The Gorilla-Human “Split”: Where Do Gorillas Hang on Our Family Tree?

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Abstract

Asking how far back our kinship with gorillas goes is a question about a fictional relationship.

How much time separated the origin of gorillas and chimpanzees? Enquiring evolutionary minds want to know! Why? Because they think humans share the chimp branch of the evolutionary tree of life, and they want to know how long it took for humanity’s uniqueness to evolve.

Evolutionary opinions about how long each step in this process took have varied greatly. Even where they took place has been hotly debated, thanks to the dearth of ancient African gorilla fossils. The 8-million-year age now assigned to nine fairly modern-looking gorilla teeth found in Ethiopia’s Afar Rift, reported in Nature in February 2016,1 has fueled the suggestion that the chimpanzee-human branch diverged from its lineage shared with gorillas much earlier than previously thought—and that it did so in Africa.

Out of Africa

Ethiopia’s Afar Rift is well known as the cradle of many fossils belonging to our supposed much nearer non-human ancestors, australopithecines like “Lucy.” The Chorora Formation, composed of volcanic debris and sedimentary rock, is believed by evolutionists to be the oldest part of the Afar Rift, far older than the layer in which Lucy was found.

Chororapithecus abyssinicus, the gorilla to which the teeth featured in the study belonged, was named for the location of their discovery. Chororapithecus means “ape from Chorora” and abyssinicus refers to “Abyssinia,” another name for Ethiopia. The teeth look very much like modern gorilla teeth. Therefore, the study’s senior author Gen Suwa explains, “Chororapithecus probably represents an ancestral branch of the gorilla lineage.”2 The authors mention the earlier discovery of another great ape’s teeth3 fossilized in a mudflow in Kenya’s Rift Valley. Because those teeth are supposedly 9.8 million years old, the authors suggest that the Kenyan species could be an ancestor of their gorilla. These African discoveries, the authors assert, plant the important events in human evolution firmly in Africa, not in Eurasia even though, as Suwa points out, until now “some scientists have forcefully suggested that the ancestors of African apes and humans must have emerged in Eurasia.”4

Beginning with the presupposition that the Chororan gorilla had evolved from a common ancestor of humans, gorillas, and chimpanzees, study coauthor Giday WoldeGabriel explains, “Our new research supports early divergence: 10 million years ago for the human-gorilla split and 8 million years ago for our split from chimpanzees. . . . That's at least two million years earlier than previous estimates, which were based on genetic science that lacked fossil evidence.”5 WoldeGabriel says, “This is the time period when human and African ape lines were thought to have split, but no fossils from this period had been found until now.”6 The researchers believe that the 8-million-year age assigned to the modern-looking gorilla teeth pushes back by at least two million years the entire timeline for the divergence of first gorillas and then chimpanzees from the line that led to humans.

In the investigation of evolutionary puzzles, scientists burdened by an evolutionary worldview generally ask “when” rather than “if.” This narrow-minded way of looking at scientific data is beautifully illustrated by the conclusions drawn from this Ethiopian gorilla’s teeth.

Discovered in 2007, the age now assigned to these teeth and other Chororan fossils is based on “geochemical, magnetostratigraphic and radioisotopic results that securely place the Chorora Formation sediments to between ~9 and ~7 [million years.]”7 As Suwa explains,

Until now, no mammalian fossils south of the Sahara have been securely dated to 8 million to 9 million years ago. Any and all fossils from this crucial time period of Africa would help unravel the story of human origins and emergence. These are the first such fossils.8

The authors are confident that the diverse mammalian fossils from the Chororan Formation—supposedly the oldest mammals found so far in Africa’s sub-Saharan desert—reveal that many different mammals evolved in Africa between 7 and 10 million years ago. Furthermore, they are confident that their results reveal which molecular clock timeline of key primate evolutionary events in human history is the correct one.

How Fast Does the Clock Tick?

To what “genetic science” does WoldeGabriel refer? To molecular clock dates. But such dates are derived from their own set of unverifiable assumptions and a fair amount of circular reasoning.

Molecular clock estimates of when humans and their supposed ape-cousins diverged from their common ancestors are based on comparisons of the genomes of living apes and people. Common ancestry is simply assumed because similarities exist. Differences are assumed to be the result of mutations. Just as a clock tells us the time because it ticks at a known speed, so evolutionists use a molecular clock to calculate how long various evolutionary steps supposedly took by assuming evolution occurred as a result of mutations at a particular rate. Of course, the acquisition of such new kind-altering genetic information from mutations has never been observed.

