I like Argument-ER, I just hate that there's a timer. If anyone knows how to get rid of it please share.

The context of the second sentence would not allow the first claim to be true. The first claim is a generalized statement about SOME mammals. The second claim goes goes into oddly specific detail about Stone Age pigs. Now ask yourself how many species of mammals exist. There's several, right? The second claim would've offered support had it included some other types of mammals. Or, if it had made the historical connection that the same "growth rings" found in the Stone Age pigs' teeth are present in some mammals today, then that would allow the first claim to ALSO be true. The way its written now, those two claims are just two random facts that offer no logical support to each other to articulate an argument.