The 43 escaped rhesus monkeys a medical laboratory in South Carolina are among the most studied animals in the world this week. And for more than a century, they have held a mirror up to humanity, revealing our strengths and weaknesses through their own clever behavior, organ systems and genetic code.

The primates with bare faces and expressive eyes were launched into space on rockets. Their genome has been mapped. They have even been stars on a reality TV show.

Animal rights groups point out that the species has been subject to investigations into vaccines, organ transplants and the impact of separating babies from mothers. At the same time, many in the scientific community will tell you how important their research is to the fight against AIDS, polio and COVID-19.

In 2003, a national shortage of rhesus monkeys threatened to delay studies, and scientists paid up to $10,000 per animal to continue their work.

“Every major research university in the United States probably has a number of rhesus macaques hidden somewhere in the basement of its medical school,” according to the 2007 book, “Macachiavellian Intelligence: How Rhesus Macaques and Humans Have Conquered the World.”

“The U.S. military and NASA also have rhesus monkeys,” wrote the book’s author, Dario Maestripieri, a behavioral scientist at the University of Chicago, “and for years they trained them to play computer video games to see if the monkeys could learn to fly launching planes and missiles.”

The research begins in the 1890s

People have used the rhesus monkey for scientific research since the late 19th century, when the theory of evolution became more accepted, according to a 2022 research article from the journal eLife.

The first study on the species was published in 1893 and described the “anatomy of advanced pregnancy,” according to the eLife article. In 1925, the Carnegie Science Institute had established a breeding population of monkeys to study embryology and fertility in a species similar to humans.

One reason for the animal’s popularity was its abundance. These monkeys have the largest natural range of any non-human primate, stretching from Afghanistan and India to Vietnam and China.

“The other reason is that rhesus monkeys, as primates do, are a pretty hardy species,” said Eve Cooper, lead author of the eLife research paper and a biology professor at the University of Colorado-Boulder. “They can live in conditions and they can be bred in conditions that are relatively easy to maintain.”

NASA rockets and the Salk polio vaccine

In the 1950s, monkey kidneys were used to make the Salk polio vaccine. NASA also used the animals during the space race, according to a brief history of animals in space on the agency’s website.

For example, a rhesus monkey named “Miss Sam” was launched in 1960 in a Mercury capsule that reached a speed of 1,800 mph (1,900 km per hour) and an altitude of 9 miles (14.5 kilometers). She was picked up in generally good condition.

“She was also returned to her training colony until her death at an unknown date,” NASA wrote.

Mapping the human genome

In 2007, scientists unraveled the DNA of the rhesus monkey. The species shared about 93% of its DNA with humans, although macaques split from the monkey family about 25 million years ago.

By comparison, humans and chimpanzees have evolved separately since splitting from a common ancestor about 6 million years ago, but still share nearly 99% of their gene sequences.

The mapping of the human genome in 2001 led to an explosion of work to similarly decipher the DNA of other animals. The rhesus monkey was the third primate genome to be completed.

‘They are very political’

For those who have studied the behavior of rhesus monkeys, the research is just as interesting.

“They share some striking similarities with ourselves in terms of their social intelligence,” says Maestripieri, a professor at the University of Chicago who wrote a book about the species.

For example, the animals are very family-oriented and side with relatives when fights break out, he told the Associated Press on Friday. But they also recruit allies when they are attacked.

“They are very political,” Maestripieri said. “Most of their daily lives are spent building political alliances with each other. Does that sound familiar?”

Maestripieri was a consultant for a reality show about some rhesus monkeys in India called ‘Monkey Thieves’.

“They actually started tracking large groups of these rhesus monkeys and naming them,” the professor said. “It was beautifully done because these monkeys sometimes behave like humans. So it’s fascinating to follow their stories.”