Final answer:
The statement that the most widely accepted theory of earliest human migration to the Americas involves crossing a land bridge from Asia is true. The Bering Land Bridge migration model and the complementary coastal migration theory are the most accepted explanations, supported by archaeological and genetic evidence. The correct option is A.
Step-by-step explanation:
The most widely accepted theory of the earliest human migration to the Americas is indeed that people arrived by crossing a land bridge from Asia. This is supported by the Bering Land Bridge migration model, which posits that during the last Ice Age, humans crossed from Siberia to Alaska over an exposed land bridge due to lower sea levels. This migration is estimated to have begun around 20,000-14,000 years before the present.
Furthermore, the coastal migration theory complements this by suggesting some groups followed the coastline, possibly by boat, which would have allowed for faster and more widespread distribution. Sites in South America that predate North American sites lend support to this idea. Consequently, most historians and archaeologists accept that both the Bering Strait theory and the coastal migration likely explain human migration into the Americas.
Over time, these early inhabitants spread southwards, creating diverse cultures and civilizations throughout the continents. Genetic evidence with markers on the Y chromosome substantiates the connection between Asians and Native Americans, making the theory that the Americas were populated via these migrations the most credible amongst the scientific community, while other theories like the Solutrean hypothesis are viewed as unlikely.