Fossil Footprints Discovered on the Roof of a South African Cave: Geological Context of Human Fossils VI

Can human footprints made in wet sand dunes be preserved as fossils? The discovery of up to thirty-five human (1) footprints on the roof of a small coastal cave says “yes.”

Footprints on the roof of a cave? How does that happen? I wondered that too when I first heard about this remarkable discovery. The footprints were identified by amateur paleontologists from Canada while visiting South Africa. They were searching for fossils in aeolianites—fossil dunes—along the southern coast. They had already identified footprints of dozens of species of animals including lions, elephants and horses in these preserved sand dunes but the human footprints were an especially exciting discovery.

Family doctor Charles Helm of Tumbler Ridge, B.C., inspects hominin footprints he found on the roof of a cave in South Africa. (Photo by: Guy Thesen) Source.

They were found in a small cave carved out by high tides in the soft sandstones of a fossilized sand dune. The footprints must have originally been made on the surface of what was a wet dune. When the sand dried, wind-born sand covered the prints. Interestingly, the footprints are found on two distinct layers of sandstone suggesting two temporally isolated track-making events are recorded at this location. Furthermore, in the very same cave there are preserved carnivore tracks on the floor of the cave.

Small cave along the South African coast containing hominin tracks, viewed from the intertidal zone (photograph by co-author ML). Figure 2 from Helm et.al., 2018. https://www.nature.com/articles/s41598-018-22059-5

How did the tracks get there?

The location where these tracks were found is very odd. Not only are they found in the roof of a cave but they are underneath dozens of feet of layers of sandstone. This sandstone is the fossilized remains of what had been a sand dune. We can infer from the evidence gathered at the fossil site a likely sequence of historical events to explain the origin of these tracks and their present condition:

At one time this specific site was much further from the seashore. A large dune field stretching 100s of miles along the southern tip of Africa was present. At one particular dune—the one we are interested in here—a large carnivore walked over leaving tracks in the wet sand. Those were preserved after drying out when more sand was deposited on top of them. After many new layers of sand had been deposited, the same process was repeated two more times but this time it was likely a modern human (1) whose footprints were preserved in the wet sand.

Typical coastline of South Africa in the area where this cave with preserved footprints was found.  The exposed sandstones are fossil sand dunes. There are 50 feet or more of material above the shoreline that was deposited on the footprints and needed to be eroded to expose them.  Image: Screenshot from Google Earth.

After these tracks were covered by sand, the dune continued to grow with dozens of feet of new layers deposited onto it. At some point, the environment changed causing the dune field to be converted into a landscape covered by vegetation. During this time the sand buried under this new landscape began to cement together forming sandstone.

The ocean levels rose and began to erode what was now a thick layer of sandstone that had been an ancient dune field. Not too long ago (tens to hundreds of years) our fossil dune of interest was finally eroded at the high-tide mark allowing for the layers of sediment that preserved the footprints to appear on the roof of the cave while also exposing the carnivore tracks on the floor of the cave.

Based on previous studies of the geology of this region the authors of the article describing these tracks believe the tracks are about 90,000 years old. If they are correct, all the events described above would have to have occurred during  this geologically short timeframe. However, as rapid as that may seem, given our current understanding of geology, these events must have occurred at least ten times as quickly in a Young-Earth Creationist (YEC) view.

Another in a long line of puzzling fossils for young-earth creationists

I have written several times about the special challenges that fossil footprints present to the flood geology hypotheses of young earth creationists (YECs):

Yet again, we find footprints in places where a YEC would not expect to find them. Even in the YEC highly shortened chronology of Earth history these sand dunes did not form until after a global flood just 4350 years ago. How did people migrate all the way down to the tip of South Africa so quickly after being divided at the tower of Babel? They had to leave their footprints, have them covered by many more layers only to form an entirely new ecosystem on top of the dunes which then had to be eroded by the ocean to reveal the ancient dunes underneath?

Despite suggestions to the contrary (see extended footnote 2), this discovery and those in the links above should provide compelling reasons to believe that fossilization of footprints can happen without a global catastrophe. After all, there are human footprints found in numerous locations in the world and all YECs recognize these as having been formed after a global flood. Hence, they must admit that footprints can be preserved in local contexts.

