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Oh, I wasn't even thinking of the granularity. I agree that some continuous function might be appropriate, but to extrapolate beyond even a few years is folly, and we need *much* more realistic functions than a simple exponential growth model to have a shot at numbers matching the actual data. Population dynamics are really, really, really tough.
/snip/
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*From:* brian whatcott <betwys1@sbcglobal.net>
*To:* phys-l@carnot.physics.buffalo.edu
*Sent:* Wed, September 22, 2010 11:00:00 AM
*Subject:* Re: [Phys-l] H. Sapiens
I imagine the granularity of the poll count, gestation time and life
span underlying annual rates of increase of Human populations is so
comparatively tiny, that a continuous function is quite suited to the
purpose.
Brian W
On 9/22/2010 8:56 AM, curtis osterhoudt wrote:
> If they say the population growth rate is "x% *per year*", then, yeah :) Hell,
> for bacteria, it might easily be 1% per minute, given a rich environment.
>
>
> Of course you're right: each of the expressions are approximations. I gave
> the "70 rule-of thumb". 72 is also commonly used, because it has several
> integral divisors. Once one starts quibbling about using 69 instead of 70, one
> might as well use the _proper_ expressions. Too, the error introduced with the
> approximations is quite manageable, and is usually lost in the noise of mutation
> rates, environmental constraints, and so on (for "simple" populations of
> bacteria or fish, say), and absolutely swamped by things like migrations and
> societal changes (for humans, say).
>
>