Evolution/Generation Time

Helgi Briem Magnusson hbriem at rhi.hi.is
Fri Oct 15 04:52:39 EST 1993


In <1993Oct14.124814.19797 at midway.uchicago.edu> pmb2 at ellis.uchicago.edu (vineland expatriate) writes:

>In article <MAILQUEUE-101.931011143225.588 at micro.uct.ac.za> ed at micro.uct.ac.za writes:
>>
>>> Ed Rybicki is incorrect in assuming that bacteria are the most 
>>primative
>>> organisms and everything evolves at the same rate.
>>Note: B-)
>>
>>Of course bacteria are "more evolved" in that they have undergone 
>>more generations than us, or whales - and the concept of "primitive" 
>>or "advanced" is mainly in the head of the observer.  BUT I never 
>>stated everything evolves at the same rate, because it patently 
>>obviously does not: longer generation times and shielding from UV 
>>and other mutagenic radiation means deepsea organisms probably 
>>evolve slower than obligate terrestrial thermophiles, for example.  

I would like to point out that almost all mutations are due to
mistakes made by the DNA polymerase when making copies and not
due to external agents such as radiation or mutagens.  Also,
while we do not know if the rate of evolution depends on the
mutation rate, it is extremely unlikely to unless a trait has
been under extremely severe selection (selective death > 0.5*N)
for a long time.  Such severe selection would tend to deplete 
genetic variability, making mutation a limiting factor.

Helgi Briem
Inst. of Exp. Path. Keldur
Dept. of Molecular Biology
ICELAND



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