As a theologian/mathematician, he approaches issues of biology like a theologian/mathematician with no biology training would - incorrectly.
He wrote a paper on human evolution a while back that is riddled with simple errors (I may expand on that at a later date), and makes a similarly erroneous implication on his blog:
I guess that’s what happens when you assume that sequence similarity
automatically means a common ancestry (of the gene). A more likely scenario is
that both cells require a protein with the same function so they have a similar
sequence by design.
Once again, an ID perspective seems much closer to
reality than the Darwinian (Lamarckian?) just-so stories.
Now, it is claimed that this came from a "biologist colleague" of his, which if true, means probably from one of the 'biologists' affiliated with the Discovery Institute or one of his colleagues at his place of employment, the Southern Baptist Theological Seminary.
So, what is the problem?
"... assume that sequence similarity automatically means a common ancestry ..."
It is NOT the mere sequence similarity that indicates common ancestry, it is the patterns of shared mutations. Sequence similarity can certainly indicate common ancestry, and for Demski and his "biologist colleague" to dismiss that denmonstrates their ignorance of the subject.
To see some of the patterns I refer to, see this sequence alignment. The patterns are obvious and striking.