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Author Topic: Has evolution stopped?  (Read 3499 times)

Offline Jerryade

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Has evolution stopped?
« on: 12/07/2008 17:19:07 »
Jeremiah asked the Naked Scientists:

hi guys, why is it that extinct animals are not evolving again from the other
animals. Is it that evolution has gone into oblivion?

What do you think?


 

Offline LeeE

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Has evolution stopped?
« Reply #1 on: 13/07/2008 20:11:39 »
I'll re-post this comment from another thread as it seems appropriate here too.

There seems to be a lot of misunderstanding about the process of evolution.  It isn't a process where existing organisms gradually adapt in response to changing conditions - this would imply that with no change in conditions there would be no evolution.

Evolution is the process where a non-disadvantaging random mutation of an existing organism creates a new organism, and this will continue to occur regardless of conditions.  This is how we end up with trivial differences within species e.g. different hair colour.

However, when conditions are changing, the random mutation may actually confer an advantage over the original organism, and thus become dominent and eventually supplant it.

Evolution is a terribly wasteful method of development because the failure rate is incredibly high - living organisms depend upon a very fine balance of many factors just to be viable and the great majority of potential mutations will be more likely to upset that balance, rather than strengthen it - the vast majority of mutations die.  This is why evolution is a very slow process.

This is not to say that an organism cannot adapt to changing conditions, but it is more like an unfit person getting fitter by doing regular exercise.  As the person gets fitter, their metabolism will become more efficient and there will be changes to their body chemistry.  However, these changes will lie within pre-existing limits and will not be passed on genetically, and so is not evolutionary.
 

blakestyger

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Has evolution stopped?
« Reply #2 on: 14/07/2008 19:40:07 »
Evolution has be seen in action in the lifetime of two researchers, Peter and Rosemary Grant.
They went to the Galapagos and studied Darwin's subject finches for twenty years through droughts and rainy periods and accumulated enough evidence to show natural selection operating during that time (small birds like these produce a generation each year) to the extent that they saw changes in the shape of the finches beak.
See: The Beak of the Finch, J Weiner, Jonathon Cape, 1994.
 

Offline LeeE

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Has evolution stopped?
« Reply #3 on: 15/07/2008 19:43:32 »
Twenty years seems quick, but it's got to happen sometime.  Did the beak mutation provide an advantage or was it just non-disadvantageous and how long do the individual birds live?  Were the droughts and rainy periods during this time scale about even or was there more of one type of weather over the other type?
 

Offline ibssz

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Has evolution stopped?
« Reply #4 on: 15/07/2008 20:27:46 »
For evolution in action the peppered moth is the best example - newbielink:http://en.wikipedia.org/wiki/Peppered_moth_evolution [nonactive]
 

blakestyger

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Has evolution stopped?
« Reply #5 on: 15/07/2008 21:10:24 »
LeeE

Sorry I can't be more precise as it's 15 years since I read this book but this may help -

http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html

Generally, small birds like these tend to live for only 2 to 3 years, often less, but they do produce a generation each year.
« Last Edit: 15/07/2008 21:14:13 by blakestyger »
 

Offline LeeE

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Has evolution stopped?
« Reply #6 on: 16/07/2008 17:30:42 »
Ta for both of those links peoples.
 

blakestyger

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Has evolution stopped?
« Reply #7 on: 19/07/2008 15:54:00 »
Evolution in action can be seen every day in human society.

Natural selection with the help of carelessness triumphs over medicine every time a patient begins to recover and fails to complete the prescribed antibiotic course. At molecular level, a bacterium develops antibiotic resistance not only by mutation in its genome but by importing plasmids, extraneous loops of DNA that live within the bacterial cell wall and are replicated and passed on with its genome during cell division., or by transfer of the plasmid between one bacterial cell and another.

Cells with the plasmid instantly acquire a whole new tranche of genetic information capable of carrying ancillary genes that have already acquired antibiotic resistance and virulence and can now side-step the designed consequences of the drug.
This works because there are a lot of them with a high reproduction rate and mutation is almost guaranteed.

DNA has a proof-reading and repair mechanism that reduces the number of mutations at each cell division but when under attack this can be by-passed to increase the number of mutations (and hence variants) that may be resistant. Not many have to survive for natural selection to begin favouring them and after exposure all surviving cells have the plasmid.

You could say that human folly/ignorance could have evolved to speed up evolution. [:I]
 

The Naked Scientists Forum

Has evolution stopped?
« Reply #7 on: 19/07/2008 15:54:00 »

 

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