Tenacious Teeth
Normally, "Sil's Skeletal Spotlight" would cover two bones--one I love and one I hate. But since I apparently like more bones than I dislike, this article lacks the second part. That, and I'm saving the most evil bone for the final article.
Teeth
Many people I know dislike teeth from an osteological standpoint. But I love them, have done since I first studied them in my undergraduate osteology class. They are the only visible parts of our skeleton, which I think makes them extra special. However, even those who don't like teeth will agree that they're the easiest bones to identify. You pick up a tooth--whole or fragmented--, and you know it's a tooth. Teeth certainly cannot be mistaken for any other part of the skeleton, and this fact facilitates a bioarchaeologist's or forensic anthropologist's job. They are fairly simple to differentiate from one another (upper central incisor vs. lower central incisor) and to side. Based on the shape (squared vs. rounded), root number (three vs. two vs. one), and the direction in which the roots lean when oriented in anatomical position (how they sit in the mouth), you can determine which side the tooth came from.
Humans have two stages of tooth growth--deciduous (primary, baby) and permanent (secondary). We have 20 deciduous teeth, which are then replaced by 28-32 permanent teeth, depending on the presence of third molars (wisdom teeth). Both primary and secondary tooth eruption occur in predictable stages, which aid bioarchaeologists and forensic anthropologists in aging a skeleton. Your upper teeth differ from your lower teeth in shape, size, and root number. My favorite examples of this are your first premolars (biscuspids). Your first premolars sit beside your canines, towards the back of your mouth. If you run your tongue along the occlusal surface (the surface on which you chew), you'll notice that your upper first premolars are splayed, sort of like an archway or the letter 'u,' whereas your lower first premolars have a much smaller occlusal surface, sort of like a narrow step or ledge.
Teeth serve many purposes. They are the first phase in the digestive process, crushing and mashing our food into manageable pieces. They are resilient, little things, often surviving when the rest of the bones have either weathered away, decomposed, or been consumed by scavengers. Anthropologically, they are certainly valuable, as identification of some early hominid (early humans) and early primate species was based mostly on their teeth. For example, we know Gigantopithecus (9 million-100,000 years ago) was the largest ape that ever lived primarily from its teeth. In biological anthropology, teeth are one of the skeletal features used to distinguish between apes and monkeys. Ape and human lower first molars have 5 cusps (the raised points on the chewing surface). This is called a y-5 pattern, because the area between the cusps is y-shaped. Monkeys, on the other hand, lack y-5 molars and instead have lower first molars with 4 cusps. But teeth can also be used to positively identify human murder victims by comparing their teeth with dental x-rays. And most interestingly, teeth can reveal countless secrets about their owners, like diet, health, nutrition, and migration patterns.
That last point is the reason I chose teeth for this article. My current research is determining what ancient Hungarians ate through stable isotope analysis of their first molars. By comparing levels of carbon isotopes (Carbon-13), I can trace the nutritional history of people who've been dead for a very long time. This has implications for disease, too, as certain mineral or vitamin deficiencies can cause illnesses that may or may not be evident in the skeleton. I won't bore you with the process of extracting those stable isotopes, but suffice it to say, I've become intimately acquainted with my ancestors' teeth.
