Red Queen Drives Groups of Mammals to Extinction: Evolve or Die

Species are rapidly declining across the globe. In fact, many researchers believe that we may be in the midst of a mass extinction event. Now, new research shows that we shouldn't be so concerned about individual species. Instead, we should be worried about animal groups, such as frogs or "big cats" ceasing to exist. A study reveals that a lack of new, emerging species can contribute to extinction.

This type of extinction doesn't occur over decades, like the changes Earth is experiencing due to human activities. Instead, it occurs over millions of years. This particular evolutionary theory is called the Red Queen hypothesis, named after Lewis Carroll's character who, in the book "Through the Looking Glass," described her country as a place where "it takes all the running you can do to keep in the same place." This "running" can be seen in biology, where the only option is to evolve or risk extinction.

In order to test this particular theory, the researchers examined 19 groups of mammals that are either extinct or are in decline from a past peak in diversity, such as horses, elephants and rhinos. Each of the groups was richly represented in the fossil record and had their origins sometime in the last 66 million years, during the Cenozoic Era.

So what did they find? The scientists discovered that while the specific cause of declining originations and rising extinctions for these groups is unclear, the mammals' deaths weren't just dumb luck. The animal groups were initially driven to higher diversity until they reached the carrying capacity of their environment. Then, their environment deteriorated and eventually led to their extinction.

"Each group has either lost, or is losing, to an increasingly difficult environment," said Charles Marshall, director of the UC Berkeley Museum of Paleontology and one of the researchers, in a news release. "These groups' demise was at least in part due to loss to the Red Queen-that is, failure to keep pace with a deteriorating environment."

The findings could reveal a little bit more about evolution and could allow researchers to better investigate the process of massive change over millions of years. It could also reveal a bit more about our own past, and explain past die-offs.

The findings are published in the journal Science.