[SOUND] [MUSIC] The rise of the mammals in the Cenozoic is really the story of big is beautiful. The earth ecosystem had opened up, and the resources were there for mammals to radiate and not only become diversified, but to become really, really big. So the modern day Earth that we're used to, there are a few large mammals, but compared to what happened to the middle part of the Cenozoic, it's nothing. We're living in a cake walk compared to what was going with size earlier in the Cenozoic. So let's look at some of the hallmark's of that. As you'll see in this image, the largest land mammalian predator that we've had during the Cenozoic was an organism that looked like a wolf, but it was actually a sheep. So it's this gigantic sheep in wolf's clothing that was a very successful predator for a long period of time within the Cenozoic. Another organism that did very well were the rhinoceros. And the rhinoceros' lineages, they became large, 2.5 meters at the shoulder, these were big organisms like the modern day rhinoceroses'. But, as we will see in this next image, the rhinoceros became several stories in height. So, actually the largest man based mammal was a rhinoceros. It had a long neck and doesn't look very rhinoceros like, but the details are clear that it's a rhinoceros. Another group of mammals that radiated in this middle Cenozoic time period were the elephants. And the rise of the elephants were quite remarkable. They also were simultaneous with the rise of the mammals that went back into the ocean and become the large predatory whales. These were the largest whales that we've had in the oceans and these were the big predatory organisms. So, again, you need to take pause if some of these, if the mammals that evolved in the ocean as whales, if they hadn't now dropped some of their body size and not been quite as successful with some of their predatory nature. Basically humans would have been excluded from water sports, right? It would have been far too dangerous to go any place near the ocean, especially with some of these big guys that are snacking on Great Whites. And we consider Great Whites to be a pretty difficult. Now another type of organism that we all take for granted, but was really important in the Cenozoic, are pigs. The pigs you think of now are like the China Poland breeds, the pigs that have been breeded by humans for a long time, and the pigs are on the order of, they're large, right. They're 150, 175 kilos in size. And you have this vision of a pig in a barnyard, right? But really the pigs that we know of today evolved from large predatory pigs as we see in the reconstruction. And these were big snarling masses of aggression and saliva and teeth and they would roam around the terrestrial landscape, and not only kill things but then feed on a carrion that had been killed previously. So the whole idea of pigs is actually quite terrifying. And again, we as humans don't realize how good it is we evolved when we did, because that land-based carnivore setting, with all the large predatory sheep, and the giant snarling pigs, it would've been really hard for humans, to have done well in that type of environment. Another type of organism that we take for granted, because now in the modern day Earth, it's pretty small, and it's a sloth. And, these sloths, in the earlier part of the Cenozoic, again, before the onset of human evolution. These were gigantic organisms. They were two to three stories in size. They weighed tons, they were big organisms, and as you can see from some of these reconstructions, there's actually controversy over to what level they were only herbivores, plant eaters or perhaps they were switch hitters and they could be omnivorous and be both carnivores and herbivores. And so they had these large extremely sharp front claws, and they were knuckle walkers, but they could rise up and then feed off of the trees. But there's now new fossil evidence that suggest that they were also meat eaters. And whether that meant they were hunters and just fed on carrion and dead bodies that they found, is unknown at this time. The elephant template that we discussed briefly, the idea of the big elephants was really to have a set of tusks that came out from the lower part of the jaw, not the upper part of the jaw. So they were extremely different looking organisms, but relatively closely related, but one thing that's important is these things got up to four meters in size and they were 15 plus tons. These are much, much larger than even the largest land-based elephants that we think of in Africa in the modern day environment. So the Cenozoic was a time where big was truly beautiful. And we saw that diversification into these large body sizes, both in the terrestrial and the marine environment. Then as we moved into the onset of the ice ages, the forcing and controlling influence of having major ice sheets flux and wane through time and develop through time. And having sea level rise and fall in dramatic fashion as a response to formation and then melting of ice sheets, it really changed the structure of what the Cenozoic stage was being set for in terms body size of the mammals. And we saw as we moved into a colder Earth an overall reduction of body size through geological time. [MUSIC]
