46
The Body Electric
DIFFERENTIATION—FROM EGG TO SPECIALIZED CELLS
by the new science of genetics. This was the notion that differentiation
was still a "one-way street," that cells could never dedifferentiate, that
is, retrace their steps from a mature, specialized state to a primitive,
unspecialized form. This assumption was made despite the fact that
chromosomes now provided a plausible means for the reversal. Re-
member, all cells of the adult (except the egg and sperm) contain the
full array of chromosomes. All the genes are still there, even though
most of them are repressed.
It seems logical that what has been locked might also be unlocked
when new cells are needed, but this idea was fought with unbelievable
ferocity by the scientific establishment. It's difficult now to see why,
since no principle of real importance was involved, except possibly a bit
of the supremacy of the mechanistic outlook itself. The mechanists
greeted the discovery of genes and chromosomes joyfully. Here at last
was a replacement for the little man in the sperm! Perhaps it seemed
that admitting dedifferentiation would have given life too much control
over its own functions. Perhaps, once genes were considered the sole
mechanism of life, they had to work in a nice, simple, mechanical way.
As we shall see, this dogma created terrible difficulties for the study of
regeneration.