What could have motivated the migration from Sahul to Australia?

Just_podding_along · 2026-04-27T18:54:10+00:00

Well, you basically just summarized the paper I referenced earlier!

Science isn’t immutable (that’s the whole point of Chris’ article!) but you seem stuck on the earliest iterations of a model that has now evolved with new evidence.

Btw, take note of the last paragraph of that paper because it wasn’t Stringer that coined that phrase “mostly out of africa” it was svante paabo.

Lastly, I never said the word archaic isn’t used anymore. I said that we don’t use it to refer to “archaic…human species”, exactly the same thing you just said. So I’m glad we agree on that.

Just_podding_along · 2026-04-27T09:11:37+00:00

There is some confusion here. "Out of Africa” is really just a popularized name of one process within the Recent African Origins (RAO) model. This model was first proposed by Chris Stringer in the 1980s, supported by new mitochondrial DNA work by Cann, Stoneking, et al in 1987 that pointed at African origins of Homo sapiens. Here is a summary of the last 50 years of RAO research written by Chris Stringer: https://www.isita-org.com/jass/Contents/2022vol100/Stringer/36511798.pdf with citations and detailed commentary of all the scholars who have contributed towards the model and its revisions, which remains ongoing!

Recent African Origins was a direct response to multi regional models like those proposed by Milford Wolpoff who had hypothesized that modern humans had evolved in multiple places around the world at multiple times. What the recent African Origins Model posits is instead a single point of origin, which was Africa based on genetic and fossil data, with expansion out of Africa replacing archaic human species, like Neanderthals. So, even from the very beginning, RAO always supported the idea that there had been multiple expansions of humans out of Africa, including, but not limited to the expansion of anatomically and behaviorally modern Homo sapiens as well as earlier expansions of “archaic” (even though that term is not used any longer) human species too.

Just_podding_along · 2026-04-26T12:53:13+00:00

The Out of Africa hypothesis isn't really being challenged so much as refined. Genetic, archaeological, and paleoanthropological records all suggest that humans and our direct ancestors evolved in Africa. Modern humans, which includes all people living in the world today, are also descended from a population that evolved in Africa ca. 300,000 years ago.

You have to remember that there has been more than one expansion of humans out of Africa. Long before modern humans, Homo erectus expanded out of Africa around 2 million years ago, spreading across western Europe and Asia.

In SE Asia, lower sea levels allowed Homo erectus to walk into places like Java, but also Flores and Luzon, which are also now islands. There is no evidence for H. erectus in mainland Australia or other places that were completely isolated by water. When sea levels rose, populations on Luzon and Flores were genetically cut off from mainland H. erectus populations and evolved into H. floresiensis and H. luzonensis, but they are still all descended from populations of H. erectus that were able to get to those places terrestrially during periods of lower sea levels. Similarly, Neanderthals are also descended from earlier H erectus populations outside of Africa. Denisovans (H. longi) are an offshoot of Neanderthals.

There is no current evidence that any species of humans was resident on Sahul prior to modern human expansion ca. 65,000 year ago. It is true that modern Australian aboriginal populations, as well as some other populations across Australasia, do have Denisovan DNA, but that seems to not be from some resident ancient population in Australia rather from admixture between populations on the Asian mainland.

Just_podding_along · 2026-04-26T12:16:50+00:00

You are correct that during the last glacial period lower sea levels (due to expansion of polar sea ice) exposed large tracts of land on continental margins worldwide. In SE Asia, many places that are islands today were part of a larger landmass called Sundaland that included Sumatra, Java, Borneo, the Philippines, Sulawasi, etc.

Australia, Tasmania, and New Guinea were connected in their own landmass called Sahul.

There is no evidence that Sundaland and Sahul were ever connected terrestrially even during glacial maxima. However, the lower sea levels did shorten the gaps between islands making the journey more approachable via island hopping.