Nevertheless, on the basis of a fairly rapid mutation rate, Suwa notes that until recently, “most scientists, especially geneticists, thought that the human-chimp split was as recent as 5 million years ago, and that the human-gorilla split was only about 7 million to 8 million years ago. This contradicted the fossil record.”9 To what fossils is Suwa referring? He’s talking about fossils of extinct apes that evolutionists believe were not really apes but rather were transitional creatures on the road to becoming human. “For example, fossils thought to be on the human side of the split such as Ardipithecus kadabba from Ethiopia and Sahelanthropus from Chad were 6 million years old—or, in the case of the Chad fossil, perhaps 7 million years old,” Suwa explains.10 However, just a few years ago, another genetics research group from Cambridge proposed that the discrepancy was due to varying mutation rates.

But now, having found a handful of modern-looking gorilla teeth deemed to be 8 million years old, the study’s authors believe that if modern gorillas were already around so long ago, then the line that led to chimps and humans must have diverged from its shared gorilla ancestry even earlier. If Chororapithecus is 8 million years old, Suwa explains, then “the actual gorilla-human split must then have been up to several million years before that,” putting the human-gorilla split “at around 10 million years ago and the human-chimp split at around 8 million years ago,” which is 2 to 3 million years earlier than most evolutionary textbooks claim.11 The study’s authors assert that the evolution of humans from apes therefore resulted from “lower mutation rates”12 and hence a slower ticking molecular clock.

Molecular clock timelines of evolution are fraught with unverifiable assumptions.

As we’ve pointed out before, molecular clock timelines of evolution are fraught with unverifiable assumptions. The greatest of these is the notion that one living creature can actually evolve into another kind, something never observed and something for which experimental science can offer no mechanism. They must assume that mutations can actually provide novel genetic material to fuel this evolutionary engine, another biologically unverifiable claim. And they have to invent a rate at which these rather magical, information-creating mutations occur to try to align with the fossil record. Insight gleaned from the gorilla genome has already thrown a monkey wrench into evolutionary notions about the nearness of our supposed relationship with gorillas.

Furthermore, even the degree of similarity that exists between various primate animal and human genomes—easily understood as a consequence of sharing our common Designer—are calculated on the basis of methodology biased toward an evolutionary interpretation and are likely overestimated. And molecular clocks are often calibrated according to the dates assigned to the fossil record. Therefore, if the current study’s results are accorded acceptance among evolutionists, the whole timeline of human evolution will change dramatically.

Determining the Dates

Of course, this extinct gorilla’s teeth have nothing to do with human origins anyway, since humans and gorillas and chimpanzees do not actually share a common ancestor. Nevertheless, it is instructive to take a brief look at the methodology used to determine their groundbreaking age in order to further understand the unverifiable assumptions in which they are rooted and the biblically accurate historical alternative explanation for their modern appearance.

The Chorora Formation, on the edge of the Afar Rift Valley, has long been regarded as over 10 million years old. This belief about its age hinges on interpretations of radiometric data that are based on numerous unverifiable presuppositions. Likewise the diversity of mammalian fossils preserved in the Chororan Formation, thanks to evolutionary presuppositions, are seen as evidence of rapid evolutionary diversification. The study of the location where the Chororapithecus gorilla’s teeth were found was thus undertaken to refine the dates assigned to it in hopes of pinpointing early key events in human evolutionary history. The younger age “determined” in the 2016 study—“only” about 7 to 9 million years—supposedly “provide[s] new insights into mammalian evolution in Africa, in a period crucial to elucidating the emergence of the African ape and human clade.”13 However, the new dates are as flawed as the old.

The authors of the study did provide a clearer picture of which fault-separated rock layers in the region correspond to each other by matching up the chemical isotopes in each part of the stratigraphic sequences. However, the unobservable radioisotope age is a worldview-based, unverifiable interpretation of the rocks’ observable chemistry.

Likewise, the addition of paleomagnetic stratigraphic comparisons does not make the millions-of-years dates applied to the Chorora Formation any more reliable. “Within the Chorora Formation,” Answers in Genesis’ geologist Dr. Andrew Snelling explains, “there are eight thin volcanic ash (tephra) beds that can be traced from outcrop to outcrop. Each resulted from a unique volcanic eruption. These beds have been K-Ar and Ar-Ar radioisotope dated. The fossil-bearing sediment layer lies between two of these, so paleomagnetism and the assumed sedimentation rate were used to determine the age of the sediment layer in which the fossils are found, and thus the age of the fossils.” Yet the dates assigned to the paleomagnetically distinct layers are based on using radioisotope dating to calibrate the paleomagnetic timescale, so how can it then be used to calibrate the radioisotope dating of the tephra beds? In any case the radioisotope dating is based on untenable assumptions, such as the notion that there has never been any contamination of the minerals in the layers and the notion that the isotopic clocks have always ticked at the same rate. In fact, Dr. Snelling, in his analysis below, points out that such assumptions are unreasonable because “recently erupted volcanic rocks are known to yield millions-of-years ages, so there is no guarantee that these tephra beds in the Afar Rift zone are not also quite young,” much younger than the millions-of-years ascribed to them.

