The Frequently Overlooked Geological Context of Hominid Fossils

The human fossil record is probably one of these least understood yet frequently discussed topics in the Christian church.  I have neither the expertise nor the desire to attempt to resolve the debate over whether particular fossils represent human ancestors or not.  I understand that human origins is a sensitive topic, especially within the conservative evangelical church today, with the historicity of Adam and Eve playing a very important role in Christian doctrine.  I get all that, and I agree that it is very important doctrinal question.

What I am interested in exploring in this post is what happens as one moves beyond the biblical discussion about Adam and Eve and attempts to apply that doctrine to the observations that we make from creation itself?

The proclamation that all humans are descendants of a historical Adam and Eve is easy to make.  However, the application and interpretation of evidence from fossil and genetic data to the question of human origins is anything but easy.

Reactions within the church to the fossil record of humans have been extremely variable, even by those that ascribe to single pair (Adam and Eve) of progenitors in the recent past. You only have to look at the reaction of different evangelical communities (see: Bones of Contention: How Will Creationists Respond to a Huge New Hominid Fossil Find?) to the recent find of a large collection of strange bones retrieved from the deep recesses of a cave in South Africa to understand how diverse the reactions to hominid fossils have been. I have commented on the current state of confusion among creationists elsewhere (see: Bones of Contention II: Ape, Human or Fraud; Young Earth Creationists Respond and Bones of Contention III:ICR Claims that Homo naledi Fossils are of an “Imaginary Creature”).

Disagreement among evangelicals over human origins is nothing new. I highly recommend reading the book, “Adam’s Ancestors” by David Livingstone. In that book, Livingstone reviews the views, primarily of Christians over the past 2000 years, regarding the origin of human races, human fossils, and other evidence of ancient human populations. Livingstone demonstrates that the struggle to interpret that data with respect to understanding human population distributions, race, variation and more recently fossils is not just a recent phenomenon but has persisted within the church for hundreds of year with many different views holding sway over time.

If a recent (<10,000 years) origin of Adam and Eve is a necessary outcome of one’s interpretation of scripture, then all fossils and remains of human-line bones must be designated as either descendants of that primeval couple or the remains of extinct lineages of primates that, though they may have been similar to humans, are not in the lineage of Adam and Eve and thus not human by definition.

But which hominid fossils belong to which group?

There is by no means a consensus among those who hold this interpretation of human origins. Some insist that some fossils—for example, those ascribed to the name Homo habilis or Homo erectus or even Homo neanderthalensis—are not human, while others insist that they are fully human descendants of Adam and Eve.  It isn’t just the physical features of the bones and their relation to humans that is debated, but the attendant evidence of culture (e.g., burial rituals, tool-making) that are found along with the bones is also hotly debated.

Strange Hominid bones from the Malapa “Caves”

With this in mind, I want to turn my attention to a strange group of caves from South Africa referred to as the Malapa caves. This system of cave and cave remains has yielded a series of strange fossil hominid bones (additional story from National Geographic). I am using the term “hominid” since there is no consensus among Christians about their humanity.  From these weird caves, described below, large blocks of rock have been retrieved, which CT-scans and X-ray technology have shown contain bones that have taken many years to extract and will continue to keep scientists busy for decades to come.

The bones previously found at this site already have been described as a new species of hominid, Australopithecus sediba. This species has been described as one of the earliest ancestors of humans, with evidence of walking upright including specialized hip and foot bones.  This particular fossil site has been widely discussed and debated among anthropologists because of the strange mixture of characters seen in the skeleton, such as non-human features of a very small cranium and long arms, yet hips and feet that suggest upright walking and possibly even capacity to run.

Young earth creationists, and even many old earth creationists such as Hugh Ross, don’t accept primate ancestry of Adam and Eve, and so they assign presumed human fossils to one of two categories: descendants of Adam or an extinct species of ape.  The features of this particular set of fossils show how difficult it can be to determine if the bones are human or ape. The new bones just revealed this year in the Rising Star cave system not far from Malapa are proving to be even more difficult to assign to one of these two categories (See: Bones of Contention II: Ape, Human or Fraud?).

