Last week I wrote a post about some new research that suggests that global warming could trigger large-scale extinctions in the next few decades. In particular, I dissected some of the objections that were leveled at the study, pointing out how irrelevant they are to the actual science at hand. Some people who posted comments raised a question that I didn’t talk much about: how did biodiversity respond to rapid climate change in the not-so-distant past?

After all, in the past 2.5 million years (known as the Quaternary Period) Earth’s climate has become particularly jumpy. It has swung in and out of ice ages that have lasted tens of thousands of years. This warm-cold cycle has been punctuated by sudden jolts,