Archaeologist: Neanderthals, a human-like species living 60, 000 years ago, probably preserved meat by smoking it. Burnt lichen and grass have been found in many Neanderthal fireplaces. A fire of lichen and grass produces a lot of smoke but does not produce nearly as much heat or light as a wood fire.
If true, the statement 'Some of the fireplaces containing burnt lichen are in regions in which lichen is not believed to have been plentiful and so would have had to have been brought in from some distance' would most weaken the archaeologist's argument.