As opposed to one or three?
In: Biology
Most animals feature some form of symmetry (dates back to our days long ago when all animals were just fancy tubes). In most ‘advanced’ land animals we have what’s called “bilateral symmetry”. That basically means that if you drew a line down our center, each half is a mirror-image of the other. Our left side matches our right side. Anything appering on the left side has an equivalent twin on the right side. Of course if we look a little deeper, we are not COMPLETELY syymetric. There are some internal organs that appear only on one side of the body with no ‘twin; on the other. But that is mostly to do with the fact that our digestive tract is the evolution of the “tube” mentioned above, and so it used to be the dividing line for our symmetry, and so some part of the digestive tract aren’t themselves symmetric, despite them no longer physically being located at our midline.
So the short answer is: because our nostrils are not in the center of our body. If theyre located off the centerline of our body, we’re gonna have a left one and a right one. You can see evidence of this by looking at the animals that DO only have one nostril. Cetaceans (whales, dolphins etc) have only one nostril (their blowhole) and it is located right in the middle of their body.
Latest Answers