that tooth thang

Currently, I’m interning at a raptor education center. Basically, I show people birds and explain all the cool things about them. Some people come in and ask really good questions like “can they see in color?” or “do they mate for life?” However, some people ask not-so-intelligent questions. The other day, a young presenter was holding an Eastern Screech Owl and was asked by a guest “what is that tooth thang in the middle of its face?”

The guest was referring to the bird’s beak.

Of course, I mentally shook my head and entertained thoughts about how ignorant one must be to not know a bird’s beak when one sees it. But later on, I began to think that maybe I was being narrow-minded. Is it so dumb so register a tooth and a beak in the same category? Could the beak be the evolutionary cousin of teeth? Perhaps.

I started looking into the matter, this time with my mind set to evolution mode. When you think about it, beaks are pretty unique and useful structures. Birds have them, and even turtles kind of have them. Some are curved into a sharp points and tear flesh. Some are flattened into a bill and sift solids from water. Some are heavy-set and can crack macadamia nuts with no problem. Others are long and tubular, perfect for sticking down into a flower and licking out nectar. Though avian beaks are diverse now, it does not change the fact that modern birds came from a single common ancestor from Dinosaura. So the beak came from a single evolutionary point. That begs the questions- why, when, and how?

Lindsay Zanno and Peter Makovicky published a study in Proceedings of the National Academy of Science where they used a wide variety of evidence to figure out what therapods ate (theropods are the two-legged dino forebearers to birds). Evidence included fossilized dung and tooth marks on fossils (remember what fossilized poo is called?! Brownie points!). They found that early therapods were largely herbivorous, but some later evolved to be omnivorous and eventually carnivorous.

Come to find out, beaks emerged FIVE separate times within Therapoda. The diverging phyla of little herbivorous dinos experienced the drift towards and pressure for omnivory, which favored selection for having a beak. One lucky lineage went on to spawn our friend Archaeopteryx, and consequently, all of the birds both past and present.

The real kicker here is that these early beaked creatures still had teeth. I entertained this lady’s question thinking that perhaps the beak arose from the same germ cells as the teeth. But no siree, teeth were still present within the beaks. Therefore, teeth are not the structural forbearers to the beak. Not even on a germ line level.

If the lady who asked about the owl’s beak was asking because she thought maybe the beak was the product of increased selective pressure for a ripping mechanism over grinding teeth, like herbivorous therapod forebearers had, then that question was pretty good. Bravo.

But judging by her description of the beak as that “tooth thang,” my first instinct was right. That lady asked a really, really, dumb question.