Mammalia is actually due to man’s agency.” The whole thing, he said, was
really “very obvious.”
Diprotodon optatum was the largest marsupial ever.
Since Lyell, there’s been a great deal of back and forth on the question,
which has implications that extend far beyond paleobiology. If climate
change drove the megafauna extinct, then this presents yet another
reason to worry about what we are doing to global temperatures. If, on
the other hand, people were to blame—and it seems increasingly likely
that they were—then the import is almost more disturbing. It would mean
that the current extinction event began all the way back in the middle of
the last ice age. It would mean that man was a killer—to use the term of
art an “overkiller”—pretty much right from the start.
THERE are several lines of evidence that argue in favor—or really
against—humans. One of these is the event’s timing. The megafauna
extinction, it’s now clear, did not take place all at once, as Lyell and
Wallace believed it had. Rather, it occurred in pulses. The first pulse,
about forty thousand years ago, took out Australia’s giants. A second
pulse hit North America and South America some twenty-five thousand
years later. Madagascar’s giant lemurs, pygmy hippos, and elephant birds
survived all the way into the Middle Ages. New Zealand’s moas made it as