With respect to the hominid fossils of the Malapa caves, Todd Wood, a young earth creationists, published an extensive review of hominid fossils in the Answers Research Journal, which is Answers in Genesis’s so-called peer-reviewed advanced research journal. In this review, Wood employs a variety of statistical measures to try to define the homo “baramin” (a baramin is the young earth creationist’s term for the “kinds” of the initial special creation events of the 6 days of creation) versus non-human ape baramin.

He concluded that most of the fossils described by anthropologists as “Homo” are descendants of Adam and Eve. This would include Neanderthals from Europe, the hobbit fossil from Indonesia, Homo habilis,  Homo erectus etc…  He also concluded that the fossils from this site described as Australopithecus sebida is also a descendant of Adam but that other species of this genus represent extinct apes.

Hugh Ross (an old earth creationist) is far more restrictive than Wood or even any other young earth creationists. He considers Australopithecus sediba and even most of the other “homo” fossil species including Neanderthals to not be related to modern humans at all.

A year after Wood’s paper was published, Answers in Genesis (AIG) published an article on this website by three of their staff that discussed how Australopithecus sediba was nothing more than an extinct ape.

I find two things interesting about this second article.  First, the authors make NO mention of Wood’s extensive analysis of hominid fossils, including the one they are specifically critiquing in their article, thus giving their audience no idea that other creationists disagree with their view. Secondly, although they dispute the dating techniques used to show the fossils are around 1.9 million years old, they do not discuss the geological context in which these fossils were found.

The geological context of hominid fossils is critical to the interpretation of those fossils:

Despite the emphasis of my long introduction, the debate over human ancestry isn’t what I am interested in commenting on with respect to this recent fossil find.  I am more interested in the context of the fossil find here, not the exact classification of the fossils themselves.

I find that, among creationist organizations, hominid fossils are poorly understood and the general public is even less aware of the extent of the hominid fossil record and its implications. If this is an accurate assessment of the state of Christian’s knowledge of fossils, then the geological context in which those fossils are found is probably a complete mystery.   I think there are two reasons for this: 1) the geological context isn’t understood and so not explained; and/or 2) when it is understood by Christian apologists, they find it so challenging to their convictions that they don’t want to discuss it.

I will try to illustrate the challenges that come with a great knowledge of the geological context of hominid fossils by examining this Malapa cave fossil site that contains the bones what for young earth creationists are considered either a fossilized extinct ape or a fossil human.

Regardless of their taxonomic status, the geological context in which they are found raise the same questions and problems for the YEC hypothesis.

The Malapa Caves: Some are just remains or “fossils” of caves

In a region just north of Johannesburg South Africa, there is a network of cave systems.   Many hundreds of new caves have been discovered in the past five years, and many contain fossilized bones.  Anyone who hears about these caves is probably picturing a series of caverns underground and assumes that the remains of hominids found there must be in the sediments in these caves.  Yes, there are still underground caves in the area, but many if not most of the caves including Malapa are actually remnants of caves, not caves themselves.

Look at the first picture (below). There is simply a rocky depression where many fractured rocks have been removed.  Yes, this is exactly where rocks with fossils of many animals and potentially humans have been found.

How could hominid bones become encased in rocks at the surface of the earth?

You may be wondering, “how can this be called a cave?”   As I just suggested, what you are looking at is the eroded remains of what used to be a cave system.  Below is a cartoon depicting what this area probably looked like in the past, when the cave system was still active and underground.

What we have left today in this area are hundreds of rocky deposits that represent the mineralized rock (flow-stone, stalactites and debris that fell into the cave and was cemented together) where cave pools and large rooms used to be.   As the cartoon depicts, a cave system is thought to have formed in these rock layers in the past but at the time the caves where 50-100 feet under the ground.

At times there were cave-ins, which created sinkholes at the surface leading down to caverns underground.  Those sinkholes became death traps where animals running along the surface could stumble down into the pits to their deaths at the bottom, in a small lake or stream. There they would decay with no scavengers and their bones would eventually become encased in stone as more debris fell on them and became cemented by the minerals in the water.

