As humans, we have a couple of things going for us: we have hard skeletons and we’re relatively large. So we’re much more likely to make it than a jellyfish or a worm. There are things, however, you can do to increase your chances of success.
Taphonomy is the study of burial, decay and preservation – the entire process of what happens after an organism dies and eventually becomes a fossil. To answer the question of how to become a fossil, BBC Future spoke with some of the world’s top taphonomists.
1. Get buried, and quickly
“It’s really a question of maintaining a good condition of the body after death – long enough to be buried under sediment and then altered physically and chemically deep underground to become a fossil,” says Sue Beardmore, a taphonomist and collections assistant at the Oxford University Museum of Natural History.
“To be preserved for millions of years, you must also survive the first hours, days, seasons, decades, centuries, and thousands of years,” adds Susan Kidwell, a professor at the University of Chicago. “That is, you must survive the initial transition from the ‘taphonomically active zone’… to a zone of permanent burial, where your remains are unlikely to be exhumed.”
There are almost endless ways that fossilisation can fail. Many of these happen at, or down to 20-50cm below, the soil or seafloor surface. You don’t want your remains to be eaten and scattered by scavengers, for example, or exposed to the elements for too long. And you don’t want them to be bored into or shifted around by burrowing animals.
“The palaeoenvironments that we often see the best fossils come out of are lake and river systems,” says Caitlin Syme, a taphonomist at the University of Queensland in Brisbane, Australia. The important thing is the rate at which fresh sediments are burying things. She recommends rivers flowing from mountains which cause erosion and therefore carry a lot of sediment. Another option is a coastal delta or floodplain, where river sediment is rapidly dumped as the water heads out to sea.
Ideally, you also want an ‘anoxic’ environment: one very low in oxygen, where animals and microorganisms that would digest and disturb your remains can’t survive.
Kidwell recommends avoiding about 50cm below the seafloor, “the maximum burrowing depth of shrimp, crabs and worms that might irrigate the sediments with oxygenated water”, which would promote decomposition and stir up the body.
“You want to end up quickly after death in a spot that is relatively low elevation, so that it is a sink for sediment, and preferably with standing water – a pond, lake, estuary or ocean – so that anoxic conditions might develop,” she says.
Getty
Very generally, anything up to around 50,000 years old is what’s known as a ‘subfossil’. These are largely still made up of the original tissues of the organism. Extinct Pleistocene megafauna found in caves – such as giant ground sloths in South America, cave bears in Europe, and marsupial lions in Australia – are good examples.
However, if you want your remains to become a fossil that lasts for millions of years, then you really want minerals to seep through your bones and replace them with harder substances. This process, known as ‘permineralisation’, is what typically creates a fully-fledged fossil. It can take millions of years.
As a result, you might skip the coffin. Bones permineralise most rapidly when mineral-rich water can flow through them, imbuing them with things like iron and calcium. A coffin might keep the skeleton nicely together, but it would interfere with this process.
There is a way a coffin might work, though. Mike Archer, a palaeontologist at the University of New South Wales, suggests burial in a concrete coffin filled with sand and with hundreds of 5mm holes drilled into the sides. This then needs to be buried deep enough that groundwater can pass through.
“If you want to be a classic bony fossil, a bit like something from Dinosaur Provincial Park in Canada, then something like a [coarse] river sand would be pretty good,” says Syme. “All the soft tissues would be destroyed and you’d be left with this beautifully articulated skeleton.”
We’ve covered the standard method for hard, durable fossils with bone largely replaced by rock. But there are some oddball methods to consider, too.
Top of the list is amber. There are astounding fossils perfectly preserved in this gemstone made of tree resin – such as recent finds of birds, lizards and even a feathered dinosaur tail in Myanmar. “If you can find a large enough amount of tree sap and get covered in amber, that’s going to be the best way to preserve your soft tissues as well as your bones,” Syme says. “But it’s obviously pretty difficult for such a large animal.”
Can’t find enough amber? The next option is tar pits of the kind that have preserved sabre-toothed cats and mammoths at La Brea in Los Angeles. Although here you would mostly likely end up disarticulated, your bones jumbled in with other animals. There’s also freezing on a mountain or in a glacier, like Ötzi the iceman, found in the European Alps in 1991.
Alamy
Another route might be natural mummification, with your body left to dry in a cave system. “There are a lot of cave system remains that get covered with calcium from groundwater, which also forms stalactites and stalagmites,” Syme says. “People like caving and so if the cave systems still exist in the future, they might happen upon you.”