The exact reasons why early humans settled last in South America are not completely understood, but there are several factors that may have contributed to this pattern.
One factor is geography. South America is the most isolated continent in the world, with the Andes Mountains forming a barrier along the western coast and the dense Amazon rainforest covering much of the eastern part of the continent. This isolation may have made it more difficult for early humans to migrate to and settle in South America.
Another factor is climate. During the last Ice Age, which lasted from about 115,000 to 11,700 years ago, much of the world was covered in ice and sea levels were much lower than they are today. This made it easier for early humans to migrate across land bridges and settle in new areas. However, the climate in South America during this time was relatively dry and cold, which may have made it less attractive for early humans to settle there.
It's also possible that there were cultural or social factors that played a role in the late settlement of South America. For example, early humans may have preferred to settle in areas where they had established communities or where they had cultural ties.
Overall, the reasons why early humans settled last in South America are likely to be complex and multifaceted, and more research is needed to fully understand this pattern.