Earliest crafted bone tools date back 1.5 million years
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Nature.

Welcome back to The Nature Podcast. This week, the earliest bone toolkit and how cells' waste disposal systems could help defend against infection. I'm Sharmini Bandel and I'm Nick Pettrichow.

A cache of bone tools has been discovered from 1.5 million years ago. We never expected that there would be bone tools there. That's Ignacio de la Torre. Along with his colleagues, Ignacio has uncovered 27 bone artefacts in Tanzania.

We know that ancient humans, or hominins, have been making bone tools for a long time, but this discovery pushes back the date on that by about a million years. And the number of artefacts and the way they were created implies that this was a pretty systematic effort on the part of the hominins, and raises questions about how sophisticated their technology was.

I called up Ignacio and asked him about what he found. So we've discovered that one and a half million years ago, humans were already making bone tools on a systematic manner. And they were doing that much more often than we previously thought. What sort of things were they making? So these bone tools are made on lean bones from very large mammals, such as hippos and elephants.

So they were picking these very large bones and they were making elongated artefacts out of the limb bones. And do we have any sense of what these might have been used for? It is very hard for archaeologists to figure out the exact function of early artefacts because we were not there. So it is all indirect evidence. But from the shape of the objects and because of some damage on the tips of these objects,

We can speculate that they were used in thrusting activities, activities where you need a point. And these objects are mostly very large and heavy. So these should have been heavy duty activities. Probably they were being used for processing carcasses. So they were using them for, you know, recharging.

remove the limb bones out of the carcasses or things like that. So these bone tools that you found, as you said, were from 1.5 million years ago. But as I understand it, stone tools have been around for around 3 million years. So what's the significance that these are bone? Okay, so humans have been making stone tools for a long time. So we knew that our ancestors were technologically able to produce artefacts and use them for a number of activities.

But it was thought that our ancestors' abilities were limited to the use of rocks. Our discovery demonstrates that humans were also using bones for all sorts of tools. So it means that they were using other raw materials apart from rocks, which has a bearing for understanding the mental abilities and the intellectual development of our ancestors.

And the other aspect for which this is relevant is because we archaeologists normally can only work with stone tools because they preserve well in the archaeological record. They don't decay, it's not organic material. Now that there is this site where we've discovered the bone tools, we realised that they were used in bones also for making artefacts. So it could be that there are many more examples of bone tools, it's just they haven't been preserved. That's exactly the point.

So it might well be the case that early humans were making bone artefacts, either earlier than even the sites that we've discovered,

or at the same time, but we simply don't know because it is not preserved in the archaeological records. Another possibility that we don't rule out is that these bone artefacts are present in other archaeological assemblages, but they haven't been recognised as such by scientists because you're not expecting to find this sort of artefacts as early as 1.5 million years ago. So it might well be the case that in those sites where bone is preserved,

These sites should be revisited again to check if there is indeed bone artifacts among the fossils that are preserved at the sites. And, you know, past research that has looked at bone tools has sometimes considered it to be like a one-off. Why do you think that this indicates that this is a more prevalent thing that might have occurred throughout more of history?

Well, that's a very good question. The fact that these humans were making bone tools in a systematic manner, so it's not just one artifact, it's not two, so it is not one-off until now. We had one discovery here, one discovery there, so it was like disconnected dots in the archaeological record. But now we have a site where these humans were making bone tools systematically. They were producing them in a very regular manner.

So our hypothesis is that this may have continued in our evolutionary history and it's a matter of trying to find the sites where this is preserved. This may be proved wrong. It might be the case that this is a one-off practice by some groups of humans that decided that they wanted to make bone tools and that is an innovation that got lost in our evolutionary history. We don't know yet. So this triggers a lot of very interesting questions. But we archaeologists think

need to search for this evidence. And do you think that this finding reveals anything about how human tool use evolved over time? Could this have led to other innovations? So this discovery of bone tools has been found in a context where we already know that there is a technological transition between two cultural traditions. What we know as the Old One

and the Acheulean, which is the next stone tool technology. The older one is characterized by a simple flaking of stone flakes off a course. So humans were just knocking one rock against another and obtaining simple sharp flakes.

