The real da Vinci code, and the world’s oldest poison arrows

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This is the Science Podcast for January 8th, 2026. I'm Sarah Crespi. First this week, a quest to find Leonardo da Vinci's DNA. Contributing correspondent Richard Stone is here to talk about what researchers hope to learn from Leonardo's genes and the new field of artomics. Next on the show, new evidence for poisoned arrows from 60,000 years ago complicates our picture of hunting during the Pleistocene.

Researcher Sven Iseksen joins me to discuss the discovery of poisonous residues on microliths. These are tiny worked stone points used on arrows in an ancient rock shelter in South Africa. Arnomics is a growing field that brings together the latest science from physics to microbiology to ancient DNA.

with art history and preservation. The idea is to learn more about art from the past and the people that made it. This Week in Science, contributing correspondent Rich Stone wrote about a broad collaboration.

trying to bring these new tools to bear on the works of Leonardo da Vinci. Hi, Rich. Welcome back to the podcast. Hi, Sarah. Good to be back. Is that a pretty good definition of art-omics? Art-a-omics? What are you calling it? I don't even know how to properly pronounce it. I've been calling it...

I looked it up. There's not even a Wikipedia page for it. So it is very cutting edge. I'll tell you, that's Science Magazine for you. Can you tell us more about this team, this Leonardo da Vinci DNA project, LDVP?

What is their ultimate aim? Well, their ultimate aim is to recover Leonardo's DNA. That's been the motivating force, the inciting question of the project since the very beginning when they got going in 2014. And so the barrier here isn't we can't sequence DNA that's as old as he is because we can go back much further. It's actually like a scavenger hunt. Like he's left all these objects. They've passed through many people's hands. It's complicated.

Leonardo is a tough target in ancient DNA for a couple of reasons. One is it's not clear where his remains are. There is a tomb in France. with some of his bones purportedly interred there, but his original grave had been disturbed and his bones had been mixed with others and then they were reburied. So, in fact, it's not clear that the bones in the purported...

tomb of Leonardo are really his, it would take quite a bit of effort to get permission to sample those bones, to dig them up. Now, there is a lock of hair that may be Leonardo's that came from the same. grave in the 19th century. Again, the authenticity is in dispute, but if those hairs do date from the time of Leonardo's death, then there could be an attempt to extract DNA from the hair.

The other complicating factor, I should add, is Leonardo did not have any descendants. There's this kind of circular thing like, oh, we found it on this art. We found it in this grave. We're not really sure that it's actually him. And how do you complete the circle and say, well...

We have evidence that this is actually him. You can go to relatives if he had kids, but all we have is kind of cousins and then kids of cousins alive today. Yeah, you're talking about a number of generations since Leonardo's day. He died. a bit over 500 years ago. The potential sources of Leonardo's DNA are his artwork. He left behind fewer than 20 paintings definitively credited to him, but he had

Loads of sketches he wrote voluminously, so there are manuscripts with his writing. These are all potential sources. There's been an amazing effort to document the Leonardo lineage. By that, I mean the da Vinci's from his father down to the present day. Leonardo was born to a prominent notary and a servant girl. He was the only son, as far as people know, from his mother.

Now, Leonardo's father was married to several other women, had a number of other children. So the genealogy has been traced to the present day. And there are several living descendants of Leonardo's father who have already provided. samples that could be used to sequence their DNA. This is a lot of generations, 20 generations. We're talking more than 20 generations. Yeah. What kind of markers can you trace over that long of a time when people are marrying and having kids with other people?

The most reliable way to trace the DNA back over generations and centuries in this fashion is the Y chromosome. So the male sex chromosome passed down from father to son. Researchers currently are focusing on the Y chromosome of the modern descendants and also from bones of Leonardo relatives, samples of DNA that have been extracted from Leonardo's sketches.

and from letters written by a cousin and all try to converge on what's called a common Y chromosome Y haplogroup. Let's go a little bit towards the art side here. This is super interesting. So, you know, you're going to... use DNA, say, oh, this is Leonardo's DNA. It's on this painting. So it's a little bit more tightly connected to him.

prominence idea. But also, this is kind of improving our ability to analyze biological, quote-unquote, contamination of art objects and say, hey, this has information for us. The researchers have developed a pretty impressive platform for analyzing biological traces from artwork, sketches, drawings, etc. It's not just the human DNA. It's DNA from all the organisms that the object came into contact with over the centuries. So, for example, from a very famous Leonardo sketch called Holy Child.

the research team was able to sequence a type of orange tree that was planted by prominent people in the Tuscany region of Italy during the period that the great master lived. indicates they're on the right track. It kind of sets the environmental stage for all the other work done on these objects. There's also from a letter that Leonardo's cousin wrote.