Furthermore, some scientists insist the changes in earth’s magnetic field—which is what is reflected in the varying magnetic polarity observed from layer to layer—take thousands of years to occur. However, that belief is based on an unproven hypothesis concerning the processes that create earth’s magnetic field in the first place. “But that is unproven,” Dr. Snelling says, “and we now have several examples of rapidly formed rocks in which such polarity changes have been recorded. This indicates such polarity changes can and do occur within days to weeks.” In fact there is good evidence that such rapid reversals in earth’s magnetic field may have been associated with the global Flood and its aftermath. See “More Evidence of Rapid Geomagnetic Reversals Confirms a Young Earth” to learn more.

A Floody Past

By focusing their attention on the age of the Chororan gorilla’s teeth rather than on how they and diverse mammalian fossils came to be preserved where they are, why they are so very much like modern gorilla teeth, and whether they even belong to a supposed human ancestor at all, evolutionists have missed the historical significance of these teeth entirely. When viewed in the light of biblical history, we see that the enormous age assigned to them on the basis of unverifiable, worldview-dependent interpretations of dating methodologies is off—way off—as the Flood and its aftermath responsible for burying and fossilizing these gorilla teeth occurred only about 4,300 years ago, as Dr. Snelling explains below in the “Fitting It All Together” section in his detailed analysis below.

Furthermore, we know from God’s eyewitness account in His Word that He created all kinds of living things in the space of just three days during the week of Creation about 6,000 years ago, designing them to reproduce “after their kinds.” This is affirmed by biological observations, for animals do not evolve into different kinds of animals but only reproduce and vary within their created kinds. All the original kinds of apes were created on the same day, Day Six of Creation Week. Representatives of all the created kinds God made were taken on Noah’s Ark at the time of the global Flood, and from them all the varieties of animals we see today descended. Thus, it is no surprise that the gorilla teeth from the Afar rift look quite modern, as all gorillas are varieties of the great ape kind God created in the beginning and are descended from those representatives of this kind that were on the Ark.

And we do not have to wonder about the biological relationship between gorillas, chimps, and humans: there isn’t one. Humans, gorillas, and chimps do share some genetic similarities. But genetic similarities—however they are calculated—are simply evidence of our shared common Designer. They are not evidence that humans and great apes share a lineage.

Furthermore, their presence as fossils in sediment most likely associated with the time soon after the global Flood, in layers in Africa somewhat deeper than those in which human fossils are found, merely reflects the fact that, as we understand from Genesis, animals disembarking from Noah’s Ark spread out across the world much sooner than the people who descended from Noah’s family and delayed their dispersal into Africa and elsewhere until forced to do so by the incident at the Tower of Babel. The rock layers and fossils, divested of evolutionary interpretations, are, as always, consistent with the history we read in God’s reliable Word.

A Closer Look at the Layers of Assumptions in Dating the Chorora Formation: A Geologist’s Perspective on the Game-Changing Dates

By Dr. Andrew Snelling

There doesn’t seem to be anything invalid in the authors’ reassessment of the stratigraphic sequence of layers within the Chorora Formation. In fact, it makes for a clearer picture to realign all the occurrences of the basal thick rhyolite unit separated by block faults which characterize the Afar Rift valley. In this instance the K-Ar and Ar-Ar radioisotope “dates” for that thick rhyolite layer are all in the same ballpark. This is to be expected if the K and Ar isotopic contents of this rhyolite represent a chemical characteristic of its composition, rather than being interpreted as an “age.” In other words, the isotopic composition is simply another characteristic of a rock that allows for outcrops of it to be compared for similarity, just like one would check if the rocks at the different outcrops had the same minerals and mineral textures. The radioisotope age is simply an interpretation of the rock’s chemistry.

As for the dating of the Chorora Formation itself, the use of paleomagnetism was employed to date the fossil-bearing bed of interest within the formation because it could not be directly dated using the K-Ar and Ar-Ar radioisotope methods. Within the Chorora Formation there are eight thin tephra (volcanic ash) beds, which can be traced from outcrop to outcrop. These represent what are called event horizons because each one resulted from a unique volcanic eruption. These tephra beds have been K-Ar and Ar-Ar radioisotope dated. However, the fossil-bearing bed of interest lies between two of these tephra beds; so to obtain an age estimate for that bed and thus the fossil of interest paleomagnetism was used.

Samples of various beds within the Chorora Formation including the fossil-bearing bed were tested for their paleomagnetism, in particular the north or south direction of the field responsible for their magnetization. This is called the polarity. If the field polarity was north, it is called normal; if it is south, it is called reversed polarity. In between the sediments which were being deposited when the field polarity was changing from normal to reversed or reversed to normal the paleomagnetic signal is termed intermediate.

