Complex sentence: The site came to public attention when in 1960 a fossilized hominid skull was found in the cave, which had only accidentally been discovered a year earlier (1959) after erosion had left small openings in the rock.
Split into simpler sentences: The site came to public attention when in 1960 a fossilized hominid skull was found. The cave had only accidentally been discovered a year earlier (1959) after erosion had left small openings in the rock.