Nature was full of sap and rioted in rude strength well up to
Quaternary times, producing extravagant forms which apparently she
had no use for, as she has discontinued them.

In all these things you and I had our part and lot; of this prodigal
outpouring of life we have reaped the benefit; amid these bizarre
forms and this carnival of lust and power, the manward impulse was
nourished and forwarded. In Eocene times nearly half the mammals
lived on other animals; it must have been an age of great slaughter.
It favored the development of fleetness and cunning, in which we too
have an interest. Our rude progenitor was surely there in some form,
and escaped the slaughter. Then or later it is thought he took to
the trees to escape his enemies, as the rats in Jamaica have taken
to the trees to escape the mongoose. To his tree-climbing we
probably owe our hand, with its opposing thumb.

In all his disguises he is still our ancestor. His story reads like
a fairy book. Never did nimble fancy of childhood invent such
transformations--only the transformations are so infinitely slow,
and attended with such struggle and suffering. Strike out the
element of time and we have before us a spectacle more novel and
startling than any hocus-pocus or legerdemain that ever set the
crowd agape.

In every form man has passed through, he left behind some old member
or power and took on some new. He left his air-bladder and his gills
and his fins with the fishes; he got his lungs from the dipnoans,
the precursors of the amphibians, and from these last he got his
four limbs; he left some part of his anatomy with the reptile, and
took something in exchange, probably his flexible neck. Somewhere