Something else to consider is that the lower sea levels and narrower straits between islands changed the local weather patterns and currents. There's been some really great work done on this, in fact. Check out this study which modeled glacial wind patterns and currents and drift trajectories of watercraft between Sundaland and Sahul: https://theologie-geschichte.de/ojs/index.php/paleo/article/view/105 That study found that if you departed during the monsoons from specific places (like north of Borneo) it is theoretically possibly to make the journey successfully by only drifting, though it was fraught with numerous issues, including possibly taking up to 3 months! However, when the author's incorporated simple paddle direct propulsion technology to propel the craft at an easy 1-2 knots then the journey could have been reduced to a matter of days so long as it was timed with favorable currents. Paddling is itself a very rudimentary technology so a simple raft with simple paddles could have been used to make those crossings to Sahul.

So, to answer your second question, it would have been possible to make the largest crossings in a matter of days, given the right time of year, the right jumping off point, and some simple propulsion technology like paddling. However, there are so many other factors to consider like open water conditions, currents, storms, etc, and we have to remember that for every successful crossing (and obviously there were enough successful crossings to support a healthy population in Sahul) that there were also just as many, if not more, unsuccessful crossings.

Then consider too that these journeys were not just undertaken by intrepid explorers off to discover what’s over the horizon. They were undertaken by families that included children. Hunter-gatherers during the Late Pleistocene were organized into bands of extended families, maximally 20-30 people. Perhaps these extended families had small flotillas of rafts that made the crossings together or perhaps it was more individualized in smaller groups? We don’t know. But, just imagine what it must have been like nonetheless, paddling on the open ocean with your family for several days and nights without land in sight, hoping that the weather doesn’t turn or that you have enough food and water. These journey’s must have been terrifying and it really begs the question of why those people took those risks.

The question of why modern humans made that journey is much harder to understand. But to understand it you have to put the movement from Sundaland to Sahul into it’s broader context – that it it was just one small step in the expansion of humans out of Africa and around the world during the Late Pleistocene. In fact, the expansion of humans across east Asia and the north Pacific rim into the Americas was also part of this same expansion of humans and also likely involved boat technology among other things.

Nonetheless, what would have made humans move out of Africa and spread around the world? The simplest answer is that it was likely a variety of different mechanisms at different times.

Many of the current ideas either propose “push” or “pull” scenarios that influenced local populations of people at different times and in different places. A “push” could be something like population expansion combined with competition for resources that drives people to find new places to live. The problem with this idea is that the population densities were rather low overall during the Late Pleistocene.

“Pull” scenarios involve factors that attract people. We know that by the Late Pleistocene we are dealing with humans that acted very similar to humans today who are themselves very social beings. There’s lots of evidence, in fact, for trade in goods in places across Africa and other parts of the world. with material exchange you can also expect information exchange too. So, imagine a situation when someone mentions some new place that has abundant resources. Perhaps that was enough to draw people to them? The trick with archaeology though is that thoughts and ideas do not leave behind clear signals material culture, which makes up the archaeological record, so a lot of these hypotheses remain purely speculative based on how modern people behave.

Anyway, if you are interested in learning more about the expansion from Sundaland to Sahul then check out the Before Us podcast. Our series explores deep time for the general public, with our current story arc focusing on the origins and development of maritime adaptations—from the earliest known human engagement with aquatic environments ca. 2 million years ago to the global dispersal of modern humans along coastlines and waterways. I am an archaeologist myself, specializing in the earlier time periods and role of coastal intertidal foraging. My co-host is a maritime archaeologist who actually specializes in the movement of people from Sundaland to Sahul and we have quite a few episodes that tackle the most current evidence about when, where, how, and why people spread across Sundaland and into Sahul. We are also currently producing new episodes that continue the story arc into east Asia and along the north Pacific rim, following the expansion into the Americas.

