ADHD advantages, and mining microbiomes

Plus, a frog that looks like a log
05 April 2024
Presented by Will Tingle
Production by Will Tingle.

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A coal mine

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This episode of Naked Genetics: has the evolutionary advantage to ADHD been uncovered? Also, We look at the microbiome of mining. And, the only vertebrate in the world that would thank you for saying that it looked like crap...

In this episode

ADHD

Is there an evolutionary advantage to ADHD?
Shivani Shukla & Aylwyn Scally

This week’s news story centres around Attention deficit hyperactivity disorder, also known as ADHD, which is a neurodevelopmental disorder which typically presents with inattention, impulsive behaviour, and hyperactivity. For those that have been diagnosed, or have been waiting a long time hypothetically, the treatments would imply that ADHD is something of a detriment in this day and age. But this study, published in the journal Proceedings of the Royal Society B: Biological Sciences, has a theory that not too long ago, such a genetic mutation may have been somewhat beneficial.

Will - I have to say for a genetic study, this has to be one of the most out there methodologies I've ever looked at. What happened, what was involved, and why were people foraging for berries?

Shivani - Yes, it's definitely different to sampling skeletons. So this time they had an interactive video game online and they had a couple hundred people essentially scavenge for berries on bushes and it was under time pressure. So they could either stay at the same bush looking for berries or they could move on to another bush, which used up time, but they may or may not find even more berries. So it was a trade off between time spent, a number of berries collected and then they took the scores of these couple of hundred people and also then screened all of them for symptoms of ADHD, which currently in the UK we diagnosed with the DSM-5 criteria. And it was found that people who displayed traits of ADHD actually scored higher and spent more time moving on to new pastures to look for berries essentially.

Will - So all these years when I've been told I'd get distracted too easily that I could just have been retorting with yes, but I'm going to find the next patch of good looking berries sooner than a potential rival.

Aylwyn - I mean, more generally, it's an example of the kind of thing that we see quite a lot in evolution where there is a particular trait behaviour. It doesn't have to be behaviour, it could also be some other more physiological trait. Something like risk of certain diseases that may actually have evolved in conditions where there was some benefit that came from that. Maybe there still is some benefit that came from that, but there's also a cost in other conditions or in other environments or at other times.

Will - It's an interesting one because I suppose in many ways, and I think the study and the later conversation around it hinted that whilst ADHD is is good for when you have rivals, it's less good for when you have to kind of attenuate berry collecting to seasons like our ancestors would've done. So again, there is still a trade off there that you'll be better against people of your own species, but you might not be able to keep time so well when you need to know the seasons well enough to collect berries naturally.

Aylwyn - Yeah, and that's going to be true of any adaptive trait to be honest. There's, it's always gonna be a relative thing. Are you doing better in this condition in this environment than people with the other version or with some other kind of behaviour there? And if so, then you'll have the advantage. But there might come a time where that's no longer the case or might come conditions where it's not the case and then you are at a disadvantage. One of the problems with trying to decide whether or not something has evolved like this is it's actually, people have found ever since Darwin, that it's actually quite easy to come up with plausible arguments for why something was beneficial. The problem is that because it's quite easy to come up with these stories, that they sometimes are given the term 'just so' stories because we're not sure if they're true or not. So how do you establish that actually something, this really was the cause that there really was an evolutionary advantage that that came from this?Rather than it just being some side effect or consequence of something else happening in evolution.

Will - Not to put you on the spot here, but is there any answer to that?

Aylwyn - There is some independent evidence and that comes from genetics from the genome. You can go and look if you have some idea about what genetic factors are associated with this trait. So in the case of ADHD, we know that there are some genes, versions of some genes that make you more likely to, to have ADHD and therefore it has, you know, there are some heritable components. Not that they're entirely causal, there are lots of other factors involved in environmental factors, but if you know that there are genetic factors, you can go and look at those gene variants and see when did they arise? Can you date the time when those variants appeared or when they rose in frequency. And we can do that now because we have all of these genomes from people all around the world and we've got ancient DNA, so we can actually go and look in many cases at genomes in the past and we can see did they have this particular gene risk allele? Was it present at one point in time or at low frequency and then high frequency later. And people have done that, I believe, with ADHD and I think they find that it's not so clear in fact this, these versions of these variants have been around for quite a long time. Neandethals, for example, have the genes that we associate with ADHD. So it's actually something that may have been with us for a very long time in our evolution. It's not so clear that it evolved recently in response to changes in human population sizes or subsistence strategists or something like this. So the story I think is still a little bit confused as to whether or not this explanation really holds.

