Final answer:
Human dentition includes four ancestral types of teeth: incisors, canines, premolars, and molars, each adapted for specific dietary functions such as biting, tearing, mashing, and crushing food.
Step-by-step explanation:
The four types of teeth considered an ancestral trait in human dentition are incisors, canines, premolars (also known as bicuspids), and molars. These teeth have evolved to accommodate different kinds of foods and have different functions. The incisors are sharp for biting into food. The canines are pointed and are superb for piercing and tearing tough or fleshy foods. Premolars have a flatter shape with two rounded cusps that are useful for mashing foods. Lastly, the molars, which are the largest, have several pointed cusps that are used to crush food, making it ready for swallowing. These four types of teeth allow mammals to process a wide range of foods, thereby aiding in efficient digestion.