Hidden clues and wombat poos: best of 2021

Let’s take a peek at how sharks begin their lives. These fish have three main ways to make baby sharks, one is by laying eggs and another is by giving birth to live young. Some species, like grey nurse or sand tiger sharks, use a mixture of the two and it can get brutal: baby sharks eat each other inside their mother! To dive deeper into how sharks reproduce, Charlotte Birkmanis spoke with Deborah Foote.

Charlotte - With everything going on, life is hectic at the moment. So how about a beach walk? Walking along the beach, you kick something with your toe. After the initial surprise wears off and you stop the dog from trying to eat it, you see a tough, dark brown spiral, about eight centimetres wide and 15 centimetres long. You dust the sand off it, stop the dog from trying to eat it again and realise it's an egg case from a Bullhead shark. And although they look quite different from the traditional idea of an egg, these empty egg cases occasionally wash up all over the world. This gets you starting to think about sharks, and of course a certain tune comes to mind... There is so much more to these creatures of the deep than just their teeth, and we have so much more to learn about them, but let's start from the beginning.

Charlotte - Where do baby sharks come from? Egg-laying is used by a small number of shark species. These eggs are often palm sized and come in a variety of colours, shapes, and textures, depending on the species of the shark. We often call these mermaid purses. Some shark species carry the young in a similar way to us, with the baby in a womb attached to its mother with a placenta, but other shark species do something in between. They produce eggs, but don't lay them. The eggs develop inside the mother and are nourished by an egg yolk until they're ready to hatch, and then they're born live. Let's find out about one species that has one of the most fascinating starts to life, though I might be a bit biased because I'm a shark scientist! For them, life starts with a cannibalistic pre-birth blood battle. It's a shark eat shark world out there.

Deborah - In Australia we call them Grey Nurse sharks, but they're also known as Spotted Ragged Tooth sharks or Sand Tiger sharks in other places in the world.

Charlotte - That's Deborah Foote from the University of Queensland

Deborah - And the pups will hunt and consume their brothers and sisters while in utero.

Charlotte - Now that is some intense family rivalry going on right there! But there's also some competition going on at the genetic level as well.

Deborah - The mother will mate with multiple partners, the pups could have different dads. Only one pup ends up being born from each uterus.

Charlotte - Yeah, you heard that right, Grey Nurse sharks have more than one uterus - they have two!

Deborah - Because they have eaten the other brothers and sisters, so by the end of it they've essentially had one father for their offspring. The first pup that hatches, so the biggest one, is the most likely to be the surviving pup because they can eat its small brothers and sisters, which are usually the ones that are from other dads.

Charlotte - But the food supply doesn't end there - after they're finished snacking on their siblings, their mother keeps the canapes coming by supplying a virtual conveyor belt of unfertilised eggs to nourish their offspring. This gives them quite the advantage when they're out in the world and have to start fending for themselves.

Deborah - They're born quite large, so up to about a metre total length, which is quite big if you're wanting to avoid being eaten by bigger fish. They've had practice already feeding themselves by eating eggs and other embryos in the womb.

Charlotte - They can also swim in the womb and even go from one uterus to the other, this may help them access those little hard to reach eggs and embryos.

Deborah - One of the reasons that this mode of embryonic nourishment has developed - so being able to feed itself inside, practice swimming inside - is that then they're at a competitive advantage when they get to the outside world because they already know how to feed themselves, they're already well-practiced at swimming and because they're quite big, they're less likely to be eaten by other predators.

Charlotte - Although somewhat scary looking Grey Nurse sharks are not aggressive. But the pups? They sure are feisty!

Deborah - The researcher that discovered that Grey Nurses eat eggs while in the womb to nourish themselves had cut open a dead pregnant female shark and was reaching inside to have a look inside the female reproductive organs, felt like he had had a bite on his finger. It wasn't enough to puncture the skin, and of course then when he opened up further and had a look at the pups, he realised that they had quite well advanced dentition. So a lot of baby sharks, before they're born, have a sheath over their teeth, but that is not the case in Grey Nurse. They have nice sharp teeth for eating those eggs and the other embryos as required during gestation.

