He said that in his opinion: "A catastrophe was not responsible for the major extinctions.

Although some populations have declined, there have been no major extinctions of wildlife in this area.

Are we entering the sixth major extinction on Earth?

It is surprising that the cycads are still extant, having been faced with extreme competition and five major extinctions.

Regressions are therefore seen as correlates or symptoms of major extinctions, rather than primary causes.

The extinction, while global in scale, was less severe than the half-dozen major extinctions in the earth's history.

Scientists have also reported tantalizing clues of meteor impacts coinciding with major extinctions.

And yet, efforts to link other major extinctions with similar impacts have largely failed.

No catastrophe was seen in surface ecosystems, yet bottom-dwelling organisms in the deep ocean experienced a major extinction.

We have not documented major extinctions yet, even as climate change drastically alters the biology of many species.