On Saturday, I’ll be giving an hour-long presentation to some seniors (you know, the over 55 set) on the topic of “Woolly Mammoths in New York State.” Well, it’s a pretty nebulous topic, and I only have an hour, so that means I can direct my presentation in pretty-much any direction I want.
You know some paleobiology is going to go in there. What is the difference between a mammoth and a mastodon, for example. And why are they extinct? Someone’s going to ask why we don’t find dinosaurs in New York. Naturally, I have to talk about geochemistry, too, since I might have done a little work with that (see my other blog post).
I guess the obvious thing for me to start with is to explain what a mammoth is, ‘cause it’s not just a big fuzzy elephant!
What is a mammoth?
Mammoths, mastodons and elephants are in a larger group of mammals called proboscidians, so named in reference to their big long noses. Mammoths and elephants are actually very similar, in skeletal and in tooth structure. Mastodons have very different looking teeth, which is an important distinction between to two ice-age dwelling proboscidian groups.
Mammoths (and modern elephants) have teeth composed of a series of plates, that form a washboard-like grinding surface which is perfect for the foods that they eat. Both elephants and Mammoths are (or were) grazing animals (like cattle are today). Mastodon teeth are smaller and have several huge cusps, which aren’t so great for grazing but are good for eating leaves and such. Mastodons were browsers, much like giraffes, for example. Because they had different diets, they were able to coexist.
The structure of the teeth is the easiest way to distinguish between mammoths and mastodons, but their skeletal structures are also distinct. Mammoths tend to be taller in the front end than in the back end, their heads held high – the top of the head being slightly higher than the shoulder. Mastodons are a little stockier, with their head often slightly lower than the shoulder.
Types of Mammoths
Mammoths in North America fall into two species: the Woolly Mammoth (Mammuthus primigenius) and the Columbian Mammoth (Mammuthus columbi). The woolly mammoth was smaller than the Columbian mammoth, and a lot hairier. Woolly mammoths lived further north, closer to the edges of the great glaciers that once covered much of northern North America. Columbian mammoths stayed further south. Only woolly mammoths would be expected in what is now New York State.
What’s special and unique about mammoths (and mastodons and elephants)?
Several things stand out as interesting about proboscidians. Here are some fun facts:
- Mammoths and elephants have only one tooth on each jaw (upper, lower; right, left) in wear at any one time. We have all of our teeth in use all the time.
- There are only six teeth in each jaw (upper, lower; right, left) that an elephant or mastodon ever gets. They grow into the mouth one at a time from the back and fall out the front when they’re worn out. Once the sixth tooth is worn out, there’s no more teeth and the mammoth or elephant starves to death.
- Mastodons have the same pattern of tooth replacement, but usually have more than one tooth at a time in use. Their teeth don’t wear out as quickly though, because they eat softer food.
- Proboscidians are in a larger group of mammals called ‘subungulates’ which are grouped together because they have hoof-like structures on their feet, but they’re not quite hooves.
- Some of the closest relatives to elephants, mammoths, and mastodons are manatees! Manatees are also subungulates and have hoof-like structures on their front flippers. They also have the same sort of conveyor-belt tooth replacement, but they aren’t limited to only six teeth.
When and why did they go extinct?
About 10,000 years ago, mammoths and mastodons, plus a lot of other large mammals that live in North America (woolly rhinos, giant ground sloths) went extinct (Wikipedia article). Most of the animals that went extinct were huge, so we refer to them as “Megafauna.” No one is certain why this happened, but it did coincide roughly with the melting back of the continental ice sheets as well as the appearance of humans in North America. It is an interesting point of controversy. There are two main camps here and then a few extra ideas (maybe the lunatic fringe?).
- Human overhunting
It is possible – even likely, knowing how we as humans are – that humans might have been responsible for the loss of the mammalian megafauna. We have been known, once in a while, to over-use resources, and it is known that humans actively hunted members of the ice-age megafauna, like mammoths.
- Climate change
We also know that climate was changing rapidly then, warming up after the end of the ice-age. The ice sheets melted back and the landscape was changed. Organisms had to adapt, and big animals like the mammoths likely had a hard time adapting.
These both seem like reasonable hypotheses. So which is it? Most scientists straddle the fence on this one: Well humans were hunting a lot, and the animals were already in trouble because of the climate change…
- Meteor impact
Because asteroid impacts have resulted in many extinctions in earth’s history (like the extinction of dinosaurs), it seems sensible that this extinction might also have been caused by an impact. There is some evidence that there might have been an impact, but some things about the extinction event are cause for skepticism. For example, why did ONLY the large mammals go extinct?
- Second-order predation
Here the idea is that not only did humans decimate the populations of the prey animals, they also hunted the predator animals (like saber-tooth tigers). Without the primary predators, the prey animals rapidly overpopulated the area, destroying their own resources and thus killing themselves off.
Humans coming from another continent would have brought a few ‘friends’ with them. Perhaps the humans brought along their own animals that carried diseases for which the native animals had no immunity. This could very quickly decimate the native population as has been seen when humans and their livestock have populated new places in modern times.
How can we find mammoths?
A common question that people ask of paleontologists like me is “How do you know where to look?” I have a standard answer for that: We look at maps, maps that geologists before us have drawn showing the various rocks exposed in an area, describing those rocks, defining their ages through various means. We look at the maps for rocks that should have the right fossils in them, and then we go out to the rocks in the real world and walk around until we find something.
At times it’s a little more sophisticated than that. We can use remote-sensing/sattelite methods and find the most probable areas using neural networks on computers. Many times though, it’s a whole lot less sophisticated. Sometimes, you just walk across a field and kick something and when you look down, it’s a fossil bone. Mammoths are often found when people bring in backhoes to dig a hole for a new pool. Their digging and suddenly there’s a bone. They were digging a new reservoir in Snowmass, Colorado, and they found what’s now called the “Snowmastodon” Site!
What can geochemistry teach us?
My own research centers on the chemical constituents of tooth enamel in fossil animals. From that, we can learn a lot about extinct species, including what their food preferences were, what the weather was doing while they were alive, and how their teeth might have grown. One of my undertakings is described here. I presented my results at the Society of Vertebrate Paleontology annual meeting a couple of weeks ago, to find out that the project I had done has actually been done before (just never published). My results were quite different, however. Through discussion with other scientists, I think we all understand the source of the differing results. Now if I can just get them to publish their work!
Recent discoveries: Mammoth mummies!
Of late, Siberia has been yielding numerous mummies of mammoths (and other mammals). The far North is a good place to look for mummies of any animal, because the cold temperatures will preserve the animals like a giant ice-box. The ice itself can encase the mummy, keeping it from becoming a meal for modern scavenging animals. Yuka Baby mammoth
Cloning of Mammoths
Because of the exquisite preservation of the mummified mammoths, there has been talk of attempting to clone mammoths. So long as the nuclei of cells are not totally destroyed by freezing or decay, a scientist could extract the DNA and create a clone. Will this be done? Should it be done?