The Wonder of Birds Flocking

What is remarkable about the starlings' behaviour is that, despite all appearances, there is no choreographer and, as far as we know, no leader. Each individual bird is just following local rules.

The numbers of individual birds in these flocks can run into thousands, yet they almost literally never collide. That is just as well for, given the speed at which they fly, any such impact would severely injure them. Often the whole flock seems to behave as a single individual, wheeling and turning as one. It can look as though the separate flocks are moving through each other in opposite directions, maintaining their coherence intact as separate flocks. This makes it seem almost miraculous, but actually the flocks are at different distances from the camera and do not literally move through each other. It adds to the aesthetic pleasure that the edges of the flocks are so sharply defined. They don't peter off gradually, but come to an abrupt boundary. The density of the birds just inside the boundary is no less than in the middle of the flock, while it is zero outside the boundary. As soon as you think about it in that way, isn't it wondrously surprising?


The body of a human, an eagle, a mole, a dolphin, a cheetah, a leopard frog, a swallow: these are so beautifully put together, it seems impossible to believe that the genes that program their development don't function as a blueprint, a design, a master plan. But no: as with the computer starlings, it is all done by individual cells obeying local rules. The beautifully 'designed' body emerges as a consequence of rules being locally obeyed by individual cells, with no reference to anything that could be called an overall global plan. The cells of a developing embryo wheel and dance around each other like starlings in gigantic flocks. There are differences, and they are important. Unlike starlings, cells are physically attached to each other in sheets and blocks: their 'flocks' are called 'tissues'. When they wheel and dance like miniature starlings, the consequence is that three-dimensional shapes are formed, as tissues invaginate in response to the movements of cells; or swell or shrink due to local patterns of growth and cell death. The analogy I like for this is the paper-folding art of origami, suggested by the distinguished embryologist Lewis Wolpert in his book The Triumph of the Embryo; but before coming to that I need to clear out of the way some alternative analogies that might come to mind - analogies from among human crafts and manufacturing processes.


Emergent behavior without collisions.

Folksonomies: biology wonder emergence

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 The Greatest Show on Earth: The Evidence for Evolution
Books, Brochures, and Chapters>Book:  Dawkins, Richard (2010-08-24), The Greatest Show on Earth: The Evidence for Evolution, Free Press, Retrieved on 2011-05-19
Folksonomies: evolution science