© Agnès Iatzoura MNHN © DR
© Agnès Iatzoura MNHN
© DR


Parasites, the engine of evolution: interview with Jean-Lou Justine, parasitologist

When Professor Jean-Lou Justine of Paris’s National Museum of Natural History explains his field, his examples sound almost like fables. For anyone wanting to make a connection between parasites and building, the Professor is quick to offer the requisite scientific vocabulary. Why can’t we, for example, talk about ‘phoretic architecture’, or ‘ectoparasitic extensions’? However we phrase it, parasites have been one of the engines of evolution — could this also be true for construction?

Read the full interview in AA 438 — Parasites ; an issue written with our guest editor, the artist Tadashi Kawamata. Please visit our online shop.

L’Architecture d’Aujourd’hui: What is a parasite?
Jean-Lou Justine:
A few words suffice to define a parasite: it is an organism that depends on another organism. However, that definition could include predators, so we must add a qualification: a parasite is necessarily smaller than its host.

AA: Why would someone become a parasitologist?
JLJ: My primary interest was zoology, but in fact this led me to specialise in parasites that live on so-called ‘wild’ fish. As such, my research has nothing do with commercial fishing, and has no economic dimension. As fundamental research, it is nonetheless important for our understanding of life. Biologists say: “Nothing in biology makes sense, except in light of evolution”.

AA: To what extent are parasites useful in evolutionary terms?
JLJ: The word ‘useful’ is not used in biology. Nineteenth century classifications have long since been forgotten, and as a result, the fox is no longer considered a “pest”. Having said that, it must be understood that all species live in perpetual conflict with each other, which forces them to evolve; parasites play a major role in this. That means that a host must evolve in order to avoid being overrun. In reaction to that, parasites change too, in order to get better at being a parasite. In many ways this context explains the importance of sexual reproduction. All things considered, this kind of reproduction is an astonishing waste of energy, since male animals do not produce offspring; they only contribute a few spermatozoa, even when they eat as much as females. We could therefore say that 50% of the available resources are wasted by males. But with each generation, this reproduction allows for the mixing of genes, and it is, in fact, this sexual mode of reproduction that makes it possible to evolve, and to resist parasites.


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