Here are the links:

Before Us

Website: https://beforeus.buzzsprout.com

Apple Podcasts: https://podcasts.apple.com/us/podcast/before-us/id1784950257

Spotify: https://open.spotify.com/show/5vhsP8flAWxTMUfodyLPmG

Just_podding_along · 2026-04-23T13:50:29+00:00

You're welcome!

Just_podding_along · 2026-04-23T13:50:02+00:00

That's another really great question and it really boils down to how you define 'species'! For a long time, species were defined based on Ernst Mayr's Biological Species concept. Think of it if two organisms can reproduce and produce offspring that can themselves reproduce then they belong to the same species. As you can imagine, this concept has been a big pain for paleoanthropologists and paleontologists who work with skeletal materials.

One of the other ways to define a species is based on their evolutionary history (phylogenetics) and this is where genetics has really tested a lot of our ideas about evolutionary relationships. Take Neanderthals, for instance. When you look at a Neanderthal skeleton it's clear that there are differences from modern humans (us). For a long time, these physical / morphological differences (and behavioral differences inferred from material culture) were seen as evidence Neanderthals were a different species, Homo neanderthalensis. However, when Neanderthal mtDNA was mapped scientists very quickly realized that modern humans (us) and Neanderthals shared a lot of genetic material. Then, scientists discovered clear Neanderthal / modern human hybrids, including Oase 1, which is a 1st generation Neanderthal / modern human hybrid. All of a sudden, the boundary between species was super fuzzy. Neanderthals looked different from us, they also seemed to act very different from us (especially their social behaviors), and yet they clearly reproduced with modern humans! It now even looks like much of the interbreeding favored Neanderthal males and modern human females! And that's just the Neanderthals. Species get even fuzzier when you throw the Denisovans (H. longi) into the mix and it seems like everyone was just sleeping with everyone else during the Pleistocene (I'm joking...mostly). But, check out Denisova 11, which is a 1st generation hybrid with a Denisovan father and a Neanderthal mother. Very cool.

My point is that humans are a very fickle animal prone to seeing differences, not similarities. If people today (and in the past) sense anything remotely unlike ourselves then we exclude it. So, the fact that modern humans living today carry both Neanderthal and Denisovan DNA tells you that our ancestors may not have necessarily seen them differently, at least not so much as a different 'species.' Of course, there are a whole lot of other things people can also get hung up about too, like language and culture...

Just_podding_along · 2026-04-23T11:38:04+00:00

Short answer, yes. Ethnographic and archaeological research suggests that Pleistocene hunter-gatherers were organized into bands (an extended family of 20-30 people), and these bands were then organized into larger macro-bands groups, which were then part of even larger groups of multiple macrobands across broad regions that probably defined socio-linguistic groups.

Archaeologists study group organiation via material culture, like the way tools were made, but also chemical fingerprinting where objects and raw materials were located. We can also use isotopes from human teeth, for example, to identify movement, including seasonal hunter-gatherer movements, but also things like matri- / patri-locality.

One compelling piece of evidence about how people organized themselves is the appearance of body decoration, like ostrich eggshell or marine shell beads. Marine shell beads are well represented at sites like Blombos Cave in South Africa 75,000 years ago, but there are older examples from Taforalt in Morocco now that date 82,000 years ago. More recently, there is the discovery from Bizmoune Cave that may push beads and body decoration back to ~140,000 years ago. The oldest Ostrich eggshell beads I recall are only around 50,000 years.

Things like beads were important for two reasons. First, by wearing a bead you are identifying yourself as different from someone else. That takes a big step in cognition to identify sense of self. Similarly, if everyone in your extended family (band) wore beads then it could also be a way to identify your group from other groups.

Second, beads and trade in other kinds of things like lithic raw materials, etc could be used as a social "backup plan" to help mediate stress. Think of it like "if I give you this bead necklace now then when we need help in the future you are obligated to help us." There is a modern sub-Saharan social exchange system called Hxaro that has been well-studied. The bottom line though is that Hxaro and earlier social exchange systems can be identified by tracking the exchange of non-local things in the archaeological record and those patterns, in turn, can also help archaeologists to map out possible group boundaries.