Now the Acheulean, which is a much more complex technology, is characterized by the production of rather sophisticated hand axes. So there is a clear technological transition there between the Oldowan and the Acheulean. It's not only technological, but also associated to different human species. This Oldowan, this simple technology of core and flakes, is often associated to Homo habilis.

Whereas the Acheulean is often associated to Homo erectus. Now, our bone tools have been found in a site which clearly belongs to the Acheulean. There is stone hand axes in the same context as these bone tools. So one of the hypotheses that we are putting forward in our paper is that these bone tool technology is

may be associated to the emergence of the Azeulium. I've talked to a lot of people working in this field over the years, and I know that interpretations can sometimes vary of the fossil record. How confident are you in your interpretation? I mean, there is no doubt that these are bone tools, so that is not going to change. What it might change is our interpretation of the evolutionary implications of our discovery.

Depending on whether we are able to push back this emergence of systematic bone tool technology, for instance, to the older one, like I was talking about this simple technology of cornflakes, maybe in the future somebody discovers they were also making bone tools systematically. We don't know. There is no evidence for that yet. So that would be a way for our interpretation to be proved wrong. Another example.

is that, as you were mentioning earlier, our discovery is just a one-off episode in our evolutionary history. Humans, 1.5 million years ago, decided to make bone tools in a systematic manner.

But then that didn't have any continuity. So indeed, our interpretations may change in terms of what the implications are evolutionarily, but definitely not as the hard evidence, which is clear that these are bone tools dated very firmly to 1.5 billion years ago.

That was Ignacio de la Torre from the Spanish National Research Council. For more on that story, check out the show notes for some links. Coming up, new research that's identified a trove of antibacterial molecules hidden within human proteins. Right now, though, it's time for the research highlights with Dan Fox. Cane toads can find their way home across long distances.

Now, researchers have put these toxic amphibians' navigation ability to the test. Scientists looked at 62 cane toads, disorienting the animals by walking them along a winding route for between 30 and 60 minutes before releasing them up to a kilometre from where they had been found.

The team then checked the toads' location about once per hour through the night. Some of the animals had been given zinc sulfate to disrupt their sense of smell, while others had magnets glued to their heads to temporarily disrupt their magnetic homing abilities. Despite these hurdles, 34 of the toads found their way home.

The distance an animal was moved did not affect its homing success and neither did blocking olfaction or magnetic sensing. The team did see that homing toads had increased neural activity in brain regions associated with navigation compared to their non-homing counterparts. Home in on that research in Proceedings of the Royal Society B.

A chunk of rock that makes up southern Tibet has been found to have originated in what is now Western Australia, potentially solving a long-standing geological mystery. Over time, fragments of the Earth's continents are rearranged across the planet by the movement of tectonic plates. The origin of one such continental fragment, the Lhasa Terrain under southern Tibet, had eluded geologists. Until now.

Researchers studied rocks from the Lhasa Terrain that date back more than 2.5 billion years. The chemistry of the rocks, as well as the zircon crystals embedded in them, showed that they experienced a series of changes that match events in the geological history of Western Australia. The work suggests that the Lhasa Terrain did not originate as a single chunk from India as previously thought, but that at least part of it came from Australia.

There's no mystery as to the origin of this research. It's published in Geophysical Research Letters.

Next up on the show, reporter Benjamin Thompson is here to tell us about a new immunological discovery. This week, a team of researchers reports evidence of a newly discovered type of immune defence centred on cells' internal waste disposal system. This system is responsive to bacterial infections and could one day be used to help fight them in clinical settings.

At the heart of this system is a large complex of proteins, which together form the proteasome. The proteasome is the waste disposal machinery of the cell, or the garbage can, if you will, that is responsible for degrading other proteins in the cells. Why? Because they finished their job, they had to be removed, they were damaged in some way. This is Ifat Merbal, who researches the proteasome.

This machinery doesn't just smash junked proteins to pieces, it unwinds them into a chain of their component amino acids, like beads on a string, and then chops this up into little amino acid segments called peptides. And this chopping up also allows peptides derived from some invading pathogens to be presented to our immune system to signal it to mount a response.

