Which islands and peoples actually belong inside Melanesia, and does the category itself still hold together?

Melanesia was coined in 1832 by Jules Dumont d'Urville alongside Micronesia, to sit beside the already-established Polynesia, originally on now-rejected racial grounds. There is no general agreement even among anthropologists about where its geographical boundaries run: whether New Guinea belongs fully inside it, whether Fiji is better classified as Melanesian or Polynesian given its historical and genetic ties to both, and how to classify Torres Strait Islander communities. Modern scholarship has moved toward defining the region by shared cultural and linguistic features rather than the original racial classification, but that shift has not settled where the lines fall.