Final answer:
The hominin diet shifted from a reliance on seasonal vegetation and hunting, to a diet rich in cooked meat and eventually to agriculture. These changes were driven by a need to support a larger brain, adapt to new environments, and increase caloric intake.
Step-by-step explanation:
The hominin diet underwent significant shifts as our ancestors adjusted to new environments and evolutionary changes. Early hominins were mainly gatherers and hunters within eastern and southern Africa, dependent on a diet based on available seasonal vegetation and game. With the emergence of Homo erectus, approximately 1.89 million years ago, notable dietary changes occurred, reflecting an increase in adaptability and environmental control. Homo erectus exhibited a larger brain, as seen in the progressive increase from about 550 cc to 1,250 cc, which had a crucial impact on dietary habits. A key area of study, known as the 'expensive tissue hypothesis' illuminates the relationship between the growing brain, colder climate, and dietary changes. Our ancestors were hypothesized to shift toward a diet richer in meat to meet the caloric requirements of larger brains. The advent of cooking allowed Homo erectus to consume softer foods, reducing the need for large teeth and jaws while providing a calorie-rich diet necessary for maintaining brain size and function. This change marked a transition from reliance solely on gathered foods to increased consumption of animal proteins. The use of fire to cook meat not only increased its digestibility but also boosted caloric intake by 35 percent or more. Ultimately, a monumental dietary transition occurred approximately 12,000 years ago when Homo sapiens shifted from hunting and gathering to agriculture during the Neolithic Age. This shift revolutionized human diet and subsistence, marking the beginning of actively cultivated crops and domesticated animals as food sources.