From Newsgroup: sci.anthropology.paleo


https://phys.org/news/2025-09-blue-indigo-year-tools-paleolithic.html

An international research team coordinated by Ca'
Foscari University of Venice has identified the
presence of indigotinrCoa blue dye compoundrCoon stone
pebbles dating back to the Upper Paleolithic. This
molecule, derived from the leaves of Isatis
tinctoria L., a biennial plant in the Brassicaceae
family native to the Caucasus and commonly known as
woad, was found on ground stone tools.

This is the first time indigotinrCoa blue secondary
compound, also known as indigorCohas been identified
on such ancient artifacts. The molecule forms
through a reaction between atmospheric oxygen and
the natural glycoside precursors in Isatis
tinctoria L. leaves, released from the cellular
vacuoles. This proves that the plant, despite not
being edible, was intentionally processed as early
as 34,000 years ago.
...


https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0321262 Direct evidence for processing Isatis tinctoria L.,
a non-nutritional plant, 32rCo34,000 years ago


Abstract

Recovering evidence for the intentional use of
plants in the Palaeolithic is challenging due to
their perishable nature as, unlike chipped stone
or bone artefacts, plant remains are rarely
preserved. This has created a paradigm for the
Palaeolithic in which plants seldom feature,
resulting in a partial and skewed perspective; in
fact, plants were as essential to human life then
as they are today. Here, we combine morphological
and spectroscopic analyses (-|-Raman, -|-FTIR) to
provide robust multiscale physical and
biomolecular evidence for the deliberate pounding
and grinding of Isatis tinctoria L. leaves 34rCo32,000
years ago. The leaf epidermis fragments were found
entrapped in the topography of the used surface of
unmodified pebbles, in association with use-wear
traces. Although their bitter taste renders them
essentially inedible, the leaves have
well-recognised medicinal properties and contain
indigotin precursors, the chromophore responsible
for the blue colour of woad, a plant-based dye that
is insoluble in water. We used a stringent approach
to contamination control and biomolecular analysis
to provide evidence for a new perspective on human
behaviour, and the applied technical and ecological
knowledge that is likely to have prevailed in the
Upper Palaeolithic. Whether this plant was used as
a colourant, as medicine, or indeed for both remains
unknown, but offers a new perspective on the
fascinating possibilities of non-edible plant use.


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