Re: Uploaded memories

Robin Hanson (
Wed, 08 Dec 1999 16:32:39 -0500

Robert Bradbury wrote:
>You should read Science News Nov. 27 1999, pg 340-341 citing an article
>in Nov. 25, Nature by Jef Huisman and Franz J. Weissing who appear to
>have a mathematical rationale for why sub-fit species can survive
>and prosper. Its fundamentally wrapped up in the number of essential
>nutrients there are. The more nutrients there are the more species
>an environment can support, precisely because of the exponential
>growth problem. A species grows until it exhausts the supply of
>the essential nutrient it is best at harvesting, then another species
>that depends on different nutrients grows until that nutrient
>becomes limiting, etc.

I read that paper and liked it, but I think you misunderstand it. It is not describing a sequence of species saturating one after another.

The paper was taking as a puzzle the fact that we tend to see a lot more species than we see essential nutrients, even though a simple model says that you shouldn't. They note that a fluctuating environment is enough to make room for lots more kinds of species, each one tuned to a different frequency of fluctuation. The paper's contribution is to then note that if different species approach equilibrium at different rates, that is enough to create a fluctuating environment which can support many species. You don't need outside fluctuations; inside ones are enough.

Robin Hanson Asst. Prof. Economics, George Mason University MSN 1D3, Carow Hall, Fairfax VA 22030
703-993-2326 FAX: 703-993-2323