How and when did life on Earth get to be the way it is today? Imagine a world without bees, butterflies, and flowering plants. That was Earth 125 million years ago. Turn back the clock 400 million years, and there were no trees. At 450 million years in the past, even the earliest insects had not yet developed. And looking back 500 million years-a half-billion years before the present-the land was devoid of life, which at that time flourished in a profusion of strange forms in the oceans.