Final answer:
The early American practice that conflicted with John Locke's beliefs about natural rights was the practice of colonialism and the Atlantic slave trade.
Step-by-step explanation:
John Locke, a philosopher of the Enlightenment, proposed the concept of natural rights. He argued that individuals possess inherent rights to life, liberty, and property, forming the basis of just governance. John Locke believed that people have fundamental natural rights to life, liberty, and property.
However, there was an early American practice that conflicted with his beliefs. This practice was the unequal institutions of colonialism and the Atlantic slave trade. Despite asserting the equality of all humans, European colonizers supported the enslavement of Africans and the subjugation of indigenous peoples, thus contradicting Locke's belief in the inherent equality and natural rights of all individuals.