Many mangroves have leaves with special evapotranspiration pores which extrude salt that dries on the leaf surface, these may have been collected for use as dome shingles, and could have been the initial source of the salt trade, coastal people bringing stacks of salty leaves inland to trade with river people for freshwater-related inland forest items.
Omega 3 oils are beneficial for human esp. infant brain functioning, cold-water fish (tuna, salmon) contain high amounts of these oils. Gupta et al have found high levels of Omega 3 oils in a slime-algae protist which live on mangrove leaves, perhaps licking or cooking these salty leaves by archaic humans also gave them omega oils?
Omega-3 biotechnology: Thraustochytrids as a novel source of omega-3 oils
(Hat trip to Rob Dudman for links)