14 DAY TRIAL // When it comes to the foods they prefer, mammals today fall under three distinct categories – carnivores, herbivores and omnivores. In a new study, experts at the National Evolutionary Synthesis Center (NESC) in Durham, North Carolina, shed more light on how the latter evolved.
Big cats, including tigers and lions, are known for their exclusive, meat-based diets. At the other end of the spectrum, cows and deers eat only leaves, grass, fruits and bark. Humans are in the middle, eating everything from nuts, seeds and leaves to the meat of other animals.
What scientists found in their new study was that omnivores did not evolve to eat everything they came across from the start. Details of the investigation were published in this week's early online issue of the esteemed journal Proceedings of the National Academy of Sciences (PNAS).
This research is the first ever to look across all three mammal types, and investigate how their respective eating habits changed over time. Compiling a clear image of how this happened was not an easy task, but NESC scientists came through in the end.
The work was carried out using funds provided by the Division of Environmental Biology (DEB), at the US National Science Foundation (NSF). “The research links dietary strategy, a basic aspect of animal ecology, with macroevolutionary diversification of mammals,” DEB program director George Gilchrist says.
“It's impressive that ecology has such a strong and clear influence on lineages stretching back millions of years. Darwin would be delighted with this paper,” the NSF official goes on to explain. He adds that data on more than 1,500 species were coalesced for this research.
This information covered animals ranging from bats, rabbits and rodents to ungulates and primates. Using each species' family tree, the investigators were able to travel back in time, and determine what the common ancestors of these species most likely ate.
Most of these mammals maintained a relatively steady feeding strategy over the course of their evolution, but some of them exhibited significant changes. Animals including primates, bears, dogs and foxes showed the most significant changes.
University of California in Davis (UCD) scientist and paper co-author, Samantha Price, says that these mammals came from ancestors that ate either plants, or meat, but not both. This is why omnivores took the longest time to develop, of all three groups.
“If there was an evolutionary race to evolve 100 species, it would take three times longer for omnivores compared to herbivores, and carnivores would be in the middle,” Price explains.