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Author Topic:   Is Earth old enough for DNA to evolve?
Minnemooseus
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Posts: 3941
From: Duluth, Minnesota, U.S. (West end of Lake Superior)
Joined: 11-11-2001
Member Rating: 10.0


Message 2 of 60 (668088)
07-17-2012 4:27 AM
Reply to: Message 1 by bcoop
07-17-2012 4:15 AM


Generation lengths bogus
The advantage of me promoting the topic is that I get first whack. I'm just going to whack one item.
a. 3 billion generations would take 60 billion years if each female reproduced at the age of 20.
In the great chain of evolution, generation lengths have not been constant. First of all, for a long time reproduction was asexual. Early life forms may have had "generation" lengths measured in minutes.
Not remotely a biologist - Others can correct me and/or elaborate on this.
Moose

This message is a reply to:
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Minnemooseus
Member
Posts: 3941
From: Duluth, Minnesota, U.S. (West end of Lake Superior)
Joined: 11-11-2001
Member Rating: 10.0


Message 44 of 60 (668186)
07-18-2012 4:08 AM
Reply to: Message 42 by caffeine
07-18-2012 3:32 AM


About the age and life diversity diagram
I think this picture is badly put together. It is labelled as if the centre is the past, and left and right are the present, but that's not actually how it's drawn, since molluscs (snails, claims and octopuses) lie right in the middle at the four billion year ago mark.
Those light lines that arch across the diagram are lines of equal age. Decreasing age radiates outward in all the directions from the 4 billion years ago marking at the bottom center. Instead of displaying the diversity of life on a straight line, they are displaying it on a clockwise outward spiral (or something like that).
The diagram is still pretty confusing.
Added by edit: I think the origin age of a major group of specific life-forms is at the inner boundary of the colored area. That is why so much boundary of the colored area is at the Cambrian explosion time line.
Added by edit 3: Note where lines end within the shaded area. That is that particular branch of the bush going extinct. The extinction times include those where a specific critter is illustrated.
Moose
Edited by Minnemooseus, : See above.
Edited by Minnemooseus, : Modify previous ABE.
Edited by Minnemooseus, : See above. Also changed subtitle.
Edited by Minnemooseus, : Modify edit 3.

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