But proteasomes aren't just found in human cells. They're found across the tree of life, including in things like yeasts, which haven't evolved a complex immune system like we have. So, given how long proteasomes have been around, might their ability to cleave proteins into peptides mean they have other, as yet undiscovered, defence functions?

Well, IFAT has published evidence that they may do, and she and her colleagues have a paper in Nature about it this week. The team found this function by rooting through the garbage made by proteasomes. Several years ago, we generated a system that is called proteosomal profiling.

What did we do? We isolated proteasomes from cells and we kept the peptides that were cleaved intact. The team took these peptides taken from human cells and looked to see if their amino acid sequences matched anything else described from various organisms.

And they found that they were matches for what are known as antimicrobial peptides. Basically, antimicrobial peptides are pieces of proteins that are tackling bacteria and are fighting against them as a first line of defense. They have different mechanisms of doing that. They can bind to the membrane of the bacteria and then rupture it.

They can prohibit or block transcription or translation of proteins of the bacteria, and they can also serve as immune modulators, if you will. And because these antimicrobial peptides were associated with proteasomes, the team reasoned that they'd likely have been snipped out of proteins.

Antimicrobial peptides are found in a wide variety of tissues and secretions, and other work has shown that some antimicrobial peptide sequences can be found within human proteins. The team wanted to know whether there could be more hidden away.

To find out, they searched protein databases and found sequences matching known antimicrobial peptides from other species, but they also found other sequences that looked like antimicrobial peptides too. And we tried to count how many potential peptides we have

taking into account the biochemical properties of antimicrobial peptides. And this yielded a number that was above 200,000 peptides across different tissues. So a lot of sequences found within proteins that looked a lot like they could be antimicrobial peptides. These were often found within proteins unrelated to the immune system. The team also looked at where these sequences were found wrong.

within the proteins. In about 28% of the cases, we actually had these peptides buried within the protein sequence and structure such that they would be released only if the protein underwent degradation. All this pointed to there being a host of potential antimicrobial peptides only accessible when a protein sequence was unwound and chopped up by a proteasome.

The team's experiments showed that inhibiting the action of proteasomes, or leaving them be but breaking down the peptides that they make, led to human cells in a dish being less able to fight off bacterial infection. And a lab-made version of one of these peptides, delivered in high-dose to mice, could protect the animals from pneumonia or bacteremia.

And when we provided the peptide as a therapy, it actually reduced not only the tissue damage, but also, of course, the bacterial infection. And even in a survival test, it allowed the mice to survive better with regards to the pathogen infection. But there was a big question left to answer.

How are these tucked away peptides being selectively cut out of proteins? It turns out bacterial infection seems to change the proteasome's function. If we infected cells with bacteria, we actually found that the proteins that are being degraded in the proteasome

were cleaved, were cut in a different manner, meaning that the scissors within the proteasome generated peptides that were different than before the bacterial infection. And how were they different? They generated peptides that had biochemical properties that are more relevant to fighting the bacterial membrane. So what was behind this shifting in how the molecular scissors were cutting?

It appears that this was down to something becoming bolted onto the proteasome. What we found there was another regulatory subunit of the proteasome, which is called PSM3, that was bound to the proteasome within one hour of infection. And independently, in a different study that was published several years ago,

People have shown in a biochemical context, not related to any infection, they showed that when this regulatory subunit is bound to the proteasome, it changes the seizure activity of the proteasome. So then suddenly it all made sense. Attaching of this PSME3 subunit changed the proteasome's activity. And the team showed that PSME3 deficient cells were less able to mount responses against a bacterial attack.

Silke Meiners is a cell biologist who studies the biochemistry of the proteasome. She wasn't involved in this research, but was impressed by the team's focus on the proteasome's garbage to find evidence that it has another role to play in immunity. And I think the entire concept that it's not the substrate which sort of enters the proteasome, but what you get out of the proteasome, that's the novelty, right? So that's really the interesting bit.

