Final answer:
Eating softer foods as a result of cooking and the need for more energy from a larger brain are hypotheses that explain why hominin dentition has reduced in size over time.
Step-by-step explanation:
The hypothesis that explains why hominin dentition has reduced in size through time includes the idea that the eating of softer foods as a result of cooking meat and plants alleviated the need for large chewing teeth and jaws. Over time, teeth became smaller, which resulted in thicker enamel. Another hypothesis suggests that maintaining a brain is metabolically expensive, so the digestive system became smaller and more suited for nutrient-dense food such as meat. These hypotheses are supported by evidence of increased use of fire and eating cooked meat at H. erectus sites.