A new comprehensive study of ancient ant fossils suggests the triumphant insect has been socializing and sparring with enemies for at least 100 million years.

The study, published in the journal Current Biology, is based on two main amber fossils -- one which trapped two fighting ants and another that captured 21 ants working in unison.

Scientists say the first is proof that ants have been warring since at least the Cretaceous period, 99 million years ago.

"That's a trait of ants," Phillip Barden, a fossil expert and research scientists at Rutgers University, said in a press release. "Many ant species do that all the time. They're always warring with either other individuals of the same species from different colonies or with different species."

Both intra- and inter-species competition for resources is common in the insect world -- as it is in the animal world. But many scientists say the greatest evolutionary asset of the ant is its tendency toward socialization and cooperation.

An ancient piece of amber trapping a dense group of worker ants is proof their teamwork began early.

"We have one piece of amber with as many as 21 worker ants trapped, and that's significant because at this time period, ants are very rare to find in fossils," Barden said. "They make up less than 1 percent of all insects in amber," he said. "So to find 20 in one piece is highly suggestive of social behavior."

There are at least 13,000 ant species living today, maybe more. Scientists believe some of them are directly related to the species of the Cretaceous period. But though they're certainly an evolutionary success story, some ancient traits haven't survived.

"They actually had these mammoth, tusk-like jaws that we think were used to impale prey," Barden said. "There's nothing like that alive today, especially not in the ant world."

The ants trapped in the newly analyzed amber wouldn't be recognized by their peers today, but no one knows exactly why they disappeared.

"It seems like they probably went extinct sometime in the 10 million years or so before or after dinosaurs went out," he said. "It could have been climate. We also think it's possible that the modern lineages actually out-competed these early ants."