Will - And Shivani, from the medical side of things because it's always been touted to me that ADHD is detrimental and it requires behavioural therapy or medication regardless of whether it's an evolutionary advantage or not. Does this kind of almost skew the way we look at it and perhaps there should be more social or medical shift in the ways that we look and treat this?

Shivani - Absolutely. And I think not just for ADHD, but things like autism, it's interesting that the term disorder or disease are being used to classify these things because I guess if you look at how societies changed before it was better to be stronger or faster when we had to hunt for our food. Things that benefited that were selected for. And now, society has moved to emphasis placed on things like intelligence or focus or academia. So how can you say traits that benefit certain jobs or how humans were tens of thousands of years ago are now a disorder. It's just sort of coming back to the fact that humans are different. Every human is different to the other human and everything lies on a spectrum and certain people are better at things than others. And in the case of autism, I mean, there've been studies showing that people with autism should really be really valued members of society. I mean they can be proficient musicians or painters or have really great focus and attention to detail and probably will outperform someone who doesn't have autism on a variety of tasks and jobs. And likewise for ADHD, it's definitely a condition that negatively affects a lot of children. And increasingly there are parents who are worried that their child isn't able to focus at school. And that's why I suppose medical professionals are quite quick to jump to things like medication or therapy because they might feel that in comparison they need that to kind of stay on average. So I think the terminology disorder is wrong and there shouldn't really be so much stigma in terms of having this diagnosis. And we should shift to how we can support these people better or how we can align them to career paths that they're better suited to because not everyone is good at the same thing. And that's what makes society function, I think.

A coal mine

The microbiome of mining
Dan Letchworth, Illumina & John Steen, University of British Columbia & Elizabeth Deyett, Allonnia & Aria Hahn, Koonkie Cloud Services

Let’s actually talk about some actual boots on the ground, honest to god genetic sequencing now. I mean, it’s been part of the introduction to the show for long enough. This stuff is pretty close to witchcraft by now. By taking a tiny sample of some organic material, you can then identify the chemical building blocks, Adenine, Thymine, Guanine, Cytosine, and uracil if you’re feeling feisty, but also the order in which they are… ordered. From that you can work out the organism, and the part of the organism that the sample came from. I mean, the applications seem endless. And thanks to my new best friends at Biotechnology company Illumina, over the next few months we are going to delve into just what the cutting edge of sequencing technology can reveal about our world.

Will - And hey, here's an idea. Let's actually talk about some actual boots on the ground. Honest to God, genetic sequencing now, I mean, it's been part of the introduction to the show for long enough. This stuff is pretty close to witchcraft by now. By taking a tiny sample of some organic material, you can then identify the chemical building blocks, adenine, thymine, guanine, and uracil if you're feeling feisty. But also the order in which they are ordered from that you can work out the organism and the parts of the organism that the sample came from. I mean, the applications seem endless. And thanks to my new best friends at biotechnology company Illumina, over the next few months, we are going to delve into just what the cutting edge of sequencing technology can reveal about our world. I know that line sounded familiar. Anyway, let's begin with a story. Like I said, the applications of genetic sequencing are absurdly wide reaching. And so if I asked you where you think genetic sequencing is currently playing a huge part in shaping our future, where would your mind go? Disease identification, absolutely. Forensics a hundred percent. But how many of you thought of mining? Mining, particularly coal mining is a controversial subject and has a reputation for contributing to global climate change that is irrefutable. However, for us to venture into a clean new world of renewable energies, we will need coal.

Dan - We need coal to make steel. A single wind turbine requires nearly five tons of copper and over 300 tonnes of steel. And to make that steel, you need coal.

