The riddle of Amelia Earhart's disappearance has only grown more complex in the 73 years since the first woman to fly solo across the Atlantic went missing attempting to fly around the equator.

One theory had it that she crashed into the sea after running out of fuel during her expedition over the Pacific Ocean. Others claimed that Earhart was executed by the Japanese for spying, was pressed into making propaganda broadcasts from Tokyo during the war, or that she secretly returned to the US under an assumed identity.

But now an array of artefacts from the 1930s and bones found on the uninhabited Pacific atoll of Nikumaroro suggest that Earhart and her navigator, Fred Noonan, endured lingering deaths as castaways on a desert island and were eventually eaten by crabs.

Researchers from The International Group for Historic Aircraft Recovery (Tighar) found what appears to be a phalanx from a finger and two other bones, one of them from the neck, alongside a host of other clues after two decades and 10 expeditions attempting to solve the mystery.

The suspected finger is being tested for human DNA. It may turn out to be from a turtle – which have similar bones in their flippers.

But the other discoveries lend credence to the theory that Earhart died on the atoll after going missing en route to Howland Island in July 1937 at the age of 41 – she was declared legally dead 18 months later.

They include part of a mirror from a woman's compact, a zip from a Pennsylvania factory and travel-sized bottles made in New Jersey as well as a pocket knife listed on her aircraft's inventory, all manufactured in the 1930s.

Alongside the goods are the remains of small fires with bird and fish bones, and empty oyster shells laid out in a row as if to collect water, suggesting someone was trying to survive on the island.

Three years after Earhart disappeared British colonial authorities, who then administered Nikumaroro, found 13 bones from a human skeleton at the site of the latest discoveries. The bones were later assessed to be "more likely female than male" and "more likely white than Polynesian or other Pacific Islander". Those bones have since been lost.

Ric Gillespie, the executive director of Tighar, said the combined evidence points to Earhart dying on Nikumaroro.

"The bottom line is we have this archaeological site on this island where so much other evidence points to the Earhart flight having ended up. We know there was this castaway found there who appears to have been an American woman of the 1930s and there's only one of those missing out there," he said.

Gillespie said that the condition of some of the discoveries added to the evidence that there were people attempting to survive on the island.

"We could see that the knife had been beaten apart with a blunt object … apparently in order to remove the blades. We can only speculate but if you're a castaway and you need to make a spear to catch fish, maybe the blades are more useful that way than still attached to the knife," he said.

Gillespie said a member of Earhart's family had provided a DNA sample for testing if the suspected finger bone turned out to be human.

But he added that the family would prefer a different ending to the Amelia Earhart story.

"A crash at sea, that's nice and clean and a quick ending. Ending up as a castaway on a waterless atoll, and struggling to survive for a time and failing and ultimately being eaten by crabs is not nearly as pretty. They're hoping that we're wrong and I can't blame them for that," said Gillespie.