"Talgua Cave, known also as the ‘Cave of the Glowing Skulls’, is a cave located in the Olancho Valley, which is situated in Catacamas, a municipality in northeastern Honduras. The cave’s name may be said to be a misnomer, as the skulls do not actually glow on their own. Instead, the piles of human bones on the surface of the cave were coated over the centuries by a layer of calcium crystals. These crystals reflect light, thus giving the bones a glowing appearance." Source: Soren Dreier.
It's still unclear who was buried in the Talgua funerary site, which has been dated to around 1000 BC, according to Wikipedia. A large number of different ethnic groups lived in the region. "Two of the most likely candidates for the lineage of the people at Talgua are the Lenca people and the Pech People (Paya)..."