Today, let's talk about the extinction of species.
The University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
Recently, at Harvard's
Natural History Museum, the Stone-Age skeletons
caught me by surprise -- strange, oversized
animals, as if someone had stirred cats, bears, and
mammoths all together.
Now biologist David Burney asks about the
extinction of species, and he looks to those
Stone-Age beasts for guidance. He finds that
widespread extinctions have occurred at different
times and in different regions over the past 30
At one time in the Stone Age, European artisans
were carving toys from bones of the last woolly
mammoths. Saber-toothed cats and giant sloths still
roamed North America. And several large Australian
marsupial species had only recently died out.
Sure enough, where we find large-scale extinctions,
we find humans gaining new technologies at the same
time. Take the Americas: How long humans have
occupied North and South America mires in debate.
But of one thing we're sure. Just 11,000 years ago
those natives began making distinctive spear and
Much of North America was a great animal preserve,
like the Serengeti Plain. Then those distinctive
spear heads appeared, and the extinctions began.
Some anthropologists offer the Blitzkrieg
Hypothesis. A human population which might've been
around for a long time before that finally
perfected the technologies of big-game hunting and
began killing off species.
That drama played out earlier in Australia -- 15 to
30 thousand years ago. That's when humans, who'd
arrived long before, mastered hunting with spears,
throwing sticks, and fire-setting.
European cave painters show giant deer and woolly
rhinoceroses. It was those same artist cave men who
perfected the tools of killing. And as they did,
species began to vanish.
Now species are dying at a far faster rate than
they ever did in the Stone Age. Burney warns us not
to read a wrong lesson from the past -- not to
shrug our present losses off. It's the large
slow-breeding herbivores that are usually destroyed
first. Those are beasts who, like you and me, most
influence their environment. When they perish, life
changes for the next largest species in turn, and a
downward cascade of extinctions follows.
As that arrow points at us, we see another, more
sinister, feature of today's extinctions. Armed
with guns, chain-saws and bulldozers, we so outrun
any hope of normal Darwinian competition among
species that we gut the natural selection process.
When the only surviving tigers and elephants are
ones that live under our care, the stage is set for
a new cascade of species extinctions. And they
could be more rapid, more dangerous, and closer to
home than we'd ever imagined.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds