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| Photo Credit en.wikinoticia.com |
As humans there are three ways we’re used to having our temperature taken: under the tongue, in our ears, and the “other” way. Regardless of our personal preferences, we can probably all agree that it is pretty darn difficult to apply any of these techniques to a dinosaur. So barring time machine development, how do we measure the body temperature of our pre-historic pals? Surprisingly, the trick is in the teeth. From molars to metabolism scientists are using some pretty “cool” chemistry to dig up answers.
To start out, let’s talk about metabolism, baby. Our metabolic rate is how fast we break down food, build up body mass, and generate heat. In general, a high metabolic rate means a higher general activity level and higher body temperature. Animals considered to be “warm blooded” have a high metabolic rate and generate their own heat internally, while “cold blooded” animals have a low metabolic rate and get much of their heat from the environment (picture a lizard sunning itself on a rock). This doesn’t mean, however, that “cold blooded” animals always have a lower body temperature, but that their temperatures fluctuate with their environment. In fact, their peak temperatures can be even higher than their “warm blooded” cousins. For this reason, these terms have been replaced by “endotherms” that generate temperature internally, and “ectotherms” that have their body temperature highly dependent on factors outside the body.
Our understanding of dinosaur body temperature has undergone a pretty major makeover over the last two decades. The image of dinosaurs as cold-blooded overgrown lumbering lizards has morphed into a portrait of a much more active and agile group of animals. This increased athletic prowess implies an increased metabolic rate, and sparked the idea that dinosaurs may have been endothermic. Being the investigative creatures that they are, scientists set out to study dinosaur metabolism and body temperature by measuring bone growth patterns, modeling behavior, and studying clues about athletic performance found in footprints. Although many of these studies pointed to an endothermic lifestyle, no real agreement on body temperature was reached.
That was until a group of researchers used the chemistry of dino tooth enamel as a trans-millennial thermometer to accurately measure the average body temperatures of some pre-historic behemoths. Wait just a second, temperature from tooth enamel? How can that work? The answer lies in the power of isotope chemistry. To understand this we have to go down the level of individual atoms of the elements carbon and oxygen. While most atoms of carbon have 12 particles in their nuclei and most oxygen atoms have 16, a very small percentage have extra neutrons and make carbon atoms with 13 particles and oxygen atoms with 18 particles. At high temperatures these “heavy atoms” act pretty much the same as all the other atoms, but at low temperatures they are more likely to bond to each other than one of the lighter atoms. You can think of this like a bad cocktail party: if everyone is really low energy you’re more likely to stick with your friends, but if the party really gets going you're going to meet and mingle with more people. In a technique called “clumped isotope thermometry” scientists measure the proportion of heavy carbon and oxygen that bonded together during tooth formation, effectively measuring the energy level of the tooth-growing party, or dinosaur body temperature.
From analyzing several teeth from large Jurassic Sauropods (“long-necks” to those who remember “The Land Before Time”) researchers calculated their body temperature to be between 36 and 38 oC. This is around the same range as most modern mammals. It’s not as simple as whipping out the thermometer from the medicine cabinet, but an inspiring example of how our basic scientific understanding of the world around us can enable scientists to solve seemingly impossible problems. Today dinosaur temperatures, tomorrow, conversations with Neanderthals? Don’t be too quick to rule it out…
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