homology or similarity ?

Gribskov, Michael gribskov at FCRFV1.NCIFCRF.GOV
Wed Jan 30 23:00:00 EST 1991

David Steffen writes:

> "In all four cases, the inserts were found to contain sequences
>  homologous to human and mouse lck..."
>but one of my grad students points out that the word homologous is
>incorrect, since it represents an inference about evolution rather
>than a statement of fact.  

My vote is that the sentence is correct as it stands.  It is clear to me
that a conclusion is being drawn.  Anyway, since EVERYONE knows that
claims of homology are inferences, there is no confusion.  One hopes
that at some point in the paper the evidence is presented to make the
inference obvious. 

The underlying question is how strong does an inference need to be, to
be stated as a fact.  This is the point that the creationists always
jump on, pointing out that evolution is ONLY a theory.   Gravitation, of
course, is also only a theory.  We infer that it exists from the
observation that things fall down.  The point is that some theories and
inferences are strong enough to be treated as facts. If your sequences
are really obviously homologous, I think you should just say so (as you

Michael Gribskov 
gribskov at ncifcrf.gov 

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