Proof of Macroevolution: (22) Nonfunctional molecular evidence - retrogenes.
Zeus Thibault
retrogenes.
Yet another nonfunctional example of evidence for common descent is
given by retrogenes. Retrogenes are molecular remnants of a past
parasitic viral infection. Occasionally, copies of a retrovirus genome
are found in its host's genome, and these retroviral gene copies are
called retrogenes. Retroviruses (like the AIDS virus or HTLV1, which
causes a form of leukemia) make a DNA copy of their own viral genome and
insert it into their host's genome. If this happens to a germ line cell
(i.e. the sperm or egg cells) the retroviral DNA will be inherited by
descendants of the host. Again, this process is rare and fairly random,
so finding retrogenes in identical chromosomal positions of two
different species strongly indicates common ancestry.
Confirmation:
There are three different instances of common retrogene insertions
between chimps and humans. Another example is provided by the Felidae
(i.e. cats). The standard phylogenetic tree has small cats diverging
later than large cats, with the blackfooted cat being the first of the
small cats to diverge. All small cats (i.e. the jungle cat, European
wildcat, sand cat, African wildcat, blackfooted cat, and domestic cat)
share a specific retroviral gene insertion. In contrast, the cat
lineages that diverged before the small cat lineage (i.e. the lion,
cheetah, and leopard) and all other carnivores lack this retrogene.
Potential Falsification:
It is incredibly unlikely, macroevolutionarily, that the cheetah, or
some other mammal (e.g. dogs, cow, etc.), could have this same retrogene
in the same chromosomal location. Conversely, it is also very unlikely,
given common descent, that one or more of the small cats which diverged
after the blackfooted cat would lack it.
This is a follow-up to my previous posts:
Proof of Macroevolution: (1) The fundamental unity of life.
http://www.deja.com/getdoc.xp?AN=514524093
Proof of Macroevolution: (2) A "nested" hierarchical organization of
species
http://www.deja.com/getdoc.xp?AN=515312382
Proof of Macroevolution: (3) Convergence of independent phylogenies.
http://www.deja.com/getdoc.xp?AN=515638573
Proof of Macroevolution: (4) Morphologies of predicted common
ancestors.
http://www.deja.com/getdoc.xp?AN=532866179
Proof of Macroevolution: (5) Chronological order of predicted common
ancestors.
http://www.deja.com/getdoc.xp?AN=533154861
Proof of Macroevolution: (6) Anatomical vestigial characters.
http://www.deja.com/getdoc.xp?AN=533264263
Proof of Macroevolution: (7) Molecular vestigial characters.
http://www.deja.com/getdoc.xp?AN=534527605
Proof of Macroevolution: (8) Evidence from Ontogeny.
http://www.deja.com/getdoc.xp?AN=537814090
Proof of Macroevolution: (9) Present biogeography
http://www.deja.com/getdoc.xp?AN=543215607
Proof of Macroevolution: (10) Past biogeography.
http://www.deja.com/getdoc.xp?AN=543382759
Proof of Macroevolution: (11) Anatomical paralogy.
http://www.deja.com/getdoc.xp?AN=543624826
Proof of Macroevolution: (12) Molecular paralogy.
http://www.deja.com/getdoc.xp?AN=544177242
Proof of Macroevolution: (13) Anatomical convergence.
http://www.deja.com/getdoc.xp?AN=544688616
Proof of Macroevolution: (14) Molecular convergence.
http://www.deja.com/getdoc.xp?AN=546155624
Proof of Macroevolution: (15) Anatomical suboptimal function.
http://www.deja.com/getdoc.xp?AN=547038036
Proof of Macroevolution: (16) Molecular suboptimal function.
http://www.deja.com/getdoc.xp?AN=550425113
Proof of Macroevolution: (17) Protein functional redundancy.
http://www.deja.com/getdoc.xp?AN=578109016
Proof of Macroevolution: (18) Functional molecular evidence - DNA
coding
http://www.deja.com/getdoc.xp?AN=578539856
Proof of Macroevolution: (19) Nonfunctional molecular evidence -
transposons.
http://www.deja.com/getdoc.xp?AN=580095313
Proof of Macroevolution: (20) Nonfunctional molecular evidence -
pseudogenes.
http://www.deja.com/getdoc.xp?AN=588612456
Sent via Deja.com http://www.deja.com/
Before you buy.
Adam Noel Harris
:Proof of Macroevolution: (22) Nonfunctional molecular evidence -
:retrogenes.
[snip]
:Potential Falsification:
:
:It is incredibly unlikely, macroevolutionarily, that the cheetah, or
:some other mammal (e.g. dogs, cow, etc.), could have this same retrogene
:in the same chromosomal location. Conversely, it is also very unlikely,
:given common descent, that one or more of the small cats which diverged
:after the blackfooted cat would lack it.
Careful. It is all too easy for organisms to lack nonfunctional DNA found
in related organisms simply because of deletion. We might expect, then,
that small cats which (by independent evidence) diverged after the
blackfooted cat could come to lack this particular insertion. We might
think that they would also lack some portion of the flanking sequences,
which could also fall victim to a deletion. However, given that
retrogenes may be unexpectedly mobile, it's possible that one could be
excised precisely.
