Megalodon's teeth reveal extinction cause?
Now, scientists believe that they can ascertain prehistoric food chains by looking more closely at the chemical composition of their teeth. Jeremy McCormack from the Max Planck Institute for Evolutionary Anthropology, believes his recent study of the giant Megalodon’s giant gnashers could lead us to the cause of its demise. Harry Lewis reports...
Jeremy - They went extinct around 3.6 million years ago, and they had a worldwide distribution. It is the last member of the so-called mega tooth lineage. And the megalodon itself could have potentially reached sizes of up to 20 meters in total length.
Harry - You were able to compare the diets of different shark species, including that of the great white shark and the megalodon, because they were at one point in time, both swimming around together, and you've used zinc isotopes to do that. How can those isotopes help?
Jeremy - An isotope of course the same element, but with a different mass. So we look at the ratio of the heavier zinc to the lighter zinc in the mineral of these teeth, and this ratio tells us how far up a food chain an animal was feeding. The way this works is that the zinc isotope ratio changes as we move along the food chain within the vertebrae remains of different animals.
Harry - Right. And why is it that teeth make for such good samples?
Jeremy - So we look at teeth because teeth are very well preserved as fossils over millions of years. And because zinc is incorporated into this mineral phase of teeth, we basically can look back millions of years, study the diet along extinct animals.
Harry - Were there any similarities then between the diets of great whites and Megalodons?
Jeremy - There is this hypothesis that the emergence of the great white shark during the early Pliocene led to competition for dietary resources between megalodons and great white sharks and our zinc isotope results show that both species fed on a similar trophic level. And now this does not necessarily imply competition, but it really doesn't reject the hypothesis of competition between both species.
Harry - I've got you. So they could have been eating pretty similar prey. Can we guess at where the diets of these two sharks may have crossed over?
Jeremy - So from fossil evidence, we know that both species, at least occasionally fed on marine mammals. So these included both toothed and baleen whales, although the baleen whales back then were much smaller than they are today. Um, but such kind of fossil evidence is rare, and it only gives us a snapshot of predator-pray interaction and does not give us the information about the regular diet of these species.
Harry - And of course, what makes it so fascinating is it's the first time that this method using zinc isotopes to infer one's position in the food chain has been used on such old samples. So there must be quite a lot more to come. This is an exciting time?
Jeremy - Yeah, that is ultimately the goal to use this new method, to investigate the diet ecology of longing animals, which obviously has important implications for their evolution. But in some cases also their extinction.