While the land is familiar, even reassuring, the sea is unknown and threatening. Why, then, did humans become seafarers? Part of the answer is that we are conditioned by our genetics to be acquisitive animals: we like to acquire rare materials and we are eager for esoteric knowledge, and society rewards us well for both. And our innate inquisitiveness drives us to explore. The pre-eminent archaeologist looks at the development of seafaring on the Mediterranean and the Atlantic, two contrasting seas, the Mediterranean without a significant tide, enclosed and soon to become familiar, the Atlantic with its frightening tidal ranges, an ocean without end. Chaired by Gabrielle Walker.