This is an interview with Sarah Nelson, one of the foremost experts on Northeast Asian archaeology. She's talking about the connection between Hongshan culture and ancient Korea. She suggests early neolithic Manchuria before Hongshan culture was closely related with Korea, but Hongshan culture itself may have been an independent development, due to its extensive jade culture and the lack of it in Korea. However, she also suggests the possibility that Hongshan people migrated to Korea and simply replaced prestige jewelry from jade to gold. Hongshan's urban legacy spread to Buyeo and then to Goguryeo. Hongshan's square pyramid also bears resemblence to such pyramids in Goguryeo and Baekje.
Pyramid of King Jangsu of Goguryeo:
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A Pyramid of Baekje in Seoul:
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She also suggests the possibility that rulers of Shilla were from the Xianbei tribes of eastern Mongolia, who were horside riders with a love for gold. She also remarks that ancient Manchuria, known as Dongbei in Chinese, was not Sinitic. In her opinion, it was Korean and Turkic, i.e. Altaic, but she also quotes a linguist of it being Koreanic and Japonic.
In any case, an interesting video about the history of Northeast Asia and the legacy of Hongshan culture in a nutshell.