Barring climate change, antibiotic-resistant “superbugs” may be the biggest problem humankind is likely to face in the coming decades.

According to a recent British government-commissioned review, Antimicrobial Resistance, which already kills roughly 700,000 people every year, may by 2050, lead to a staggering 10 million deaths annually.

In this backdrop, any insight would be invaluable into the origin and evolution of antibiotic resistance in bacteria that can help scientists develop a new class of antibiotics and disinfectants.

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Scientists studying the enterococcus family of bacteria — one of the main categories of modern-day superbugs — have now unearthed something surprising. It turns out antibiotic-resistant enterococci have been around for a long, long time — since much before dinosaurs first walked on the face of Earth.

In a study published Thursday in the journal Cell, the researchers shed light on the evolutionary history of these pathogens, which are fast developing resistance to even the so-called last-resort antibiotics, due to their high consumption among humans.

“By analyzing the genomes and behaviors of today’s enterococci, we were able to rewind the clock back to their earliest existence and piece together a picture of how these organisms were shaped into what they are today,” Ashlee M. Earl, group leader for the bacterial genomics group at the Broad Institute of Massachusetts Institute of Technology and Harvard University, said in a statement released Thursday.

“Understanding how the environment in which microbes live leads to new properties could help us to predict how microbes will adapt to the use of antibiotics, antimicrobial hand soaps, disinfectants and other products intended to control their spread.”

The study pegs the origin of these bacteria to around the time of “animal terrestrialization” — a period, roughly 450 million years ago, when life made its first foray into land.

As animals crawled out of the water, they took their gut bacteria, including enterococci, with them. While most intestinal microbes died when exposed to the harsh terrestrial environments, many enterococci survived, and over time developed resistance to dryness, starvation and natural disinfectants.

This is the adaptation that allowed these bacteria to not only survive outside the wet and nourishing environs of their hosts’ guts, but also modern, human-made antibiotics and disinfectants in hospitals.

“We now know what genes were gained by enterococci hundreds of millions of years ago, when they became resistant to drying out, and to disinfectants and antibiotics that attack their cell walls,” study leader Michael S. Gilmore, a senior scientist at Massachusetts Eye and Ear Infirmary and director of the Harvard Infectious Disease Institute, said in the statement.

“These are now targets for our research to design new types of antibiotics and disinfectants that specifically eliminate enterococci, to remove them as threats to hospitalized patients.”