Teeth fossils from millions of years ago can explain why we have the teeth in our mouths today. Teeth are very crucial to humans because our jaw and teeth act as a feeding mechanism for humans and if it were not for teeth, we would not be able to chew our food, voice our opinions, or even carry normal conversations like we do today. Humans have four different types of teeth: incisors, canines, premolars, and molars. Our incisors are the four front teeth that have a wide and flat shape. The purpose of these four front teeth is solely for cutting through food that we eat.
Our canines are the teeth on each side of the incisors and have a very pointy sharp shape. We have two on the bottom of the jaw and two on the top. These four teeth help tear up tougher food that the incisors cannot tear. Humans today have 8 premolars; their shape is wide, with ridges and depressions. The function of our molars is to crush and grind food into small pieces to prepare for food digestion. Lastly, there are 8 molars in mouths today as well, which also shares the same purpose as premolars. Each tooth has its importance in our mouths.
Paleontologists decided to take it amongst themselves to search for teeth fossils to answer one simple question that they had: Are there rules that govern how hominin tooth size evolves? The evolution of human teeth shows that we can predict the size of the teeth from hominin fossils. Scientists can track the jaws and teeth of Homo sapiens that have evolved from our last common ancestors, chimpanzees. Human teeth and jaws are smaller today than in the past. In the past it is believed that the jaws and teeth were bigger than today because teeth were used most commonly for breaking up huge pieces of food.
Today, we have utensils to cut up the food that we eat before putting it in our mouths, leaving our teeth to do less work. A major difference between teeth of today’s humans and ancient teeth is the wear patterns. Another noticeable change is in the dentition and the jaw. Humans today have fragile jaws and smaller teeth than from people living 25,000 years ago. In the past, jaws and teeth of hominins were very robust and strong; their jaws were able to handle any kind of tough foods. The canine teeth of humans living long ago were much larger and more animal-like.
Teeth found by archaeologists have shown extreme wear, often down to the roots. Softer foods today lead to teeth being more crooked and also leads to gum disease and tooth decay. With softer foods being a factor, the human jaw has to work less therefore leading our jaws to shrinking compared to how large they were in the past. Tooth shape is linked to the position of the jaw. Scientists discover clues on how humans might have evolved into the future. In the journal, Nature, biologist, Dr. Alistair Evans, from Monash University, shows his readers how the teeth from humans evolved from hominins.
According to Encyclopedia Britannica, Hominins are any member of the zoological “tribe” Hominini of which only one species exists today–Homo sapiens, or human beings. Dr. Alistair Evans and his colleagues based their study off of hominin tooth sizes while trying to figure out what rule governed the evolution and development of teeth in hominins. This study provides a development-based expectation to examine the evolution of the unique proportions of human teeth. While on their journey, Dr. Evans and his crew found two types of hominins: the species that we classify as Homo and australopiths.
These scientists discovered an activator mechanism that affects tooth size in mammals, mainly post-canine teeth in hominins. Dr. Alistair Evans discovered that the tooth size remains constant with tooth size in australopiths, which is an extinct genus of hominins. Dr. Alistair Evans stated: However, in species of Homo, including modern humans, there is a tight link between tooth proportions and absolute size such that a single development parameter can explain both the relative and absolute sizes of primary post-canine teeth (Nature).
Basically, scientists can use the size of one tooth to predict the size of another tooth around the same time period. Teeth are like puzzles, once you have one piece, you are bound to find another piece that fits and matches. There are many factors of the change in teeth. One main factor is the foods that we eat today versus the foods that hominin and our distant ancestors were eating when they were alive. As mentioned previously, “teeth as a feeding mechanism in an oral cavity (mouth) are functionally and locationally linked with jaws” (McCollum).
Foods in modern society do not require the same chewing capabilities since the invention of utensils for cutting up bite-sized pieces for eating. Wisdom teeth indicate the evolution of humans over time. Most humans in today’s world do not have room to accommodate the four additional wisdom teeth. The reason for this is lack of room includes changes in diet and living conditions in people today. The canine teeth of hominins living long ago were much larger than current human teeth.
Dr. Alistair Evans and his colleagues revealed that molars also differed in size depending on the era of the teeth and the geographic location where these teeth fossils were found. Molar sizes were gathered from studies where they studied three different types and all three molars had almost no wear to them and were measured as a part of the research. Fossils have shown evidence of a decrease in size in their jaws and jaw muscles, teeth, temporomandibular joints, tongue, lips, cheeks, and mucous membranes.
All research protocols were reviewed and granted exemption by Arizona State University’s Institutional Review Board and the Burlington Growth Center, and informed consent was obtained for all human subjects. No statistical methods were used to predetermine sample size. The research that Dr. Alistair Evans performed confirms that molars, including wisdom teeth, do follow the sizes predicted by what is called ‘the inhibitory cascade’. The inhibitory cascade is the rule that explains the reason why one tooth shape effects the tooth shape and size next to it.
This discovery leads to every scientist thinking that evolution is a lot simpler than they thought it was. Dr. Evans tells the journalist: What’s really exciting is that we can then use this inhibitory cascade rule to help us predict the size of missing fossil teeth. Sometimes we find only a few teeth in a fossil. With our new insight, we can reliably estimate how big the missing teeth were. The early hominin Ardipithecus is a good example – the second milk molar has never been found, but we can now predict how big it was (Nature).
It is fascinating to see that even if a fossil is missing, scientists can still predict what the missing piece could possibly look like or what size it could have been just by using the data that is already given to them in the fossil that they found. Dr. Evans and his international anthropologist team that he led from Finland, USA, UK, and Germany, were able to use 3D imaging to see inside the fossil teeth of hominins.
After performing an extensive study on hominin and human teeth, Dr. Alistair Evans and his colleagues hypothesized a decrease in tissue activation, which drives the change in tooth proportions in Homo sapiens. The decrease in tissue is the reason why there are different proportions in teeth for almost every era leading up to today’s time. Scientists understood that teeth could tell us about the lives our ancestors lived and how their teeth have evolved and changed in size over the last 7 million years. Paleontologists have worked for decades to interpret these fossils and looked for new ways to extract more information from teeth.