IOW, insertions in the same position are unlikely, but lacking an
insertion doesn't tell us much. I place the same caveat on comparisons of
the human and chimp genomes. Finding a whole gene present in chimps but
not humans or vice versa shouldn't be too surprising, because it could
result from a deletion in the other lineage. We can seek evidence for
such an event by looking to gorillas or other apes.
I appreciate this series, Zeus. The sooner you can complete the arduous
task of referencing all of the claims, the better. A comprehensive FAQ of
this sort would be a great asset.
-Adam
--
Opinions expressed are not necessarily those of Stanford University.
PGP Fingerprint = C0 65 A2 BD 8A 67 B3 19 F9 8B C1 4C 8E F2 EA 0E
Zeus Thibault
You are correct, and this caveat is a good example of why naive
falsificationism does not apply to scientific methodology. When we observe
what is superficially thought to be a falsification, we do not throw
everything out the window. A good scientist looks for valid reasons why this
*potential* falsification has been observed. An important point here is that,
ideally, any reason given to "explain away" a potential falsification should
not be ad hoc. The reason given should be independently testable. And this
is exactly how you have addressed the problem. The observation that sequences
flanking the retrogene are also missing would independently support the
secondary hypothesis that a deletion event had occurred, even though these are
quite rare. Do you know of any experimental studies supporting precise
excision of a retrogene? I was under the impression that though it is
possible (given enzymatic reversibility) that it just does not happen. Even
if it does happen with low probability, an occasional observation of a precise
retrogene deletion is consistent with the hypothesis of common descent, as
long as the fraction of precisely deleted retrogenes is low. Actually, *if*
precise retrogene excision is a rare yet possible event, then the observation
of *no* precisely excised retrogenes in a large sample would be a curious and
statistically improbable observation.
> I appreciate this series, Zeus. The sooner you can complete the arduous
> task of referencing all of the claims, the better. A comprehensive FAQ of
> this sort would be a great asset.
Thanks, and be assured that I am working on it.
Zeus
Adam Noel Harris
[...]
:Do you know of any experimental studies supporting precise
:excision of a retrogene? I was under the impression that though it is
:possible (given enzymatic reversibility) that it just does not happen.
No, I know of no such observation.
[...]
Mike Goodrich
writes:
>Subject: Proof of Macroevolution: (22) Nonfunctional molecular evidence
-
>retrogenes.
>From: Zeus Thibault <zthi...@hotmail.com>
>Date: 24 Feb 2000 16:59:05 -0500
>
>Proof of Macroevolution: (22) Nonfunctional molecular evidence -
>retrogenes.
>
>Yet another nonfunctional example of evidence for common descent is
>given by retrogenes. Retrogenes are molecular remnants of a past
>parasitic viral infection. Occasionally, copies of a retrovirus genome
>are found in its host's genome, and these retroviral gene copies are
>called retrogenes. Retroviruses (like the AIDS virus or HTLV1, which
>causes a form of leukemia) make a DNA copy of their own viral genome and
>insert it into their host's genome. If this happens to a germ line cell
>(i.e. the sperm or egg cells) the retroviral DNA will be inherited by
>descendants of the host. Again, this process is rare and fairly random,
>so finding retrogenes in identical chromosomal positions of two
>different species strongly indicates common ancestry.
>
>Confirmation:
>
>There are three different instances of common retrogene insertions
>between chimps and humans. Another example is provided by the Felidae
>(i.e. cats). The standard phylogenetic tree has small cats diverging
>later than large cats, with the blackfooted cat being the first of the
>small cats to diverge. All small cats (i.e. the jungle cat, European
>wildcat, sand cat, African wildcat, blackfooted cat, and domestic cat)
>share a specific retroviral gene insertion. In contrast, the cat
>lineages that diverged before the small cat lineage (i.e. the lion,
>cheetah, and leopard) and all other carnivores lack this retrogene.
>
>Potential Falsification:
>
>It is incredibly unlikely, macroevolutionarily, that the cheetah, or
>some other mammal (e.g. dogs, cow, etc.), could have this same retrogene
>in the same chromosomal location. Conversely, it is also very unlikely,
>given common descent, that one or more of the small cats which diverged
>after the blackfooted cat would lack it.
>
> ------------------- Headers --------------------
>
>Path:
>lobby!newstf02.news.aol.com!portc05.blue.aol.com!wn4feed!worldnet.att.net
!128.223.220.26!arclight.uoregon.edu!logbridge.uoregon.edu!newsfeed.stanfo
rd.edu!ediacara.org!there.is.no.cabal
>From: Zeus Thibault <zthi...@hotmail.com>
>Newsgroups: talk.origins
>Subject: Proof of Macroevolution: (22) Nonfunctional molecular evidence -
>retrogenes.
>Date: 24 Feb 2000 16:59:05 -0500
>Organization: Deja.com - Before you buy.
>Lines: 113
>Approved: rob...@ediacara.org
>Message-ID: <8949i2$dgs$1...@nnrp1.deja.com>
>NNTP-Posting-Host: darwin.ediacara.org
>X-Article-Creation-Date: Thu Feb 24 21:58:28 2000 GMT
>X-Http-User-Agent: Mozilla/4.7 [en] (Win95; I)
>X-Http-Proxy: 1.0 bx6.deja.com:80 (Squid/1.1.22) for client 128.138.134.88
>X-MyDeja-Info: XMYDJUIDzthibault
>
>