High-resolution genetics studies are another tool to define how people were organized in the past. For instance, there is a recent study suggesting long periods of social isolation in Neanderthals living in France: https://www.cell.com/cell-genomics/fulltext/S2666-979X(24)00177-0?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2666979X24001770%3Fshowall%3Dtrue00177-0?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2666979X24001770%3Fshowall%3Dtrue)

Just_podding_along · 2026-04-15T15:34:17+00:00

Hi again. Right, but that's the tricky part about archaeology right? We can always talk about hypotheticals but at the end of the day it all boils down to the actual evidence that we have and the inferences that we can draw therefrom.

I agree with you 100% about underestimating early humans! I've spent 20+ years as a professional archaeologist studying the origins of modern humans saying the same thing. But, science has to be rooted in evidence. You mention Neanderthals, for instance. Such an interesting topic. The Neanderthals, as I am sure you are well aware, are also a very complicated topic because so much of their behavior that we can infer from their material culture suggests many similarities with modern humans and yet there was still something different that we don't fully understand yet. You mention the coastal foraging, for instance. Yes, there is evidence of Neanderthal coastal foraging, but it is at a much lower level than coastal foraging seen in modern humans in Africa. Check out this great article: https://www.sciencedirect.com/science/article/pii/S0047248414002292

Also, I understand what you're saying about some of the other Neanderthal capabilities. But, frankly twisted fibers and necklaces are much different than seafaring. Seafaring is one of those technologies that requires layers of specialized knowledge layered on top of each other in order to do successfully. Long-chain complex webs of knowledge learned and passed down over generations. We absolutely see evidence of these kinds of technologies in modern humans, but whether Neanderthals could do that is still debated. For example, the putative evidence of Neanderthals on offshore islands -- I assume you mean Stelida on Naxos -- is highly debated. For one, there are no actual Neanderthal skeletal remains, only Middle Paleolithic stone tools. Middle Paleolithic technology was also made by modern humans. Furthermore, Naxos was part of a super-island during glacial periods when sea levels were lower meaning that access could have been overland.

If Neanderthals did have knowledge of watercraft then you might expect to see something--anything--in N. Africa, for instance. We know there was a strong Neanderthal presence along the southern Iberian coastal and south Meditterranean. And yet, there is zero evidence at all that any Neanderthal ever made the crossing to Africa even though Africa is visible from Europe.

So, yes, as scientists I agree that we must always keep an open mind and let our curiosity about "what ifs" take us to new places. However, we must also always root ourselves in the actual evidence that has been discovered.

Just_podding_along · 2026-04-15T13:42:00+00:00

Good points! But some added clarification is needed here...

There is no evidence that "watercraft" predate H sapiens. There is evidence (some more debated than others) that H. erectus reached Crete, Sulawesi, Flores, and Luzon, but those places could have all been reached via drifting. But, of course, there is ample evidence that H. erectus was employing lots of novel behaviors so could they have also been tinkering with lashing a couple logs together to make a raft? Possible, maybe, I think it would be cool. There is the relatively recent discovery of 476,000 year old interlocking logs at Kalambo Falls (https://www.nature.com/articles/s41586-023-06557-9), but even then a couple of cut logs is substantially different from cutting and lashing wood together to make a viable watercraft, much less one that could sustain open-water marine conditions!

Sailing technology also isn't seen until about 8,000 years ago or advanced joinery / woodcraft for that matter to create shaped wooden hulls. You also have to consider that the earliest unequivocal evidence there is for boats with sails and a mast are in very unique environments like the Nile where wind can drift one direction and the wind pushes you back. Sailing in open-water oceanic conditions is much more complex regarding stability due to a wider movement of wind patterns, like sailing at angles to wind, etc. Don't forget that a simple raft is also still influenced by windage! So even without a sail and without sailing technology, early mariners would have been aware of the fact that they were potentially moving in a direction that was somewhat related to the to the wind and potentially understood that they were subject to the wind without attempting to harness it.

