Basically, it's the
cesspit where we all come from.
Millions of years old, it gets occasionally
disinfected by an
ice age or a
KT-event, though some might prefer that to happen a bit more
regularly.
We like to think that we're floating about somewhere at the
deep end of it, though that's probably just our
human egotism speaking -- the
selfish gene, again.
Generally speaking, it smells and is in dire need of a chlorine treatment.