Scientists are not sure when this extinction crisis began—it could have started 10,000 years ago, or during the industrial revolution, or this century. But we are definitely seeing an extinction "spasm" right now, say the Berkeley scientists, especially among our clammy, froggy friends. This extinction is unlike the five that came before it, according to the paper's authors from UC Berkeley, because it has nothing to do with any asteroid impact, or volcanic surge, or great sea cooling. Instead, it may have almost everything to do with us. Amphibians made it through last time, when the dinosaurs disappeared. But with new, people-driven pressures on biodiversity, the survivors are now some of the most vulnerable.