It was snowing butterflies - C. Darwin

Un altro opuscoletto della Penguin. I wanted to copy down this excerpt before I forget (Darwin is talking about South America):

It is impossible to reflect without the deepest astonishment, on the changed state of this continent. Formerly it must have swarmed with great monsters, like the southern parts of Africa, but now we find only […] mere pigmies compared to the antecedent races. The greater number, if not all, of these extinct quadrupedes lived at a very recent period […]. Since their loss, no very great physical changes can have taken place in the nature of the country. What then has exterminated so many living creatures?

Darwin tries to answer its own question:

In the Pamphas there are no signs of violence, but on the contrary, of the most quiet and scarcely sensible changes.

So a sudden violent event is ruled out. One more hypothesis:

At Bahia Blanca I endeavoured to show the probability that the ancient Edentata, like the present species, lived in a dry and sterile country such as now is found in that neighbourhood.

So it was not a climate change either. Another hypothesis:

In some countries, we may believe, that a number of species subsequently introduced, by consuming the food of the antecedent races, may have caused their extermination; but we can scarcely credit that the armadillo has devoured the food of the immense Megatherium, the capybara of the Toxodon, or the guacanaco of the camel-like kind.

So it cannot have been competition for food, either. Summing up:

One is tempted to believe in such simple relations, as variations of climate and food, or introduction of enemies, or the increased number of other species, as the cause of the succession of races. But it may be asked whether it is probable that any such cause should have been in action during the same epoch over the whole northern emisphere […].

Whatever happened must have been a gradual, global event, resulting in the extermination of most giant terrestrial mammals. The question remains for Darwin open, we can today find an answer in Sapiens:

American fauna 14.000 years ago was far richer than it is today. When the first Americans marched south from Alaska into the plains of Canada and the western United States, they encountered mammoths and mastodons, rodents the size of bears, herds of horses and camels, oversized lions and dozens of large species the likes of which are completely unknown today […]. South America hosted an even more exotic menagerie of large mammals, reptiles and birds.

This is more or less consistent with what Darwin says. But then?

Within 2.000 years of the Sapiens arrival, most of these unique species were gone. […] We are the culprits. There is no way around that truth.

It was men all along!

I find there is something very dramatic about Darwin witnessing a mysterious extermination and dwelling on the possible reasons without knowing that his own species brought it about. It has some Memento vibes to it?