How ancient humans crossed the vast ocean; Brain training for dementia; Life of science legend Maggie Aderin

0:01When Johann Rall received the letter on Christmas Day 1776, he put it away to read later. Maybe he thought it was a season's greeting and wanted to save it for the fireside. But what it actually was, was a warning, delivered to the Hessian colonel, letting him know that General George Washington was crossing the Delaware and would soon attack his forces. The next day, when Raw lost the Battle of Trenton and died from two Colonial Boxing Day musket balls, the letter was found, unopened, in his vest pocket. As someone with 15 ,000 unread emails in his inbox, I feel like there's a lesson there. Oh well, this is The Constant, a history of getting things wrong.

0:40I'm Mark Chrysler. Every episode, we look at the bad ideas, mistakes, and accidents that misshaped our world. Find us at ConstantPodcast.com or wherever you get your podcasts.

0:58What's the furthest you've ever traveled? on a log, floating on the water. Like, well, one metre? Oh, pitiful. You need to be like your ancestors. Thousands of years before the invention of compasses or sails, prehistoric people crossed oceans on logs, or maybe rafts of logs. We're talking 50, 80 kilometres. How did they do it? We're getting into that today. Also on the show, we discussed a 20-year study showing that a kind of brain training called speed training can reduce the risk of dementia or a dementia diagnosis by 25%, which is some of the most impressive results we've had for years around brain training.

1:34For the first time, they have tested an intervention against dementia in a randomised controlled trial, which is what we need to prove causality. Also today, we're delighted to welcome space scientist and TV presenter Maggie Adderin. We're going to be talking about all things space and Maggie's memoir, Star Child, My Life Under the Night Sky. I always say reach for the stars, no matter what your stars are. And I think because I've had this big, crazy dream, just by having the dream, it's enabled me to do things I would have never thought possible.

2:04Welcome to the world, the universe and us from New Scientist. I'm Dr Penny Sardegna. And I'm Dr Rowan Hooper. So let's start with the mystery of the dispersal of ancient people across a watery planet. Yeah, it does make me think of Moana, this. People looking, gazing across the ocean and just wanting to go there, you know, and they managed to get to places they couldn't see from the land. And they have to sail overnight. have to use the stars to navigate. How did they do that? Yeah, and it seems to be one of these things that's inherently human. The more we learn about how we dispersed around the planet, ancient people did just take that leap of faith.

2:39They figured it out and they went out there. And what I love about this kind of science is that it tells us about the brains of, you know, what were these ancient people thinking? Mike Marshall has reported on this story for us, all about ancient seafaring. Hi, Mike. Hello. So this particular story this week, then, is about evidence the ancient people got to Malta, right? Perhaps first you could tell us why it's impressive that they got to Malta particularly. So Malta is one of the most remote islands in the Mediterranean. The nearest land is Sicily, which is about 85 kilometres north, which today, you know, you just hop on a ferry for a few hours, that's nothing.

3:16But if you imagine we're, you know, 10 ,000 years ago, Malta is suddenly very difficult to get to. It's far enough from Sicily that you can't see it over the horizon, at least if you're at ground level. And if you paddle there in a canoe, it's going to take over 24 hours. So you're not going to be able to do it during daylight hours. You're going to have to navigate by starlight, which means you're going to actually have to understand something about navigating by the stars. So in short, if we were thinking about Stone Age people and sort of easy places to go by boat, Malta would not be one of them.

3:49No, I mean, it seems on the face of it somewhere that would be really hard to get to. And it's generally been thought that particularly hunter gatherers, which is what humans were for most of our existence, just wouldn't have had the know how to either build the craft or to navigate across that sort of distance. but the evidence says that in fact they did get there we know this because a team of archaeologists led by Eleanor Sherry at the Max Planck Institute of Geoanthropology excavated a sinkhole in northern Malta and what they found there is abundant evidence of people being there so there were ash from hearths there were stone tools butchered animal bones like deer bones and all this stuff is about eight and a half thousand years ago.