There is no doubt that the preservation of footprints, just like all other fossils, is a very rare event and does require a fortuitous (for a paleontologist) set of circumstances to occur. This discovery of footprints in fossil sand dunes is a snapshot one of those rare events. These footprints were formed in just the right place and time to be preserved by a small-scale event. This is not unlike what we see in tens of thousands of other locations where footprints of many organisms are found. A flood (let alone a global one) is not required to produce footprints and the context of footprints frequently excludes such an event or is at best neutral with respect to extent of the event that caused the preservation of the footprints.

This post continues a series examining particularly challenging (for all evangelical Christians but most particularly those of the young-earth persuasion) geological contexts in which human fossils have been found. The other posts can be accessed with the following links: 

The Frequently Overlooked Geological Context of Hominid Fossils

Geological Context II: Neanderthals and the Italian Supervolcano

Geological Context III: The Origins of the Dmanisi Skull

Geological Context IV: The Pit of Bones: A Death Chamber Time Capsule

Geological Context V:  Human Fossil Footprints Found Below Ice Age Deposits

Footnotes:

1.  A New Pleistocene Hominin Tracksite from the Cape South Coast, South Africa. The authors think the footprints probably belong to Homo sapiens (modern humans) but they can’t be sure they don’t belong to another hominin species (eg. Homo naledi)

2. YECs and Fossil Footprints. Countless numbers of footprints made by hundreds of kinds of organisms are preserved in hundreds of individual layers of the geological column. Millions of these tracks have been identified from just the tiny fraction of the rocks that are exposed at the surface of the Earth. But how were so many footprints preserved?

In innumerable Facebook commenters and personal conversations I have had with young-earth adherents, I have been assured that footprints can’t be preserved as fossils—at least not by any process that occurs today. At an Answers in Genesis conference I attended, a speaker mocked the idea that footprints of dinosaurs could be preserved by conventional geological methods, pointing out that it would be silly to think that footprints on a beach or even muddy lake edge would last long enough to harden into rock and be preserved. Unfortunately, these speakers are usually not experts and are overgeneralizing to try to influence their geology-naïve audience. They create a “footprint problem” that doesn’t exist so that they can provide a “better” solution. This idea that footprints aren’t expected to be found in the fossil record is even promoted by the top YECs geologist, Dr. Snelling, at Answers in Genesis. Here he addresses dinosaur footprints:

Biblical geologists, on the other hand, say it is the conventional geologists who, in fact, face a dilemma. If geologic change takes place slowly, surely footprints made in mud would be obliterated by wind and rain long before the prints were covered by new sediments and hardened into rock.

Dr. Snelling is perfectly willing to allow his audience to believe that conventional geology has no explanation for fossilized footprints even though he knows that many footprints can be and are preserved under conditions that we observe today. He makes what sounds like an obvious point—who would deny that as you walk around you would have no expectation that your footprints will become “fossilized?” Dr. Snelling and other YEC speakers take this common knowledge of their audience and then show long sets of dinosaur tracks and then ask, “how then could these have been preserved?” The answer, they say, is found in the Noahic global flood in which cataclysmic waves of sediments immediately covered the tracks of these animals preserving them in the rock record, even though they offer no specifics as to how this may occur.

YECs believe that special circumstances are required to explain footprints but since they believe that all, or nearly all, of them were produced in the span of one year during a flood, the huge number of prints contained in the rocks would require that a large percentage of all of the footprints made by animals running around trying to escape the flood had to be preserved. This is an extraordinarily optimistic scenario, which is not supported by the relatively slow pacing evident in most fossil trackways in things like impression depth, amount of contact between the ground and the foot, the seemingly random direction of the trackways and the amount and direction of material displaced with each step.

In the ancient earth scenario, only a few footprints of the millions made by a single individual of a population of millions of individuals need be preserved every thousand years or more to account for the observed footprints in rock. Even if only 0.000000001% of all footprints left by dinosaurs, mammals and humans were preserved, the geological record would contain billions of footprints. And it does!


Editing provided by LC

A bootprint preserved in hardened sand below sea level in Death Valley National Park.  My shoe for scale. Photo: Joel Duff

Comments

  1. Intriguing information, as usual, Joel. Thank you for these posts.

    Liked by 1 person

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