“You see the importance of slight differences in teeth, then?” the scientist said. “Some of these days, when you think that the details of an animal’s bones or teeth are dry learning, remember how here, on the Libyan Desert, you saw for yourself the dawn of the elephant’s tusk suggested in the slight extension of the second incisor of the Moeritherium, or the beast of Lake Moeris.” “And were his feet like elephants’ feet, too?” “Yes, in a measure, but with one great difference.” “What was that?” “Moeritherium was a marsh animal, Paleo-mastodon was not.” “How can we tell, Uncle George?” “By the feet. Then, the later animal had a trunk and the former did not.” “How does that show up?” “By the length of the legs and the neck. There is reason to think that the legs of Moeritherium were fairly short and his neck long enough to reach the ground, certainly long enough, when he was standing in water, to enable him to eat marshy vegetation. There is no sign of a long upper lip, like that of a tapir, nor a trunk like that of an elephant. Now in Paleo-mastodon, his legs were longer and his neck shorter. Therefore, even if we had no other signs, we could be sure that he must have had a trunk.” “Oh, I begin to see now,” said Perry. “If an elephant had a long neck, he wouldn’t need a trunk. A trunk is a scheme used by a long-legged and short-necked animal to get food to its mouth. But I always thought a tapir was on the way to an elephant because of the long upper lip.” “And now you see that the upper lip of the tapir and the trunk of the elephant are the result of the same principle operating on two entirely different kinds of animals, for if you just looked once at the feet of a tapir and at those of an elephant you’d never make the mistake of supposing them to be even distantly related. The teeth are different, too, everything’s different, except the lengthening of the lip. It never occurred to you to think that an ostrich and a giraffe were related because they both have long necks?” “Of course not.” “Or a hump-backed salmon and a camel because of the hump?” Perry laughed. “Then don’t get led astray by superficial resemblances. Remember the importance of the feet as a means of telling on what kind of soil an animal lived, and the teeth in telling what kind of food he ate, and that will help you more in paleontology than anything I know. You’ll trace some queer relationships by feet and teeth, Perry, between pig and hippopotamus for example, and between goats and oxen.