Evolution/Generation Time

Ananias Escalante aescalan at SANGER.BIO.UCI.EDU
Fri Oct 15 10:29:54 EST 1993



Dear netters,


I don't understand in which context the phrase "more evolved" is used. In
my understanding say that something is more evolve that other things is
like try to "add apples with pears" (a bad translation from spanish).
There is not something else "better adapted" to be an apple that an apple,
therefore if I say "an apple is more "primitive" than a pear because it
emerges first during the fruit salad evolution" I should be clear that the
word "primitive" is only refered to an "ancient origin" and it is not any
statement about the organism itself.

If "more evolve" is refered to evolutionary rates (as appears to be), the
controversy about use generation time or chronological time does not have an
easy answer. If we apply the "generation time criteria" we could say that
the bacteria lineages could potentially have more changes accumulated than
others, however: 1) we are assuming that selection acts in a similar way
on any genome independently of they ecological context, 2) the entity that
we call "bacteria" is something that we can define as a comparable
group with something else..... and this second is my problem. If I will
make any comparison the first thing that I look for is clear up that my
groups only are deferent in the phenomena that I want to compare. If I
want to compare "evolutionary rates due to generation time", I can do it
between two bacteria "species" (isolates, strains, clonets or however you
want to call it).... but try to compare between groups that do not have any
relationship is equivalent (at least for me) to say "given that 3 is bigger
than 2, I conclude that 3 is bigger than 2", why? because you are comparing
groups that appears separate for million years (chronological time) and
living in complete different environments, and you say that all the
differences observed in evolutionary rates are due to a different number of
generations is hard (at least for me), and after that say that an specific
group is more evolve is like to say "given that this group was created in
the day 2 and this other on Saturday night after God took his nap, I
conclude that the group that was created in the day 2 is older than the
other one". Where the limits are in order to make a not trivial
comparison? I don't know. If this note looks confuse for you, you are
right... I am confuse! .... sorry for my grammar, spelling and anything
else...... 

				Ananias Escalante
				Graduate Student

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Ananias Escalante                       |  E-Mail:
Dept. Ecology and Evolutionary Biology  |  aescalan at darwin.bio.uci.edu
University of California Irvine         |  aescalan at dino.conicit.ve
Irvine, CA 92717, USA                   |  PHONE: (714) 856-8295
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