The uniformity of the earth's life, more astonishing than its diversity,
is accountable by the high probability that we derived,
originally, from a single cell, fertilized in a bolt of lightning as the earth cooled.
It is from the progeny of this parent cell that we take our looks;
we still share genes around, and
the resemblance of the enzymes of grasses to those of whales is a family resemblance.
~ Lewis Thomas
from The Lives of a Cell