Will - That's Illumina's Dan Letchworth by the way, he's going to be talking us through quite a lot of this. So if we must continue to mine for coal for the moment at least, we must also contend with the other stuff that appears when you dig a big hole in the ground.

Dan - So one of the harmful byproducts of mining is selenium. Selenium is a naturally occurring element, but the problem is that mining tends to grind and chew up the rock and expose a whole lot more selenium to the surface than would naturally be uncovered. And because the mining process breaks up the rock into tiny pieces, suddenly the surface area is vastly multiplied. And those are usually just exposed to the atmosphere, exposed to the air and water. And so precipitation from rain and snow runoff that can, uh, carry these leftover bits of selenium into the water supply into rivers and streams.

Will - By the way, if you weren't sure, that's bad.

Dan - Selenium is a required element for cell function in animals. All animals, humans included, use selenium as a natural part of their metabolism. But just like the phrase goes, the dose makes the poison. High enough concentrations of selenium can cause growth defects in fish, and it can adversely affect their population numbers. And unfortunately, if selenium levels get too high in the water supply, communities that rely on that water to drink can also have negative health effects as well.

Will - So what to do then with this excess buildup?

Dan - The companies I spoke with were Teck resources and Rio Tinto. Teck in particular has implemented selenium eating bacteria. What Teck does is they introduce this bacteria to the waste rock piles with a small amount of the carbon based food that the bacteria eat. And as a part of their metabolism, these bacteria take the dissolved selenium and convert it into a harder, more solid form selenite crystal, which is then heavier and it's easier for humans to keep outta the water supply.

Will - A species of bacteria is capable of treating metals like selenium. That's pretty amazing. But perhaps not all that surprising. As the University of British Columbia's John Steen explains...

John - Microbes have been around metals for a long, long, long time. They're evolved to interact with metals and, some quite specifically, they use metals for metabolism. They use metals for their energy systems. The reason why we have deposits of iron ore around the world is because of microbes and what they were doing billions of years ago.

Will - And so that begs the question... What else is out there? If there really are, as some have estimated, 1 trillion species of microbes undiscovered beneath our feet, what might they be capable of? Well, that's where Illumina and the Mining Microbiome Analytics Platform, or M-Map to its friends, comes in. A plan to find out if anything underground can help us out on the surface. Here's Allonnia's Elizabeth Deyett to explain that a bit better.

Elizabeth - I think that microbes offer an untapped potential in a lot of different areas. And what M-Map is really trying to do is understand that potential at a much deeper level than we've ever been able to have before. And a lot of times our capabilities are limited by what we can, what our own samples can tell us. But what M-Map is doing is sort of allowing the collective community and all of the samples that come in from various sources to help enhance an individual's project while still having data security parameters on it.

Will - Yes, exactly. And naturally genetic sequencing has a huge role to play in this.

Dan - So it all starts with the target being 15,000 samples of soil and rock from different mine sites. And what Illumina does is extract the DNA present in those soil samples and sequence it. And then through the secondary analysis software, you can piece together the original sequence of all the life forms present in that soil. From what we've heard so far in the project, about 80% of the life forms they found have been previously unknown, undescribed, species of bacterias.

Will - So that is a lot of new potentially helpful microbes already. And if you can sequence new microbes, you can find out what they do and perhaps more importantly share that knowledge with the group. So it says Koonkie Cloud Services, Aria Hahn.

Aria - We've developed statistical software that will find novel genes of a known function. And so you might be interested in methane production, for example. And so we're able to find new genes that were previously we didn't know that that's what they were doing and say like, we're pretty sure that this is doing methane production as an example. As we find those novel genes as well, we're again able to put that back into M map so that if you try to see what is happening in my samples, you can benefit from all of that prior knowledge.

Will - And the shared knowledge is already bearing fruit.

Dan - About 20% of the copper being mined in the world is being mined through hydrometallurgy, which uses either strong acids or, more frequently these days, bacteria to leach the copper from the source rock, which is, as you can imagine, a much more environmentally friendly way to do it. Bacteria can bind the fine sand particles that would otherwise get tossed up into the air and create a potentially hazardous breathing situation for mining workers. They can use bacteria to help with dust suppression.

