Complex sentence: Prior mortuary activity had either taken a less obvious form or contemporaries retained some of their burial knowledge in the absence of such activity; dozens of men, women, and children were being buried in the same caves which were used for burials 10,000 years beforehand.
Split into simpler sentences: Prior mortuary activity had either taken a less obvious form or contemporaries retained some of their burial knowledge in the absence of such activity. Dozens of men, women, and children were being buried in the same caves which were used for burials 10,000 years beforehand.