Complex sentence: Mary and Louis spent the years 1935 to 1959 at Olduvai Gorge in the Serengeti plains of northern Tanzania; the site famously yielded many stone tools, from primitive stone-chopping instruments to multi-purpose hand axes.
Split into simpler sentences: Mary and Louis spent the years 1935 to 1959 at Olduvai Gorge in the Serengeti plains of northern Tanzania. The site famously yielded many stone tools, from Oldowan choppers to multi-purpose hand axes.