Complex sentence: The majority of the skeletal fragments were found in canyons under fine silt and sand and date from 7,000 to 12,000 years old, with some specimens found to be even older.
Split into simpler sentences: The majority of the skeletal fragments were found in canyons under fine silt and sand. They date from 7,000 to 12,000 years old, with some specimens found to be even older.