Question

marked by hostility or aggression
existing since the beginning of time
happening so much it seems endless
extremely hungry
done in a calculating and often deceptive way
characteristics passed from one generation to the next
perpetual
cunningly
belligerent
heredity
ravenous
primordial

Explanation:

• "marked by hostility or aggression" matches "belligerent" (belligerent means hostile/aggressive).
• "existing since the beginning of time" matches "primordial" (primordial means existing from the start).
• "happening so much it seems endless" matches "perpetual" (perpetual means continuous/endless).
• "extremely hungry" matches "ravenous" (ravenous means very hungry).
• "done in a calculating and often deceptive way" matches "cunningly" (cunningly implies calculating/deceptive actions).
• "characteristics passed from one generation to the next" matches "heredity" (heredity is about inherited traits).

Answer:

• marked by hostility or aggression: belligerent
• existing since the beginning of time: primordial
• happening so much it seems endless: perpetual
• extremely hungry: ravenous
• done in a calculating and often deceptive way: cunningly
• characteristics passed from one generation to the next: heredity