It was quite a different experience then. My brother and I drove down here from Wyoming and we were kind of nerds in a sea of flower children. But it was really interesting. I felt kind of like a tourist. As he mentioned, there were episodes of mass extinctions in the past.
Most paleontologists speak of five major episodes that occurred millions of years ago.
Another period of mass extinction, which was not as large or widespread, occurred just about 15-25,000 years ago at the end of the Pleistocene when about 80 percent of the large mammal fauna in North and South America and Australia all went extinct. Some scientists speculate that humans had played a part in this extinction. Today, most biologists will agree that we are in the midst of another period of extinctions. We don't really know how extensive it will be relative to previous events, but it is qualitatively different because it's primarily being caused by human beings.