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Offline Kenny

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Common ancestor question
« on: 25/05/2010 17:54:33 »
Is "Common ancestor" a species or an individual when talking about a common ancestor of two species?
In other words, does the separation from one to two species origin from a group of the earlier species or from a single individual from that species? For ex. common ancestor of humans and Chimpanzees.


 

Offline LeeE

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Common ancestor question
« Reply #1 on: 26/05/2010 09:14:08 »
The term 'Common Ancestor' can be used legitimately in either context, but the absolute bottom line is that Evolution is the result of random mutation in an individual.

Because the nature of the mutation is random, and because the possible range of mutations is potentially infinite, the chances of exactly the same random mutation occurring to two individuals is correspondingly unlikely, so ultimately the term Common Ancestor will refer to an individual.
 

Offline echochartruse

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Common ancestor question
« Reply #2 on: 31/05/2010 17:08:01 »
In The Origin of Species Darwin considered natural variation not to be necessarily
random. He commented, however, that it is reasonable to treat them as random because
their cause and origin were unknown [Darwin, 1859].

Today when we enquire about such changes in DNA, we find they are necessary particularly when considering the survival of the species.

The mechanism within the species networks to alter the genome in each and every individual for its survival.
This mechanism is shared throughout species and individuals.
Changes in the genome are required within a group if the group is to survive.

We share a common mechanism.

Changes in the genome is the effect not the cause of evolution.

Quote from: http://www.scientificamerican.com/article.cfm?id=universal-common-ancestor
But in the past couple decades, new doubt has emerged in some circles. Microbiologists have gained a better understanding of genetic behavior of simple life forms, which can be much more amorphous than the typical, vertical transfer of genes from one generation to the next. The ability of microbes such as bacteria and viruses to exchange genes laterally among individualsóand even among speciesóchanges some of the basic structural understanding of the map of evolution. With horizontal gene transfers, genetic signatures can move swiftly between branches, quickly turning a traditional tree into a tangled web. This dynamic "throws doubt on this tree of life model," Theobald says. And "once you throw doubt on that, it kind of throws doubt on common ancestry as well."
« Last Edit: 31/05/2010 17:15:03 by echochartruse »
 

Offline imatfaal

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Common ancestor question
« Reply #3 on: 01/06/2010 14:26:11 »
Echo

Your post and the choice of section of the SciAm article you have quoted gives the impression that Douglas Theobald's Nature article casts more doubt on the existence of a common ancestor; whereas his quantitative statistical analysis provides ever more proof for existence of a common ancestor.

I will quote the title of the SciAm article and subtitle which I believe gives a better idea of the contents
Quote
The Proof Is in the Proteins: Test Supports Universal Common Ancestor for All Life
One researcher put the basic biological assumption of a single common ancestor to the test--and found that advanced genetic analysis and sophisticated statistics back up Darwin's age-old proposition
http://www.scientificamerican.com/article.cfm?id=universal-common-ancestor&page=2

The full article from nature is here
http://www.nature.com/nature/journal/v465/n7295/full/nature09014.html

 

Offline echochartruse

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Common ancestor question
« Reply #4 on: 07/06/2010 02:35:04 »
Echo

Your post and the choice of section of the SciAm article you have quoted gives the impression that Douglas Theobald's Nature article casts more doubt on the existence of a common ancestor; whereas his quantitative statistical analysis provides ever more proof for existence of a common ancestor.

I will quote the title of the SciAm article and subtitle which I believe gives a better idea of the contents
Quote
The Proof Is in the Proteins: Test Supports Universal Common Ancestor for All Life
One researcher put the basic biological assumption of a single common ancestor to the test--and found that advanced genetic analysis and sophisticated statistics back up Darwin's age-old proposition
http://www.scientificamerican.com/article.cfm?id=universal-common-ancestor&page=2

The full article from nature is here
http://www.nature.com/nature/journal/v465/n7295/full/nature09014.html



Science suggests that the mechanism is the same. In a martian world wouldn't all living things have the same mechanism to survive and be most probably different to earths creatures?

Science has found a common protein in all living things, which statistically draws the conclusion that life on earth evolved from a common ancestor.

Quote from: http://www.scientificamerican.com/article.cfm?id=universal-common-ancestor
By plugging these sequences into various relational and evolutionary models, he found that a universal common ancestor is at least 10^2,860 more likely to have produced the modern-day protein sequence variances than even the next most probable scenario (involving multiple separate ancestors).
 

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Common ancestor question
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