Prehistoric humans came from China to the Americas in two waves 

A genetics study finds that some of the first arrivals came from China during two distinct migrations: the first during the last ice age, and the second shortly after.

As the last continents to be settled by humans, the question of how and when people first came to the Americas has long intrigued scientists.

A new genetics study published Tuesday in Cell Reports finds that some of the first arrivals came from China during two distinct migrations: the first during the last ice age, and the second shortly after.

"Our findings indicate that besides the previously indicated ancestral sources of Native Americans in Siberia, the northern coastal China also served as a genetic reservoir contributing to the gene pool," Yu-Chun Li, one of the report authors, told AFP.

Li added that during the second migration, the same lineage of people settled in Japan, which could help explain similarities in prehistoric arrowheads and spears found in the Americas, China and Japan.

It was once believed that ancient Siberians, who crossed over a land bridge that existed in the Bering Strait linking modern Russia and Alaska, were the sole ancestors of Native Americans.

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More recent research, from the late 2000s onwards, has signaled more diverse sources from Asia could be connected to an ancient lineage responsible for founding populations across the Americas, including Bolivia, Brazil, Chile, Ecuador, Mexico and California.