Puppies lack two senses at birth: sight and hearing. It takes a minimum of 10 days to two weeks for their final two senses to develop. Although lacking their sight and hearing might seem odd to human beings, puppies develop in a way that is advantageous to their species.
Newborn puppies bear little resemblance to adult dogs. They have massive heads with pronounced muzzles suited to nursing. Their legs are short and possess only enough power to scoot their bodies along the floor or ground. Newborn puppies cannot stand. Neither can they hear; their ear canals remain sealed shut. Finally, they cannot see because their eyelids are also sealed. Newborn puppies are entirely helpless and must stay close to their mother and littermates to stay warm.
Dogs as Predators
According to Stanley Coren, Ph.D., this helplessness makes perfect evolutionary sense. Newborn herbivores emerge fully functional after their mothers’ long pregnancies because they have to be able to run with the herd, in part to escape predators. However, long pregnancies would interfere with predators’ ability to hunt and to survive. Puppies continue to develop after leaving their mothers’ wombs because doing so is in the best interest of the canine species in terms of survival.
The Nervous System
Puppies’ central nervous systems are incompletely formed when they are born. The brains, spinal cords, and nerves are all present in their bodies, but the nerves cannot transmit electrical impulses in an efficient way because they have not been coated with enough myelin yet. Myelin is the fatty layer that carries messages along the nerves. In normal, healthy puppies, the myelinization process takes several weeks, after which puppies can make more purposeful movement.
Puppies’ optical nerves are developing along with the rest of the central nervous system, making them very sensitive to light. In addition, the eyes themselves are still forming behind the lids. Sealed eyelids protect the nerves and membranes of the delicate organs from hazards such as light or grit. Once the eyes have fully matured, puppies’ lids start to open. For this reason, it is extremely important to let a puppy’s eyes open on their own, rather than trying to hurry the process along and force them to open.