Final answer:
Early Homo ancestors likely migrated out of Africa and spread into Eurasia due to climatic changes that made resources scarce and the advantages of upright locomotion. Their migration was a complex process driven by the pursuit of food and adaptability to new environments, contributing to the diversity of human species and their global spread.
Step-by-step explanation:
The most likely explanation for why early Homo ancestors left Africa and spread into Eurasia includes a combination of climatic changes and the necessity for survival resources such as food. As the climate in Africa became drier, it affected the availability of plants and animals, pushing early humans to migrate in search of more abundant resources. This era marked the period when Homo erectus began to utilize the advantages of their upright locomotion which allowed them to travel over longer distances, follow the game, and exploit a variety of food sources. The locomotion of Homo erectus was not a maladaptation but an evolutionary advantage that free their hands for tool use and facilitated their migration.
While Homo erectus exhibited longer-term migration patterns, habitation near water sources also indicates the pursuit of various prey. This nomadic lifestyle of following the game, along with the adaptability to new environments, propelled the spread of Homo erectus beyond Africa and into Asia and Europe. Over time, this led to a diversity of human species, including the interbreeding with Neanderthals and the spread of Homo sapiens globally, showcasing the role of migration in human evolution.