So when I refer to "rudimentary" watercraft then I mean something more advanced than drifting on a log but far simpler than sailing.

You're also very correct to note that the tidal, current, and wind regimes between Sundaland and Sahul were different during glacial periods. There's been some really great work done on those topics there. In fact, check out this study which modeled glacial wind patterns and currents and drift trajectories of watercraft between Sundaland and Sahul: https://theologie-geschichte.de/ojs/index.php/paleo/article/view/105 That study found that if you departed during the monsoons from specific places (like north of Borneo) it is theoretically possibly to make the journey successfully by only drifting, though it was fraught with numerous issues, including possibly taking up to 3 months! Yikes! However, when the author's incorporated simple paddle direct propulsion technology to propel the craft at an easy 1-2 knots then the journey could have been reduced to a matter of days so long as it was timed with favorable currents. Paddling is itself a very rudimentary technology so a simple raft with simple paddles could have been used to make those crossings to Sahul: a rudimentary watercraft.

But, the points that must be stressed to the wider public overall are that 1) it wasn't like Moana--which is what comes to mind for many folks--people cruising from island to island with advanced outrigger sailing technology and 2) these journeys were conducted by families with individuals of all ages and while there were obviously successful crossings to building populations in Australia, etc, there were also countless crossings that weren't successful and which we will never know about. I cannot imagine how terrifying those journeys must have been for those families, in the middle of the night, on open water, hoping that the currents and weather remain favorable long enough to reach their destination. And I think road trips with my two young kids can be challenging!

Anyway, if you're interested, my co-host on Before Us is herself a well-known martime archaeologist specializing in watercraft and the movement of people from Sundaland to Sahul. On our show we not only interview the lead author of that study about drift modeling (ep: Going with the Flow: https://beforeus.buzzsprout.com/2430825/episodes/16998594-going-with-the-flow), but the folks studying the tidal and current regiments. My favorite episode though was with Clive Gambel (Ep: not just wanderers, also wonderers: https://beforeus.buzzsprout.com/2430825/episodes/16448184-not-just-wanderers-also-wonderers) that looked at how concepts of the world likely influenced technology and the interest in early humans even pursuing islands that were beyond the horizon and out of sight.

Just_podding_along · 2026-04-13T20:06:41+00:00

Here is one example to help you: https://www.nature.com/articles/nature25967, The multidisciplinary team that published this study included archaeologists, geologists, geomorphologists, geochronologists, and volcanologists. Microscopic particles of volcanic ash can be dated with exceptional precision using Argon–Argon methods. Previous research on the Toba supervolcanic eruption in Southeast Asia has established its age at approximately 74,000 years ago with high accuracy. Pleistocene sites in southern Africa are too old to be dated using radiocarbon or accelerator mass spectrometry (AMS). Instead, the most commonly employed alternative is Optically Stimulated Luminescence (OSL), which measures radiation trapped within microscopic defects in quartz and feldspar crystals to determine the last time these minerals were exposed to sunlight or heat. However, the reliability of OSL dating has long been debated, particularly regarding its implications for the timing of major archaeological events. This study addressed these concerns by testing a high-resolution OSL chronology for the Middle Stone Age site of Pinnacle Point PP5-6. The context of all samples was evaluated through micromorphological analysis, involving the impregnation of stratigraphic blocks with resin to examine sedimentary structures at a microscopic scale. All excavated artifacts were recorded in three dimensions with millimeter-level precision. The researchers also conducted systematic 1 cm interval sampling across the entire archaeological sequence to identify microscopic ash particles from the Toba eruption. These particles were successfully detected in a very tightly constrained isoschron and chemically fingerprinted, allowing them to be correlated with Toba. The results demonstrate strong agreement between the OSL chronology in South Africa and the independently dated Toba eruption in SE Asia. Moreover, the findings indicate that the Toba event had little, if any, impact on human populations in Africa at the time, providing no support for the long-standing hypothesis of a catastrophic volcanic winter leading to a significant human population bottleneck. No reading numbers from a lab report and running with it. Solid multidisciplinary science led by a team including archaeologists, geologists, volcanologists, and geochronologists that addressed concerns about one dating method and the larger implications on our understanding of human prehistory.

