Freethought & Rationalism Archive

Kevin Dorner · 08-29-2002, 05:47 PM

Quote:

The theory stems from a study of DNA in 35 chimps conducted by the Biomedical Primate Research Center in the Netherlands. The chimps in the study were found to share an unusually uniform cluster of genes in the area that controls their immune systems' defenses against disease.

"Chimps show more genetic variation than humans in all areas � with this one exception, which is seriously condensed," said Dr. Ronald Bontrop, who led a Dutch team that worked with statisticians from the University of California.

...the chimps' lack of genetic diversity, found in genes related to the immune system's defense against disease, suggests that a lethal sickness attacked chimps in the distant past.

This unknown disease would have wiped out all or almost all chimps that didn't have the right immune system genes to fend it off, leaving the survivors with a uniform set.

This, combined with the knowledge that modern chimps are largely immune to the AIDS virus and its simian variants, pointed toward an AIDS-like disease as the culprit.

<a href="http://www.cbsnews.com/stories/2002/08/29/tech/main520192.shtml" target="_blank">Chimps Suffered AIDS-Like Plague</a>

<a href="http://www.pnas.org/cgi/content/abstract/182420799v1" target="_blank">PNAS link/abstract</a> (subscription required for full article)

scigirl · 08-29-2002, 06:07 PM

Kevin,

Awesome links!

I have always wondered how much microbes have influenced our evolution. Now we are starting to find out how much.

scigirl

Valentine Pontifex · 08-29-2002, 07:06 PM

I have a question for the genetics whizzes?

How do they get the 2 million years ago figure?

Obviously this had to have happened after the human/chimp split. Since the bonobos have the the lack of genetic diverity in question than logically it had to have happened before the common chimp/bonobo split which they are suggested happened 2 million years ago. Well this is still a large period of time. I don't see why it could not have happened 6 million years ago, for example. And also I don't see that the notion it must have happened before the chimp/bonobo spit is that solid (though it is the simpliest explanation) since both populations could have gotten the disease independently and the result would probably been the same for both. Another possiblity is that species/species transmission of the disease.

RufusAtticus · 08-29-2002, 07:19 PM

I'd have to read the paper, but off the top of my head:

You can calculate the strength of a bottleneck. This strength depends on the effective population size, Ne, and the time from the bottleneck. If you can estimate Ne and calulate the bottleneck strength, the age falls out. Of course, I could be mistaken since it's been a while.

ksagnostic · 08-31-2002, 07:45 AM

Quote:

Originally posted by LordValentine:
<strong>I have a question for the genetics whizzes?

How do they get the 2 million years ago figure?

Obviously this had to have happened after the human/chimp split. Since the bonobos have the the lack of genetic diverity in question than logically it had to have happened before the common chimp/bonobo split which they are suggested happened 2 million years ago. Well this is still a large period of time. I don't see why it could not have happened 6 million years ago, for example. And also I don't see that the notion it must have happened before the chimp/bonobo spit is that solid (though it is the simpliest explanation) since both populations could have gotten the disease independently and the result would probably been the same for both. Another possiblity is that species/species transmission of the disease.</strong>

I guess that's my question as well (and genetics is definitely NOT my area). Wouldn't the same "genetic reduction" result in the descendents of the survivors of the same disease even after a split? How would one figure out whether the disease was a one time plague that went through a single population, resulting in a bottleneck, or whether the disease went through several populations, who independently had survivors with the same genetic reduction that allowed them to survive the disease? And please (if this question is valid) explain this carefully, because I am at a very remedial, basic level when it comes to genetics.

[ August 31, 2002: Message edited by: ksagnostic ]

[ August 31, 2002: Message edited by: ksagnostic ]</p>

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08-29-2002, 06:07 PM	#2
scigirl Veteran Member Join Date: Jul 2001 Location: Seattle Posts: 4,261	Kevin, Awesome links! I have always wondered how much microbes have influenced our evolution. Now we are starting to find out how much. scigirl

08-29-2002, 07:06 PM	#3
Valentine Pontifex Veteran Member Join Date: Jul 2001 Location: Orion Arm of the Milky Way Galaxy Posts: 3,092	I have a question for the genetics whizzes? How do they get the 2 million years ago figure? Obviously this had to have happened after the human/chimp split. Since the bonobos have the the lack of genetic diverity in question than logically it had to have happened before the common chimp/bonobo split which they are suggested happened 2 million years ago. Well this is still a large period of time. I don't see why it could not have happened 6 million years ago, for example. And also I don't see that the notion it must have happened before the chimp/bonobo spit is that solid (though it is the simpliest explanation) since both populations could have gotten the disease independently and the result would probably been the same for both. Another possiblity is that species/species transmission of the disease.

08-29-2002, 07:19 PM	#4
RufusAtticus Veteran Member Join Date: Nov 2001 Location: NCSU Posts: 5,853	I'd have to read the paper, but off the top of my head: You can calculate the strength of a bottleneck. This strength depends on the effective population size, Ne, and the time from the bottleneck. If you can estimate Ne and calulate the bottleneck strength, the age falls out. Of course, I could be mistaken since it's been a while.

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