Pregnancy’s effect on ‘biological’ age, polite birds, and the carbon cost of home-grown veg

Benjamin Thompson

Hi everyone, Benjamin from the Nature Podcast here. This time of year, we tend to do something a little bit different with the show and this year is no different. We're going to do a bit of a deep dive into some of the stories that have appeared in the Nature Briefing over the past few weeks. And joining me to do so once again, are Noah Baker, Noah, how're you doing?

Noah Baker

I'm very well, thank you, Ben. How are you?

Benjamin Thompson

Yeah doing okay, thank you very much. And the third member of the team today is Flora Graham. Flora, hi.

Flora Graham

Hi, great to be here. Thanks for having me.

Benjamin Thompson

Excellent. Well, listen, let's crack on then. Noah, why don't you go first, this week. What's caught your eye on the Nature Briefing recently?

Noah Baker

So this is a story that I've been reading about in Nature. And it's about a paper that was published in the journal Cell Metabolism and it's all about ageing and pregnancy.

Benjamin Thompson

And presumably, there is a link between the two.

Noah Baker

Yeah, so specifically, what we're talking about here is what's called biological ageing. What does that term mean to you?

Flora Graham

I know that when I go to the gym, I get on a kind of a special weighing machine, and it passes a current through my body, and then it tells me like everything that's gone terribly wrong in my decision making in my entire life. And one of those things is my biological age. So I would be very interested to know what this actually is.

Noah Baker

Yeah. So interestingly, biological age is separate from chronological age. Chronological age is what we do with birthdays. Biological age is essentially a measure of your systems, how they're doing, how your biology is doing. And one of the metrics that scientists can use, one of the most sort of robust metrics to assess biological age is what's called methylation. Now, we are gonna get to pregnancy in a minute. But before we do that, I'll start with what we mean by methylation. So methylation is a really classic example of an epigenetic process. So that's the modification of the way that your genes work, rather than changing your genes or the DNA itself. And an important thing about epigenetic changes is that they can be reversed. And they can also be influenced by the environment in a way that changes how the DNA works, but doesn't change the DNA itself. And that's going to be very important in a moment. Anyway, in this case, imagine methylation is these little methyl groups like chemical tags that can attach to your DNA complex and change the way that your DNA is expressed. These build up over the years, and the level of methylation can be directly linked to what scientists call your biological age. And there's lots of things that impact methylation: stress, disease and an additional thing is pregnancy. Pregnancy can increase the methylation of your genes and so therefore, as some of the scientists in this story are saying, can increase your biological age.

Benjamin Thompson

So being pregnant then, makes you biologically older?

Noah Baker

Yeah, so there's a few ways to actually think about this. But in a very, very raw way, some of the scientists here are saying that you could argue that during pregnancy, one's biological age can increase by a few years. So you sort of skip ahead a few years in that nine month period. But what's particularly interesting is that this latest paper is suggesting that in the three months postpartum, that can be reversed to some extent, so there can actually be a reduction of biological age. So the additional methylation during pregnancy can be undone to certain extent, depending on a few other factors that they brought up. So maybe you age during pregnancy, but then you de-age again, after you give birth.

Flora Graham

Until your baby starts waking up at night, every five hours, maybe every five hours on a good night. I mean, this resonated with me this study, I think that anybody who has been pregnant can sympathise with the fact that you feel at certain times, like you're about 1,000 years old, huffing and puffing up the stairs. And then it kind of all returns back not necessarily to how it was before but in some kind of new, slightly different arrangement. It's definitely a transformative process for your entire body. So yeah, in some ways, I read this and I thought, you know, this doesn't surprise me. But it's great that there is a kind of deeper analysis into the kinds of changes that our bodies experience when we're pregnant. I thought that was very cool.

Benjamin Thompson

I mean, it's interesting to me as well, from an evolutionary sort of angle, like why this happens, you can see why maybe getting biologically younger would be useful when you have a child because you want to, you know, help them survive, right? So being young, inverted commas could be a useful one there. But I don't really understand why getting biologically older would be useful?

