Lonesome George, the only remaining Pinta Island giant tortoise, has died on Sunday on the Galapagos Islands.

Fausto Llerena, Lonesome George’s caretaker, found the tortoise’s remains in the direction of his watering hole on Santa Cruz Island, reported the Galapagos National Park in Ecuador.

The cause of the tortoise’s death is unclear and an autopsy to find out the cause has been planned. Lonesome George has been kept in a cold chamber to prevent decomposition prior to the autopsy.

The tortoise was discovered in 1972, on Pinta Island and was assumed to be 100 years old. Till the creature was found, it was thought that giant tortoises of Lonesome George’s type, Geochelone nigra abingdoni, had been extinct.

The park, the shelter for the tortoise, has tried several times to breed Lonesome George, but failed. “The plight of Lonesome George provided a catalyst for an extraordinary effort by the government of Ecuador to restore not only tortoise populations throughout the archipelago but also improve the status of other endangered and threatened species,” the park reported.

It added, “Lonesome George’s legacy will be an increased effort in both research and management to restore his island of Pinta and all of the other giant tortoise populations of Galapagos,”

According to the park’s website, there are, 20,000 giant tortoises left in Galapagos Islands, situated about 1,000 kilometers (620 miles) off Ecuador’s coast. Charles Darwin visited Galapagos in 1835 and his research led to revolutionary theories about evolution.