So far in the history of life on Earth there have been five Great Extinctions. One was caused by the giant meteor that hit what is now the coast of Mexico, two by freezing in the oceans and the lowering of the sea levels, one by huge, widespread volcanic eruptions, one (probably) by gigantic meteorite showers.
They were all many millions of years ago — all but the sixth Great Extinction, which has barely started. That is the one the scientists are calling the “Holocene,” and its cause is annihilation of species of birds, animals and — especially, for example — edible fish.
And the cause of that is Us.
How do we cause extinctions? Oh, we have lots of ways. For fish, we harvest the tastiest ones en masse until there are none left (it’s estimated that we have removed nearly 90 percent of large fish from the sea). We destroy habitats. Most of all, we cause global warming. Anyway, our work in this matter has gone far enough for scientist to refer to the present as a new age, the Holocene.