[extropy-chat] Desirability of Singularity (was Are ancestor simulations immoral?)

Martin Striz mstriz at gmail.com
Wed Jun 7 20:58:44 UTC 2006


On 6/6/06, Anders Sandberg <asa at nada.kth.se> wrote:

> And why that temperature? In the end 37 C is a kind of compromise. Higher
> body temperature means faster kinetics for many processes, faster nerve
> conduction velocities (increasing body temperature by 0.2 degrees improves
> cognition in some tests; beyond that there is no improvement) but also
> higher metabolic costs (increasing exponentially with higher temperature)
> and in males increased mutation frequency. Basal body temperature seems to
> be set by evolutionary adaptation to a particular environment and
> ecological niche, varying within related species quite a bit and it is
> possible to push the enzyme kinetics quite a bit with sufficient
> evolution.

Extremophiles demonstrate that peptides can be designed for optimal
activity within a wide range, from close to freezing, to close  to
boiling (all life perforce lives within the confines of acqueous
solutions).  However, I dn't think you adequately explain why 37 C
would be an optimal trade off.

Why have most warm-blooded animals converged on 35-40 C?  My educated
guess would be that, since most airborn microbes have enzymes
optimized for ambient atmospheric tempratures (20-30 C), warm-blooded
potential hosts ratcheted up their homeostatic setpoint as a defense
mechanism.  Enzymes tend to denature at just a few degrees above their
optimum (actually, they continue to work faster above the so-called
"optimum" but the percentage of denatured enzymes in the population
starts to increase, so the total enzyme activity of the population is
seen as a decrease, and the whole thing looks like a bell curve).  So
by maintaining our thermostatic setpoint a little above atmospheric
temperatures, we can fight off many microbes.  Of course, over
evolutioanary time, persistent pathogens evolved enzymes that function
at an optimum of 37 C.

In other  words, if it weren't for pathogens, we would probably have
lower body temperatures, because the energy cost increases faster than
the metabolic rate.  Actual metabolism/energy efficiency is better at
much lower temperatures.

Cheers,
Martin



More information about the extropy-chat mailing list