Shells with holes in center excavated from sites in Israel and Algeria may be the oldest known evidence of personal decoration, an international research team reported on Thursday.

The findings, appearing in the June 23 edition of the journal Science, indicate that the shells are 100,000 year-old beads, supporting the idea that modern human culture emerged gradually in Africa and the Middle East instead of bursting forth later in Europe.

Until recently, researchers generally believed that the first signs of modern human culture appeared 40,000 years ago when modern humans arrived in Europe.

Jewelry probably conveyed many aspects of people's social and cultural identities, and most archaeologists agree that personal decoration was one of the most important expressions of modern human culture, according to the researchers from France, Britain, and Israel.

In year 2004, the same group reported the discovery of perforated shells from the Blombos cave in South Africa. These beads were dated to about 75,000 years ago.

In this study, they found bead-like shells from the sites of Skhul in Israel, and Oued Djebbana in Algeria. The shells were the same genus as those found at Blombos and were perforated in a similar way.

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

The sample size is small, but relatively larger than today's shells. It seems to confirm their old age, since the species was bigger 100,000 years ago than it is today, the researchers said.

And the two sites, possibly up to 90,000 years old, are so far from the sea that the shells must have been intentionally brought there by ancient humans, most likely for beadworking.

Studying modern Nassarius shells from Mediterranean beaches, the researchers also determined that shells with single holes in the center are rare in nature.

Therefore, ancient humans must have purposely perforated or deliberately picked out such shells for possible symbolic use, the researchers concluded.