Noah Baker

So I think this starts to speak to some of the question marks in this study. So one big question mark is whether or not we really should be talking about ageing in this context at all. So there are researchers that are quoted in this piece saying methylation, which is this marker of biological age happens in response to all kinds of things in the body. And it could happen in response to a whole bunch of genes being activated that happen during the process of growing a foetus, for example. There's loads of genes that are activated in that process that may not be activated at other parts of the body. And so maybe we need to be thinking about entirely different terms in the context of methylation and pregnancy. And this is a relatively new field. So it might be that we don't need to be saying ageing in the future, we should be saying something else. But for whatever reason, there does seem to be this epigenetic response to pregnancy. And that's perhaps not surprising that the researchers in this story no one is particularly surprised that this happens. What is interesting, though, is that it reverses and that there are different things that can impact how much it reverses. So for example, in the research that they've been doing here they've seen that people that are close to being classed as obese, for example, before pregnancy, have a lesser reduction of biological age. This, you know, which I would say with inverted commas, you know, in light of what I've just spoken about. Additionally, things like breastfeeding could potentially impact this so someone that exclusively breastfeeds may have a greater reduction in this methylation than people that don't breastfeed at all, or use a combination of breastfeeding and formula feeding, for example. People aren't quite sure exactly how or why this is happening and it's certainly there's a lot that needs to be understood. But there was some indication that there are people that three months postpartum had a lower biological age than they did at the very beginning of their pregnancy. And so it's potentially possible that there is a kind of a rejuvenation going on during pregnancy, but they didn't have any studies from before pregnancy. And so this is something that researchers are kind of keen to now find out about whether or not the process of being pregnant giving birth might actually end up with a rejuvenation of your biological age – question marks still exist here.

Flora Graham

I mean, it brings to mind some of the other findings and evidence about the physical changes that go on when you're pregnant. Because of course, I say this slightly tongue in cheek, there's a somewhat of an arms race as well between the foetus and the pregnant parent because the immune system has to be suppressed in some ways in order to, you know, host another person in there. On the flip side, there's been shown to be some benefits to the foetal stem cells doing things like potentially helping with some forms of heart disease. And I think that Noah's point is very well made, which is the fact that there were almost systems in place through breastfeeding and other things that kind of like help you get back to the place that you were before, hopefully, or get back to, you know, a healthy place where you can have more children, I guess, if you're speaking from an evolutionary perspective. It just goes to show that the whole cycle of pregnancy is much more than just the time when you're carrying the foetus.

Benjamin Thompson

And this methylation/de-methylation thing is being explored more widely in terms of ageing in general, I suppose, like trying to be youthful, whether or not it is the end all and be all it obviously remains to be understood. But like, I wonder if there's more insights that can be taken from this that could be applied in other aspects of preventing age-related diseases, for example.

Noah Baker

It's certainly very possible, methylation and the increase of biological age has been associated with disease in the past, it's been associated with trauma, there's all kinds of things that it can be associated with. So there's an awful lot to understand here. I think it's also really important to mention that there are researchers quoted in this piece that were very keen to make sure that people were not alarmed by this. In the worst-case scenario, they're saying, we're talking about a couple of years here, but there's loads of things, diet, all kinds of stuff that can affect biological age, and people shouldn't be thinking having a pregnancy is cutting years off my life, that's not really helpful. And additionally, things like breastfeeding, whilst they've seen this interesting effect that they may want to study. It certainly isn't the case that if you aren't breastfeeding, you're shortening your lifespan, for example, there are a lot of reasons to do a lot of different things and there are a lot of moving parts here. So these are interesting things that people could consider, but certainly not things that people should be taking life lessons away from.

Benjamin Thompson

I mean, that is genuinely a fascinating thing. And so I think we can add another one to the list of strange things that pregnancy does to the human body, of which I am sure there are many, many more that are just waiting to be discovered. I'm gonna shift gears a little bit here and move on to my story this week which couldn't be more different. And it's a story that I read about in Scientific American is based on a Current Biology paper, and it's about gestures. Okay, now, we gesture all the time, right. Like I waved when you both arrived on this video call that we are chatting on now. And these things are called symbolic gestures, okay. And often they replace words, right. When I'm waving, you know that I mean, kind of ‘Hello’. We do them all the time. But they're quite rare in the animal kingdom, but I think researchers have discovered another animal that might do this very specific sort of gesturing.

Noah Baker

I mean, I don't want to anthropomorphise too much. But I tell you now my dog certainly gestures to be all the time I know exactly what she's saying by the movement of her head. But that could just be because I've trained to do so.

Flora Graham

I think one of the key aspects here is this is a gesture that's not necessarily like pointing at something, but it means something else, like a word, if that makes sense–

Noah Baker

–mmm okay–

Flora Graham

–so it's not like, Oh, I'm pointing at this ball or hand me this ball, like a wave doesn't have any inherent meaning.

Benjamin Thompson

Yeah, that's right, Flora. So those kinds of pointing gestures are known as deictic gestures, right. And a lot of animals do this, you know, fish, corvid birds, chimps, or what have you. And it's like, there is some food over there, go and get it, for example. So that's that kind of gesture. The symbolic gestures are very, very different. These are ones that are kind of abstract.