DNA was sequenced from that and the malaria parasite turned up there. And malaria was a problem in that region in Italy during that period. You could really put together an intriguing environmental picture. that gives you more confidence that the DNA you're pulling from these objects dates from that period.

Do we care about what is in Leonardo's DNA? So beyond just like sequencing it and saying it's an identity thing, do we care about how the DNA is configured? Some people say that Leonardo was the smartest person in history. Genius is a very complicated thing. You're not going to get a single genius gene. But Leonardo was known for tremendous visual acuity.

He could see patterns in moving water like eddies and vortices that today cameras can capture and you can slow down the speed. You can see these patterns after image processing. Leonardo could see with his naked eye. He could see the alternating beating wings of a dragonfly. Dragonflies have two sets of wings. When you see them flying around, like if you're a normal human with normal vision, it just looks like a blur.

Leonardo drew the two pairs of wings and noted that they beat in an alternating pattern. You know, it's amazing he could pick up on that. One ultimate kind of goal of the project to recover Leonardo's DNA is to go beyond the Y chromosome to other chromosomes that could give clues to whether he had a rare allele. that could have endowed him with this tremendous visual acuity. And it could be at the level of the eye or it could be at the level of the brain, right? We don't know.

Because we do image processing. We have kind of a refresh rate on our vision. Any one of those things could be slightly different person to person. Absolutely. It's all speculative, but maybe you could look in the descendants of. the da Vinci family to see if any rare alleles of, for example, potassium channels in the retina appear in contemporary generations. You mentioned a few places that have been sampled from.

notebooks or letters or this one painting. Is the hope then to like go over the Mona Lisa and see what she has going on? Are there going to be more investigations of the paintings she's left behind? The team certainly hopes that... what they view as intriguing findings, the potential identification of the da Vinci Y chromosome haplogroup, that that is going to open doors for them, perhaps provide access to...

collections of letters and manuscripts that da Vinci wrote that could contain samples of his DNA because a lot of these samples of his writing have been kept under very strict conditions with limited to no access. the potential for modern contamination is much lower. So the team hopes to access these, gather more DNA, hopefully corroborate the initial findings that they have now, and hopefully...

make some progress on reconstructing other parts of the great master's genome. There are a lot of techniques being brought to bear here. There's dozens of researchers from different disciplines. physicists, microbiologists, chemists, people who do ancient DNA, they're all kind of putting a hand in here. And that has resulted in techniques that...

They're very good at not disturbing the works or not destroying the works and still getting a sample that you need. And that can be applied more broadly. Da Vinci is, of course, a wonderful reason to kind of start this project. You know, as you say, like this. giant in history, but it does spread out to other works, other artists, other parts of this field. So it's worth noting that archaeomics is not just DNA collection.

It's a variety of biological and chemical techniques to extract useful information from historical objects. So there's been a big push. at the Metropolitan Museum to expand this toolkit and apply it to mysteries that have long perplexed art curators. Just one example was a famous English painter named Thomas Gainsborough. He had played in some of his writings. He painted and he sketched. To protect his sketches from the sulfuric London smog, he would dip his sketches in skin milk.

And there was a really ingenious project that found milk proteins in Gainsborough sketches. This is just one of the applications of these new toolkits to try to solve. long-standing mysteries. We've kind of flicked at the fact that there's many different collaborators here, but there are physicists involved in this. What role have they been playing in kind of looking into da Vinci, his DNA, or this bigger project?

