Dog fetus at 60 days
At this point, the puppy has also developed its defining sense of smell and hearing. Dogs have nearly 200 million scent receptors in their nose, as opposed to a human's 5 million. Just days after birth, a puppy can detect smells at concentrations 100 times weaker than those detectable by humans. If a human touched a glass and set it down, a dog could pick up the scent of the human nearly two weeks later.
After day 30 in the fetus, unborn pups form eyeballs and vision similar to a color-blind human, who can't discern red, yellow or green. Scientists believe that dogs' color blindness adapted from their earliest ancestors who needed to compete for prey against other animals during nighttime.
Dog ears are much more sophisticated than humans', too. When pricked up, the ear reflects sound similar to when a human cups an ear with a hand. This adaptation helps hunting dogs detect high-octane noises given off by rodents. The dog can also hear sounds four times farther away than humans can.
Finally, the dog already has its whiskers, which are as sensitive as a human's fingertips. This makes it possible for dogs to sense the presence, size and shape of nearby objects just by detecting vibrations in the air.
December 8, 2006 4:00 AM PST
Photo by: Pioneer Productions
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