Using wear patterns on teeth to infer diet is a common palaeontological technique and has allowed scientists to find out all sorts of cool things about what ancient animals ate and how they lived. In this study they've used teeth to show that cougars (which survived the widespread extinction of the last ice age) had a more varied diet than many of their contemporaries that became extinct, such as saber-toothed cats.
The suggestion that varied diet increases survival potential is not a new one. Many of the creatures that have survived through repeated mass extinctions are slimy things like fungi and molluscs that will ingest anything they come across.
Being happy to eat bones would definitely have helped cougars avoid going hungry. However, this study from a couple of years ago (by the same lead author) http://www.sciencedaily.com/releases/2012/12/121226222838.htm suggests that saber-tooths and mammoths were doing pretty well food-wise themselves. The new paper offers one explanation for the cougars survival, but there was probably a combination of many factors that led to the extinction of other large mammal species around at the time.
Among the La Brea cougars, the researchers found significantly greater variation between individuals than they did in the other large cats, including saber-toothed cats.