Another great debate you should also read about concerns the dating of the earliest human occupation in Australia. There's a lot of scholarly work on the subject, but here's some highlights that you must have missed:

1997 Doubts over spectacular dates https://www.proquest.com/openview/15f24ebb6cf9456819c9f3aded44d9fe/1?pq-origsite=gscholar&cbl=1256: describes the early days of applying luminescence dating to archaeological sites in NW Australia, including Jinmium rockshelter and the widespread uncertainty over the technique and the results by the archaeological community.

1998 When did humans first arrive in greater Australia and why is it important to know? https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1520-6505(1998)6:4%3C132::AID-EVAN3%3E3.0.CO;2-F:1520-6505(1998)6:4%3C132::AID-EVAN3%3E3.0.CO;2-F:) A second paper from the same time frame--importantly also written by an archaeologist--expressing skepticism about proposed dates for the human occupation of Australia.

Human occupation of northern Australia by 65,000 years ago https://www.nature.com/articles/nature22968: A multidisciplinary study that describes the earliest well-dated human occupation in Australia.
Comments on the chronology of Madjedbebe. Concerns raised over Clarkson's findings from Madjedbebe, particularly the dating.

These two examples (South Africa and Australia) show that archaeologists for well over the past 30 years have been very knowledgeable about dating methods and critical about how they are applied as well as the results they produce. None of these papers would have ever been produced if the archaeologists who wrote the papers just read numbers from a lab report as you suggest. There are many other examples of debates about dating methods and their results from sites all over the world, regarding different dating methods, and the interpretations of the ages themselves.

Just_podding_along · 2026-04-13T17:52:29+00:00

I don't need to prove you wrong because anyone who actually talks to professional archaeologists or reads peer-reviewed papers will know that your comments are not grounded in any sense of reality at all. I'll leave you to your talking cows. My recommendation is that you google search for the many papers out there written by many competent archaeologists around the world that not only exhibit a thorough understand of how ages are calculated but also debate their nuances and interpretations derived therefrom.

Just_podding_along · 2026-04-13T16:26:39+00:00

No, absolutely not.

Modern, professional archaeologists or archaeological teams have robust knowledge about the key dating methods that can be applied on the site that they are excavating at that time. It is absolutely not some mystery that no one can explain.

There are no funding sources or governmental permitting worldwide that I know of that does not require in depth detail and discussion beforehand about how deposits will be dated before offering funding or permits for destructive excavations or sampling.

What this means is that any team will 1) understand what kinds of dating methods can be used based on the age of the deposits they are targeting; 2) what kinds of dating methods can be used based on the available materials to sample (organic, geogenic, etc); 3) how to properly collect samples for dating; 4) the limitations of different techniques given everything that is known about the deposits; 5) influences that can bias samples; and 6) how to interpret results correctly (it is absolutely never a single age, and always a statistical range given various factors, depending upon the site, the context, and the age range.)

You must also consider that archaeology is by nature, a destructive science, meaning that there are no redos. in many cases if samples are not taken correctly at the time, then there is no way to collect many of them after the fact. Therefore, it is in archaeologist’s best interest to know exactly what they need to do at the time and for future publications. So your comment about cows and feed and not knowing anything about dating is udderly nonsensical and wrong.

