Travel Reference
In-Depth Information
may be that the fi rst Precambrian ancestor to undergo the fl ip did so by a feat
of contortion worthy of the Boneless Wonder in a circus sideshow. Its body
rotated 180° behind its head, leaving its head in the original orientation.
Saint-Hilaire's explanation of the body plan dif erence between arthro-
pods and chordates, widely ridiculed at the time, has turned out to be cor-
ing in stages. And the rearranged organism was more likely to have survived
if it was a small simple Precambrian creature than if it was a larger and more
complicated creature living at some later point in time.
Recreating the Precambrian
We cannot yet recreate the drastic developmental mutations of the Pre-
cambrian in the laboratory, because we have no Precambrian organisms to
experiment on. But it is not beyond the realm of possibility to make and
study similar changes in simple laboratory organisms available today.
A good candidate for such experiments is the tiny roundworm
Caenorhab-
ditis
, which is a mere one millimeter long. This worm normally lives in soil,
but it can easily be raised in the laboratory. And its development is delight-
fully simple and predictable. An adult worm's body is made up of exactly 959
cells, no more and no less.
Caenorhabditis
has genes for Hsp90 and other chaperonins. It is now pos-
sible using molecular techniques to “knock out” this and any other of the
genes of these little worms. It has been found that damage to the Hsp90 gene
causes problems with the worms' metabolism and shortens their lives.
Suppose that we damaged these and other chaperonin genes in the
worms and placed the resulting mutants in a variety of new environments?
Would it be possible to select for worms with a dif erent body plan? Could
some of these changed worms survive, and even thrive, under the altered
conditions that we impose on them? Perhaps we could produce changes in
these worms that are as far-reaching as the dramatic reorganizations that
happened to our tiny ancestors during the Precambrian, more than half a
billion years ago.
