About 90% of you isn't actually "you". In terms of cell count, a typical human being is outnumbered roughly 10 to one by the microbes that reside in and on their body. You and the microscopic beasts inside you are a complex ecology; mess about with one part, and unexpected things might happen.

When we take antibiotics, we're hammering that ecology, sometimes not for the long-term good of us or the beasts.

There was a truly remarkable article on just this topic in Nature a couple of months ago: "Stop the killing of beneficial bacteria" by Martin Blaser of New York University (Nature 476 pp 393-4; see also article about it in the New York Times.).

Maybe you've never heard of Archaeopteryx. But it's held a special place in the theory of evolution for over 150 years. The word means "ancient wing", and it's the name of a strange fossil, half-bird and half-reptile; it had, for example, both feathers and teeth.

A German miner found the first one in 1861, two years after Charles Darwin published The Origin of the Species. It was considered by many to be a perfect "missing link" in his theory of evolution by natural selection. Indeed, it's been a mainstay of his theory.

Until recently, that is.

Last week in Nature there was a very illuminating paper, called "Controllability of complex networks" by Liu, Slotine and -- particularly -- Barabasi.

Albert-Laszlo Barabasi has been in the complexity field for many years, and has brought illumination to many areas, from engineering and natural systems like ecology to complex social systems. (He also writes compellingly good books for the non-scientist.)

The idea of 'controlling complex systems' seems much too general to do any real mathematics with, but the authors of the Nature paper show very clearly that