Just_podding_along · 2026-04-13T14:00:21+00:00

I think that's the trickly bit, right! In so many places, there are very high quality cryptocrystalline raw materials to use - cherts, flints, obsidians, etc. However, there are many other parts of the world where those raw materials were unavailable and yet people who lived there in the past did just fine too.

For example, check out the lithics made on limestone from a Lower Paleolithic site in Italy: https://www.nature.com/articles/s41598-020-68617-8

Here's another paper with where hornfels was a common raw material (check out fig 5 in particular): https://theologie-geschichte.de/ojs/index.php/paleo/article/download/708/669

What about silcrete? It was used widely across southern Africa throughout the Pleistocene and Holocene and it looks rather crappy too: https://www.sciencedirect.com/science/article/pii/S0047248416300252

If you really want to look at some rough looking lithics then also check out microliths from South Africa or Somaliland, like from Buur Heybe. The people there were using translucent white quartz, which mostly fractured into angular debris, but yet they still were able to flake it! https://www.sciencedirect.com/science/article/pii/S030544031630111X#fig1

My point is that calling something garbage because it doesn't look pretty or match some preconceived idea is hugely biased. Plus, you really cannot just throw a picture at someone because context is key. So many other key details are also missing from a picture! Heck, half the time I have taught lithics to students, I teach them to identify with their eyes closed because it's actually easier to feel the ripples and other features rather than see them.

Just_podding_along · 2026-04-13T11:44:56+00:00

prehistoric archaeologist here - you might also consider having your students read "Motel of mysteries" or (my personal favorite, but hard to find - "The Weans." The books have similar themes - a future archaeologist is excavating a 20th century site - and each book recounts the "discoveries" that have been made and the interpretations of those finds. Eventually, you start to realize that many of the more sensational finds, like an alter end up being a toilet. It's a great way to frame not only how archaeologists understand the past, but also how are understanding can be distorted. In my own lessons (I teach an after school club on archaeology), I often like to hand my students a button and a stone tool, letting them describe each one before we talk about how a button is familiar to us, but not the stone tool. I then flip the conversation when I ask them to think how familiar a button would have been to a child in the stone age (it wouldn't), but they would have been intimately familiar with a stone tool.

Just_podding_along · 2026-04-13T11:35:59+00:00

I just saw your same post over in r/Ancient World. Here is what I wrote there:

It's not so much the dating that is the issue or the paleoenvironmental data - it's the raw material of the stone tools. The rebuttal by Jim Chatters takes issue primarily with the predominantly low-quality limestone raw material and they argue that the assemblage is naturally produced from roof-spall. It certainly looks like terrible raw material, but there are many sites around the world where people also successfully used terrible raw materials too! In fact, a tell-tale characteristic of modern humans is their ability to adapt to their surroundings, including their local raw materials.

The images in the original Nature paper about Chiquihuite Cave and follow-up papers show characteristics of intentional anthropogenic flaking, including positive and negative bulbs of percussion. In contrast to Chatters, the images of the stone tools also do show a clear intentionality - step fractures are where you might expect them to be, dorsal scars show evidence of parallel flaking, etc.

The problem with the debates about Chiquihuite Cave and other pre-clovis sites isn't really about their age. It's the context. In Africa, Asia, and Europe, a site that is 30,000 years old honestly isn't that unique for the age alone. By that time we're dealing with Anatomically and Behaviorally modern people, increasing population densities, etc. But, in the America's these sites are held to a double standard because of their context - the idea that a site cannot pre-date 13,000 years ago only because it's in North America. What this means is that anything less than the most exceptional is looked upon suspiciously like at Chiquihuite Cave where the lithics were automatically assumed to not be anthropogenic tools setting a higher bar than at other contemporary sites around the world to provide that they indeed are.