Silke says that the method the team used to look at the trash associated with proteasomes is a powerful one. But she says there are a lot of questions about how the system actually works. For example, she wants to know how proteasome-derived peptides can avoid being chopped up by other enzymes designed to break them down even more. There are many, many proteases which usually cleave all those peptides into amino acids.

The main question is, if these peptides are generated in the cell, how are they protected from all the swimming around proteases and to be secreted out of the cell? Silke also says there are questions about the role of the PSME3 subunits that changes the proteasome's activity. Because while proteasomes are found throughout cells, she says this isn't the case for the subunit. Usually, if the cell is intact,

It's only in the nucleus. It's never seen the cytosol, right? So it could only affect degradation of nuclear proteins. As we've said on the podcast many times, the human immune system is complicated. And IFAD also says there's a lot to understand, such as how many of these peptides are secreted and to what levels, whether there's pathogen or tissue specificity for them, and why this system isn't set off by a person's healthy bacteria.

There's also the question as to how many of these potential peptides actually have antimicrobial properties. But if questions like this can be answered, IFAT thinks there might be a rich seam of peptides waiting to be mined from within our very cells, and that purified versions of these molecules could one day even act as clinical antibiotics. These peptides, if we now produce them from the outside,

we may very well utilize them in many different cases, in cases of infectious diseases, in cases of people that have a compromised immune system, like in the case of transplantation, like in the case of patients of cancer that are being treated and having an immune system replaced, but also in many different additional biotechnological applications. But of course, it's still on us to explore that and provide the proof of concept.

Ifat Merbal there from the Weizmann Institute of Science in Israel. You also heard from Silke Meiners from the Research Centre Borstel in Germany.

Finally on the show, it's time for the briefing chat, where we discuss a couple of articles that have been featured in the Nature Briefing. Sharmini, what have you been reading this week? So I've been reading this article in Nature about ice hunting robots headed for the moon. Wow, that is many sci-fi words together. I like it already. Yeah, I know. It's great, isn't it? It's a big year for the moon. I think we were chatting about this last year, sort of looking ahead to all the sort of moon excitement and

And now, yeah, we're getting into the moon excitement. And this particular story is looking at the missions who are interested in water. Where is the water on the moon? Can we find out where the water is? And how will that potentially then help us to put people back on the moon, have a moon base maybe, be able to make fuel on the moon? Very important. Water on the moon. We need to find out where it is. And so these robots are going hunting for this water, I guess. How would they manage that? Okay, so there's two that just launched last Thursday.

One of them is a NASA orbiter. It's called Lunar Trailblazer, which is lovely. And the article says it will follow a leisurely trajectory, which I love. It's just going on a little jaunt and it's going to...

arrive or enter its final orbit around August and map the surface. And that's basically trying to produce the highest resolution maps of where the water is on the moon. This is all focused on the lunar south pole, because that's where the researchers think that there is potentially a lot of water. And then the other craft that launched on Thursday was

It's supposed to land really soon, actually. A non-leisurely trajectory, I assume. And that is a lander by a private company based in Texas. And that contains NASA instruments, including an ice hunting robot drill. It's all the good words. It's going to land on the moon, drill down into the soil, get a little pile of sort of crumbly moon soil up.

And then there's a mass spectrometer, which is going to analyze the pile for water and like volatile substances that might be sort of escaping off it. And that isn't that unusual, I guess, a private company going to the moon. We've talked on the podcast about a few different ones. So it seems like it's a bit of a trend for private companies to be going there now. Yeah. So NASA is basically paying these private companies to take their instruments into space or in this case to the moon and

Although it's been slightly tricky. There've been quite a few mishaps, shall I say. So this particular company, Intuitive Machines, it's called from Texas, they had a lunar spacecraft that soft landed successfully on the moon last year, but then it fell over, which is not so good for the solar panels. And there've been other attempts that have crash landed or sort of been flung off into space.