The same could have happened to any human or ape living in the area. Maybe they attempted to climb down into the cave and slipped, or maybe they were thrown in, or they were chasing an antelope and just fell in.  However they fell into the cave, they were killed on impact (yes, there is an entire paper dedicated to examining the bone fractures to determine cause of death) and preserved where they lay.   These “caves” today are identified by these hard rock formations in shallow depressions that represent the hardened rocks of cavern lakes and pits that filled with material.

Over time, the rock that formed the cave ceiling gradually eroded to where the ground surface is today.   So, for much of this area, what once were the filled cavities of caves now are exposed as rocky remains that are left.  Hundreds of these cave “deposits” have been examined.  Most have NO fossils in the preserved cave stone at all. This is probably because most of the cave system of pools never had an opening to the surface above them when the sediments and minerals formed to fill the space.  Only a few of these cave deposits have fossils, but when they do they have a LOT of fossils and all of them represent species that are extinct today.  In some cases, hundreds of different animals have been identified in one cave deposit as the sinkhole/death trap just continued to collect victims over time.

The geological context is quite clear for these fossils.  They are found locally in abundance in rocks that are clearly of cave origin based on chemical composition.  The animals bones that are found show no sign of scavenging, and so it appears that all died in place rather than being dragged to a common location.

Yet, all these fossils are found essentially at ground level or just a meter or two below ground level today.  Below is a map of a cross-section of one of these filled in cave pit deposits in which the Australopithecus sediba fossils were found.   You can see these fossils were found just a couple of meters below the general land surface. This rock is fractured and eroding now that it is exposed, and scientists have pulled pieces of rock out of this pit and have been doing CT-scans to look for bones of primates.  The rocks are full of bones of other animals again indicating these are the remains of animals that have fallen into “death trap.”

How long did it take for all these events to occur leaving us with the current eroded remains of former caves?  Standard geological models and radiometric dating suggests that the formation of the death trap, fossil formation and erosion of the caves, has occurred over a span of 2 million years.  The rocks in which the caves formed would be far older.

Let us contrast this reconstruction of history with that of the young earth creationist who has something less than 4500 years of chronological time at their disposal.

Geological Context and Young Earth Views on Human Fossils.  

By now you have probably guessed why I have suggested that the geological context of these fossils is in many ways more challenging to explain than the fossil bones themselves.

Within the young earth hypothesis, how might the presence of these bones be explained?

First, we have to ask when these fossils are predicted to have formed.  For the YEC, cave deposits are formed in rocks that lie upon even more layers of rocks that bear fossils. Because fossils represent death and death did not occur until sin entered into world, all of this fossil-bearing rock must have been deposited by a global flood.

A logical extension of this idea is that the caves in such rocks must be post-flood in origin. Furthermore, any remains of animals or humans that are found inside of caves must represent materials that lived and died after the flood and the formation of the caves.

So right away, this puts the origin of these fossils after a global flood, which YECs believe occurred 4500 years ago.  But how long after the flood?  If the fossils of A. sibida do represent descendants of Adam and Eve, as a few creationists believe, then that puts their origin even later in their YEC timeline, since the same creationists believe that all people were congregated at the Tower of Babel several hundred years after the flood prior to their dispersal across the globe including South Africa.

So here is the series of events that YECs must propose:

• Cave formation after the rock layers of the cave formed in a flood 4500 years ago.
• People, albeit very long-armed small brained versions of humans, traveled down from Babylon sometime after 4250 years ago to South Africa
• At least one individual met his/her unfortunate demise by falling into a pit in a cave, probably from a sinkhole.
• After that individual fell and hundreds of other animals also met their accidental demise the same way, they were all gradually cemented together by minerals in the cave water that dripped and ran through them.
• The rock that had formed the ceiling of the cave and the mouth of the pit eroded. This involved eroding of up to 100 feet of solid rock from the entire region.

