Neoteny / Juvenilization

Some dogs look and act forever young

Like puppies, the adult dogs of many breeds are small, with short snouts, floppy ears, and large eyes. Scientists call these puppy-like features neotenic -- most of us just call them cute.

Puppy-like behaviors -- playing, nuzzling, frolicking -- also appeal to many of us, and even elicit our care. If behavior and appearance are genetically linked, then breeding for one may bring the other.

Long nose, short nose -- depends on how the skull grows!

The skull of a wolf or dog pup is about as wide as it is long. But as the pup grows, the shape of its head changes. An adult dog's head is usually much longer than it is wide because later in development, growth in skull length overtakes that of skull width, such as the Airedale to the left.

However, some breeds continue to grow like young puppies for a longer period. In short-snouted breeds, the snout grows more slowly in length than in width and may stop early, resulting in adults with puppy-like faces, such as the French bulldog to the right.

Long-snouted breeds are born with typical puppy proportions, but their skull grows more rapidly in length than it does in width. Growth in skull length overtakes width earlier in development and they end up with longer noses, such as the Saluki to the left.