How did mammoths grow up? It's a simple question, but one that has been difficult to answer. Much of what paleontologists know about the great Ice Age beasts come from teeth, bones, and comparisons to living elephants, but our knowledge of their early lives has been restricted by a lack of well-preserved mammoth calves. Now that has changed.
As presented last week at the 71st annual Society of Vertebrate Paleontology meeting in Las Vegas, Nevada, paleontologists have now been able to peer inside a pair of little mammoths and search for clues about how mammoths got their start in life. We've got detailed scans — plus some high-res 3-D animations showing every detail of the mammoths' anatomy.
One of the little mammoths – Lyuba – has already been the star of her own National Geographic special and is still on tour among museums in the United States. But the second calf – named Khroma – is just making her debut. Both of the exquisite specimens were CT-scanned so that researchers could examine their guts without picking the mammoths apart, and preliminary findings about the pair were presented at the conference by graduate student Ethan Shirley and paleontologist Daniel Fisher from the University of Michigan.
The world of the two baby mammoths was slightly different from our own. During their time the great expanses of Siberia were carpeted by a cold, dry grassland flecked with shrubs called the "mammoth steppe." Both mammoth calves died at about the same time in their lives. According to Fisher, the two were within days to weeks of being the same age. Daily lines of growth on their little teeth – called neonatal lines – confirm this. And Khroma, like Lyuba, seems to be female based upon CT scans of urogenital tract. But that is nearly all the two mammoths share in common.
So far, more is known about Lyuba. Previous studies identified her as a little woolly mammoth who died approximately 42,000 years ago. But no one yet knows the geologic age of Khroma. A carbon dating test on Khroma returned an infinite result – an indication that she probably died before 100,000 years ago and is therefore beyond the range of carbon dating. Further tests to ascertain how long ago she trod across prehistoric Siberia are planned.
Exactly what species of mammoth Khroma belonged to is also a mystery. In addition to shorter legs, Khroma also has a wider, more robust skull and what Shirley and Fisher are calling a "moustache" of little bumps created by small bits of bone around her tiny tusks. At first they thought these traits meant Khroma is a male and that sexual differences showed up at an early age in woolly mammoths, but this doesn't appear to be the case. Either the differences are part of the natural variation in woolly mammoths, Shirley and Fisher propose, or Khroma may be a different species.
Lyuba and Khroma are also opposites in terms of their preservation. Less flesh hangs off the bones of Khroma, but the remaining soft tissues are actually better preserved. Shirley and Fisher suspect this is because Khroma was quickly frozen and covered up soon after she died. Lyuba, on the other hand, has a greater quantity of more poorly-preserved flesh. Fisher proposes this is because Lyuba was "pickled" by bacteria during a period which she laid out before final preservation. The pickling process not only preserved Lyuba's flesh, but she may have been so rank during this phase that no scavenger wanted to take a bite.
The two baby mammoths were not the first of their kind to be discovered. Nor are they likely to be the last. In the Russian high Arctic, Fisher explained, mammoth tusks can be a substantial boon to poverty-stricken people who send those fossils into Japan and China's hungry ivory markets. (At this time, the trade in fossil ivory from Russia is legal.) Rare specimens with intact soft-tissues – such as Lyuba, Khroma, and Dima before them – are often found as a result of the tusk hunts. Researchers just have to hope they can get to them before they disappear into the marketplace.
Check out some more videos, and scan images, in our gallery.