XMRV Evilution: Its more than just change over time
Posted on: July 20, 2011 12:00 PM, by ERV
The simplest, simplest definition of evilution: Change over time.
Your children are different from you. You are different from your
parents. Your parents are different from their parents. And so on and
so on and so on.
But if Person A is older than you and has different DNA, that doesnt
automatically mean Person A is one of your parents. If Person B is
younger than you and has different DNA, that doesnt automatically mean
Person B is your child.
You might think the above statement is obvious, but that is precisely
the faulty reasoning used in a previous publication on
XMTV/MLV-like/whatever viruses in Chronic Fatigue Syndrome, according
to a recent publication in Advances in Virology (this journal creeps
me out. i dont know why it exists. which probably means it will have
an impact factor of 29 in a year).
Endogenous Murine Leukemia Viruses: Relationship to XMRV and Related
Sequences Detected in Human DNA Samples
Lo et al published sequences of MLV-like viruses they found in
archived samples, modern samples, and fresh samples from some
individual patients. The sequences were different! Hurray! Evidence
that MLV-somethings are infecting humans!
... Not so fast.
Simply having differences between sequences does not make a
quasispecies shifting in response to immune selective pressure. The
differences have to make sense. The fresh sequences are related to the
newish sequences which are related to the old sequences. A
phylogenetic tree of the sequences should look like this:
[figure]
The youngest samples are different but related to the middle-aged
sequences, which are different from but related to the old sequences.
Thats not what Lo et al found. They found something like this:
[figure]
YAY! Differences! Well, no. The 'differences' between the sequences
was not evolution. Their data was contamination, and they were just
detecting different mouse ERVs at each time-point. When you add ERVs
into the phylogenetic tree, 'MLV-like viruses' were not evolving. They
were climbing up and down a tree of ERVs.
[figure]
When someone in Coffins lab purposefully contaminated reactions by
putting vanishingly small quantities of mouse DNA into PCR reactions
(1/100th of a cell), they got the exact same 'tree' as Lo et al.
[figure]
There is more to evilution than 'change over time'. You can make any
number of mistakes and find 'change' where there is none. There has to
be a relatedness, and that relatedness has to make sense.
The most likely explanation for Lo et als data is that they found
mouse ERVs over and over, not that they found retroviruses in patients
that just happened to evolve along ERV lines.
Occams razor takes a slice of the XMRV--> human pathogen hypothesis.
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