Think of earthquake cities and places like San Francisco or Los Angeles spring to mind. But London is also seismically active. 200 years ago, there was an earthquake under Trafalgar Square. Dr Richard Ghail from Imperial College London meets Adam Rutherford on the banks of the Thames to discuss the fault lines under their feet and what engineering challenges this poses.

In the beginning, there were chemicals. A geological blink of the eye later, there was LUCA, the last universal common ancestor; a complex cell. How the chemistry became biology is one of the biggest mysteries in science. New studies from University of North Carolina researchers chips away at this unknown, offering evidence on how the genetic code developed in two stages. Adam meets Dr Matt Powner, a chemist at University College London studying the origins of life, to find out how researchers try to answer this fundamental question.

How do we know what our landscape used to landscape? Pollen, from buried mud layers, offers a picture of sorts. By gathering tiny pollen grains, and identifying the plant species at different ages, Dr Ralph Fyfe from Plymouth University builds up a picture of European landscapes thousands of years ago. Peak deforestation happened several thousand years ago, as our pyromaniacal ancestors started forest fires to clear land for agriculture. Roland Pease reports.

A plague is killing thousands of common frogs in ponds across the UK. Ranavirus causes ulcers on the skin and haemorrhaging. A team at Exeter University has noticed that ponds with fish are more likely to have an outbreak of this virus. Amber Griffiths urges Radio 4 listeners to leave their ponds to the wildlife, and keep frogs and goldfish apart.

400 USO SIGHTINGS IN CALIFORNIA: WHY ARE THEY MAKING THEMSELVES KNOWN?

Reality Check with Ross Coulthart

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