Ghostly Traces of Ancient Behemoths

A recent article in the New York Times described challenges facing the Iraq Museum. Heavily looted in 2003 during the US invasion, it reopened in 2015 with a considerable collection, yet still struggles with public engagement. Not surprising, as there appear to be few resources to help visitors, such as audiovisual aids or docents. But what struck me most were the words of Iraq’s Cultural Minister, Abdulameer al-Hamdani, who said, referencing the artifacts in display cases, “In a box, art has no soul.”  His statement revolved around context: if you don’t understand what you’re looking at, its impact may not be as powerful.  As NY Times journalist, Alissa Rubin, explained, “Great works like the three-foot-tall Warka vase…are arresting sights but much more so when their history is explained.”

This resonates strongly for me when thinking of paleontology.

It’s easy to be impressed with larger fossils, articulated skeletons displayed in life-like poses. Regardless of one’s level of interest or knowledge, we can appreciate a mounted Triceratops. We know what that is. When you learn about the research done within the bones, however, and discover how scientists are learning about growth rates, blood vessel volume, what that blood vessel volume means for the way that dinosaur looked, whether areas of the body were covered in keratin or scales, that mounted skeleton takes on an entirely new meaning.  It becomes fleshed out in our mental images.  It goes from, “yes, that is an impressive fossil” to “WOW.  What an incredible animal!”  And, consequently, we have more connection to it.

That connection, to me, is the “soul” referenced by Mr. al-Hamdani. The details an ordinary person wouldn’t see when looking at fossils are the very things that bring that extinct species back to life.

 

Image of ‘Cliff,’ the Triceratops fossil at the Boston Museum of Science, photo taken by Jeanne Timmons. (‘Cliff’ might imply we know the sex of this animal; we do not. I don’t believe this was named by museum staff.)

 

When a friend of mine mentioned an upcoming trip to White Sands National Monument, it was with a sense of excitement, and I was happy for him.  White Sands was a name I recognized. It was, after all, the site of an incredible discovery unveiled last year: Giant Ground Sloth fossil footprints interacting with fossil hominid footprints. Evidence that humans may have been stalking that sloth, perhaps hunting it or, as Ed Yong at The Atlantic suggested in his piece about the discovery, maybe toying with it. Whatever their intent, hominids were doing something that repeatedly caused the sloth to turn abruptly and leave prints suggesting defensive movement.  

Paleoart of the possible interaction between a Giant Ground Sloth and ancient hominids, as depicted by Alex McClelland from Bournemouth University

 

That research put the National Monument on the map for many of us. I’d read the research and the articles about it.  I had a general idea of what was there.  “Footprints preserve terminal Pleistocene hunt? Human-sloth interactions in North America” (the 2018 paper of that discovery) mentioned that sloth and hominid footprints are only two of several species that left tracks so long ago in what is now New Mexico.  Preserved tracks remain of camelids, canids, bovids, felids, and proboscideans (most likely Columbian mammoths, although mastodons are possible, too).

So I understood my friend’s excitement, and I shared it to the degree of what little I knew of White Sands at the time, but I think it’s fair to say our levels of excitement were distinctly different.

 

Image of fossil hominid footprint inside a fossil Giant Ground Sloth footprint, photo courtesy of David Bustos, White Sands National Monument, New Mexico

 

 

Then I connected with scientists actively researching there.  Dr. Sally Reynolds, Dr. Matthew Bennett and David Bustos are three of the co-authors on the aforementioned paper, and they are among the authors of yet another paper on White Sands to be published in this August’s edition of Palaeogeography, Palaeoclimatology, Palaeoecology.

Soft-sediment deformation below mammoth tracks at White Sands National Monument (New Mexico) with implications for biomechanical inferences from tracks” offers detailed insight into mammoth footprints and how they impacted the ground upon which they walked. To do so, the scientists analyzed the rock below the tracks themselves.

This study is arguably an asset to ichnologists, those who specialize in fossil traces such as bite marks, scratches, footprints and more. It provides richly detailed graphics and descriptions of how the mammoths’ foot pressures affected the sediment. Because hominid tracks intersect and even step into mammoth tracks, these footprints are analyzed as well.

Admittedly, this information might not be first choice among those who aren’t ichnologists, but I guarantee you their interpretation of this information might be.

Understanding what these footprints reveal is like opening a window into a moment of that animal’s life.  It can tell us about the possible weight and size of the animal who made them; the stride of that animal; whether it was walking, limping or running; whether it was alone or not; and it tell us about the environment in which it walked.  These are clues into the behavior of the animal, an entire realm beyond its physical make-up.

 

 

Screenshot of mammoth footprint analysis (deformation structures) at White Sands by Bennett et al, “Soft-sediment deformation below mammoth tracks at White Sands National Monument (New Mexico) with implications for biomechanical inferences from tracks” 

 

 

This is exactly what interests Dr. Sally Reynolds, Senior Lecturer in Hominin Palaeoecology and Deputy Head of the Institute for Studies of Landscape and Human Evolution (ISLHE) at Bournemouth University.

