Researchers have unveiled two “hyperrealistic” reconstructions of adult sisters who lived and worked in a brutal mining community in what is now the Czech Republic more than 6,000 years ago.

The stunning, 3D reconstructions are based on a new analysis of the sisters’ remains, which were unearthed more than 15 years ago from a prehistoric chert mine in the South Moravian region. New evidence suggests the sisters worked in the mine, extracting heavy rocks for tools and weapons.

The burials still have a number of mysterious details that continue to puzzle scientists. For example, the sisters were buried with the remains of a small dog, whose skull archaeologists found near the top skeleton but whose other bones were unearthed near the bottom skeleton, according to the study. More perplexing still was the discovery of a newborn baby whose remains lay on the older sister’s chest but had no genetic relationship to either woman.