Charlotte - And this pregnancy can go on from nine to twelve months, that's a long time for the Mum to be carrying around pups squirming around and eating each other inside her. So the next time you see a shark gliding around, or watch one on TV, think of the investment that the mother has gone into to get it this far

Sally Le Page took a walk through this endangered habitat to find out more about the history and science of peat bogs and what is being done to save them...

Sally - I’ve managed to escape the home office to go on a little walk through one of the key ecosystems when thinking about climate change - peat bogs. Here in Cambridgeshire we have a vast expanse of lowland peat called the Great Fen, where I am now, part of the Fens that represents 27% of England’s peatlands. Peat is a remarkable substance, and we're not just talking about anyone called Peter! Peat is a type of soil that forms over thousands of years in wet, boggy conditions. Moss plants like sphagnum moss photosynthesise and absorb carbon dioxide in the air, using that carbon to grow. In normal soils, when plants die, microbes use oxygen to break down the dead plant material releasing some of that carbon dioxide back into the atmosphere. But because peatbogs are so waterlogged, there isn’t enough oxygen for the moss to break down and so as long as the peat stays wet, the carbon is trapped.

Sally - This makes our peatlands incredibly important stores of carbon. Peatlands cover only 3% of the world’s land surface, but hold 25% of the global soil carbon. And the UK has more peatland than vast majority of countries around the world - 10% of our land area is covered in peatland habitats. It’s estimated that there is over 3 billion tonnes of carbon stores in the UK’s peatlands, which is equivalent to all the carbon stored in the forests of the UK, Germany and France combined.

Sally - There we go. Over this little wooden bridge.

Sally - Now, not only is the peat disappearing into the atmosphere through oxidation, the dry peat can be literally blown away in the wind. As a result of all of this the land is sinking.

Sally - Here we are, this is where I was walking to. I am stood in front of two, what look like Victorian lamp posts on the edge of a wood in the middle of nowhere. Very bizarre. They are about three of me tall; what's that, four metres tall? And they're called the Holme Posts. As I get closer I can see these black labels with years on them, a bit like when you mark off your kids' height on a door frame to measure how much they're growing, but unfortunately these markers are not measuring growth. Quite the opposite. The first one at the very top I can just about make out says 1848. That is just the year before they drained the mere and with an awful lot of foresight they pushed these posts down as far into the ground as they could go until they reached the solid clay layer below. Back in 1848 the top of this incredibly tall post was level with the ground. Then as they drained the mere, I can see the next marker down is 1860, that's already a good one and a half, two metres down. That drop in the level of the land is mostly from all of the water being removed. Then we go down further 1870, 1875 we're now at my eye level, 1892 we're at my belly button. Then of course my feet are currently at ground level in 2021. That is four metres worth of carbon stored in that peat that is now released into our atmosphere.

The Wildlife Trust are behind restoring this Great Fen for biodiversity, but they're also researching ways in which we can use the land productively to grow food and building materials without draining and degrading the peat soil underneath. A few days earlier, Sally travelled down the road to an experimental farming site on the Great Fen called Water Works to find out more from restoration manager, Lorna Parker.

Lorna - The project is called the Water Works project, and it's an exciting opportunity to showcase a new form of farming. Up to two centimetres of soil lost in terms of land height every year. In places that soil is already very shallow, but even in the deeper areas, you might be looking at another 80 years of farming and then no more peat soil left anyway, and we need to find another choice.

Sally - What would the farmers do when the peat runs out?

Lorna - Underneath the peat is a layer of really heavy clay. So it's much harder to farm. And before you get there, a lot of this peatland is actually quite acidic as well because we were at the seaside about 5,000 years ago. There's all sorts of geology under our feet that make it very complicated to farm.

Sally - Either it's 80 years of farming vegetables, business as normal, and then kind of farming crisis for this area. What's the alternative?

Lorna - That's what we're hoping to show. We're kind of trying to demonstrate a new form of farming, which will look at crops that you can grow in wet soil. We can trap that carbon, lock that carbon back in, but also hopefully produce food, fuel, fibre and medicines.

