Mammals May Be Nearly Half Way Toward Mass Extinction

If the planet is headed for another mass extinction like the previous five, each of which wiped out more than 75 percent of all species on the planet, then North American mammals are one-fifth to one-half the way there, according to a University of California, Berkeley, and Pennsylvania State University analysis.

Many scientists warn that the perfect storm of global warming and environmental degradation — both the result of human activity is leading to a sixth mass extinction equal to the “Big Five” that have occurred over the past 450 million years, the last of which killed off the dinosaurs 68 million years ago.

By combining data from three catalogs of mammal diversity in the United States between 30 million years ago and 500 years ago, UC Berkeley and Penn State researchers show that the bulk of mammal extinctions occurred within a few thousand years after the arrival of humans, with losses dropping after that. Although modern humans emerged from Africa into Europe and Asia by about 40,000 years ago, they didn’t reach North American until about 13,000 years ago, and most mammal extinctions occurred in the subsequent 1-2,000 years.

Science Daily