The Rise of Roots Leaves Earth Cool

Science blogger extraordinaire Carl Zimmer explains how leaves arose on the Earth's land plants at an extraordinary time--in the early Carboniferous, when a severe greenhouse climate gave way to glaciers. This was 50 million years after land life emerged. What kept leaves from evolving? New research seems to show it was the greenhouse, caused by carbon dioxide levels some 10 times today's. What broke the greenhouse was the development of roots--an early example of life changing the global environment. Keep up with him and many others in my Blogs list.