PREHISTORIC Europeans were spicing up their food with garlic mustard more than 6,000 years ago, according to new research into the surprising complexity of Stone Age cuisine.
Detailed microscopic analysis of residues found on fragments of Stone Age pottery is revealing how Mesolithic people used herbs and spices to give extra flavour to meat-based broths.
One plant - garlic mustard (Alliaria petiolata) - has been identified so far, and as the research proceeds scientists hope to identify other spices and herbs used for prehistoric flavouring.
The new evidence challenges the view that plants were exploited by ancient hunter-gatherers "solely for energy requirement rather than taste", said Dr Hayley Saul of the University of York, a lead researcher on the project.
Not only were Mesolithic cooks developing more complex meals prepared for taste as well as nourishment, they were also catering for relatively large family groups - feeding up to 15 people at a time and cooking with large clay pots.
The new evidence comes from an archaeological site called Stenø on the island of Zealand in Denmark.
However, the discovery almost certainly has implications for understanding early cuisine throughout Europe and beyond.
It is believed, but not yet proven, that Mesolithic cooks were also using caraway seeds, blue fenugreek and horseradish.
Certainly, Mesolithic-style cuisine survived into the succeeding Neolithic period and beyond - as similar traces of garlic mustard seeds being used to flavour both meat and fish broths have been found at Danish and German sites dating from some 350 years after the Mesolithic evidence.
The key evidence was provided by the "fossilised" remnants of mustard seed cells found within carbonised animal fat adhering to fragments of cooking pots.
Determining the type of plant cells relies on a trick of nature.
All plants absorb silica from the soil and, as a result, in some species, a silica "skin" forms around some of the cells - in the case of the garlic mustard seeds, just five microns across.
Although the cells themselves have long disappeared, the tell-tale silica skins - known as phytoliths - survive and therefore allow scientists to identify particular species of plant.
Dr Saul, of the BioArCH research centre at the University of York, said: "The traditional view is that early Neolithic and pre-Neolithic uses of plants were primarily driven by energy requirements rather than flavour. As garlic mustard has a strong flavour but little nutritional value, and the phytoliths are found in pots with terrestrial and marine animal residues, our findings are the first direct evidence for the spicing of food in European prehistoric cuisine.
"Our evidence suggests a much greater antiquity to the spicing of foods in this region than is evident from the macrofossil record, and challenges the view that plants were exploited by hunter-gatherers and early agriculturalists solely for energy requirements, rather than taste," Dr Saul added.
The new Stone Age spice evidence is being published in the open access on-line science journal PLOS ONE.