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“What to us was surprising was that we did not see a similar kind of pattern in any of the previous mass extinction events that we studied,” said geoscientist Jonathan Payne of Stanford University, the study’s lead author. “So that indicated that there really is no good ecological analogue . . . this pattern has not happened before in the half billion years of the animal fossil record.”

These losses in the ocean are paralleling what humans did to land animals some 50,000 to 10,000 years ago

The researchers conducted the work through a statistical analysis of a 2,497 different marine animal groups at one taxonomic level higher than the level of species – called “genera.” And they found that increases in an organism’s body size were strongly linked to an increased risk of extinction in the present period – but that this was not the case in the Earth’s distant past.

Indeed, during the past 66 million years, there was actually a small link between smaller body sizes and going extinct, marking the present as a strong reversal. “The extreme bias against large-bodied animals distinguishes the modern diversity crisis from all potential deep-time analogs,” the researchers write.

The study also notes that on land, we’ve already seen the same pattern – and in fact, we saw it first. “Human hunting has been extensive for many thousands of years on land, whereas it’s been extensive for a couple of hundred years in the oceans,” says Payne.

Thus, humans already drove to extinction many land-based large animal species in what has been dubbed the Late Quaternary extinction event as the most recent ice age came to a close.