You can talk about Leonardo's tremendous visual acuity, but how can you study it if Leonardo has been dead 500 years? One way to do it is to try to reconstruct. The scenes that he sketched, for example, there are some very well-known Leonardo sketches on water, water flow, the formation of eddies, vortices downstream from the pier of a bridge.

just tremendously detailed sketches he made. Two members of the da Vinci project are actually hydraulic engineers, and they set out to reconstruct the flows that Leonardo was sketching as best as they could. and then tried to estimate the frames per second that his eye, Leonardo's eye, would have had to have been able to process to be able to see these patterns. And they came to the conclusion...

that Leonardo would have been able to resolve frames per second at a much higher rate than people normally could distinguish. He's seeing like at 100 hertz, but... The rest of us are seeing like 30 to 60 hertz. That's what the researchers propose. It's, of course, very tentative, but based on their reconstructions, if there's a bell curve of what's called...

flicker fusion frequency, this ability to determine motion in frames per second. So he would have been at the far end of the belt curve. I think normal...

Television footage, movie footage is at 30 frames per second, thereabouts. You don't see each individual frame. And I would emphasize, it's not superhuman, but like I say, it's a bell curve. And there are... potentially variants of potassium channels in the retina and other potential genes that allow people to differentiate frames per second at this extraordinary level.

That's so cool. And we both got to use our movie knowledge. Yeah, this is not the usual fare for a science article. Thank you so much, Rich. My pleasure, Sarah. Thank you. Rich Stone is a contributing correspondent for Science. You can find a link to the story we discussed at science.org slash podcast. Stay tuned to learn about the earliest poison arrows found so far.

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poisoned arrows to hunt. This week in Science Advances, Sven Isaacson and colleagues provided new evidence of this advance in hunting technology from as far back as 60,000 years ago in the Pleistocene. Hi, Sven. Welcome to the Science Podcast. Hi, thank you. Great to be here. This is such an interesting collaboration. When I looked at who was on this paper, it really is pulling from all different aspects of science. So what was your role in this work?

My role is as the organic residue analysis expert. So I came in sort of... Third in this work, providing the skills and knowledges to do this analysis for my colleagues. And then they contributed their knowledge of hunting technology and psychology from tens of thousands of years ago and dating. So there's really just a really interesting mix of work coming together.

at this one site in South Africa. Can you tell us a little bit about the site and then we'll get into the poisons. It's called the Umla Tisana Rock Shelter. It's in Kvazulu-Natal in South Africa. It's been excavated. years ago in the late 1980s, I think. It's a rock shelter where the different soil layers are stratified. They're stacked on top of each other. The analysis that our

South African colleagues have done on these layers show that it's a very intact stratigraphy. So there's anthropological artifacts in a stack of layers that are natural. What they've also done is to use a dating method that's called Optically Stimulated Luminescence. That is kind of dating when the last time these sand grains saw daylight. and the posits where the microliths that we've been analyzing for this paper where they were found that that layer was dated to approximately 60 000 years old

And then we're going to go in a little deeper here and say there was poison on these microliths, which are used for hunting. So we'll get into how you detected that poison was present on these arrows. Yes, so that's... sort of a known phenomenon from historical times and also from earlier prehistoric finds that in southern Africa, poison has been used in hunting. It's been sort of the question of, can we trace how far back this practice goes?

says this site also well preserved and one of our co-authors marlies lombard who has been going through the lithic materials and analyzing how far back you can find traces of bow hunting She identified these points as projectile points or weapon points. And on some of them, she saw that there are actually macroscopic visible residues on them.

some have been analyzed to that they sort of contain adhesives so they can be used to sort of glue the tips to the shaft so what we didn't done now is that we collected microscopic samples Well, still visible, but very small samples from these visible residues on the surface of 10 of those. So we selected the ones that looked promising for this sort of first study. And then we applied.

fairly standard procedures. So you did gas chromatography. Gas chromatography, mass spectrometry. Right. GCMS, if you've ever heard of it. GCMS, yes. And you're not getting, this is poison. You're getting, this has... poison that was sitting here for 60,000 years degraded into something. And you could say that's a signature of the poison. Yes. And actually, these components that we have identified.

the two most significant of them, they are actually the active components from this component. And what we don't see in any research paper, and especially not in this, is sort of the background work. We have been analyzing. extensive body of ethnohistorical materials, and that was very crucial for this, involving sifting through hundreds of components to identify the chemical properties most likely to survive in very old contexts.

pre-name type compounds that we actually identified are among those. How long has somebody been hanging around that you've been able to confirm before? The oldest samples that we've analyzed in our group, it's like a thousand years old. And already there, you see a difference in how the trays look compared to the ethnohistorical materials. In other analysis, the earliest ones are like 7,000 years old or something like that.