Sally - This is the fab word 'paludiculture'.

Lorna - It's a good one isn't it? It will be a word that most people won't have come across before. 'Paludi' is 'swamp', so it's swamp agriculture. What we're going to do is go for a walk on our wet farming pilot project, the Water Works project, and have a look at some of the new crops that we're going to grow and hopefully excite you about the possibility of the things we can do with those crops in the future.

Sally - I'm already very excited. The cows are already very excited. Let's go. We've walked over some little raised strips. We walked over some ditches, where are we now?

Lorna - Okay, so we're in the corner of one of our new wet farming beds. This one we're sat in at the moment is what we're hoping will be a future food crop for the fens, and which is manna grass. It's a cereal crop, which would need some crop development, but could be a porridge or a sort of flour.

Sally - I'm looking at one of these seed heads now. I mean, it's not much to look at compared to an ear of wheat for example. You can barely see the seeds. What will the seeds look like?

Lorna - They'll be small, like a kind of millet-type grain, that you could have in your posh ancient grain porridge for example, or you could mill it into possibly low gluten flour.

Sally - You've got to ask, what does it taste like?

Lorna - I don't know yet, because this is our first year. So we haven't harvested any. I think the seed is so precious at the moment, we'll probably grow more plants with it rather than eat it.

Sally - You're going to spend years of work creating this food that you don't even know tastes any good?

Lorna - I hope so. We can add a jam to our porridge. I'm sure it'll be fine.

Sally - When you're thinking of plants that can feed lots of people in wet soil, the automatic choice would be rice. So why aren't you growing rice here?

Lorna - We're looking at rice. The climate in the UK is not ideal for rice at the moment, but you know, with global warming it's going in the right direction. Our plant nursery is actually looking at different strains of rice to find ones which grow in the most similar climate to what we have here.

Sally - As you can probably hear, this field is a lot wetter than the other one.

Lorna - Yeah. We've come to have a look at our bullrush field.

Sally - And what can we use bullrushes for?

Lorna - Bullrush is pretty epic as well actually. It's got a structure when it grows, where it traps lots of air inside its stem. It can be absolutely fantastic for fibreboard, so for construction materials that insulate at the same time. For cavity wall filling, you can shred it and blow it in, in place of artificial products. It would be really exciting, I think, to grow products and then build local houses from something that's sourced only a few miles away.

Sally - Yeah, totally.

Sally - We are next to probably one of the biggest plots, I would say, of the ones we've been to and it's covered in - very familiar to any allotment grower - a weed membrane. What is going to be here?

Lorna - Okay. So we've got about 150,000 plugs of this tiny bog moss that we're going to plant of several species underneath the mesh, and it will grow into a sort of carpet of green under there which will be a really good crop for us to harvest and lock that carbon in the soil.

Sally - Growing moss as a crop. How is that going to be useful?

Lorna - There's lots of ways. I could talk for hours just about the moss. Moss is really exciting. One of the most exciting things that we're hoping to do with the moss here is grow it and harvest it as a substitute for compost, for growing vegetables.

Sally - Right now there's been this big move of not buying compost that's got peat in it, right? Is this what's going to be in the bags of compost instead?

Lorna - We're hoping to go bigger than that. We're hoping this will be what growers of vegetables that you eat in the supermarket are going to use to grow their small lettuce plants, for example, rather than buying in peat from peat that's been harvested from peat bogs in the wild.

Sally - Wow. Not only will this moss stop people digging up the peat for the sake of the peat. It will also stop the peat here from drying out and we still get vegetables.

Lorna - Absolutely. The moss is amazing because it can control its own environment. It can control its own water. It can control weeds. It's antibiotic. It's super absorbent. It's like a hero plant.

Sally - You really are in love with this moss aren't you.

Lorna - It's a bit of a worry, isn't it?

Sally - If you had a magic wand, what would you do with all of the peat bogs and former peat bogs in the East of England?

