Life in the Universe

Life on Earth and on the Moon

Why were ocean tides important to the evolution of life on Earth?

All animal life on Earth used to live only in the oceans. Scientists think that, for the evolution of land-based life on Earth to occur, it would have been important to have a transitional zone between ocean and land; that is, shorelines that were at times dry, then at times wet, over a long and regular cycle. This way, animals could evolve by slowly adapting to life in drier environments. Over millions of years, these animals could eventually evolve into animals that lived and breathed exclusively on land. Areas with regular, vigorous ocean tides provide just such a transitional zone, becoming wet and dry over and over again every thirteen hours or so. Thus, land-based animals like humans may well have had their evolutionary start in the tidal basins and tide pools of ancient continental coastal areas. Without the Moon, such tides would not be present, so the Moon has also proved to be vital to evolution on Earth.


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