Is there other Life in the Universe?
In recent years astronomers and biologists have
discovered that many of the molecules essential for life - purines, amino acids,
etc. - seem to be widely distributed in the universe, and hence might gain a
foothold on other suitable planets. Some maintain that these seeds of life,
“transpermia,” wafting through the universe are the most likely reason for the
origin of life on earth. But whether life on this planet began by a unique,
fortuitous combination of elements in Darwin’s “warm little pond” or was
jump-started by transpermia from afar, bear in mind that there is no evidence
of any form of life during earth’s first billion years. Only at about 3.8
billion years ago have we found evidence for the first life forms,
prokaryotes - simple cells without an organized nucleus. The phrase “from amoeba
to man” is commonly invoked to suggest the great span of evolutionary history,
but biologists know that the development of organized, self-replicating
organisms from unorganized lifelike beginnings was an even more momentous step
in evolution. What emerged from the
original “blue-green algae stage”? Bacteria and their kin, the eukaryotes, and
they have thrived!
Stephen Jay Gould has famously remarked that, if
we were honest, we would call this epoch not “the age of mammals,” but “the age
of bacteria.” It is sobering to realize that each of our bodies contains more
bacteria than the total number of all humans and proto-human hominids
throughout all history. Today we devote
enormous energy to cultivating the bacteria we like, and developing antibiotics
against those we don’t like. Because of selection the latter strategy is
clearly beginning to fail. One could argue that the bacteria have expertly
manipulated us toward their goals,
not ours, and that an objective
observer would not only declare bacteria “winners in the evolutionary race,”
but might also add that they are also the kind of organisms most likely to
survive after a human-induced Armageddon. From one point of view we are minor
actors in a scheme of which we are largely unaware. From another point of view
bacteria illustrate how very simple organisms can become spectacularly
successful - aided immensely, of course, by invading complex organisms, and
bending these hosts to their own purposes.
Contributed by: Dr. Irven DeVore
|