Lorna - Most of the peat here is farmed. I would like to see ways that we can use it productively because that's a really important part of the local economy and the local culture, but in a way that can protect it forever. If we don't do something now it will be gone for future generations. If we can do that in a sustainable way, which has all these other benefits and build our houses from it, then what's not to like about that.

While fireworks have been filling the skies over this past week, sparks flying between two people pursuing a romantic connection is less of a given. But there might be a way to find out which couples are destined to click: if their heart rates synchronise when they see each other! Julia Ravey…

Julia - They look all right actually. Definitely not. Oh, that's a cute dog. Right up my street. It's a match. When it comes to finding a potential partner, it's hard to know what to look for. A great sense of humor, intelligent conversation, a matching pulse. Well, maybe the last one is what matters. With millions of people in the UK turning to dating apps, our criteria for finding ‘the one’ can be applied before we even go on a date. But sometimes no matter how much a person may be your type on paper, when you meet them face-to-face that connection, that spark is missing. So we decide 'they're not for us' and we move on to the next swipe right. A big question I've always had is what is that spark? So many of us use it to determine if a person is a good fit, but what gives us the physical green light? I spoke to...

Eliska Prochaskova - Eliska Prochaskova and I'm a researcher from Leiden University.

Julia - Who thinks she may have cracked the connection code.

Eliska Prochaskova - When people are looking for a romantic partner, they want to have chemistry. They want to feel a connection with that partner. And while this is something that everybody says, it's really hard to describe what it actually is and can we measure it?

Julia - Eliska and her colleagues, tested this by setting up a blind date experiment. Two people would enter compartments of a space separated by a sliding hatch. They would then do a '3, 2, 1, big reveal' for a few seconds to let the participants rate each other on physical attraction alone. They then let the dates chat for a few minutes and just be in each other's company.

Eliska Prochaskova - At the end, we asked them again how attractive the partner is. We also asked them whether they wanted to go on another date. This really allowed us to see how the attraction changes over the period of dating, and whether they become more attractive.

Julia - This was all while wearing devices, which measured their heart rates, how sweaty they got, and track their eye movements. But these devices definitely didn't get in the way.

Eliska Prochaskova - They completely forgot they're wearing them and we could see a person running and wanting to go to the toilet. We had to stop that person because we're like "We can literally see what you're doing".

Julia - Although the participants in the study show gestures we associate with being attracted to someone, like eye contact and smiling, Eliska found a different measure was the best at predicting attraction.

Eliska Prochaskova - We measured all different types of expressions. So, we measured nonverbal, smiling, laughing, and flirtatious behavior, we also measured eye contact. What we realised was that the main predictor of this click or this chemistry which people have, was the synchrony between the partner's heart rates and their skin conductance, which are unconscious responses which you cannot control. The more synchronized, the more attracted the partners become to each other.

Julia - Why do you think heart rates matching up might influence attraction?

Eliska Prochaskova - At the moment, scientists know that synchrony between people's physiology like heartily skin conductance happens in many different contexts. It's a phenomenon which we, for example, observe between mother and child, when there are, for example, hugging or when they're playing. From that, we know that this kind of synchronicity often leads to powerful bonding.

Julia - With so many of us now dating online this research can teach us how to increase the chance of having that spark on a first date.

Eliska Prochaskova - About 50 million people who are dating online, using different types of apps, they base their choice on attractiveness. What we observe in our study, what is really important for two people to really establish this connection, is a level of emotional synchronicity, what the physiology actually measures. That means that it's important that people actually put their emotions out and therefore reveal their emotions in order for the other person to explore them, to see them, and also feel them in their own body.

Julia - So there you have it, be open and vulnerable or a first date may be the key for allowing that spark to ignite. Or alternatively, ask your date to come equipped with a heart rate monitor, and put your scores on the doors at the end of the night. "Second date? Nah mate. You were a solid 74 beats per minute, when I was running on an 81. All the best for the future."

