Author: BBC World Service

What would you discover inside the stomach of a sea lion? CrowdScience listener Robyn found out first-hand when she volunteered at her local museum in Adelaide, Australia. The team dissecting the specimen removed around 30 rocks from the animal’s stomach, and Robyn wants the Crowdscience team to find out how and why they got there.

Presenter Anand Jagatia uncovers a whole world of rock-munching creatures, from ostriches to ichthyosaurs. In search of answers we investigate Canadian sea lion research, and rummage through the vaults at the Natural History Museum in Bamberg, Germany.

Presented by Anand Jagatia Produced by Emily Bird

Image: Australian Sea Lion (Neophoca cinerea), Hopkins Island, South Australia Credit: Stephen Frink via Getty Images

The Aurora Borealis – also known as the Northern Lights – won’t be at their peak activity much longer, and the Unexpected Elements team dreams of going north to see them. And that has got us looking at the science of navigating our way north!

We hear about how humans have been using the sky to navigate for millennia, and we learn about how relying on GPS may be impacting our memory ability.

And while humans use maps to get around, how do animals know where to go on their long migrations? To find the answer, we speak to Dr Kayla Goforth at Texas A&M University who studies exactly how sea turtles and monarch butterflies innately know how to navigate the world around them.

We also learn why polar bears keep themselves ice-free, and we hear old records of the first men to reach the North Pole.

All that, plus many more Unexpected Elements.

Presenter: Caroline Steel, with Andrada Fiscutean and Phillys Mwatee Producer: Imaan Moin, with Alice Lipscombe-Southwell, Noa Dowling and William Hornbrook

Pain, particularly chronic pain, is hard to research. New therapeutics are hard to screen for. Patients are not all the same. Sergui Pascu and colleagues at Stanford university have been growing brain samples from stem cells. Then they began connecting different samples, specialised to represent different brain regions. This week they announce their most complex “assembloid” yet, one that even reacts to hot chilli, passing a signal from the sensory neurons through to the thinking bits. The hope is that it can provide insights on how pain, and potential painkillers, work.

Human brains are notoriously large, particularly infants. Whilst for primates the human pelvis is quite narrow, to allow us to walk and run on two legs. This notoriously makes childbirth, well, not as straightforward as most other species. This evolutionary “obstetric dilemma” has been debated for decades. Marianne Brasil, of Western Washington University, and colleagues, have published this week a huge study of contemporary human genes and anatomies available from the UK Biobank to shed some more light on this ongoing compromise.

Malta is an island in the Mediterranean no less than 80km from land. So how come Eleanor Scerri and colleagues have discovered archaeological evidence of hunter-gatherers living there from 8,500 years ago? And they didn’t just visit and leave. They stayed for perhaps a millennium before farming arrived. Maybe a rethink of what nautical capabilities our ancestors had in the deep past is needed?

A year ago, Science in Action gate-crashed a conference looking at plans for meeting the forthcoming arrival of asteroid Apophis in 2029. This year the meeting is in Tokyo, and Richard Binzel, emeritus professor of Astronomy at MIT, gives us an update on how the space agencies are hoping to collaborate to maximise the scientific value from what will be a global, visible, phenomenon in just 4 years. Is there enough time to get our collective wits together?

(Image: 3D illustration of Interconnected neurons with electrical pulses. Credit: Getty Images)

Presenter: Roland Pease Producer: Alex Mansfield Production co-ordinator: Josie Hardy