Geology Reference
In-Depth Information
Feel the beauty and dignity of this 2-billion-year-old cooperative association.
Sense how the supplies of energy liberated by the mitochondrion allows your liver
cell to carry out the many vital tasks keep you alive.
Now return to your normal size, and open your eyes. Look around at the more-
than-human beings that surround you. Know how they, like you, are the descend-
ants of ancient single-celled beings that learnt the subtle art of cooperation. The
mitochondria teach us that independence is impossible—that we all depend on
each other.
The Dance of Oxygen
By the end of the Archean era, the amount of oxygen in the atmosphere gradually in-
creased as life became ever more adept at producing and burying carbon fixed from the
air by photosynthesis. Amazingly, for the last 350 million years oxygen in the air seems
to have hovered around the 21% that is close to optimal for large multicellular beings
such as us. How has our animate Earth managed to regulate oxygen so effectively? It's a
complex story, so we'll tease out only some of the details as they have been worked out
by some of Lovelock's scientific descendants, namely Tim Lenton, Andrew Watson and
Noam Bergman.
The first thing to note is that atmospheric oxygen cannot increase above 25% without
triggering massive fires that would burn most of the land vegetation to ashes within a
relatively short time. With this much oxygen in the atmosphere it wouldn't even matter
if all the world's plant material was wet through and through—a global wildfire would
burn it all to cinders anyway. If oxygen in the atmosphere declines to 13-15%, fires can-
not start in even the driest vegetation, yet the continuous presence in the fossil record of
partially burnt plant material, commonly known as charcoal, over the last 350 million
years tells us that oxygen levels have never been low enough to prevent fires, nor high
enough to totally burn up all the vegetation. The fossil charcoal hints at a compelling
Gaian oxygen-regulation story involving surprising interactions between life, rocks, at-
mosphere and oceans.
The Flame of Life
