In Mexico’s underwater caves, a glimpse of artifacts, fossils and human remains
184 points by pseudolus 2 days ago | 53 comments
  • petesergeant 2 days ago |
    How do you make cave diving scarier? Skulls. Turns out the answer is half-buried human skulls.
    • temp0826 2 days ago |
      Been living in the Yucatan the last couple of years. The Mayans believe that cenotes are gateways to the underworld, so it's kinda on point. When people are having bad luck (injuries etc) and there is one nearby, they will pray and make offerings to the spirits that inhabit them. And if that doesn't work they will fire guns into them to scare them away.
    • hinkley 2 days ago |
      Crabs. Click click.
  • sparrish 2 days ago |
    Such amazing photography of those underwater caves.
  • lxe 2 days ago |
    That photography... wow!
  • throwup238 2 days ago |
    Anyone visiting the Yucatan peninsula should take a day to go swimming in a cenote. It’s a magical experience even without diving into the underwater caves (they have some scary signs with warnings about that).

    > There’s a symbiotic relationship between the passionate and technical cave explorers who investigate every hole in a cave in their free time (and just for fun) and those in the scientific community who want to study these prehistoric materials but cannot reach where they’re hidden in the underwater darkness.

    The lack of cavers in general is becoming a bigger and bigger problem in archaeology and paleoanthropology. Since a lot of archaic human species were quite a bit smaller, they managed to make very elaborate caves their home that are hard for the average adult to navigate. Underwater archaeology is still in its infancy so the training isn't explicitly part of anyone's education.

    Last year there was a story [1] on the front page about research into Homo naledi in the Rising Star Cave [2] that was only made possible because they were able to find six petite paleoanthropologists cavers who were able to fit through a "vertically oriented 'chimney' or 'chute' measuring 12 m (39 ft) long with an average width of 20 cm (7.9 in)" to the Dinaledi room in the back of the cave. They found 1,500 human bones there and still have a lot left to excavate.

    [1] https://news.ycombinator.com/item?id=36344397

    [2] https://en.wikipedia.org/wiki/Rising_Star_Cave

    • Bufgaric 2 days ago |
      Diving in the cenotes is pretty damn awesome though! You just have to make sure to dive the ones that have been explored and have designated routes. My third and fourth dives after getting my open water certification were in cenotes around Playa Del Carmen and that experience was just mind blowing. Would love to do it again.
      • technothrasher 2 days ago |
        A friend of mine made a bunch of films about his cenote diving. This one give a pretty good idea of what it's like: https://www.youtube.com/watch?v=99z8JgxdDmc

        He also has some amazing IMAX footage of cenotes, among other caves, in his film Ancient Caves, which is still playing on a few IMAX screens, though it's run is mostly over. https://www.youtube.com/watch?v=MSZL9YbXDGs

        • Bufgaric a day ago |
          Thanks so much for sharing this! Quite wonderful. I'd love to go back with my 360 camera to get some footage because flat screen video never quite catches the feeling of being in those kinds of spaces.
      • dahdum 2 days ago |
        > My third and fourth dives after getting my open water certification were in cenotes around Playa Del Carmen and that experience was just mind blowing.

        Overhead diving, especially in caves, is extremely dangerous without extensive training. Too many operators down there will take new divers on very questionable “cavern” tours with sections of no natural light / visible exits, single primary lights, and single tanks.

        Do your due diligence and remember nothing in the cave is worth dying for.

        • chrisfosterelli a day ago |
          In the Yucatan most divers consider there to be a difference between 'cavern diving' and 'cave diving'. Cave diving requires extensive training and is very dangerous. In cavern diving you stay within the naturally illuminated part of the cave and, while there might be something overhead of you at periods, you're not functionally farther from a safe exit than you would be at 130ft depth with no overhead. Of course any overhead obstruction is an added risk but that situation happens in regular recreational diving too.

          It wouldn't surprise me to hear that some tour operators bend the guidelines but the diving I did there felt appropriately careful.

          • dahdum a day ago |
            Cavern diving certification is still a multi day course, open water certification does not prepare you for it. The 130 ft PADI guideline (AOW cert) applies to open water wreck diving and is quickly broken at most sites I’ve seen. Dos Ojos is particularly sketchy. On overcast days it can be impossible to see an exit at several points even when not silted out. Your guides will usually be side mount with two tanks, backup lights, and a safety spool. That redundancy isn’t for you, it’s because they are trained not to take the same risks you are. Caves are pretty awesome though.
        • Bufgaric a day ago |
          In this particular case it was a very spacious set of cenotes with a guiding string along the safe route. So it felt pretty safe. It was also the day after we had done some open water diving so the dive master got a feel for our skills (I would assume) and none of us were particularly foolish. I doubt I'd ever want to go diving in actual caves with anything even remotely tight for space.
    • Teever 2 days ago |
      How small do you have to be to do this kind of work?
    • BurningFrog 2 days ago |
      Seems like small cave exploration robots are well within reach for current technology.