Flora Graham

Like flipping the bird would be the classic example. It's not offensive in and of itself, but you wouldn't want to see it in polite company.

Benjamin Thompson

True enough. And speaking of birds, and so the other animal that seems to be doing these symbolic gestures is called the Japanese tit, Parus minor, is this little bird, okay, right. And they are found all over East Asia. And some researchers in Japan have been studying these and they seem to be doing something very, very specific. Okay, so it looks like they're doing the ‘after you’ gesture. Now we need to be careful to anthropomorphise as you say, but it's the first evidence of a symbolic gesture in a bird. And the way they went about it, right, they analysed the behaviour of eight breeding pairs of these birds and looked at 321 nest box visitations, okay, as pairs brought food back for their young. And it seems like when the birds came back, often one of them would kind of wave their wings. And then the other one would go in, and the wing waving was ‘after you’. So females did it more than males, and the one who fluttered entered second, regardless of kind of the order that they arrived. And the researchers say that this hits the criteria for being a symbolic gesture, it only happened when a bird’s mate was present, it stopped when the mate entered the nest box, there was no physical contact between them and the gesture was aimed at the mate, not at the box. So it wasn't this kind of ‘look over there’ pointing aspect. And often that you know, it didn't happen, and when it didn't happen, there was no ‘after you’. So it seems like this is potentially what this is. And one of the researchers quoted says that it is strong evidence of being a symbolic gesture, because the other bird knows what it means. Because inherently it doesn't have meaning but the other bird knows what it means and what it's supposed to do.

Flora Graham

Was it like a kind of romantic gesture? I mean, we obviously know that birds are capable of spectacular displays. Is this a kind of mating ritual thing?

Benjamin Thompson

I mean, it's a great question. I think currently, the answer is *shrug*,to use a gesture, I suppose. One of the researchers behind it says that maybe by doing this gesture with their wings, rather than making a noise, they're potentially protecting themselves from predators. But this is one of those things where it's kind of hard to know, just yet. But these birds are kind of remarkable and the team behind it have been studying them for absolutely ages and discovered that they really have quite detailed songs that have different meanings. And we've talked in the podcast before about how birdsongs can be, you know, very, very complex and in ways that we can't necessarily understand. So it seems that maybe we can add this kind of symbolic gesture to the mix as well.

Noah Baker

Are there any other animals that do symbolic gestures outside of people, and Japanese tits.

Benjamin Thompson

There is some evidence in great apes, as I understand in chimps, and I think in orangutans, but very, very rare, because it's thought that it requires a lot of cognitive power to have this kind of abstract meaning to a thing. aAnd why humans have gestures like this is kind of unknown. One hypothesis is that because we walk on two legs, our hands were free to wave them around a little bit more. And maybe that's the case with these birds as well, they sit on a branch, and their wings are free to kind of flail with meaning. But I imagine that there's the potential there are a lot more of these gestures just waiting to be found out there in the animal kingdom.

Noah Baker

First and foremost, my miniature Goldendoodle rolling her eyes when she sees a puppy. I guarantee you that as a symbolic gesture to say to me ‘stupid puppy’.

Flora Graham

It makes me think about people who use completely gestural language, right? There's lots of evidence that humans’ capacity for language is not just based on hearing and speech. It's based on gesture, it's based on the many sign languages that have developed in all sorts of different backgrounds. And so I think that yeah, maybe there's a separation between gestural language and non-gestural language here, maybe we have more to learn about that. I mean, I'd love to think that these Japanese tits are making all sorts of gestures at us and we’re just not getting them. And they’re like, ‘look at these idiots, they don't even understand, you know, what a beautiful day it is’.

Noah Baker

I love animal behaviour things. But maybe next we should… hang on … you can't– you can’t really hear this, but I'm sort of shuffling my wings to say, ‘after you Flora’, ‘what's next, Flora?’ Symbolically, I'm gesturing to Flora. What's your story this week?

