Final answer:
Adjacent seawater benefits coastal human populations by its thermal conductivity, which leads to climate moderation due to the high specific heat capacity of water.
Step-by-step explanation:
The important physical property of adjacent seawater that benefits human populations living on the coastline is its thermal conductivity. Adjacent seawater has the ability to absorb and store heat due to its high specific heat capacity. This means that the seawater can absorb large amounts of heat without a significant rise in temperature, leading to a moderation of the coastal climate.
This property is crucial for creating more temperate climates, which can influence local weather patterns and provide a more stable environment for communities living near the coast. The stability of temperature due to this property is particularly beneficial as it affects agriculture, fisheries, and overall living conditions by reducing the extremes of heat and cold often experienced further inland.