4:32So this is before, well before people were sort of farming in this area. These were hunter gatherers who had made this journey, we presume from Sicily all the way to Malta. Wow. This is another thing I love about the story is that they were hunter gatherers. And, you know, over the recent years, Mike, I guess we took them for granted a lot, but hunter gatherers could do a lot more than we gave them credit for, right? Oh yeah, absolutely. I mean, the hunter gatherers are people who were often kind of dismissed by Western science as being sort of primitive or savage and just lacking in sophistication.

5:08But in fact, living as a hunter-gatherer requires an incredible amount of knowledge about the world around you that a lot of us would sort of be completely oblivious to. And the fact that they were able to sort of figure out how to build and assemble a craft that would be able to be seaworthy and then plan to sort of go all the way across, beyond the horizon to find this island is sort of one more evidence, one more piece of evidence of just how much hunter gatherers and prehistoric peoples in general were able to do. I find it fascinating because one of the things I discovered quite recently is archaeoastronomy and the fact that people did look up at the night sky and used it to navigate.

5:49And I think it's something that sort of when people say, you know, why stargaze? It's because we've always done it. And there's something magical about it. and I always have this image in my mind of sort of yeah primitive people not even being able to communicate with words but just being mesmerized by the night sky so it's something I think fundamentally in all of us and it pushes us to you know pushes us to the limits you know maybe across the sea but out into space as well yeah I think there's a desire to know more and that's that's a great connection isn't it we navigated by the stars then and we're still going to the stars now or hopefully we are and i think we've really underestimated how much astronomical knowledge these people have because there's no written records so you're kind of having to like infer this stuff but there is good evidence for example from australia that aboriginal australians could predict lunar eclipses with quite a surprising degree of accuracy given that they weren't making written records but they do seem to have understood when they were going to happen and they had ceremonies built around when that would when they would occur yeah so reading the night sky.

6:50And speaking of inferences, Mike, you know, we knew that people, ancient people, were in Malta by what they left there rather than finding their boat. Boats are really hard to preserve, aren't they? What's the oldest boat? So the oldest known boat is called the Pessa Canoe. And it was found in a peat bog in the Netherlands. And it's about 10 ,000 years old. It looks it as well. I looked at a picture of this and it is literally like a trunk of a tree like hollowed out. Yeah. Like, can you imagine going to sea in that? It's a bit like, you know, the rides you get at theme parks in a lot. Yes, except much more unstable.

7:30And yet there is good evidence. We've mentioned Australia already that people got to places like Australia long before the oldest canoe and a lot earlier than we used to think. 65 ,000 years ago, potentially. Yeah. So, you know, modern humans were sort of, you know, there was this big expansion out of Africa, sort of perhaps around about 70 ,000 years ago. So people sort of assumed, oh, they wouldn't have got to Australia for quite some time after that. But no, there is evidence of people there, you know, potentially as early as 65 ,000 years ago. And that is a really impressive thing, because you have to cross an awful lot of ocean gaps.

8:08It's not just one little gap that you have to nip across it's multiple gaps between islands you know or you're having to sort of go through what we now think of as indonesia all the way to new guinea and then into australia itself there were times in prehistory when this was actually easier than it is now so um during um you know as the as the ice age is sort of waxed and waned sea levels rose and fell and at times when sea level was lower there were huge expanses of land that were exposed in these in these places so that a chunk of what is now Indonesia was actually connected to mainland Asia and New Guinea and a few other islands were connected to what's now Australia there was this huge exposed landmass called Sahul and so it was somewhat easier to get there but there was always there were always multiple seaways that had to be got across some of which you know have quite treacherous currents in them so it was yeah it was always going to be multiple sea journeys that required an awful lot of planning and forethought.

