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Emergent Systems Working Group

February 12, 2004
Ted Wong
Why Evolution by Natural Selection Isn't Emergent

(this outline first appeared at http://emergent.brynmawr.edu/eprg/?page=WhyEvolutionByNaturalSelectionIsntEmergent)

Many people think evolution by natural selection is emergent.

There is no designer.
Enormous complexity came out of iterations of simple rule(s).
This complexity includes well defined levels of organization.
Organisms interact with each other, both directly and through interactions with the shared environment.
Unpredictable outcome: Gould's tape would replay differently.
But (just to be clear) what is the emergent phenomenon? I can think of a few possibilities:

The emergent phenomenon is diversity. Here you have to think of the growth of the Tree of Life, and the fractal-like form of the tree emerges from all the various lineages bifurcating off of one another.
The emergent phenomenon is cognition. Or it's photosynthesis or some other amazingly complicated feature of some organisms.
The emergent phenomenon is organization, and the agents can be anything in the "lower" levels: atoms, molecules, macromolecules, cells.

Is biodiversity emergent?

I press dough into a mold. The dough takes on the shape of the inside of the mold. Putatively emergent phenomenon: global shape of the dough.
Yes: dough molecules interact with themselves and with the mold. Global dough shape is the sum of the molecule positions, but the molecules weren't placed in position by a designer.
No: the dough's final shape was merely transferred from the (designed) mold to the dough. The shape didn't arise in the dough molecules; in fact it constrained the interactions available to the molecules. You can tell the direction of pattern transfer because the final dough shape is predictable from the mold shape.
An earthquake knocks dough off a shelf into a coconut shell. The dough takes on the shape of the inside of the shell. Putatively emergent phenomenon: global shape of the dough.
Yes: neither the pressing of the dough into the shell nor the shape of the shell was intended by a designer.
No: again, the global shape of the dough didn't arise from interactions among the dough's component molecules. There was still a designer: the shell.
An earthquake knocks dough off a shelf into a balloon. The balloon fills with dough and assumes its full-inflation shape. The dough takes on the shape of the inside of the balloon. Putatively emergent phenomenon: global shape of the dough.
Yes: the global shape of the dough was a collaboration between the dough and the balloon.
No: it's not real collaboration, because the balloon's final shape is determined by the distribution of latex density (or something like that), which was itself designed by a balloon engineer.
A bunch of helium-filled balloons are released into Schwartz Gymnasium. Balloons accumulate in the high points of the ceiling. Putatively emergent phenomenon: the distribution of balloons.
Yes:
No: again, you know where the high points are, so you know where the balloons will go. Here there isn't even the question of interactions among balloons.
A growing population of organisms spreads by diffusion across a phenotype space. Because of selection, organisms tend toward fitness peaks. Putative emergent phenomenon: biodiversity.
Yes:
No:

Is complicated adaptation X emergent?

If peak X in a phenotype space is occupied, is that peak (or its occupation) emergent?
In a diffusion process, is the position of some particle ever emergent?

Is organization emergent?

Sure.


How is emergence important in the study of evolution?

Development is emergent. A butterfly's camouflage pattern is ultimately the result of selection by predators and bark patterns (which together make a sort of designer). It proximately results from local interactions among cells and morphogens. That's where emergence comes in, and that's what's fascinating about the evolution of development. Selection acts on the agents by selecting global behaviors.


Additions, revisions, extensions are encouraged in the Forum and/or at emergent.brynmawr.edu

Participants for October 28, 2003: Ted Wong, Paul Grobstein, Jim Marshall, Doug Blank, Karen Greif,
Al Albano, Anne Dalke, Mark Kuperberg, Alan Baker, Tim Burke, Hannah Wilhelm, Jim Wright (12)




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