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Author Topic:   Seagrass 'tens of thousands of years old'.
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 5 of 15 (650864)
02-03-2012 11:53 AM
Reply to: Message 1 by Pressie
02-03-2012 7:13 AM


I have never heard of such a scientific theory.
This may be a reference to Muller's Ratchet. However, bacteria, which are asexual, do seem to have made it through the last billion years or so.
I’ve never seen or heard such an allegation by scientists anywhere.
Me neither.
However, it is generally held that multicellular eukaryotic organisms won't last very long, because they are peculiarly vulnerable to disease. A disease which gets one of them will get them all, because they're clones of each other.
Therefore, it is a fact that such organisms tend to go extinct shortly after evolving asexuality, and so that if you use molecular clocks to measure the age of an asexual multicellular eukaryotic species, the age will be small.
The exception that proves the rule is bdeloid rotifers. They are asexual, and have been around for ages. Richard Dawkins (in The Ancestor's Tale) described their existence as an "evolutionary scandal". However, in the last year or so it's been discovered that although they don't have sex as such, they do participate in lateral gene transfer, which is a good substitute.
I think Dr Arnaud-Haond may be a little confused about what evolutionary biologists think the problem is with asexuality.
Edited by Dr Adequate, : No reason given.

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 Message 1 by Pressie, posted 02-03-2012 7:13 AM Pressie has not replied

Replies to this message:
 Message 7 by bluegenes, posted 02-03-2012 1:45 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 8 of 15 (650918)
02-03-2012 2:06 PM
Reply to: Message 7 by bluegenes
02-03-2012 1:45 PM


I saw no signs of confusion ...
Well, if she's talking about Muller's Ratchet, then that's not a reason why asexual organisms should go extinct, because they don't. But if she's talking about the handicap that asexual multicellular organisms suffer in the Red Queen's Race, then she's not talking about Muller's Ratchet. It seemed to me that she's conflating the two and so being wrong about both.

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 Message 7 by bluegenes, posted 02-03-2012 1:45 PM bluegenes has replied

Replies to this message:
 Message 9 by sfs, posted 02-03-2012 3:36 PM Dr Adequate has replied
 Message 10 by bluegenes, posted 02-03-2012 4:31 PM Dr Adequate has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 11 of 15 (651024)
02-03-2012 8:56 PM
Reply to: Message 9 by sfs
02-03-2012 3:36 PM


It certainly is a reason why asexual organisms might go extinct. Asexual organisms with small populations, that is.
Well any small enough population will be wiped out by genetic drift. Yes, if they're asexual, M.R. will be part of that.
Where did she conflate them? The authors do list both Muller's ratchet and inability to adapt to parasites as dangers that clonal organisms need to avoid (in the paper's introduction), but I see no suggestion that they have them confused.
I was just talking about the quotes that have been quoted from the article, I haven't read the paper. The quotes are in fact confused, which is why they confused Pressie.

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 Message 9 by sfs, posted 02-03-2012 3:36 PM sfs has replied

Replies to this message:
 Message 12 by sfs, posted 02-03-2012 9:45 PM Dr Adequate has not replied

  
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