9:09And also, even earlier humans, right? So Homo erectus went to Flores, right? And evolved into hobbits. Like, well, I wanted to say that the hobbits went to Flores, but you know, Frodo and Sam in their canoe. But no, they, so Homo erectus was seafaring. Maybe accidentally, we don't know, but... Yeah, so this is where it gets more contentious because there is evidence of early hominins on islands really early. So there's evidence that someone, we don't know who, was on Luzon, which is one of the big islands in the Philippines, over 700 ,000 years ago. There are stone tools on Sulawesi from a little over a million years ago.

9:54You can sort of look at that in the same way that you look at the Malta evidence and go, okay, well, they were there, they must have got there somehow. Now, does that imply that therefore that they had some kind of watercraft and some kind of seafaring capability? The trouble is that sometimes animals do cross oceans accidentally and it's difficult to eliminate that. Sounds like Monty Python. I accidentally made it across this island. Are you a Eurasian swallow? But yes, accidental crossings. This is also our best explanation for how monkeys got to South America. Am I right? Is we just think they got there somehow by accident.

10:34That's right. Because, yeah, there are monkeys in South America. We know from genetics and so forth that they are quite distantly related to the monkeys that you find in Africa and Eurasia. But there's no fossil record of them having gone to America the easiest way, which would be to go up into Siberia, hop across into Alaska and then down through the Americas. But, you know, the trivial thing. But there's no fossil evidence of that at all. The only thing that seems to make any sense is that somehow they went west across the Atlantic. This would have been tens of millions of years ago at a time when, due to continental drift, the Atlantic wasn't as wide as it is now.

11:10But it's still, you know, a pretty extreme thing. But I mean, the monkeys are there. We need a Pixar animation about this. Yeah, we're going to cross it. Yes. Yes. But so if monkeys are accidentally turning up in South America and Homo erectus or something similar is accidentally on the island of Flores, what is it about the journey that ancient people took to Australia that seems more deliberate? I think it's the argument that researchers are making about this is that it's multiple journeys in quite a short time span. So instead, the people that are on Luzon, it's sort of one bit of evidence from several hundred thousand years ago.

11:48So essentially one crossing in a million years, maybe, to get there. You can explain that away. But getting all the way through these different islands, all the way across into Sahel, requires multiple crossings. And it all seems to have happened within a few thousand years, so really quite rapidly. That becomes just much harder to explain away by accident. That looks much more like intentional planned crossings, particularly because there's at least some evidence of trade among some of the islands of like things being transported, which really sort of starts to make you think, okay, you know, they've got some boats and they're going back and forth.

12:24Well, and also that's what it tells us, Mike, isn't it? More about the ancient mind as it was and how complex it was able to consider long-term, multiple stage trip, the trading that you'd need to do. You know, that's the insight that we, that's what I love about these stories. It gives you an insight into the mind of our ancient ancestors. I mean, you're seeing a degree of planning because you have to think, okay, well, that's where I want to go. So I need to build this kind of boat. And, you know, building a boat is a complicated business. You're going to have to gather wood and all these other materials, put it together, probably test.

13:00That's a lot of planning and forethought. It also, I think, points to cooperation. You're not going to build any kind of large boat by yourself. You're probably going to do that in a group. So there's evidence there of people working together in a sort of coordinated way. And I think also it points up something that we perhaps don't often talk about in these sorts of topics, because it sort of feels a little bit like a squishy thing to say. But I think it just says courage. Maybe you have some evidence that there's land over the horizon. Maybe you can see birds flying over. Maybe you can see smoke rising from a wildfire or something.

13:34But even so, it still takes a serious backbone, I think, to hurl yourself out into the sea in a hollowed out log or a raft that you've lashed together with twine and hope that there's going to be something there. I think that speaks to cooperation, planning and courage. But I think it also shows intent because you were mentioning the trading and things like that and that happened quite rapidly. So it wasn't just sort of moseying along and sort of bumping into it. It was, OK, let's go and do this. Let's expand the empire. Let's see what's beyond. And so I find that quite interesting because I keep thinking that they were quite self-focused, but they were looking beyond.