So it's early days in a way, but there's two other commercial missions like on their way to the moon right now. And one of them successfully landed just a few days ago. The other one, I think, still on the way. And they're not looking for water. They're closer to the equator rather than the watery South Pole. But all in all, basically just a lot of missions doing a lot of

fact-gathering and really prepping for potentially humans to return for the first time since the Apollo missions over 50 years ago. Yeah, it certainly sounds like it's getting quite busy on the moon and I'll be very keen to see if people ever go back there because I missed it the first time around so it'll be nice to see this time. For my story this week, we're coming back down to Earth and it's a story about climate change and

and how an important ocean system may be more stable than we maybe had considered against climate change. Okay, so ocean system. This is like the different currents, like the Gulf Stream and things like that, which...

potentially at risk from changing weather climate they could stop flowing or go backwards and things like that exactly that so this is a story that i was reading in nature based on a nature paper about a system of currents known as the atlantic meridional overturning circulation

And this is very catchy. It's also called Amok, which is a bit catchy. Amok, okay, we'll go with Amok. Go with Amok. And Amok is quite well known because it is the set of currents that means that Europe, where we live, is a lot milder than it would otherwise be because warmer water is being brought from the south.

And then once it reaches the very top of the Atlantic Ocean, it brings the colder water and nutrients and that sort of thing down southwards. And it goes on in sort of a circulation. And there's various other parts of it that circle around the whole world.

And so there's been some question marks about this one because there has been some research that's indicated that climate change could weaken this and that would be bad because it would lead to flooding, drought, changes in rainfall, a lot of stuff that you don't really want happening. And, you know, as you may have read in the past, like maybe Europe will get very cold and that sort of thing. So weakening would be bad. And there's even been suggestions that it could collapse quickly.

And so in this study, what they've done is they've looked at a bunch of different climate models and they've looked at very extreme versions of climate change. So they looked at a scenario for where carbon dioxide levels have quadrupled from pre-industrial levels.

and a scenario where there's just a huge amount of fresh water from melting ice caps in Greenland, which are both scenarios that could happen, but they are on the extreme end of the scenarios. And so they've looked at what would happen to this set of currents then, and it seems like while it would weaken, it probably wouldn't collapse altogether. Okay, okay. So in some ways, good news that in their most extreme models...

It's not collapsed. It's not just completely sort of stopped flowing and going to sort of change everything.

but it might still weaken. And you did list a lot of bad effects of weakening just a moment ago. So do they have any more insight into how much it would weaken? Unfortunately, there's a lot of unknowns here. Like climate change will probably have an effect on it and it will probably weaken it to an extent. Quite how much it gets weakened is unclear, but at least in this case, this set of currents doesn't collapse altogether. And the reason that they think that is there are very strong winds here.

in the southern ocean, the ocean around Antarctica. And this plays a big part in what's going on here. And it's quite complicated how all the different things interact, but essentially those winds seem to prevent this AMOC from collapsing altogether. But yes, as you say, weakening isn't good either. And of course, the solutions to that are to mitigate the worst effects of climate change. And that means reducing the amount of emissions we do, trying to suck it out of the air when we can, if it's possible, and reducing

you know, prevent ice caps melting, which also has a big impact on this. Because the other thing is, obviously we think about the human associated changes that I mentioned, but obviously there are a lot of nutrients and other things that many animals rely on, so it could have a big impact on biodiversity. And if

If it were to change or collapse, then one thing that could happen is there'll be basically an opposite kind of circulation would happen in the Pacific instead. And, you know, in that situation, everything is very different to what we've got now. And it could cause quite a lot of chaos. So definitely things we can do to prevent AMOC from running AMOC.

There certainly are things. And yeah, it seems that the main takeaway from this is it will be somewhat stable at least to the end of the century. After the end of the century, you know, all bets are off essentially. But at least for now, it seems to be somewhat stable and there are sort of mitigating effects to it collapsing altogether. But at the same time, we need to prevent the weakening as well by trying to do as much as we can to tackle climate change.

Thanks, Nick. And for more on those stories, you can check out the show notes for some links and a link of where you can sign up to the Nature Briefing to get more like them directly to your inbox. That's all for this week. If you want to keep in touch, you can follow us on X or Blue Sky, or you can send an email to podcast at nature.com. I'm Nick Poucher-Chow. And I'm Sharmini Bundell. Thanks for listening.

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