The concept among Europeans of "Melanesia" as a distinct region evolved gradually over time as their expeditions mapped and explored the Pacific. Early European explorers noted the physical differences among groups of Pacific Islanders. In 1756, Charles de Brosses theorized that there was an "old black race" in the Pacific who had been conquered or defeated by the peoples of what is now called Polynesia, whom he distinguished as having lighter skin. In the first half of the nineteenth century, Jean Baptiste Bory de Saint-Vincent and Jules Dumont d'Urville characterized Melanesians as a distinct racial group.