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Re: Digits, Digits, Digits!!
In a message dated 6/10/01 12:53:48 PM Eastern Daylight Time,
email@example.com writes: Steve
<< Also, as I said before, it isn't quite as easy to lose an entire digit.
It may be somewhat easy (speaking in an evolutionary tone) to lose a gene
that codes for a protein, such as SHH, that creates digits, but it would be
very difficult to lose the SHH gene, the cartilage gene, the osteocyte gene,
the muscle genes, the nerve genes, etc., etc. Digit formation is something
that is very polygenetic, as several genes code for it. It may be somewhat
"easy" to duplicate these genes, as with Alfonseca, but it is probably
difficult to lose all of them (not impossible, as is evident, but difficult).
With my first post, suggesting that the muscles and tendons earlier used
in the outer digits whould have provided a means of flexing the wrist or
ankle (allowing it to then flex independently of the toes), all the genes did
not need to be turned off, just those of some bones. The muscles, tendons,
and blood supply would still be used. Or, just the fact that the toe
migrated, allow the same result (with out loss of halux for instance).
I would think it easy enough to prove it wrong (or confirm it) in bird
feet. Do some tendons, originating in the drumbstick area, run parallel to
the tendons connecting to the toes, but attach to the metacarpals? If so, on
both sides of the foot? Would these same muscles / tendons in lizards go all
the way down to the toes? Of course, any conclusion would be for the foot