Human Evolution: The Biology of Man

Human Teeth: A Good Start to the Story

We will begin our analysis by looking at our teeth. The reason teeth are important when studying the past is due to the evolutionary pressure they are subjected to. While we take teeth for granted, losing a tooth in the wild may make eating food impossible and kill off the individual. As a result, teeth are one of the most rapidly changing organs when there is pressure to survive. This is a great tool to observe human evolution for this reason. Now, let’s look at the size and shape of human teeth:

Our Molars

Compared to ancient hominid species, our teeth have undergone two key changes. First, we have much smaller molars. While our ancestors had molars as large as our thumbnails, our molars are about as big as the nail of our pinky finger. This change is important because it tells us that while ancestral hominids needed to crush and grind high fiber, low calorie foods to get energy, our species had a lifestyle that enabled access to more nutrient dense foods.

Our Faces

The second point regarding teeth is the structure of our facial bones. Ancient hominids had very wide and thick facial bones. While this may seem irrelevant to teeth and diet, the thickness of facial bones plays a crucial role in how an organism consumes food:

When you chew on something like a stick of celery or stringy meat, you will eventually feel your jaw fatigue. This fatigue is largely due to the stress that muscle contraction places on your facial bones. In fact, the fatigue you feel is due to bone damage and deformities building up in your face. While these damages are easily repaired when you stop eating, it is a time consuming process.

When our ancestors foraged on fibrous food for energy, there was not enough “chew-free” time for repairs to occur. If they stopped eating their low nutrient food for more than a couple hours, they would not get enough energy to sustain themselves and survive. As a result, evolution favored thicker facial bones capable of withstanding long hours of chewing.

In the case of our species, access to nutrient dense foods made the cost of chewing more manageable. Thus, human evolution replaced thick facial bones with less metabolically expensive facial bones that we all wear today.