14:12We can take a lesson from that maybe.

14:19Now we have a study that feels almost too good to be true, that playing a brain training game for a relatively modest amount of time could actually prevent dementia. Have they really proven this? Alexandra Thompson is here to tell us. I would say yes. Yes. So we've heard a lot about cognitive reserve. So this is the idea that playing a musical instrument or learning a second language changes the brain in a way that helps you stay sharp into old age. But all of that research, as much of it as there is, it's observational. They've observed a correlation between X and Y, doesn't prove cause and effect.

14:53But now, for the first time, they have tested an intervention against dementia in a randomized controlled trial, which is what we need to prove causality. You said first time there, haven't there been things like hearing aids for example that have been used in a randomised controlled trial to see if they prevent dementia? Yes, so for a long time there was an observation between hearing loss and dementia and then for the first time a couple of years ago they tested giving hearing aids to people to see what the outcome was and they found that for people who are particularly susceptible to dementia because maybe they have a condition like diabetes which is thought to increase the risk wearing hearing aids did reduce their risk of cognitive decline but they measured things like memory problem solving decision making this is the first trial that has actually measured dementia diagnoses amazing because i mean that is the thing with dementia is it can take decades to develop so you need to do an experiment do a thing and then follow it for a really long period of time is that what they did they did they followed for 20 years 20 years which is really unprecedented Wow.

15:56So what did this particular study involve then? So it had almost 3 ,000 people aged 65 or over, and they were randomly assigned to one of three intervention groups or a control group. So one group engaged in speed training, which obviously tests speed, but it also tested their attention and their peripheral vision. The other two intervention groups took part in memory or reasoning training. And it was really quite intense. So they had to do two approximately one hour sessions a week for five weeks, and it got progressively harder. This was not your average crossword. This was really quite challenging.

16:29And half of the group were then randomly assigned to have booster sessions. So that's four additional one-hour sessions at the end of the first year and another four at the end later on. And then 20 years later, the researchers looked at their Medicare claims data for dementia diagnoses and found that those who completed the speed training with booster sessions were 25 % less likely to be diagnosed with Alzheimer's or a similar type of dementia than the control group. And no other intervention had that effect. Not the memory training, not the reasoning training. It was this kind of speed training that had the effect.

17:01And you said modest, but that's really modest amount of training to have an effect like that, isn't it? It is. I mean, it's, you know, an hour at a time over and over again getting harder. That is quite intense, but even so, it does feel almost too good to be true. Because it reminds me of the cognitive reserve stuff that you mentioned. And, you know, it sounds great speaking languages, playing instruments. Lovely. Keeps you sharp. Often in the studies that find that, it's people playing an instrument an hour a day. I don't have time to play an instrument an hour a day. But this is like something you could actually maybe fit into your kind of ageing plan.

17:32You see the app. I want the app. Let's make one. What nightmare if you're in the control group? Yes, 20 years. 20 years. And you go, and then, oh. That often happens, doesn't it? Then sometimes they stop studies. Go, OK, this is unethical to have people in the control group anymore, but not in this kind of one. So tell us more about speed training. So it seems to be unique in that it relies on implicit learning. So that's sort of when you're learning without consciously trying to. Oh, best kind. Which is the best kind. So research suggests that there's something about this learning that has a very long-lasting effect on the brain.

18:09It seems to build a sort of brain reserve that then acts as a buffer against cognitive damage. Also, if you're learning how to sort of divide your attention more accurately, maybe it has knock-on effects so there's a long link between socializing and exercising and a lower risk of dementia so maybe the effects are more sort of as a consequence right and uh one thing i wondered with this is you know um they had a certain number of sessions a certain number of boosters what if you were playing it once a week for 10 years you become immortal yeah could that have an even bigger effect i mean possibly the fact that it was very specifically the booster session suggested there is a dose response but we need to better understand the optimal amount it might plateau i suppose the first thing this made me think of was um you know those tests you have to do in the uk before you learn to drive you have to do the hazard perception test it did look like that yeah because they had to tell where a car was and then a road sign okay and as they went on there were more distractions in the periphery and they disappeared quicker It sounds like fun too.

