Metabolism may explain fossils vs. genes evolution mismatches

[bh480@scn.org]

From: Ben Creisler bh480@scn.org

Although not strictly about dinosaurs, this topic could be 
relevant to issues in dinosaur and bird evolution. 
Unpublished abstract and paper in pdf form available 
online:

http://xxx.lanl.gov/abs/q-bio.PE/0404027

For nontechnical discussion of the research, see:
http://www.charlotte.com/mld/charlotte/news/nation/8982633.
htm?1c

Metabolic Rate Calibrates the Molecular Clock: Reconciling 
Molecular and Fossil Estimates of Evolutionary Divergence
Authors: James F. Gillooly , Andrew P. Allen , Geoffrey B. 
West , James H. Brown 
Subj-class: Populations and Evolution; Genomics

Observations that rates of molecular evolution vary widely 
within and among lineages have cast doubts upon the 
existence of a single molecular clock. Differences in the 
timing of evolutionary events estimated from genetic and 
fossil evidence have raised further questions about the 
existence of molecular clocks and their use. Here we 
present a model of nucleotide substitution that combines 
new theory on metabolic rate with the now classic neutral 
theory of molecular evolution. The model quantitatively 
predicts rate heterogeneity, and reconciles differences in 
molecular- and fossil-estimated dates of evolutionary 
events. Model predictions are supported by extensive data 
from mitochondrial and nuclear genomes. By accounting for 
the effects of body size and temperature on metabolic 
rate, a single molecular clock explains heterogeneity in 
rates of nucleotide substitution in different genes, taxa, 
and thermal environments. This model suggests that there 
is indeed a general molecular clock, as originally 
proposed by Zuckerkandl and Pauling, but that it ticks at 
a constant substitution rate per unit mass-specific 
metabolic energy rather than per unit time. More 
generally, the model suggests that body size and 
temperature combine to control the overall rate of 
evolution through their effects on metabolism.