New from Science Daily:

“Across species from fish to mammals, they [researchers of this study] found that rates of protein evolution showed the same body size and temperature dependence as metabolic rate. Specifically, their mathematical model predicts that a 10-degree increase in temperature across species leads to about a 300 percent increase in the evolutionary rate of proteins, while a tenfold decrease in body size leads to about a 200 percent increase in evolutionary rates.”

From these results the authors conclude that “rates of protein evolution are largely controlled by mutation rates, which in turn are strongly influenced by individual metabolic rate.” It is well known that many physiological characteristics and population density correlate with metabolic rate (e.g. body size and relative metabolic rate). Now I suppose we can add this correlation to the list.

It appears the authors have observed something intuitive and subtly ground-shaking: the operation of an organism’s metabolism can influence the rate of introduction of mutations into that individual. This suggests that the dynamics of cellular metabolism, which are encoded in the genome and altered through evolutionary history, can in some way set the rate of change of the genome itself1. By no means does this suggest or implicate behavior in controlling such introduction, rather the idea that through history, genomes have been able to take a more active role in buffering against probably deleterious changes to itself, via the construct of a metabolism encoded by the genome.

Unfortunately the authors decided to focus on the significance of spontaneous mutation in being the driving force of protein evolution, rather than the ability of the organism (with its genome altered through its species’ historical interactions with the environment) to influence this mutation rate.

Definitions

• ascomycetes: meitotic progeny (spores) are encased within a shell called an ascus (sac)

  Includes yeast and morels

  Status of the S. cerevisiae genome

• basidiomycetes: Spores are produced on the outside of a cell called the basidium, which is a reproductive structure.

  Includes mushrooms and puffballs

• zygomycetes: Produce spores within which the gametic products will fuse (zugotos = yoked, joined)

  Includes bread molds

I recently learned the following of Darwin (although I mistakenly forget the source).

When Darwin left to head to the Galapagos, he believed in creationism, that is that the world had geographic “centers” of creation where God placed species, which whence spread around the world.

At what point during the growth and development of an organism do we consider it to be autonomously directed? That is, what level of complexity or developmental inertia must an organism achieve before we should consider it a distinct, independent living entity? This can be separated into two questions.

1. What is an organism’s inherent potential for autonomous re-generation as a function of its genetic architecture?
2. How is the proportion of this potential realized as a function of (developmental) time?