黑种 (and the parallel terms
黄种,
白种) come from the late-19th/early-20th-century three-race typology that mainstream genetics has long since rejected. The phrase still appears in older Chinese textbooks and 1980s-90s reference works, but in current writing
黑人 (black people) is neutral, while
黑种人 sounds dated. Treat
黑种 as a historical/technical term, not everyday vocabulary.