“At some point,” he added, “they taught us to forget that.”

After 14 years, archaeologists have penetrated about 32 feet below what was the original ceiling. Along the way, they found thousands of recycled tools in the cave, including bone hammers and reworked flint stones. With aged, glossy surfaces broken by newer, rougher razor edges, the flint tools were part of a vast collection of knives apparently used for butchering, cleaning animal hides and cutting vegetable matter. Some of the blades are as sharp as a scalpel and as small as a thumbnail.

Recycling came naturally to these early humans, a habit largely neglected in modern-day Israel, where a current television public awareness campaign features children in superhero outfits pilfering plastic bottles from under their parents’ noses for recycling.

Amir Peretz, the minister of environmental protection until last month, was about to push through draft legislation to phase out the use of plastic bags at Israeli supermarkets. But he resigned, citing his opposition to the 2015 draft state budget and the lack of peace negotiations with the Palestinians, and his initiative was shelved.

At the cave site, there is evidence that prehistoric humans were not always so thrifty, but that the behavior evolved. Life in the region dates back at least 1.5 million years, but Professor Barkai said that a dramatic change had occurred here 400,000 years ago. He said that for some unknown reason the elephants that had served as a main food source apparently disappeared, prompting a change of menu and lifestyle for the inhabitants of Qesem Cave, near the town of Rosh Haayin.

In the quest for survival, Israeli archaeologists say, the cave dwellers here began hunting fallow deer instead of elephants. At the same time, they discovered the delights of a hot, home-cooked meal — and apparently invented the barbecue.