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COSMIC CATASTROPHES & THE EVOLUTION OF LIFE
From Timo Niroma <timo.niroma@tilmari.pp.fi>
There seems to be a tendency to set evolution and catastrophism
as
opposite ways of thinking. That's a big misunderstanding. As if
Darwin or the concept of evolution would need some defending
against some mystical, religious or supernatural concepts, there
is coined the term punctuated evolution. I see no need for any
such term. Evolution as a theory in the form as Darwin put it,
needs refinements in the same way as Einstein refined the
theories
of Newton. Nothing more, nothing less.
So what has changed since Darwin to warrant this discussion or,
more specifically, what has to be added or refined? In short, the
paraphrase of the "survival of the fittest" must be
enlarged to
the "survival of the fittest of the luckiest".
Evolution as such
has no ultimate goal. It has only temporary goals, as long as we
see the universe as a changing place.
Taking as an example our home planet, the Earth, it seemed for
billions of years, from some 3.8 billion of years ago (when the
bombardment in the Solar System lowered to its nowaday level) to
some 800 million years ago, a suitable place for micro-organisms
to fill every niche available to them. At some places there most
probably was some cooperation between some micro-organisms that
was
nearly or exactly like multi-cellular life.
That could be the case even today if not something had happened
800 million years ago. The surface of Venus heated to the point
of
melting, Earth was all covered in ice and snow, Mars had its
atmosphere, and probably also oceans, blasted into space, thereby
killing probably all life that might have been there at the time,
as also happened on Venus. Whatever happened, a nearby supernova,
a nearby gamma burst, a superflare from the Sun, you can add this
list, is anybody's guess.
Then about 600 million years ago the Solar system recovered. Not
however to its previous stage. Mars and Venus had lost their
biosphere, but the Earth's biosphere either partially survived
under the ice- and snowcover or at least was reborn very quickly.
Whatever happened, the evolution continued on Earth as before,
but
now under greatly changed circumstances. The Precambrian
Ediacara-fauna is a most beautiful example of its force. The
Earth
has never since seen so great a biodiversity. The changed
environment was suitable for multicellular life, there was a
clear
advantage for different functions for different organs to act as
a
whole organism.
When the tens of millions of years went on, the recovering Earth
changed and/or the populations grew until either the changed
environment was not suitable for all Ediacara fauna or the Earth
became too small to such a large biodiversity. The fittiest of
the
luckiest, those that were on the right place at the right moment
survived and the Cambrian world was born. It would be here today,
somewhat changed, but principally as it was half a billion years
ago, unless something unusual again happened. Whatever it was, it
wiped 96% of the genera of Earth's bioshere into oblivion 250
million years ago.
It looks like the Earth changed to a tropical place without ice
anywhere, not even on the poles. With all the conditions
favorable
for life, there grew on Earth a fauna that was as big as the
Earth's gravitation allowed animals and plants to be. It was the
era of dinosaurs and the great fern trees. Evolution has no
direction, so the fauna changed only when circumstances changed,
for example because of the movements of the tectonic plates, but
the changes were statistically random. For some 170 million years
dinosaurs lived here without any indication of any change in
intelligence or any other essentials. They would still be here
today, essentially unchanged, unless a medium-size, 10-km
asteroid
would not have hit the Earth at a place now called Yukatan 65
million years ago. Without this blast we wouldn't most probable
be
here.
After this earthly big bang Earth has been a battle ground
between
micro-organisms, insects and mammals and some more minor groups.
We know of no trend in the evolution of micro-organism and
insects, only random adaptations to changing environments. But
one
change has been so huge and dominating that this trend-like
change
has demanded trend-like change from mammals for them to adapt.
The last 50 million years the Earth has continually cooled
disregarding some standstills and minor warmings that all have
been temporary. The last phase in this climatic deterioration has
been the oscillating temperature that began as a minor series of
events about 3 million years ago and changed to the famous
100,000
ice age oscillation some 800,000 years ago. Even the highest
temperatures (socalled interglacials) have been colder than any
phase on Earth during the last 65 million years, and probably
over
200 million years.
Be the reason the continental drift (a continent on the southern
pole), the rise of Tibetan plateau, something inside the Sun, a
change in our cosmic environment in the galaxy or something else
or all or part of these, the fact is that intelligence became a
new advantage for survival in this cooling environment. Although
there occurred a cessation, even a slight direction change some
million years after the great impact events 35 million years ago,
which led to the extinction of primates in the northern
continents, hominoid diversification began in Africa 24 million
years ago (at Oligocene/Miocene boundary). But it was
"only" a
great increase in biodiversity that lead - besides other changes
-
to a fauna of very different primates.
When the cooling began anew 14 million years ago, there appear
the
first hominoids in Africa that are generally called as
"advanced".
When chimpanzees left the branch that led to men about 4.5
million
years ago, when Australopithecines diversified from Homo about 3
million years ago and lastly when the Aorounga impact in Tsad
800,000 thousand years ago (on a much older crater) separated the
European and Asian Homo from the Southern African Homo, there was
room for an intelligent niche and gene pool that through small
mutations was ready to take this niche. And through the
mitochondrial Eve and Out-of-Africa behavior this genus, Homo
sapiens, was ready to go to the conquest of the Earth.
Chimpanzees
lost this "opportunity" and, so it seems, have not much
changed
during the last million years.
Evolution has many faces.
Timo
Niroma