      Any HN billionaire up for funding the development?

    • Mistletoe 2 days ago |
      I'm curious, is the theory that Homo naledi carried their dead through that tiny shaft to be buried there or was there another way in?
      • astrange 2 days ago |
        The lead scientist who discovered it (Lee Berger) certainly thinks they did; they haven't found any way they could have accidentally fallen in from the surface and there are no (or almost no?) bones from any other species. He further claims they have evidence of intentional fire use and rock art.

        Approximately every other paleoanthropologist is extremely skeptical of this and also constantly mad him for other things like putting preprints on bioRxiv, having too many TV shows, going to space with fossils, etc.

        On the other hand, every paleoanthropologist except him seems to run on a system where they never reveal any discoveries or share their work with anyone and take 30 years to write up what they have found in case someone steals their dig sites. It kinda seems like he's right.

    • anal_reactor 2 days ago |
      I'm sorry but I watched enough YouTube to know that out of all ways to die, cave exploring, and especially underwater cave exploring, is not for me.
    • bokohut 4 hours ago |
      I am very fortunate and grateful to have experienced this with my family as well.

      It was surreal and other worldly to me while swimming underground in crystal cold waters surrounded by fibrous tree roots hanging down from high above. How did these fish get in here?

      • defrost 4 hours ago |
        Roe aka released mature fertilised masses of fish eggs often stick to sea grasses until fish hatch ... buut ...

        Given a good tropical storm these get shaken up, scattered about, float to the surface, and get picked up by water spouts, waves, and other events that can carry them into the air and then at the mercy of the winds and sleeting rain movements .. some of which will shed into inland sinkholes, etc.

        Further, much of the Southern North American and Central American land form is crossed by limestone and and underground river systems that are fed by water above ground; where water flows eggs can follow.

  • aegypti 2 days ago |
    A well-known example is the figure of a woman at the entrance of Cenote Dos Ojos; while it was not sculpted as such, it is a carefully selected speleothem that resembles the silhouette of a woman and was intentionally exhibited on a pedestal to decorate the cave entrance, evidence of paleoart from more than 8,000 years ago that anyone can visit.

    Are there any images of this?

  • api 2 days ago |
    Caves like these always make me think of what might be beneath the surface of Mars, Europa, or many other bodies in the solar system with sub-surface oceans.
    • EdwardDiego 2 days ago |
      Imagine being in the first submarine on Europa.
      • bicx 2 days ago |
        And finding human remains
        • michaelwilson 2 days ago |
          ...under "a few" to 20 kilometers of ice even.

          * Richard Greenberg suggests "a few" kilometers. * Robert Pappalardo suggests ~20 kilometers.

        • Cthulhu_ 2 days ago |
          Or waking something up <_<
          • CatWChainsaw a day ago |
            R'lyeh is in the south Pacific, go back to sleep sir.
        • api 2 days ago |
          There are a whole bunch of creepypastas about things like the first mission to Mars finding a human skeleton in an old Soviet space suit and something written on a rock nearby.

          Stuff like: "We are not allowed to leave... they will be coming..."

      • api 2 days ago |
        I desperately want to see that in my lifetime. I give high odds that there's something alive under there. Maybe just single celled organisms or simple worm-like things like what lives near vents in Earth's oceans, but anything would be mind-blowing.

        Then I want to see if its biology chemically resembles ours. If it does, it means some form of panspermia is true and the idea that life originated on Earth is the last remaining geocentrism.

        There is a good sci-fi flick about it:

        https://en.wikipedia.org/wiki/Europa_Report

        Of course for a film they made it a manned mission when IRL we would never do that, not just because it would take too long to get humans out there but because of contamination (in either direction).

  • paulcole 2 days ago |
    Wow, 3 of my favorite things in one place.

    If there was also an HN flame war about RTO vs. WFH down there I might never leave.

    • EdwardDiego 2 days ago |
      Can't WFH in a cave...
      • defrost 2 days ago |
        Sure you can: https://www.airbnb.com.au/rooms/9906314 (one of many)

        Coober Pedy's a long standing still active mining "cave" town - and there are others about the globe, some going back a thousand years and more.

        • hinkley 2 days ago |
          Somewhere in the long dark ago I saw a human interest story about a hermit who made himself a house in a cave. It was still a cave, but it was clear that someone at least slightly civilized lived there.
          • defrost 2 days ago |
            Entire old Italian villages on peak outcrops were built by cutting into the limestone leading to a montage of { caves + stone houses }.

            There was a chap from that family background (he was born in the UK perhaps but his father wasn't) who rennovated an Ye old Englishe cave dwelling ...

            https://www.granddesignsmagazine.com/grand-designs-houses/th...

            There are channels carved out in the rock for cabling and wood fire chimmneys, etc.