19:11Yeah, it is quite fun, yeah. But, you know, aside from this one particular game, are there other ways that we can maybe try to get some of these benefits? I think so. I think anything that involves any kind of learning, but maybe particularly implicit learning. So it could just be a sport or taking up a new hobby. And at the very least, you'll enjoy yourself. OK, let's talk to Maggie now. Space scientist Dame Dr Maggie Adderin worked on the James Webb and Gemini telescopes. You've been host of The Sky at Night, the greatest astronomy show on TV, president of the British Science Association and science educator in general.

19:51And through that, you've had a huge impact over the years, speaking to tens of thousands of children and influencing, you know, hundreds of thousands more. So there's a lot to get into. But let's start with your new book, Starchild, My Life Under the Night Sky. And And what I thought when I was reading it was basically the first thing was, my God, you've done a lot. So what prompted you to write it? Oh, so I hadn't anticipated writing my autobiography. But in the science communication I do, I talk about the science. But I also like to talk a bit about my backstory, especially for kids. And so I was doing that and I did that at Penguin Random House, my publisher.

20:33And they hadn't heard that before. Oh, that was quite interesting. you have an interesting background have you considered writing your autobiography not really yeah i'm not that old but yeah it sprang out from there yeah i mean it does there is it does feel like a great work of outreach in parts because there's a lot of stuff effectively you're saying look i did this and so can you which is perhaps what you do in you know part of your day jobs you know going around places um so yeah so perhaps that was part part of the prompting behind it it It is. And because I like to try and sort of encourage people.

21:08I always say reach for the stars, no matter what your stars are. Because as a child, I used to watch The Clangers and Star Trek. And I actually, both physically and metaphorically, I am reaching for the stars. I want to get out there. And it's been the driving force of my life. And I think because I've had this big, crazy dream, I haven't been out in space. I may never do it. But just by having the dream, it's enabled me to do things I would have never thought possible. yeah and so and that's what i like to say to the kids but not just to the kids anyone i speak to because i do lots of corporate events and other things i do sort of cruise ship talks as well wow and sometimes it's what the demographic is sort of you know i don't know 60 to 80 i think yeah still have a big crazy dream because it drives you on yeah and so i try and get that sort of message out in any way shape and form i can yeah and so to do it as a sort of my life story and to do it as a book just seemed like a great opportunity yeah yeah so there's loads of things that jumped out at me in the book and um so first of all went to 13 schools in 12 years yes i heard a gossip that sounds like hard work for you well actually it's funny because i didn't really realize that it was happening and that that wasn't happening to other people and when i go out to schools i say this to kids sometimes how naughty were you yeah no no it wasn't like that i wasn't expelled just because my payments broke up when i was quite young and so i there There was an ongoing custody swinging from one to the other.

22:31But yeah, and some schools just closed. They didn't touch them. But yeah, it racked up. And the things I didn't realise until I did, years ago, I did Desert Island Discs. And then we were doing the research for Desert Island Discs. And they said, oh, yes. So we were going through the list of schools. You're like, 30. And so some were literally, oh, hi, bye. It's just passing through. I bet they've got plaques there, even though you were there for one day. Maggie Adrain was a pupil here. I poke my head around the door. so another one that jumped out at me when you were four your dad asked you which Oxbridge College are you going to?