And that is, of course, something that I was concerned that it's such a big jump in time. Yeah, absolutely. It's a factor of 10. I was very sort of not having high hopes when we started to see if that we actually.

get something out of this. So I was positively not surprised, but I mean, you know, you always had the hope. How many of the tips that you tested had remnants on them of the poison? It wasn't a subset. As I said, we collected... samples that look promising we selected 10 samples and on those we found traces on five so i think that is well a very good result

Definitely. And we don't know if that means that they only poison half of them or if that's just what survived. No. And I mean, we selected samples that look promising and on those, we found traces on half of them. So there are some hundreds of... points only at the Umla Tisana rock shelter. So there's more work to be done. And you can say this is not the adhesive. This is a poison from a plant that we know about today that people have been using for millennia.

These two components, bufanidrine and epibufanizine, they are known in the amaryllis family of plants, but there's specifically one of them, the bufonidisticha, that is commonly used still. as an arrow poison for hunting. And it has a distribution that also this site is sort of in the middle of it. And it's been around for a long time. What are some of the other very old ones? What do we know about poison arrow technology kind of?

We don't know very much. I mean, there's been analysis on materials from South America and from Southern Africa, but you need to have samples and you need to have technology. that you have a material where you can get this signal from. So you have context, like in this case, stone points, weapon points, they're made from stone, because it's quite common all around the world to use with bone points.

wooden points, and those materials don't preserve. The context is very important. This might not be the oldest.

in the world, but it's the oldest we've found so far as far as we know. It's the most findable of the oldest. Can we talk a little bit about what a hunt would have been like? How big is a microlith? The size of these microliths is like the nail of your little finger. We think these are most probably arrows, and it's small arrows and small bows. It's not like these very strong ones. These points have been probably used for the hunting of quite small prey, like small...

antelopes, small bush pigs. Very small. So they're not going to stab an animal and damage it very much unless they have a poison on it. At least in historical times and in the ethnological materials that we have and also in the prehistoric materials where we actually have. found them together with shafts they're made so that they should break off and stay in the wound in the animal and sort of distribute the poison and the poison as such is not

so strong that the animal would drop dead on the spot. They need to be understood in the context of persistence hunting, that you wound the animals and then track it until it lies down and you can take care of it. That's where my colleagues come in with the sort of the psychology of it as well. Since the effect of the poison is, I mean, it's biochemical rather than physical. So it's not necessarily visual or obvious. So this takes some cause and effect thinking.

to sort of figure this out. And also what the poison does is that it shortens the time spent in tracking during persistence hunting. It suggests capabilities of complex cognition and also like a developed working memory to be able to do this. Well, you're also harvesting something and breaking it down to a useful material.

applying it to something else that you built. It's a very complicated technology that we can now see going back so far in time. Another thing that also is that this is evidence of the use of plants for other things than just food and tools i mean we know that people have been eating plants foods and we've been using plants for making tools but i mean here's the compounds efficiency as hunting poison depends on both

preparation and dosage. In lower doses, it may very well have had medical applications. So we're into the sort of early evidence in the realm of using drugs, medicines and poisons. That's also fascinating. Could you look at other poisons that are used in other parts of the world, like as you said, in South Africa or South America and say, well, this poison looks like it would stand the test of time. Can you work backwards like that? That's part of what we're doing now.

I'm still going through this ethnohistorical material that we have to look. What kind of components can we expect to find? There's a lot of residues from different poisonous glycosides. compounds that are like water solvable that probably will not survive very long and we've been looking at residues from that kind of poisons as well and there might be survivors of those in

these thousand years old samples that we haven't analyzed before. But again, these are compounds compared to the ones we detected now that are much more susceptible to decomposition and leaching. Thanks, Sven. This has been really fun to talk about. Thank you. Sven Isiksen is a professor of archaeological science at Stockholm University. You can find a link to the Science Advances article we discussed at science.org slash podcast.

And that concludes this edition of the Science Podcast. If you have any comments or suggestions, write to us at sciencepodcast at aaas.org. To find us on podcasting apps, search for Science Magazine. or listen on our website, science.org slash podcast. This show was edited by me, Sarah Crespi, and Kevin McLean. We had production help from Podigy. Our music is by Jeffrey Cook and Wen Khoi Wen. On behalf of Science and its publisher, AAAS, thanks for joining us.