Chris Chesterfield got the fright of his life when he bent over to look at his underwater traps. The Cornish fisherman was expecting to pick out his usual catch of spider crabs or cuttlefish. Instead, he found himself wrestling with an octopus. "You've only got one or two arms pulling them up," he says, "and they've got eight pulling you down!"

The largest specimens are four feet long. "They just throw their tentacles over the top of you and turn inside out, literally. When they come out of the pot, they stick to the deck, stick to your legs - it's endless."

In a normal year, Chesterfield catches half a dozen octopuses. But on a single day last month, he hauled in around 150.

Other fishermen have had similar experiences. "I've been fishing for 40 years and I've never experienced this amount," says Cameron Henry, who has sometimes found two or three octopuses in the same pot. "You can imagine how fun it is to get them out," he says.

According to Matt Slater of the Cornwall Wildlife TrustA charity which organises volunteers to monitor sea life among other things., there have also been a huge number of sightings by divers and snorkellers.

Population booms among octopuses in Britain are incredibly rare. The last one was in 1948In 1948 octopuses were reported all along the south coast of England from Land's End to Sussex., and the one before that in 1899.

It is not clear why we may be seeing one now. Though a single female octopus can lay 50,000 eggs, normally only a few of them survive. But it could be that more are hatching thanks to good conditions - including a rise in sea temperatures because of climate change.  

Matt Slater is delighted: "They are such amazing, alien creatures - one of the most intelligent animals in our oceans - and to witness a population explosion in our local waters would be incredible."

Their intelligence was brought home to many by a remarkable film called My Octopus Teacher. It shows how a photographer called Craig Foster developed a friendship with an octopus he found while diving in an underwater kelpA large brown type of seaweed. It can grow as fast as half a metre per day. forest off South Africa's Western Cape.

In one extraordinary sequence, the octopus is hunted by a pyjama sharkA comparatively small shark which gets its name from its striped body., but escapes by making lightning-fast decisions about how to hide and camouflage herself.

As for octopuses being "alien" creatures, a team of researchers published a scientific paper four years ago suggesting that this was very close to the truth. The idea had already been suggested in a book called Other Minds by Peter Godfrey-Smith, who called cephalopods  "an island of mental complexity in the sea of invertebrateA cold-blooded animal with no backbone. Insects, spiders, worms and crabs are all invertebrates.  animals".

The researchers suggested that a meteor brought octopus eggs to Earth. Or it brought a virus which infected a population of primitive squid and caused them to evolve into octopuses. Their theory was based on the creatures' extraordinary attributes: large brains, sophisticated nervous systems, camera-like eyes, flexible bodies and ability to camouflage themselves.

These, the researchers wrote, "seem to be borrowed from a far distant 'future' in terms of terrestrial evolution, or more realistically from the cosmos at large".

Yes: They are such unusual creatures, and seem to have developed their extraordinary attributes so quickly, that they cannot have evolved in the same way as the rest of the natural world.  

No: There is absolutely no evidence that we owe their presence to a meteor.  Not one of the researchers who wrote the paper is a zoologist, which explains why they came up with such a crazy idea.

Or... It is possible that all life on earth ultimately comes from outer space. Almost all the elements that make our existence possible are found in the stars that make up the Milky Way.