“I’m interested in the footprint in the behavioural context,” she wrote in an email. “What do the footprints tell us about the snapshot of activity taking place?”

“I like to think in terms of how these people used their landscape,” she continued, referencing her work understanding the paleoecology of an area and how that impacted ancient hominids. “I ask myself and the team questions like:

  1. Where was the water? Were they waiting by the water to ambush the prey animals?
  2. What were they eating? Plants, insects, animal prey?
  3. What sort of technologies did they have for collecting these? Evidence of hunting, but also gathering, trapping etc.
  4. What sort of toolkits did they have to use? Stone tools, fire etc.
  5. What were they afraid of? Predators, poisonous snakes, etc. These animals are still largely resident in the region today. There is much recent ethnographic and ecosystem evidence that can be considered when reconstructing the ancient worlds of these people.
  6. Group size? Gender roles, presence of children, roles of children.”

While he focuses more on ichnology, that sentiment is echoed by Dr. Matthew Bennett, Professor of Environmental and Geographical Sciences, also at Bournemouth University.

“I am now more interested in behavioural ecology derived from footprints – basically how one animal (human or not) interacts with another,” he wrote. “This for me is where the excitement and new research frontier is.”

 

Fossil hominid footprint within a fossil mammoth footprint at White Sands, photo courtesy of David Bustos

 

Both scientists have published on fossil hominids–footprints and bones–and associated ichnofossils of other species for years. Their collective expertise lends crucial understanding to an area in which there are not just a few footprints here and there, but thousands upon thousands.

More importantly, these footprints—in some cases—go on extensively.

“Some of [the trackways] go for half a mile or a mile. We have a camel track that [is] almost two miles,” David Bustos, Resource Manager for White Sands explained by phone.  “Because these prints are so long, they allow you to see interactions that you wouldn’t see at other places. They’re so unique. There are prints all over the world, but to have prints that extend for such a long distance and keep interacting with other animals or people is very unique.”

I want to reiterate that point, because this is where my enthusiasm for White Sands became almost palpable: the tracks at that site are not only profuse, they can be followed over 1-2 miles.  If relatively short trackways have provided great insight into extinct behavior, these tracks offer potentially unparalleled revelations.

“[T]he thing about it is,” he continued, referencing the sloth and hominid trackways described in the 2018 paper, “it’s not the only occurrence.  This is happening over and over across Monument lands.”

 

Screenshot of fig. S3. from Supplementary Materials for “Footprints preserve terminal Pleistocene hunt? Human-sloth interactions in North America”

fig. S3. Map of part of the study site. The map shows sloth and human tracks as well as track density across the whole site (inset). Note the non-linear sloth trackways and sudden changes of direction. “Flailing circles” occur only in association with human tracks.

 

“We see human, mammoth, Giant Ground Sloth, and camel prints commonly together across the monument. Occasionally you’ll see bison and occasionally you’ll see dire wolf or American lion or some type of felid.”

“The proboscidean prints we have are amazing. We have thousands of these prints at the monument. (They are probably the most numerous track type we have.) In the tracks, you can see young and old animals.  Some places you can see the prints of the young running in circles and then nudging up against the larger animals perhaps to say ‘hello’ or [to] nurse.“

A fossil Giant Ground Sloth trackway at White Sands, photo courtesy of David Bustos.

 

But there’s a twist: seeing some of the tracks depends upon just the right environmental conditions.

As David explains, “You’ll walk by the same area for years, [and] then the conditions will change. There is now a fine salt crust on the surface, and in the crust you’ll find a whole new set of prints, only to be gone the next day. These are the trackways that we call ghost prints.”

“[We saw] thousands of new prints we’ve never seen before,” he said, illustrating just one example. “And they were gone two or three days later. You couldn’t see them anymore. [S]omething changed with the soil that didn’t leave a fine salt crust over everything.”

Alarmed, I asked him if this meant they were gone for good.  He assured me that, “They’re still there, so if we were to look for them with GPR [ground-penetrating radar] or scrape back the soil, they would be there. But they’re not visible to the naked eye. You can’t see them.”

Ghost tracks (or “ghost prints”) aside, there is another, more ominous threat to the trackways: erosion.  This has lead David Bustos and his team at White Sands to work diligently to preserve as much as they as quickly as they can.  They are a small operation.  They’ve looked to outside groups and experts to help understand the fossils, see the value of the site, get the word out and help save the footprints.  To that end, they have actually excavated tracks.

“[The footprints] that we have brushed open [are] a small sample of [specific trackways],” David expressed. “There might be 2-3,000 prints, and, of those, we might open up 15 prints or so.  [The reason we excavate them at all is to get a better] understanding of the different types of prints, how they differ from each other (are toes visible,  how deep are the prints, how did they walk, were they slipping in the mud), and to get [good] measurements for the gait and stride and pace and all of those types of things. After the measurements are taken and prints documented, the prints are filled in.”

