People living on the Israeli coast 120,000 years ago strung ocher-painted seashells on flax string, according to a recent study in which archaeologists examined microscopic traces of wear inside naturally occurring holes in the shells.

But 40,000 years later and 40km (25 miles) away, people at Qafzeh Cave seemed to prefer collecting clam shells with little holes near their tops.

The holes were natural damage from scraping along the seafloor, but people used them to string the shells together to make jewelry or decorations.

Tel-Aviv University archaeologist Daniella Bar-Yosef Mayer and her colleagues examined five shells from Qafzeh and found microscopic striations around the edges of the holes—marks that suggest the shells once hung on a string.

Wear marks around the holes suggest hanging on a string, and other wear marks on the edges of the shells suggest that the shells rubbed against each other, so they probably hung close together.

They even made strings of wild flax and hung shells—with natural holes—on them, then examined the resulting wear marks under a microscope?

The tiny marks left behind by a flax string rubbing against the edges of the hole looked just like the marks on the Qafzeh shells.

Even though the string itself didn’t survive, the wear marks on the shells reveal its presence.

According to Bar-Yosef Mayer and her colleagues, someone invented string.

This would allow you, for example, to make a rope that will tie together wooden logs to make a raft (or to tie a rigout to a canoe),” Bar-Yosef Mayer told Ars.

String also means people can make things like fishing nets, more complicated kinds of animal traps, and new kinds of clothing and bags.

But without looking for the same kinds of wear marks as the ones on the Qafzeh shells, it’s impossible to say whether the Cueva de los Aviones Neanderthals were using string or leather.

“It would be reasonable to assume that much like the Qafzeh shells, these were also strung in order to be displayed,” wrote Bar-Yosef Mayer and her colleagues.

So far, no one has examined those shells for traces of wear from string, however.