I think it should be obvious that compacting this scenario into a 4500 year old chronology stretches all bounds of credulity and credibility.

How can so much rock erode over a few thousand years with no obvious means of erosion other than rainfall and some wind?   One might be tempted to suggest that the past climate was radically different but that can be tested by the deposits themselves.  Pollen, spores and other plant material blown into the death pits have left a columnar record of past climate from bottom of the pit to the top of the pit.  A very thorough examination of this material reveals that the climate of this region has remained very similar (the same plants lived in the area) over the lifetime of the pits filling.

Thus, no mechanisms for a massive, fast erosion of rock appears to be available to permit the erosion of millions of tons of rock of this huge area where hundreds of old caves are now exposed.

The conventional scientific dating of this pit is that it was a cave with an active water system a bit over 2 million years ago. It then became filled several hundred thousand years later, and it has been sitting there since then while the land eroded above to expose these remains.   For YECs, there are only 4000 years to fit the development of the cave, the pit formation, and the filling of the cave with remains, solidifying into rock and then erosion of the top layers of rock.

I would suggest that the geological scenario that I have presented is why the geological context of this and another similar fossil hominid finds is rarely reported in the creationist literature.  

With respect to other Australopithecus species found in same area, in other ancient fossil caves I sometimes see that they are reported to have been found in caves deposits or even described as being found in death pit deposits. But until I researched this site myself, I had no idea that the rocks that many of these fossils were found in were just sitting practically at the surface and not found deep underground in a cave.   I certainly never would have gotten this impression from any creationist literature, nor do I suspect that any committed YEC advocate would have any idea where these fossils were really found.

Now, many who have read this far may be thinking that this doesn’t really matter much because they don’t believe that the fossils found in these cave deposits are either human ancestors or descendants but just an extinct ape.  While this might help remove these fossils from having to fit them into an Adam and Eve scenario, I don’t think that suddenly makes these fossils a non-issue.

I say that because no matter whose bones are found in these rocks, the fact is there are bones found in cave deposits that are still a post-flood deposit according to young earth creationists.  And this seems impossible under the YEC hypothesis.

As a result their very presence raises the same questions about the age of these rocks.   Animals still had to make their way from the Ark down to southern Africa. Hundreds of them had to fall in this hole, which in itself likely happened over thousands of years rather than short period of time.   The cave system then had to fill with debris and then the rock over the cave had to completely erode to expose the rocks that encase the fossils.   All of this still had to happen in less than 4000 years, so the classification of the bones themselves does not help resolve the challenge of the geological context in which the bones are found.

The issue with the geology of these sites is therefore less about human origins than it is that these sites speak to the age of the earth.

Conclusion

The geological context of fossils adds another degree of complexity to the interpretation of these fossils.  I am not certain how to explain the fossils themselves in context with the Biblical record if the world were young or old. But I do know that within a YEC context, where flood geology is used to explain present day geological phenomena, the presence of fossils in these rocks is a serious, probably insurmountable, problem.  The YEC literature expends a lot of energy and page space on their web site to explaining away the intermediate features of these fossils, and while that effort is not especially convincing, their geological timeline for a fossil site such as Malapa is so far-fetched that ignoring the context of the fossil finds seems to be the only response.

I have only provided one example of how the context of the fossils presents challenges to a young earth interpretation of the fossils.  There are other famous fossils that I think all evangelicals would claim as human because of the types of cultural items found along with them, but for which the geological context is just as challenging.   All too often, the YECs present us with fossils extracted from their historical/geological context and displayed in museums and articles.

But context is always key.

Few Christians would expect to be able to interpret a verse from the Bible without having some knowledge about the context of that quote, including the larger story that it is found in, the historical context of the entire book, and the entire scope the of scriptures.   Likewise, the geological context of a fossil is important because it is speaks in large part about the history of the fossil and puts boundaries on the possible interpretations that one can make about it.

As a Christian, I don’t feel like I should be scared of the context of fossils and shielded from it, even if I don’t fully understand how to interpret the fossils in the context of the scriptures.

** This article is an updated version of one I published in July of 2012