The Sixth Extinction: An Unnatural History

raises a key point. Everything (and everyone) alive today is descended
from an organism that somehow survived the impact. But it does not
follow from this that they (or we) are any better adapted. In times of
extreme stress, the whole concept of fitness, at least in a Darwinian sense,
loses its meaning: how could a creature be adapted, either well or ill, for
conditions it has never before encountered in its entire evolutionary
history? At such moments, what Paul Taylor, a paleontologist at London’s
Natural History Museum, calls “the rules of the survival game” abruptly
change. Traits that for many millions of years were advantageous all of a
sudden become lethal (though it may be difficult, millions of years after
the fact, to identify just what those traits were). And what holds for
ammonites and nautiluses applies equally well to belemnites and squids,
plesiosaurs and turtles, dinosaurs and mammals. The reason this book is
being written by a hairy biped, rather than a scaly one, has more to do
with dinosaurian misfortune than with any particular mammalian virtue.
“There’s nothing ammonites were doing wrong,” Landman told me as
we packed up the last fossils from the creek and prepared to head back to
New York. “Their hatchlings would have been like plankton, which for all
of their existence would have been terrific. What better way to get around
and distribute the species? Yet here, in the end, it may well have been
their undoing.”