The first person to write about Sasquatch was J.W. Burns, who collected accounts from people in his community for a 1929 Maclean's magazine story, so he was writing down what other people told him. Some people say a big, hairy creature called Bigfoot lives in forests in the northwest of North America, and it is said to be covered in long, dark hair. John Green kept a database of 1,340 Sasquatch or Bigfoot sightings in North America, from the early 19th century to 1995. Yet no body or bones of Bigfoot have ever been found. Scientists who want to test such a creature need something they can hold in a laboratory, and one thing people have offered is hair.

The Oxford team said science should neither reject nor accept a claim without examining the evidence, so it ran a systematic survey of hair samples. A systematic survey is one that follows a plan. The team sent out a call for hairs on 14 May 2012 through the Museum of Zoology in Lausanne and the University of Oxford. A hair said to come from such a creature is a sample, and a sample is a small piece of something that can be studied.

The Oxford team tested hairs said to come from Bigfoot, the Yeti and similar creatures. Almost all came from known animals such as bears, horses, cows, raccoons and sheep, and bears fit with another finding. Researchers plotted Bigfoot sightings in a 2009 study and found they roughly matched the habitat of the American black bear, and some scientists think people who report Bigfoot may be seeing bears, which can stand up on two legs. Professor Sykes said that tests showing hairs came from known animals do not mean the next one won't be something new.

Other teams have tested hairs from the Himalayas. In 2017 a team led by Charlotte Lindqvist found that eight hairs said to be from the Yeti came from bears of the Himalayas. A ninth sample, a tooth, was from a dog. The Yeti is a creature that some people say lives in the mountains, in the same way that Bigfoot is said to live in North American forests. In this test, the samples that had been offered as traces of the Yeti turned out to belong to bears and a dog, and none of them belonged to an unknown creature.

Water can hold DNA as well. Animals and plants leave bits of DNA in the water around them, from shed cells and waste, and scientists can collect it and read it. Loch Ness is a very big lake in Scotland, about 23 miles long and about 800 feet deep, and some people believe a big animal lives there and call it Nessie. In 2018 scientists from New Zealand took more than 250 water samples from Loch Ness to find out what lives there. Scientists have also tested the water in Loch Ness and found lots of fish and eels.

The Loch Ness eDNA survey found about 3,000 different DNA sequences, mostly from tiny things such as roundworms, plankton and small crustaceans. A DNA sequence is a short stretch of the genetic code that can be matched to a kind of living thing. Eel DNA turned up in nearly every Loch Ness water sample, so there are a lot of eels there. Finding eel DNA in Loch Ness was not a surprise to the team, since eels were known to live there. So the eel result agreed with what people already knew about the loch.

Eel DNA does not tell how big the eels are, so the 2018 team could not rule out giant eels or say that they exist. The same survey found no plesiosaur DNA in Loch Ness. A plesiosaur was a sea reptile that died out about 65 million years ago, and some people thought Nessie might be one, and in the survey results there was no trace of such a reptile at all. No bones, bodies, feeding signs or droppings have been found that would support a monster in Loch Ness either.

The team's leader, Neil Gemmell, said he did not believe in the monster, but added: "wouldn't it be amazing if I was wrong?" Scientists and TV teams had also swept Loch Ness with sonar, which uses sound to find things under water. Searches in 1987 and 2003 found no monster. From 1958, four sonar expeditions at Loch Ness were launched, first by the BBC and then by Oxford, Cambridge and the University of Birmingham. Sonar finds things by sound, while DNA reads the traces that living things leave behind, so the two methods look for different signs.

Some animals that were once known only from stories have since been studied. The giant squid was once known only from sea-monster stories, but it is a living animal of the deep ocean. The first video of a live adult giant squid in the wild was shot in 2012 near Chichi Island, Japan, by a submersible that followed the animal about 900 meters down. A Natural History Museum giant squid, caught by accident in a trawler in 2004, was frozen right away, so DNA samples could be taken. In 2013 those samples helped show that giant squid are probably one species, though some scientists still argue about it.

Words to know

• systematic: planned and orderly
• sequences: stretches of code
• plesiosaur: old sea reptile
• trawler: fishing boat
• survey: wide, planned check