The number of teeth in human adults is usually smaller then the number they were born with. Sometimes teeth need to be pulled for medical reasons. Sometimes the number of teeth declines because a tooth is knocked out while playing a sport.
Most of the time, humans have a lower number of teeth because wisdom teeth are extracted. It is a normal cycle. Babies are born with no teeth. Next, the baby teeth come in. Later in life the number of baby teeth begins declining as they fall out. Later these baby teeth are replaced by adult teeth. Around our early twenties wisdom teeth come in behind our adult molars. Very rarely do humans keep these wisdom teeth anymore. The human race no longer needs the same number of teeth to survive.
When “cavemen” were around, these third molars were a welcomed blessing. Many times the adult molars had already fallen out and they needed more chompers. Now, this added number of molars is no longer needed for humans to eat. There have been many cases in the present day where humans have been born with only three wisdom teeth. This is de-evolution reducing the number of human teeth. It is nature’s way of simplifying the human body. Studies show that diet appears to have a great deal to do with this decline.
Humans that live in developed countries where processed foods are the norm tend to have a hired rate of the missing third molar in children born in those areas. Not only is mother nature taking away the number of human teeth we have, but she is also making our jaw smaller. It is very rare that a person can comfortably house the third molars anymore. This is why they are usually extracted before they have broken the surface of the gums. As time goes by, and humans learn how to care for their teeth better, the numbers will probably decline further.
Maybe one day, the number of human teeth will decline to where there are no third molars.