 

Images of the various types of proboscidean footprints found at White Sands: what they look like above ground and then images of what they look like underground; photos and graphics from the National Park Service.

 

 

Despite their hard work, it is not always enough.

“We were seeing places where we know we’ve lost large-scale sets of prints and tracks from soil erosion,” he stated.

David compared the loss of those prints to a significant loss of books from the Library of Congress.  Losing those fossils is like losing an enormous “volume of data.”

“[T]hey’re incredible in the stories that they tell you,” he said.  “A mother carrying a child. Or an old person limping along w/a larger group. Or maybe a younger person sprinting along the larger group (deep prints that are nearly three times the length of a walking stride). You see people interacting with each other.  And you see people interacting with the megafauna.”

Still, he is hopeful.

“It’s been an amazing project and we’ve had a lot of great support from everyone who helped us to get where we are.”

“It seems like every year there’s more and more  discoveries.  We’ve looked at maybe less than 1% of 51,000 acres that could contain trackways.”

The published research done by David, Sally, Matthew and their co-authors is far from finished.  Offering me tantalizing clues, I would encourage everyone to keep an eye out for what comes next.

As far as the secrets revealed by White Sands National Monument, this is only the beginning.

Partial screenshot of an image from “Soft-sediment deformation below mammoth tracks at White Sands National Monument (New Mexico) with implications for biomechanical inferences from tracks” that illustrates where in White Sands the research was done and the megafauna that left footprints

 

*****

There is currently a Senate bill to make White Sands National Monument a National Park!!

More info here: https://www.govtrack.us/congress/bills/116/s1582/text/

Dr. Matthew Bennett has freeware that, as he describes it, “allows you to capture tracks digitally using photogrammetry (20-40 oblique photos with a digital camera), but crucially it provides you with a series of tools to analysis and compare those tracks. Unlike many 3D programmes that have to cater for lots of users with different requirements, this is purely for footprints.”

Find out more here: DigTrace, http://www.digtrace.co.uk

 

References:

  1. Bennett, Matthew R., Bustos, David, Belvedere, Matteo, Martinez, Patrick, Reynolds, Sally C., Urban, Tommy; Soft-sediment deformation below mammoth tracks at White Sands National Monument (New Mexico) with implications for biomechanical inferences from tracks; Palaeogeography, Palaeoclimatology, Palaeoecology, 1 August 2019
  2. Bustos, David,  Jakeway, Jackson, Urban, Tommy M., Holliday, Vance T., Fenerty, Brendan, Raichlen, David A., Budka, Marcin, Reynolds, Sally C., Allen, Bruce D., Love, David W., Santucci,  Vincent L., Odess, Daniel, Willey, Patric, McDonald,  H. Gregory,  Bennett, Matthew R.; Footprints preserve terminal Pleistocene hunt? Human-sloth interactions in North America; Science Advances, 25 April 2018
  3. Bustos, David, Much More than a Sand Box: Fossil Tracks from the Lakes of the World’s Largest Gypsum Dune Field, Park Paleontology News – Vol. 09, No. 2, Fall 2017
  4. Bustos, David, National Park Service, Lake Lucero Ranger Minute, YouTube, Nov 21, 2016
  5. Bustos, David, Love, David W., Allen, Bruce D., Santucci, Vincent L., Knapp, Jonathan P.; Diverse Array of Soft-Sediment Fossil Vertebrate Tracks from the World’s Largest Gypsum Dune Field, GSA Annual Meeting, Denver, 2016
  6. Martin, Anthony J., Dinosaurs Without Bones, Pegasus Books, 2014
  7. National Park Service, White Sands National Monument, The Pleistocene Trackways of White Sands National Monument, 2013
  8. Rubin, Alissa J., In Iraq Museum, There Are Things ‘That Are Nowhere Else in the World‘, NY Times, June 9, 2019
  9. Yong, Ed, Fossilized Human Footprint Found Nestled in a Giant Sloth Footprint, The Atlantic, April 25, 2018
  10. White Sands National Monument, New Mexico, USA

 

What a great honor and a pleasure to connect with Sally Reynolds, Matthew Bennett and David Bustos!! Sincere thanks to all of you!!  Sally, your kind responses to my emails, your fascinating answers to my questions, and your constant support on Twitter have been great.  Matthew, thank you for your detailed responses at a time when you were incredibly busy.  David, thank you for responding to my emails and for making time to discuss my questions further by phone.  I wish all of you the best with your research, and I cannot wait to read what comes out next!!

This post would not have been possible without the thoughtfulness and help of my friend, Dick Mol.  Dick: You are a wonderful and generous person. THANK YOU. This post is dedicated to you and Friedje.

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