands. three adult children) is a former career international bureaucrat with the Council of Europe in Strasbourg. His main achievements there were the Lisbon Convention on recognition of qualifications and the Kosovo law on school education. He retired in 2006 to a little white house in Andalucia, His first wife Patricia Morris died in 2009 after a long illness. He remarried in 2011. to the former Brazilian TV actress Lu Mendonça. The cat overlords are now three. I suppose I've been invited to join real scholars on the list because my skills, acquired in a decade of technical assistance work in eastern Europe, include being able to ask faux-naïf questions like the exotic Persians and Chinese of eighteenth-century philosophical fiction. So I'm quite comfortable in the role of country-cousin blogger with a European perspective. The other specialised skill I learnt was making toasts with a moral in the course of drunken Caucasian banquets. I'm open to expenses-paid offers to retell Noah the great Armenian and Columbus, the orange, and university reform in Georgia. James Wimberley's occasional publications on the web

3 thoughts on “Cui bono?”

  1. The flower blossom/pollen example is not esp. appropriate since pollen is a source of food for bees and other animals and there is no evidence that it alters bees' instinctive behaviors in a self-destructive way, which toxoplasmosis does to rodents.

    Incidentally, Carl Zimmer recently wrote about a study of the effect of the parasite on chimps. It affects their response to the urine of leopards, one of their predators, but not tigers, which do not prey on chimps.

    In looking for this, I also came across a study of the effect on humans, a correlation between being infected and their frequency of bouts of extreme rage. Who knows if this will hold up.

    1. Fair enough on the mutual benefit to the bees. How's that different from the drug smugglers?

      Wikipedia claims plausibly that as bees are totally dependent on flowers, these must have evolved initially to work with more polyvalent species like beetles. In a way the flowers created the bees from specialized wasps. That's manipulation too, though benign.

  2. T. Gondii is a nasty organism, but I've long thought that it had great potential to be modified into a therapeutic vector. As an intracellular parasite, it has the built in capacity to travel through tissues, cross the blood-brain barrier, avoid triggering immune reactions, and even enter and leave cells without killing them.

    All you'd have to do is remove some of the nastier properties, and add the ability to drop off a payload under specified circumstances, and it would rock as a way of delivering drugs and genetic modifications.

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