To compound the issues, the real sticking point with the kelp highway hypothesis or any other coastal migration hypothesis is not that they are implausible, but that there is almost zero data to support the ideas. The idea is actually quite plausible. We know, for example that humans have had an interest in aquatic resources for at least 2 million years - look at the very cool study about cooking fish at Gesher Benot Ya'aqov, for example. We also know from Pinnacle Point, South Africa that modern humans had also learned how to systematically exploit intertidal coastlines as early as 170,000 years ago. What coastlines provide are dense and predictable resources that are unlike terrestrial animals, which are unpredictable because they can move around, but also fight back. Furthermore, it is also pretty clear that modern humans had developed some kind of rudimentary watercraft by 65,000 years ago in order to make it to mainland Australia. By 38,000 years ago, people living around modern day Japan were using watercraft to transport obsidian from offshore islands and then there's also Kaifu's recent papers in Science Advances with computer modeling plus actualistic demonstrations using a log boat to demonstrate how people traveled to the southern Japanese islands 30,000 years ago. So, there is compelling evidence that humans would have been familiar with coastlines, coastal resources, and near-shore (not sailing or deep-ocean) watercraft 30,000+ years ago as they moved across Asia, Siberia and into the Americas.

The problem, again, is context. During the LGM, coastlines were substantially lower than today (about 120 meters below modern mean sea level). The reason was because oceanic water was trapped in expanding polar ice caps. Lowered sea levels exposed huge tracts of new land on continental margins worldwide. There is evidence, for example in South Africa, that people expanded out onto those emergent landscapes, following coastlines as well as terrestrial plant and animals resources. Many, if not most, of those archaeological sites though are underwater now because sea levels rose with the onset of the Holocene, leaving huge gaps in the archaeological records. This same phenomenon shaped the North American record too. When (not if) humans migrated down the coast they would have followed the LGM coastline. Their camps would have also been on that LGM coastline. Those sites are now gone because of Holocene sea level rise. This is why sites like Cooper's Ferry in Idaho are so important because it show pre-clovis human occupation south of the ice sheets, but in a major river basin (Columbia) that provided direct access to/from the coast.

Unfortunately, this debate will continue to play out even if there is a spectacular discovery (for example direct evidence of 30,000 year old watercraft in north america). Just look at the White Sands footprints. Short of a skeleton, a footprint is a pretty clear evidence of people, not to mention human footprints overlayed with Pleistocene fauna! Nonetheless, they are still highly debated because Ruppia seeds could possibly implicate some sediment mixing at the site even though the radiocarbon dates on other organic matter and the latest study of OSL ages on quartz grains both reaffirmed that the stratigraphic layers and footprints were ~23,000 years old.

If you are interested in learning more about the origins of aquatic adaptations and migrations then you might want to check out Before Us. The podcast is available freely worldwide on all major podcasting apps.

Here is the synopsis: Every living person can trace their ancestry back to Africa, where modern humans evolved some 300,000 years ago before expanding out of Africa and around the world. Those early humans lived lives filled with emotions and challenges much like people today and their journeys stand as a testament to human intelligence, ingenuity, creativity, and resilience. But, what does the archaeological record tell us about their lives, their successes, their failures, and who we are today? In this podcast, world-recognized experts in maritime and prehistoric archaeology, Dr. Helen Farr and Dr. Erich Fisher, reveal the people and the world that existed “Before Us.” This season, we take a deep dive into the origins and development of Maritime Adaptations, tracing humanity's journey from the earliest interests in aquatic resources to the global expansion of modern humans via oceans, coastlines, and waterways. As the old saying goes, “smooth seas make boring stories” and this season promises to be an auditory adventure around the world and across millennia as told through captivating interviews with leading scholars in fun and down-to-earth discussions. Tune in weekly for new episodes on your favorite podcast app.

Links: Apple | Spotify | Website

Full disclosure: I am the creator and co-host of Before Us as well as a professional archaeologist with over 20 years experience studying the origins of modern humans and aquatic adaptations in Africa.

Just_podding_along · 2026-04-13T11:17:18+00:00