We’re well into Autumn now which often ushers in a perennial problem: leaves on the line and delayed trains. It seems bizarre that something as mundane and fragile as leaves can bring public transport to a halt in the 21st Century, but it is a serious problem. Tannins in leaves react with iron in the rails to produce a super-slippery surface that the train wheels slide over. Thankfully, mechanical engineers at the University of Sheffield may soon be riding to our rescue with a way to make this commuting catastrophe a thing of the past. Sally Le Page reports…

Train announcment - We are sorry to announce that the 1822 train to Cambridge has been delayed due to leaves on the line. We are sorry for any inconvenience caused.

Sally - Ugh, the announcement we all dread to hear. But leaves? Why are high-tech trains in the 21st century thwarted by leaves? Roger Lewis explains.

Roger - Every autumn as the leaves are falling from the trees, these are crushed by the passage of trains and you get some chemical reactions taking place in the interface that create this black material that adheres to the railway track very well. You'd find it very hard to scratch it off even if you were poking the track with a screwdriver or a metal blade, which means that trains struggled to brake safely, but also to accelerate away from stations which causes delays and makes passengers unhappy.

Sally - So the leaves are chemically bonded to the track. It's not just like when I'm walking on the pavement and the leaves are all wet and mushy, it's a bit slippy. It's more than that.

Roger - It is more than that.

Sally - And how do we currently deal with them?

Roger - So at the moment, network rail use what are called railhead treatment trains, which fires water at the rail head under very, very high pressure. The pressure is so high that if the train stopped and the water kept going, it could possibly cut through the rail.

Sally - Cut through solid steel?

Roger - Yeah.

Sally - That is incredibly high, and must use a lot of water as well.

Roger - It does. This is one of the problems with the trains. They can only run a certain distance before they need refilling.

Sally - So your solution involves using dry ice. What is dry ice, other than the thing you put in fancy cocktails to make them go all smoky?

Roger - The pellets we use are basically solid carbon dioxide. Now that sounds very bad. We don't like carbon dioxide at the moment, but actually all the carbon dioxide we use is recaptured from other industries that are putting it out into the atmosphere. So most of it comes from the fertiliser industry. Basically you have to compress it under very high force so that then it turns into a solid. Then you have to keep it very cold to keep it solid. So when it comes out of our machine and hits the railhead, it's at about minus 70 degrees centigrade.

Sally - How are you using dry ice to remove this slippy layer from the track?

Roger - We fire it onto the top of the railway track in a stream of air, which is actually going at supersonic speed. So you've got these pellets going at very high speed. Because they're cold they make the leaf layer brittle. And then because they're back in the atmosphere, they turn back into a gas. So you've got lots of little air explosions, almost, across the top of the railway track. So you've got three mechanisms there which are acting to break up and remove the leaf layer.

Sally - I'm imagining a machine gun firing continuously little ice pellets. Does it look anything like that?

Roger - That's kind of how it works, but that's not how it looks. It doesn't look as exciting as that, I'm afraid.

Sally - You've got these dry ice machine guns strapped to passenger trains. Can they just run as normal? Will this happen during the normal commute from London to Cambridge, or does the train have to be going particularly slowly for it to work?

Roger - That's a good question. At the moment, railhead treatment trains, for example, are designed to run at 60mph. A lot of passenger trains on local lines would typically run at that speed or a bit less. So we've obviously been targeting high speed operation. We were testing it on a full-scale wheel rail test at 60mph. We've run on track on a train at 40mph. And hopefully this autumn we'll be able to go a little bit faster. The good thing about cleaning on a passenger train is that hopefully we'll be able to stop the really heavy contamination building up. So if we can clean more frequently, we can do a lighter clean, which is obviously much easier at higher speed.

Sally - It's a bit like brushing your teeth often so you don't have to go to the dentist and get horrible treatments done.

Roger - Yes, quite.

Sally - And how long do you think it's going to be until we no longer have the dreaded announcement of "this train has been delayed due to leaves on the line"?

Roger - I'd like to say very soon. I think our systems will be underneath trains probably within a couple of years, but we can use it already on a railhead treatment train or road-to-rail vehicles. So we're already cleaning the track with it

Sally - And it can't come soon enough. Now, when is that next train arriving?