“So this python is full of gas. You set it down by the campfire because you’re going to eat it. Somebody kicks it or steps on it, and all this hydrogen shoots out of its mouth.” Hydrogen, as the you and I of today know but the you and I of the Pleistocene did not know, starts to be flammable at a concentration of 4 percent. And hydrogen, as Stephen Secor showed, comes out of a decomposing animal at a concentration of about 10 percent. Secor made a flamethrowery vhooosh sound. “There’s your fire-breathing serpent. Imagine the stories that would generate.