A super-sized snake in prehistoric Colombia tells scientists about the future of global warming.
A hot story about a big snake. I'm Bob Hirshon and this is Science Update.
Scientists recently found bones from a 60-million year old giant snake in Colombia—a snake that weighed a ton, and was as long as a school bus. Paleontologist Jonathan Bloch of the Florida Museum of Natural History was on the team. He says the find also tells us about climate, because cold-blooded animals depend on ambient heat for their metabolism.
Snakes that are living in the warmest climates today are as large as they can get, for the temperature that they live at. In order to make a larger snake, you have to increase the mean annual temperature.
Bloch says it must have been ten degrees hotter in Colombia back then—contrary to a leading theory that tropical climates don't change as much as others. So today's warming trend may have an even wider impact than we thought. I'm Bob Hirshon for AAAS, the Science Society.
Making Sense of the Research
In science, you can't always measure everything directly. For example, you can't travel a century into the future to find out what the climate will be like then, nor can you go back in time and take photos and movies of dinosaurs. You also can't dig down to the center of the earth and take samples from its core, or get inside an animal's mind and experience what it thinks or senses.
Yet, scientists still know quite a bit about dinosaurs, the earth's core, animal senses, and where the earth's climate may be heading. To do that, they rely on inferences: conclusions drawn by combining indirect evidence with logical assumptions. Everyone makes inferences: for example, if you see a friend come in from outside with a wet umbrella, you infer that it's raining out, even if you haven't looked out the window or heard it on the news. You assume, logically, that someone would only use an umbrella to keep off the rain, and that only rain would be likely to have gotten the umbrella wet. Is it possible that your friend is a clean freak and was only washing his umbrella? Maybe, but very unlikely, unless you already knew that.
In this case, a collection of vertebrae, or spinal bones, in modern-day Colombia led Bloch's team to make an inference about the climate in the prehistoric tropics. Sounds confusing, right? But as it turns out, there are several scientific inferences that got them from point A to point B.
First, they know that the vertebrae are snake vertebrae, based on their knowledge of anatomy. Using ratios and proportions from snake anatomy, they also can calculate how long a snake would have to be in order to have backbones that size. (Similarly, a forensic scientist could tell about how tall a person was from the size of his thigh bone). Furthermore, because they found lots of these vertebrae, from at least 28 individual specimens, they can conclude that this giant size was normal for the snake species in question.
Next comes the inference about climate. Unlike warm-blooded animals, like people, which generate and maintain their own body heat, cold-blooded animals, like snakes, depend on the outside environment to heat their bodies. If you've ever done any cooking, or even microwaving, you know that smaller objects cook more quickly than larger objects. For the same reasons, the larger a cold-blooded animal, the warmer the climate would have to be to keep its body temperature at a biologically functional level.
Using mathematical equations that relate body size to climate, the researchers calculated that the temperature in this part of the world must have been 10 degrees warmer than it is today. (At the time, the continents were located in different places, but this spot still would have been in the tropics.) That contradicts a popular theory that the tropics aren't as susceptible to global warming as are other areas. If tropical regions will, in fact, heat up as much as the rest of the world, that will make climate change an even thornier problem than many scientists thought. Imagine the effects on places like Delhi, India, where temperatures as high as 118 °F (48 °C) have already been recorded.
Bloch's team made some other inferences as well. For example, the snake would have been larger than anything else at the time, so it could have easily eaten whatever it liked, including primitive crocodiles! They also suggest that the extinction of the dinosaurs may have set the stage for this giant snake to become king of the land for millions of years.
Now try and answer these questions:
- How do the scientists know how big this snake was?
- How did they draw conclusions about the climate from the size of the snake?
- Can you think of other examples of inferences you make in everyday life?
- What is the difference between an inference and a guess? Are inferences foolproof? Why or why not?
Read about other giant prehistoric animals in the National Geographic News article Australian Cave Yields Giant Animal Fossils.
The Science Careers article Skeleton Keys, from Science magazine, describes how forensic anthropologists analyze bones to discover facts and circumstances surrounding crimes.
Another National Geographic News article, Do They Really Look Like That? The Science of Dino Art, describes how artists use real science to create illustrations of the prehistoric world.