A deceptively simple question....

The series starts by answering a question: ‘What is the ocean?’

We know it’s big, salty and wet but how did it get so big, why is it salty and why is it so important to life on earth? And what do we know about how these three things made the ocean the perfect place for the beginning of life itself? We meet the scientists studying the conditions in deep sea hydrothermal vents to find out where and how it all began.

How did we get from single celled organisms to the incredibly diverse ocean ecosystem we have today?

After two billion years of painfully slow evolutionary change what happened to scramble the system and allow the earth to get messy with life? The answer again lies in the ocean. Ben finds out how changing conditions in the ocean allowed animals to evolve from their single celled origins to the huge diversity we see today, and meets some of the first weird and wonderful animals to roam the ocean bottom in Evolutionary Explosions.

During the Cambrian Explosion we find the first examples of every major animal group, including the line to which we belong - the vertebrates. In Rise of the Fishes Ben finds out more about our distant ancestors - the fish. Making up half of all living vertebrates, fish are the most successful backboned animals on the planet. And they are the group to which we owe the evolution of teeth, jaws, and even our limbs.

Almost ever since the fish started to adapt to a terrestrial lifestyle, nosing their way onto land as the first tetrapods, they’ve been finding their way back again. Ben finds out how the ocean allowed the transition from ocean to land to happen - and then how time and again vertebrates have found ways to return to the water.

Except for the whales and dolphins we tend to think of the ocean as devoid of intelligent life. In Three Second Memory? Ben finds out more about some surprisingly clever marine animals.

After four billion years of the ocean influencing life on our planet, in the last 100 years the tides have turned. Humans have started to influence conditions in the ocean on an unprecedented scale. In A Sea Change, Ben learns of the effects on ocean life of over-fishing, plastic pollution and climate change.