Flora Graham

I mean, I have to say this one, as soon as I read it, I thought, ooh, this feels a little bit controversial, because this is about a paper — that was in Nature Cities — where the author's looked at the carbon emissions of gardening. Now not gardening just for flowers and pleasure, but urban efforts to grow food. So we're talking about community gardens, allotments that are tilled by individuals, maybe even kind of larger-scale social enterprise community gardens. And what they did is they surveyed urban gardeners in the United States and Europe. And they also looked at the carbon emissions of kind of conventional commercial farming in those regions. And they found that the carbon footprint of food from urban agriculture is six-times greater than conventional farming. Now, I think most of us who enjoy a good weekend down the allotment or growing vegetables in our back garden are quite taken aback by that news, like a lot of us are supporting that kind of work in order to reduce, let's say, food miles, for example, you know, we think that, well it's not being flown in. But the fact is that there are a lot of economic pressures on commercial farming that offer incentives as you can imagine, just to make things as efficient as possible. So you know, the less petrol you use, the less plastic you use, the less money you spend, the more profit you make. Whereas what they found when they were surveying — and these are real world urban agriculture projects. I mean, obviously, they don't have like drones looking at everybody's allotment, so you know, it is what it is in terms of data — but what they found was, people were using synthetic fertilisers, people are using plastic materials, people are not necessarily running equipment for many years — they’re buying new strimmers, things like that. And the upshot is that there just wasn't the same kind of efficiency pressures, people were not necessarily doing their composting in the most efficient way possible, as you can imagine, you know, if you're just kind of doing it as a hobby. So the authors who, you know, they're keen gardeners themselves, kind of were hit with a lot of blowback. As you can imagine, this is not the news you want to hear when you're doing your best to grow a worthy tomato. What they said is, you know, we can use this information to understand where are the areas that we can improve, so that really, we can get those carbon emissions from these programmes down, because, of course, allotments and community gardens and things they have social benefits as well. It's not just about environmental benefits, and the authors take pains to really point out, these are the ways that cities can really help community gardeners improve these things. So how can we help people share equipment, so that equipment’s being used broadly over a long time? How can we connect sources of urban waste and maybe use those materials for things like raised beds and stuff? So you're actually creating more of a circular economy rather than heading down the garden centre for those brand new scaffolding boards.

Noah Baker

Absolutely. I mean, this is a fascinating story. And I agree, certainly, potentially controversial. And I think one of the things that's important for us to really highlight as we talk about this is, I'm sure these researchers, and certainly us talking about this are not trying to demonise people trying to do a good thing. I think what we're really highlighting is that there are often things that get overlooked a little bit when we talk about climate-change impacts. People talk a lot about food miles, for example, but they don't talk very much about the impact of continually buying new things, for example, and the manufacturing process of doing that. And so I think quite often there's more to think about than meets the headlines. And maybe that's really the highlight here is maybe think about those additional costs. It's not, don't do farming anymore, especially as you say Flora because there are huge amounts of quantifiable socioeconomic benefits to having things like city farms and city gardens, from wellbeing, from access to green space, from development programmes for social gatherings. I mean, there's so many other reasons this has beneficial, it's just giving some really specific areas that we could reduce the climate impact of these kinds of ventures.

Flora Graham

Right, right. And if we are going to try to improve and optimise our systems, then there's no point in shying away from the complexity that that often entails. And there were a few cases where locally-grown food did come in on par, or even trump commercially-grown food. And those are the ones that take a lot of heat, water, greenhouses. So as you can imagine things like tomatoes, things like asparagus and stuff like that. So that's another option, you can target your home growing to those really big-ticket items in terms of carbon emissions. And who knows, leave the potatoes to your local professional.

Benjamin Thompson

And were there any other compounding facts as well? Because often with these kind of large-scale modelling exercises, they have to say, well, actually, we couldn't include this particular facet. And that might make a difference, anything like that.

Flora Graham

Absolutely. So in this case, they were looking more at the day-to-day of the farming itself. So there are things like the carbon emissions of grocery stores, for example, you got to keep these things on shelves, you've got food waste. So in order to factor those in, they use kind of standardised numbers. So they did factor it in but it wasn't to the granularity of the aspects of you know, like how much synthetic fertiliser is being used, for example.

Noah Baker

And there certainly are ways I mean, people reading this could look at ways that they could directly impact their own personal footprint in terms of their own allotment, for example. I have a very dear friend who are gardeners and they were a trained horticulturalist before they went into gardening, and throughout the entirety of the summer, you have to wee in a bucket there so they can use it as a natural fertiliser for their tomatoes because they don't believe in buying fertiliser, because they're like we made loads of fertiliser ourselves. There are things that one can do and if you want to get into that there's loads of resources out there about ways that you could try to reduce your carbon footprint in your own personal growing endeavours.