Will - But what if you found a useful detoxifying gene but in a bacteria that is on the whole still harmful to humans? That might not be a problem either.

Dan - If the scientist analysing the data from M-Map discovers a potentially useful gene that could, for example, clean a toxic compound that is found in mine soil, but it's in a bacteria that would be harmful to humans. Genetic engineering scientists could transport that gene into a different bacteria and then encourage that bacteria to reproduce with that gene. So you have a new kind of bacteria that performs that toxin cleaning function without being harmful to humans.

Will - So this is a rapidly developing field, but one that has already shown immense promise. And isn't it so enticing to think that a key to clean energy development could already be there just beneath our feet?

Aria - It's really easy to focus on the world that we can see and we all do this in our, in our day-to-day lives. because we have to, and it's practical and it makes sense. But the more that I learned about microbes, the more that I learned that this is their planet and they are actually responsible for its maintenance and health. They were here long before we were, and they will be here long after us. And so to understand them is to understand in a lot of ways what has given life to us and our planet and everything that we do see. And so there's something I think just existentially beautiful about that concept.

Flying frog

18:14 - The frog that evolved to look like poo

An animal that would love to be down in the dumps...

The frog that evolved to look like poo

To round off this month’s Naked Genetics, it’s time for quirks of evolution. And let me whisk you away to the tropical rainforests of western Indonesia...

Will - Look at this place. Beautiful isn’t it? Let's have a look around.

There’s an estimated 300,000 species of animal in Indonesia, that’s more than 4 times as many as in the UK. All of that life, all of those natural processes will inevitably lead to a lot of.. You know, waste. So, do keep your eye out for any excrement that might be around.

No, I’m serious. You need to keep your eye out. Otherwise today’s specimen has probably just bamboozled you.

Let us examine the curious case of Wallace's flying frog. The adult tree frogs are a delightful green and white, with big beady yellow eyes… and any normal programme trying to extol the virtues of this frog would absolutely focus on the adaptation in the animal’s name. Wallace’s flying frogs have such large feet with so much webbing in between their toes, that they can move from tree to tree by gliding. And that’s pretty magical. But Attenborough already covered flying tree frogs, so let's talk about something else.
Whilst the adults are a feast for the eyes, they are crucially green. That’s good news if you have many predators, and live in a rainforest. However, the juvenile frogs, having developed from being tadpoles, are red. That seems like a pretty bad idea in a green rich environment.

But, they aren’t just red. They’re red with brown and white speckles on them. And if you’ve ever returned to your car and found that a bird has left its business on your pride and joy, perhaps you can see where this is going. This remarkable amphibian has evolved a unique and ingenious camouflage strategy: it is the first vertebrate that we know of that evolves to resemble faecal matter.

Welcome back by the way to everyone that quickly went off to have a look at one.

And I’m sure you all agree, it’s pretty convincing. The mottled shades of brown and red. The coloration is not uniform but rather varies in texture and tone, mimicking the irregularities and inconsistencies found in…yeah. Additionally, the frogs often adopt a posture that enhances their resemblance to a lump of waste, by remaining motionless for long periods.

It was clearly convincing enough for scientists at the university of Vienna to put them to task. At the Schoenbrunn Zoo, wax replicates of frogs were placed into aviaries containing predatory birds. Some wax frogs were green, some completely red, and some had speckles like our dear old flying frogs. And whilst the red replicas were attacked significantly more than the green ones, that rate dropped by half when the red frogs had a ‘faecal flourish’ added to them.

So, the paper postulates, or maybe it poo-stulates. No it definitely doesn't. The paper postulates that, unsurprisingly, predators do not want to eat something that looks like poo.

And, whilst it’s a pretty gross theory, it’s not without precedent. There are a few other species, like the swallowtail butterfly caterpillar and the ‘bird dropping’ spider - no really- that really do make for excellent excrement. Biologically, a lot of species are hard wired to be repulsed by poo. And sure, it carries disease, or organisms that carry disease. Definitely something worth having, but at the same time, means there’s very little in the rainforest that wants to drop by some droppings on the off chance that it is a frog. It is simply not worth the risk, and I think that’s fair enough.

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