Ants from nearly 100 million years ago, trapped forever in amber in modern-day Myanmar, were both social and prone to doing battle – just like modern ants.

That was the finding of a new study out of Rutgers University published in the journal Current Biology.

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The amber samples contain some of the earliest ants ever found, from 99 million years ago during the Cretaceous, of a lineage distinct from modern ants. They were revealing on several levels.

“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. They make up less than 1 percent of all insects in amber,” said the study’s lead author, Phillip Barden, in a release.

“So to find 20 in one piece is highly suggestive of social behavior,” the fossil insect expert and Rutgers-Newark postdoctoral fellow added. Social behavior in ants -- competing for survival as one large group of thousands to millions vs. as individual creatures -- is considered a possible reason for their longevity.

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Meanwhile, these weren’t especially pacifistic ants. One of the amber samples captures, literally, a battle between two brawlers, albeit one declared an eternal draw by Mother Nature.

“That’s a trait of ants,” Barden said. “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.”

Intriguingly, the ancient ants studied by Barden had a fighting feature not seen in modern ants: “mammoth, tusk-like jaws” that Barden posits were useful for stabbing their prey.

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One mystery remains, though: What happened to these ants? They went extinct, but for reasons yet unknown, even though it looks like they had the tools -- social structures and fighting skills -- to stand the test of time.

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