In fact, the oceans, as we know them today, are no older than 200 million years, about 1/20 of Earth's history. The origin of the oceans is closely linked to the formation of the atmosphere and the cooling of the planet and the formation of the lithosphere.
Use Bangladesh for example. It's population is about 160 mil people. It's land area is small, and people are crowded; the density causes people to be nearby each other, and don't have enough room for their own land.
