Extreme Bodies

The babirusa’s upper canines don’t grow downward as normal ones would. Instead, they grow directly up, through the top of the skull bones and out through the skin on the snout. Babirusas use them for display and in fights against mating-season rivals.
Wildlife/Peter Arnold, Inc.

Let's be honest, some mammals look bizarre - giant teeth, deadly feet, skin covered in everything from piercing quills to impenetrable plates of bony armor, and six-foot long hands.

Despite our differences, all mammals inherited the same basic body features - some type of hair or fur; backbones; and mammary glands, among others. But, clearly, an amazing variety of creatures have evolved over the 200-million year history of mammals.

How could mammals evolve such a wide variety of seemingly strange features? Well, evolution proceeds by acting on the tiniest differences among individuals.

For example, a mammal with a distinguishing feature like large front teeth might have an advantage in one particular environment. Over time, as individuals with that trait produce more offspring, all or most members of that species might have large front teeth. Eventually, some might end up with extreme adaptations--like giant tusks.