roebroeks and palmer need to heat the bark to 400 degrees centigrade.ny less and it won't produce pitch. any more and it will simply burn. after eight hours, any pitch should have condensed on the stone within the skull. yeah. oh, look at that. yeah, that's a bit dry. narrator: today, roebroeks and palmer manage to extract only a tiny smear of pitch. that's not much. narrator: they are on the right track, but it isn't nearly enough to glue a spearhead to a shaft as the neanderthals did. it seems this experiment is on too small a scale to produce enough pitch. neanderthals must have figured out how to scale up the technique in a way we haven't yet reproduced. however they managed it, the neanderthals had evidently mastered a complex thermal process. the neanderthals' extraction of pitch and their distinctive toolmaking suggest their technology was more advanced than previously thought. what's more, artifacts like these have been found across a wide area of europe. and this raises a question. how did neanderthals communicate these complex ideas? could it