Marean figured the early people, probably women, had to trudge two to three miles to where the mussels, clams and snails were harvested and to bring them back to the cave. Then they put them over hot rocks to cook. When the food was done, the shells popped open in a process similar to modern-day mussel-steaming, but without the pot.

Marean and colleagues tried out that ancient cooking technique in a kind of archaeological test kitchen.

''We've prepped them the same way,'' Marean said in telephone interview from South Africa. ''They're a little less moist (than modern steamed mussels). They definitely lose some moisture.''

Marean also found 57 pieces of ground-up rock that would have been reddish- or pinkish-brown. That would be used for self-decoration and sending social signals to other people, much the way makeup is used now, he said.

There have been reports of earlier but sporadic pigment use in Africa. The same goes with rocks that were fashioned into small pointy tools.

But having all three together shows a grouping of people that is almost modern, Marean said. Seafood harvesting, unlike other hunter-gatherer activities, encourages people to stay put, and that leads to more social interactions, he said.

Yet 110,000 years later, no such modern activity, except for seafood dining, could be found in that part of South Africa, said Alison Brooks, a George Washington University anthropology professor who was not associated with Marean's study. That shows that the dip into modern life was not built upon, said Brooks, who called Marean's work ''a fantastic find.''

Similar ''blips of rather precocious kinds of behaviors seem to be emerging at certain sites,'' said Kathy Schick, an Indiana University anthropologist and co-director of the Stone Age Institute. Schick and Brooks said Marean's work shows that anthropologists have to revise their previous belief in a steady ''human revolution'' about 40,000 to 70,000 years ago.