23:05My father saw the power in education and fortunately I saw the power in it too but that was quite a challenge for me but yeah this is what he used to say to us because he had immigrated from Nigeria and he felt that the UK was quite hostile when he came in sort of the late 60s oh actually sort of in the late 50s early 60s there were signs you know so no blacks no dogs no irish yeah and so and he had four daughters and he really wanted us to survive and thrive yeah and so education was yeah it was drummed into us for a very early age and hence you know what oxbridge college are you going to go to yeah um but for me um i felt a little of a failure because when i did start the education system because i had undiagnosed dyslexia um i was put at the back of the class you know with the safety scissors and the glue and so I felt that education was the key and yet I wasn't doing well at it yeah and it's funny because I only got formally diagnosed with dyslexia uh actually about six months ago I know because I'd always been aware well I hadn't always been aware it became more and more apparent that I was likely to be dyslexic but when I went for the test my daughter said don't do it mum the game's up you might not be dyslexic but it was fine I'm dyslexic so and then obviously you did do well at school or you know you went to university went to imperial but um the only black woman on your physics class in your physics year at imperial and i wondered about that and i and you know the other thing is you've got there's a barbie doll made in your image and i wondered like imagine being a student you know being the only black woman in your year at imperial and someone could tell you you know in 20 30 years there's going to be a barbie doll made in your image.

24:49Yeah, right, mate. And then another thing like that is when you're working on the Gemini telescope and you remember making your own telescopes when you were a teenager. Yes. So there's this thread running through from the stuff you did when you were younger to stuff you're doing now and looking back on it and it all sort of fits together like a telescope. Yes, the pieces come together. And it's interesting because I suppose it's storytelling. telling it's the way you interpret it and it's quite interesting because um i i made my own telescope because i used to listen to the sky at night and patrick moore would say yeah with a telescope you can see this and i bought a telescope we were living in a council flat in camden and so it wasn't very good it had plastic lenses suffered from chromatic aberration but then i discovered sort of looking through an um an adult education magazine you can make your own telescope but i recently went back to the adult education sort of establishment and they told me that it was an adult education and I was only 14 so I had to get special permission from my teachers at school and also from my father to actually attend the class and I'd forgotten all about that.

25:59And to learn how to make the telescope. Yes because I was going to an adult education class but as a child and so one of the things that came out in the biography which I wasn't really aware of is a certain amount of determination yeah i'm gonna make a telescope nothing's gonna stop me so um yes and i wasn't so much aware of that at least at the time anyway well i i wanted to ask about the moon as well because i read your book of the moon a few years ago as well um and at the time i was getting really into the moon and i bought a big map of the moon with all the craters on it and i've got a little telescope as well and i just also love even if you live in london you can just look at the moon and it just brings so much joy doesn't it and wonder yes um so tell us a bit about your love of the moon because that comes through in the book as well oh yes i always describe myself or that's what a term my father used to use as a self-certified lunatic the self-certification is very important because i'm just a lunatic and but my father used to tell me about how he used to um the moon was his friend because he was brought up in nigeria and I think it was about a 12-mile cycle ride from his home to his school.

27:07And when it was dark, the moon would guide his way because the roads were unlit. And then just as you say, growing up in London, in intercity London, you don't often see the stars that clearly, but the moon shines through and it lights up the city beautifully. And so the moon was my father's friend and so it was my friend too. Also, I'm an insomniac. And so when everybody else was asleep, I'd be wandering around the house and you open up the curtains and there's the moonlight and the house doesn't seem so scary. So throughout my life, the moon's been my friend. And so another crazy dream. I do want to go and walk next to the footsteps of Neil Armstrong.

27:45As a self-certified lunatic, I'm hearing about Artemis and I'm doing a podcast around that. And the idea of getting to the moon and seeing it up close and personal. So Maggie, I have a really long running argument with Rowan about building on the moon because he wants to look up and see buildings on the moon surface. I think, you know, to look up and see structures on the moon that we've put there, you know, scientific research and stuff like that, I think that would be amazing if you could see them from Earth. But Penny... But I think it's a tragedy. You know, our ancestors have always looked up and seen the same moon.