            Also bookable for retreats: https://www.therockhouseretreat.co.uk/

        • EdwardDiego 2 days ago |
          Okay, Australian Outback holes weren't what I was thinking of. Was mainly thinking about the ability to get a wireless connection underground being pretty rough, especially when it's a cave filled with water. (Sonar based wireless? Sofi?)
          • defrost 2 days ago |
            Fibre in a cable would work, as would regular ethernet cable - many tourist caves are wired for light show effects.

            There are a good number of caves (eg: one former tourist cave on a property I once owned in the WA S'West Karri forrest) that have solution pipes that go straight down from the surface into the roofs of various chambers - they're good for running cable.

            Circling back to mining, underground mines can be vast systems of tunnels with custom trucks and trains running about in addition to borehole machines and other stuff - Mining Comms is a whole field with hybrid cable + transmitter (with repeater) hubs, etc.

            Not saying this is cheap or easy, but it's all doable - and for the DIY home handy type it can cost time and effort rather than money if they have access to mining auctions | closing down | old stock etc.

            • 082349872349872 2 days ago |
              I ran into a fellow a while back who was attempting to repurpose in-mountain bunkers as datacenters, so he presumably had some plan for getting the bits in and out — ethernet over power? (the natural water cooling is a plus, and wet limestone sure cuts down on potential covert channels, so maybe there'd be a market among the paranoid?)
              • defrost 2 days ago |
                Sticking with being Born Sandy Devotional they're kinda handy for Saying it with Flowers and Burying Her Deep in Love: https://www.youtube.com/watch?v=h0OwLIY9moA

                Good acoustics and laying utilities in and out is a handy skill for farms, concerts, and apocolyptic bunker builing.

                • 082349872349872 20 hours ago |
                  Whether animal or vegetable, it's wise to plan one's post-apocalyptic logistics better than a novelist wight: https://www.angryflower.com/348.html
          • nomansland 2 days ago |
            look, as a current cave diver and a former devops/survivor of the past 25 years of silicon valley, one of the reasons why diving in the jungle is so delightful is that pagers don't work in the underworld. Now, don't go ruining our last safe spaces.
      • paulcole 2 days ago |
        My productivity is so much higher in a cave. MBA types just don’t get it. It’s all about protecting their above-ground real estate interests.
  • Qem 2 days ago |
    > Among the many extinct species that lived in this region are members of the family Megalonychidae (including the genus Megalonyx, Greek for “large claw”). Fossils of these giant ground sloths are commonly found in the caves, as they probably took refuge within them, such as members of the genus Xibalbaonyx (“great claw of Xibalba”), a polar bear-sized ground sloth with big claws that measured up to 12 feet in height and weighed nearly a ton. They are joined by members of related families, including the genus Nothrotheriops, a grizzly bear-sized mammal that reached five feet tall and weighed 1,000 pounds.

    It's unfortunate DNA doesn't preserve well in humid environments. Those many bones could provide a lot of genetic information otherwise.

    • astrange 2 days ago |
      There's a newer[1] technique called paleoproteomics that work by looking for remnants of known proteins in bones, storage containers, cave dirt etc.

      https://en.wikipedia.org/wiki/Ancient_protein#Palaeoproteomi...

      [1] heh

      • Qem 2 days ago |
        Nice. But IIRC not all DNA code for proteins, so some of it would remain unrecoverable by this method.
  • sfeng 2 days ago |
    If you are a SCUBA diver, but always wished that diving was a bit more technical and rigorous, I highly recommend trying cave diving [1]. You can do a cenote tour in just an afternoon, and if you’re hooked a few weeks of training (spaced over time) will make you into a radically better diver.

    1- https://www.underthejungle.com/en/cave-cavern-training/

  • adolph a day ago |
    Extraction of the article's timeline with years ago zero padded to illustrate time spans:

      66,000,000: the cataclysmic impact of the Chicxulub asteroid
  66,000,000: end of the dinosaur age
  66,000,000: mammals began to dominate the lands once ruled by dinosaurs.
  27,000,000: formation of the Panamanian land bridge 
  27,000,000: Great American Biotic Interchange. 
  00,200,000: fossilized shell of a loggerhead sea turtle (Caretta caretta) perished in the cave 
  00,025,000: first Homo sapiens crossed into America over the Bering Land Bridge at least 
  00,013,000: evidence found in the cenotes points to human settlements 
  00,013,000: first Homo sapiens arrived on the Yucatán Peninsula at the end of the last ice age 
  00,013,000: end of the last ice age 
  00,010,000: megafauna species abrupt extinction 
  00,008,000: evidence of paleoart 
  00,008,000: last time the shallow caves on the Yucatán Peninsula flooded 
  00,004,000: The Maya established their civilization on the Yucatán Peninsula
  • exabrial a day ago |
    Holy macro, after the whole incident a few years back with the kids trapped in the cave, I had _no idea_ how treacherous cave diving is.

    Optimistic case is you have to swim straightforward, completely blind, while not panicking, in the dark, using just whatever guide wire/rope you set on your way in. Oh and the water is probably nipple-freezing hard.

    I'm a purveyor of extreme sports but nope, I'll leave this to the UUVs. Nope on a rope.