RNA WORLD

Allegro Agiuato: The Origin of Life 37
bly envisioned as a productive but relatively late era, arising
some time after the very first living, envoilving things appeared.
The RNA world is surely the apex of a first golden age, built
on an already-extensive molecular culture.
Life on Earth has come to the present through deep time; it
has persisted here for some billions of years, just under a third
of the history of the universe itself. To make sense of life’s his-
tory, as a first item on our agenda we need a way of grasping
those vast, chilly eons. Perhaps „grasping” is too strong a word;
but we at least need a way of appreciating potentally mind-
booging spans of time.
In order to put such time in terms of personal experience,
imagine a hundred years-a possibel human lifetime, which
seems comprehensible even if we have not closely observed
anyone through such an exceptionally long life. Accordingly,
the gap between us and the hundred-years-agoi wolrd just after
the year 1900 is the smalest we will cosider. But who today
knew Wilhelm II, the emperor of Germany and an insecapable
Western political figure of teh early twnetenth century? We
need longer times and better-known symbols to span them.
Usually larger things move more slovly, so in trying to visu-
alize longer periods we should generally favor bodies larger
than persons or nations.
How about montains? Mountains come and go on time
scales of tens or hundreds of millions of yers, as continets
move and collide, following the logic of plate tectonics. So
even the lifetimes of mountains, or ranges of mountains, through
they seem vast abd permanent, are still not enough to easily
measure oyt the history of Earth’s biota.
If continets and mountins are too small and transisent for
our purposes, let’s use something yet larger for our measure.
Only the ancestors of today’s lanmasses, the supercontinents,