Phytoliths and the "First Use of Spices in European Cuisine"

The headlines seem so positive:

Archaeologists Uncover First Use of Spices in European Cuisine

and

Prehistoric Europeans Spiced Up Their Food

But allow me to protest that this research shows nothing of the kind. English paleobotanist Hayley Saul and her colleagues have been looking for phytoliths in samples of charred food from Neolithic Europe:

In their latest research, Saul and her colleagues looked at small samples of charred material scraped from the inner surfaces of pottery fragments from two sites in Denmark and one site nearby in northern Germany. Of 74 samples, 26 included phytoliths with a globular shape and a distinctively wrinkled surface, Saul says. Their average size was about 7 micrometers across, less than half the diameter of the finest human hair. When the researchers compared the phytoliths from the residue with those produced in the stems, leaves, and seeds of more than 120 European and Asian plants, the only ones that matched were those made in the seeds of garlic mustard (Alliaria petiolata), a biennial herb that grows in a swath from Europe through Central Asia to northern India and western China.

Garlic mustard has no special nutritional value, but its seeds do spice things up. Presto, Neolithic people spiced their food.

Spot the problem? The database of plants with well understood phytoliths that these researchers worked with only includes 120 species. Out of the, what, 120,00 species of plants that grow in Eurasia? How can they possibly conclude anything from that? How do they know that there aren't a thousand other species that produce phytoliths closely resembling those of garlic mustard? They don't. Science quotes some other phytolith experts as concurring that the ones Saul found seem distinctive, but then they have not seen phytoliths from most of the plants in Eurasia, either.

I actually know something about phytoliths, because I spent years trying to use them understand what plants prehistoric American Indians were using in their camp sites by the edge of tidal wetlands. We had a couple of large studies done, and they produced no results; none of the candidate species (goldenclub, arrow arum, pickerel week, cattails, wild rice) produce phytoliths than can be reliably distinguished from the others. Phytoliths are just another one of those archaeological techniques that seem very promising but in practice have never proved anything to my satisfaction.

So maybe Saul is right, but it will take a whole lot more basic work in phytoliths before we know.