The article covers this:

> Researchers have found remnants of cannabis at ancient sites in Central Asia before, but the latest discovery points to the intentional use of plants with high levels of the active compound, THC, and to cannabis being inhaled rather than ingested.

and later:

> “To our excitement we identified the biomarkers of cannabis, notably chemicals related to the psychoactive properties of the plant,” said Yimin Yang at the University of Chinese Academy of Sciences in Beijing. Specifically, the scientists found cannabinol, a substance produced when THC is oxidised. Given the lack of other cannabis breakdown products, the scientists believe the plants were selected to be high in THC, but whether they were cultivated or found in the wild is unclear.

The best stuff [0] is still obtained by simply rubbing flowers between the hands until enough resin accumulates, it wouldn't surprise me if they had already figured that one out.

[0] https://en.wikipedia.org/wiki/Charas

We have much better extraction methods these days using solvents.

More efficient maybe, which isn't really top priority from a user perspective. Personally, I prefer my smoke without a touch of solvents.

Bubble Hash (mixing with ice and filtering frozen resin) is a natural alternative that comes close, but the processing still lowers the quality.

The solvents are evaporated off if you process your hash correctly.

And with solvents like CO2 that evict the chamber without any intervention under STP, it is actually even more certain that the solvents leave.

While I don't share the GP's taste for charas, 'better' is relative. Many people do not care for this industrial approach to something they regard as quasi-sacred, in the same way that many people are turned off by overly processed food.

Probably residues from high potency parts like flowers.

Most likely higher then a wild plant, potentially implying cultivation.

Or simply processing many plants into hash such has been done for millenia in various cultures around the world.