kurt@fluke.UUCP (Kurt Guntheroth) (08/07/84)
Warning, I am not a molecular biologist...but
The most primitive life form might not even look to you as if it was alive.
Remember how single cells replicate themselves; they just split in two. Of
course nowadays this process is highly organized, and the two halves are
identical, but this isn't necessary. A simpler cell without so many
organelles and without any DNA could just split when it got too big.
Usually each half would retain enough structure to go on living, and if it
didn't, so what. Of course, considerable variation (mutation) would result...
Cells nowadays have complex internal structure with many organelles, but
this is not necessary either. Remember, the early oceans are generally
thought to be a warm soup of fundamental necessities. Finding molecular
building blocks for growth in such an environment is easy, and cells
wouldn't need to digest food so much as simply absorb it.
I don't think that one cell emerged from natural selection so much as I
believe a wide variety of almost-cells emerged. For instance, there is
strong evidence that the mitochandria (sp?), contained in nearly all cells as
an organelle, were a primitive cellular form that was fortuituously absorbed
by another primitive cell type. Mitochandria have their own separate genetic
code distinct from the nuclear one, replicate themselves, and in general
exhibit most characteristics for a unicellular creature. (There is an
interesting article on Scientific American on Mitochandria from the beginning
of this year.)
And don't count on the most primitive life form just starting out to produce
insulin. It had maybe enough structure to keep its molecules together most
of the time, and a few useful enzymatic reactions to construct pieces of
itself. Add to this the chemical tendancy for globs of these complex
molecules to stick together, and you have all you need to develop life.
--
Kurt Guntheroth
John Fluke Mfg. Co., Inc.
{uw-beaver,decvax!microsof,ucbvax!lbl-csam,allegra,ssc-vax}!fluke!kurt