Excavators took a chunk of sediment from the Qesem Cave's 300,000-year-old hearth and cut it into thin slices to examine under a microscope.
These sites represent some of the earliest definitive proof of fires deliberately maintained and used for cooking, although nearly 800,000-year-old hearths are reported from a site in Israel.
The oldest hearths, which were used 13,200 years ago, showed no signs of fish, just waterfowl and mammals.
Salmon bones had already been recovered from the 11,500-year-old hearths, but not the 11,800-year-old one, making this analysis the earliest evidence of salmon consumption in the Americas.
Options which were evaluated during the study included; (i) rehabilitation of the existing eight-year old multiple hearth unit; (ii) addition of a new multiple hearth; (iii) addition of a new fluid bed system; (iv) drying, composting, or land application.
And though rooms at Sextantio feature Philippe Starck-designed sinks and modern beds, there's usually a fire going in the old stone hearth of the small breakfast room whose ceiling is black from centuries of cooking fires.
The house's spacious main kitchen is in the walk-out basement, a common feature of that period; it has a flagstone floor, a pantry, and a cream-colored Aga stove set into the old cooking hearth.
Since the fluid bed system became operational, the old multiple hearth system has been maintained on standby as a backup, but its use has not been required.
Also still in the house are the sleek Art Moderne fireplaces she created to cover up the old stone hearths.
The discovery, experts say, helps explain the transition from the oldest known hearths, made of stone, to clay structures like the ones at Dolni Vestonice in the Czech Republic.
