Why do scholars reject the idea that Polynesians originally came from South America?

Scholars reject the theory that Polynesians originated in South America, a hypothesis famously championed by Thor Heyerdahl, because it is inconsistent with extensive linguistic, archaeological, and genetic evidence pointing to an Asian origin.123

While Heyerdahl’s 1947 Kon-Tiki expedition demonstrated that a voyage from South America to Polynesia was possible, modern research confirms that the ancestors of the Polynesian people were Austronesian speakers who migrated from Southeast Asia. Archaeological evidence, particularly the distribution of Lapita culture pottery, traces this migration from Taiwan through the Philippines, Indonesia, and the Bismarck Archipelago before reaching Fiji and western Polynesia.1234

Linguistic studies further support this, showing that Polynesian languages belong to the Austronesian family. Although the presence of the sweet potato—a crop of South American origin—in pre-European Polynesia indicates some form of contact, it does not support the theory of a South American origin for the population itself. Instead, the consensus among anthropologists and historians is that the settlement of the Pacific was a deliberate, eastward expansion by skilled maritime explorers from Asia.5214