Human culture developed slowly in northern Africa and the Middle East rather than bursting forth in Europe, suggest scientists, who have discovered what may be the oldest shell beads dating back 100,000 years.

Dr Francesco d'Errico of the National Centre for Scientific Research in Talence, France and colleagues report their findings in today's issue of the journal Science.

Until recently, researchers generally believed the first cultural signs emerged 40,000 years ago when modern humans appeared in Europe.

But d'Errico and colleagues say the new shell beads, from Israel and Algeria, were made for decorative purposes and show progress came much earlier in northern Africa and the Middle East.

"Modern humans in Africa developed behaviours that are considered modern quite early in time," says d'Errico.

"These people were probably not just biologically modern but also culturally and cognitively modern."

Jewellery and other forms of personal decoration were one of the most important early expressions of human culture, says study coauthor Dr Marian Vanhaeren of University College London.

Searching museum collections

The researchers say that, searching through museum collections, they found bead-like shells with holes in them from sites in Skhul, Israel and Oued Djebbana, Algeria.

These were similar to shell beads dating back 75,000 years found in a previous study by d'Errico and Vanhaeren in South African caves.

These South African shells are now firmly believed to be decorative beads, the study says.

To be certain, the researchers say they wanted to find beads from more than one site in the same region dating to the same period, to confirm that bead working was underway earlier than previously thought.

Samples of the shell beads: it is rare for natural Nassarius shells to have single holes in their centre, say the researchers (Image: Marian Vanhaeren and Francesco d'Errico)

"It's very important to establish the chronology of these modern types of behavior, and this paper constitutes we think a significant advancement," d'Errico says.

Dating the shells

Archaeologists excavated Skhul in the early 1930s using less meticulous methods than archaeologists use today, so the researchers had to do some additional work to determine exactly where the shells came from and how old they were.

One of the site's sediment layers contained a series of human skeletons, which recent dating efforts placed at 100,000 to 135,000 years old.

Coauthor Dr Sarah James, a researcher at the Natural History Museum, London, where the Skhul specimens are kept, analysed the crust of sediment stuck to one of the two shells and found that the shells came from the same sediment layer that the skeletons did.

The shells, Nassarius gibbosulus, are scavenging marine snails that live in shallow waters and are now only found in the central-eastern Mediterranean.

The relatively large size of the shells from Skhul and Oued Djebbana also seems to confirm their old age, since this species of snail was bigger 100,000 years ago than it is today, the researchers say.

Oued Djebbana was excavated in the late 1940s. Currently just a single radiocarbon date is available, indicating that the site is more than 35,000 years old.

Based on the technology and style of the stone tools found there, however, the site could be up to 90,000 years old, the researchers say.

The sample size is small, but the researchers argue that Skhul and Oued Djebbana are so far from the sea - 200 kilometres in case of Oued Djebbana - that the shells must have been intentionally brought there, most likely for beadworking.

By studying modern Nassarius shells from Mediterranean beaches, they also determined that shells with single holes in the centre are rare in nature and that Skhul and Djebbana inhabitants must have purposely perforated or deliberately picked out such shells, arguably for symbolic use.