Possible Clues:

• Oil-rich crop
• Oil producer in plant entertaining our relatives
• Yellow oil-rich crop
• Type of oil
• This could produce oil from river and deep sea, possibly
• Man's close kin digging into tall grass for source of oil
• Oil-producing plant primates found in tall grass
• Source of cooking oil
• Part of plant yielding oil
• Grass hiding wild animals is potential source of oil