Flora Graham

I would say that the effect of synthetic fertiliser was a big takeaway for me that it's absolutely something to be avoided. And another one that surprised me was composting, I had been under the impression that composting was kind of objectively good all the time. And again, this is certainly not to say do not do composting and throw your waste in the bin. But I had not realised that if you're not composting optimally, it can actually out-gas quite a bit and you're really not achieving the full benefit that you could be achieving. And one of the aspects that the paper argued for is what can municipalities and regions do, for example, collecting food waste. I'm lucky enough where I live that that's what they do so they can have large central composting where they ensure that it's done in the most carbon efficient way possible. And then, of course, you've got all the factors of distributing that to people and everything else. But it's an aspect that I hadn't really realised I needed to educate myself on and I look forward to swotting up on the how to compost effectively and make sure it all comes out as healthy as possible.

Benjamin Thompson

Well, I can say that my attempts to grow vegetables have yet again been thwarted by the squirrels who just eat all of them. In terms of symbolic gestures, they are definitely giving me the eyes when they're doing it as well. So ‘ya boo’ to them, I would say, right. Well, listen, let's have one more quick curtain-raiser for something that's coming up next week. And that is an eclipse, a total eclipse, which will be on the 8th of April, sweeping a narrow track across North America as the Moon passes in front of the Sun, and it's gonna be a very exciting time for science.

Flora Graham

I am just like frozen with jealousy about this eclipse, it's going to be so fantastic. And it doesn't surprise me that everybody I know in North America is travelling to get into that path of totality, because it is going to be a life-changing event. Don't forget to wear your eclipse glasses. Everybody be safe.

Noah Baker

I totally agree. I was living in the US in North America last year. And now I've come back. And now there's the eclipse. I thought, oh, God, I would have definitely been travelling over to go and see that. It's particularly interesting scientifically as well, because it's happening during the solar maximum, right?

Benjamin Thompson

Yeah, that's right, we're coming up to a time when the Sun is at its most active. And as we've covered on the show before there's a lot we don't know about our nearest star. In particular, this kind of area outside it called the corona, which kind of spreads millions of miles out into space from the surface of the Sun. And when the Moon passes in front of it, researchers can get a really good look at this kind of swirling maelstrom of charged particles. Because one of the things researchers kind of can't figure out is, why it's so much hotter than the Sun itself? And also this area is where the Sun can fire out charged particles towards the Earth, which can affect things like telecommunications, and all that sort of thing. So researchers are really going to get all eyes and ears on this as best they can. So NASA's sending up rockets to have a look, there are points and telescopes at it as well to see how Earth's atmosphere is going to respond, planes are being sent up with special equipment. I mean, there's a bunch going on here. But as Flora said, like, be careful, don't look directly at the Sun look what happened to Isaac Newton when he did it. So I'm not sure what the official advice is, but make sure you follow it.

Flora Graham

And I have to give a shout out to a couple community science initiatives as well that are asking people to get their observations down. We've got a couple of NASA funded efforts, one is called the Eclipse Soundscapes Project and they are particularly focusing on, you know, obviously the visual aspect can be overwhelming, if that's something that you can observe. But there are a whole range of multi-sensory observations that can be recorded, sound data, there's another NASA project called Globe Eclipse, which is asking volunteers to record the air temperature and the clouds during the event. So get out there, collect that data, because yeah, it's not gonna happen every day.

Noah Baker

And in the coming days, there's gonna be more Nature coverage on all of this content. Look for stories coming up, we're going to be be tracking things that scientists are looking at, photographs people have taken, there's gonna be an awful lot of stuff to keep your eye out for. So do watch out for it.

Benjamin Thompson

And I will say, many years ago, in the UK, I remember a partial eclipse and it's quite eerie, like the birds go silent. It's like a big cloud has passed in front of the sun.

Flora Graham

That's another project that scientists are going to be doing. They're gonna be observing zoo animals, to specifically observe the response of animals. Obviously, this is in a particular setting to the eclipse because yeah, I think we have all these kind of vibe checks that we feel and we sent during the eclipse. I also saw a partial one, and it just transformed something kind of ineffable, and I’m sure the animals were all madly gesturing to one another.

Noah Baker

I saw a partial eclipse on a river in the Amazon. And it was so underwhelming in every way, we stopped for two hours to try to film it. And it was so rubbish, nothing really happened. It just got very slightly cold. I thought, wow, I’m in the Amazon, how cool. But no, it was a bit rubbish.

Benjamin Thompson

On that upbeat note, then I guess, I mean, well, shall we call it there for this week's Briefing Chat podcast. As Noah says, keep an eye out on the website for all of your eclipse news. And of course, we'll put links in to what we've talked about today so you can have a look at those as well. And there'll be a link on where you can sign up for the Nature Briefing to get even more stories like this delivered directly to your inbox five times a week. So all that’s left to say for this week's show is Noah and Flora, thank you so much for joining me.

Flora Graham

Thank you so much.

Noah Baker

I'm gesturing. Thank you.