The gravelly sand bed containing the gorilla Chororapithecus fossils is just above a tephra bed dated at 8.02 Ma (the average of 8.18 ± 0.15 Ma by K-Ar and 7.86 ± 0.10 Ma by Ar-Ar). Overlying the gravelly sand bed containing the fossils is an ~5 m thick predominantly silty bed, which is capped by another tephra bed, dated at 7.74 Ma (the average of 7.67 ± 0.17 Ma by K-Ar and 7.82 ± 0.11 Ma by Ar-Ar). A paleomagnetic transition occurs just below the 8.02 Ma tephra bed, but the overlying sediments including the fossil bed are normally magnetized. Using the tephra bed’s radioisotope age of 8.02 Ma this transition is equated to the corresponding polarity transition boundary of 8.072 Ma on the paleomagnetic timescale. So then interpolating the sedimentation rate between this polarity transition and the overlying 7.74 Ma tephra bed yielded an 8.0 Ma estimate for the Chororapithecus and associated fossils.

Assumptions Abound

Now there are two crucial issues with this dating procedure, apart from the unprovable assumptions on which the components of it are based. For radioisotope dating to be an accurate clock, one needs to know the starting conditions, that there was no contamination of the system while it has been operating, and that the clock needs to have always ticked at the same rate. (See “Radiometric Dating: Problems with the Assumptions.”) However, we can only study these clocks as they operate in the present. What they were doing in the past has to be assumed, that is, it has to be assumed that they have always operated the way they do today. But why should they have always operated the same way? Contamination is known to occur even today, and why should they have always operated at the rates we observe today, when other physical processes are known to have operated faster in the past? These assumptions are not only unprovable, they are unreasonable.  No scientist was there in the past to observe how they were then operating. So this places a big question mark over the K-Ar and Ar-Ar radioisotope ages obtained in this study. For example, recently erupted volcanic rocks are known to yield ages of millions of years, so there is no guarantee that these tephra beds in the Afar Rift zone are not also quite young due to very recently being erupted.

Next there is the so-called paleomagnetic timescale. First, it has been assumed that the changes in magnetic field polarity have occurred over tens of thousands of years or more, due to the assumption that the earth’s magnetic field is generated by a dynamo in the core. But that is unproven, and we now have several examples of rapidly formed rocks in which such polarity changes have been recorded. This indicates such polarity changes can and do occur within days to weeks. Furthermore, the absolute dates within the paleomagnetic timescale have been established by dating the rocks which have normal, intermediate and reversed polarities by radioisotope dating methods, especially K-Ar and Ar-Ar. So how can this paleomagnetic timescale then be used to date the change in polarity in these Chorora Formation sediments to establish an age for these fossils? The paleomagnetic timescale was set up using radioisotope dating in the first place, so how can it then be used to calibrate between radioisotope dates of two tephra beds? That is simply self-fulfilling circular reasoning!

And that “interpolation” between the paleomagnetic date below the gravelly sand fossil-bearing bed and the radioisotope date of the tephra bed above the overlying silty bed is based on assuming a constant SLOW rate of deposition of the silty material, which was never observed! To begin with a gravelly sand bed requires rapid deposition due to the large grains and gravel particles in it having to be transported by swift water currents. And the tephra beds are due to violent volcanic eruptions. So this area was hardly a calm environment. Added to that, silty material is known from field observations and laboratory experiments to also be deposited rapidly. Thus the whole Chorora Formation could well have accumulated rapidly under local catastrophic conditions within weeks to months, not over the claimed hundreds of thousands of years.

Fitting It All Together

So where do the Chorora Formation sediments and volcanics which contain these Chororapithecus fossils fit in the biblical framework of earth’s history? The first clue is that these teeth are quite “modern” looking gorilla teeth. The second clue is that gorillas still live today in the forests of central Africa. Within the biblical framework of earth’s history these gorillas must have migrated to their present home in central Africa from where they got off the Ark in the mountains of Ararat after the Flood. Since the Afar Rift zone is a continually active tectonic feature on today’s land surface, it obviously started to form as the Flood ended as plate tectonic activity decelerated, and then calmed even further in the immediate years following the Flood. This rift zone which connects to central Africa through the adjoining Ethiopian rift would provide an ideal migration route for gorillas and their kind on their way from the mountains of Ararat around the coast of northern Africa and into central Africa in search of a suitable environment to call home. But at that time in the first decades after the Flood there was still residual local catastrophism occurring, so it is not surprising that some of those migrating gorillas got swept away in a local super-storm event in the Afar Rift zone as a hurricane blew in from the Indian Ocean due to the warmer post-Flood ocean waters to be rapidly buried in sediments and fossilized. Residual explosive volcanism must have also been occurring, as evidenced by the tephra beds.

So the gorilla Chororapithecus is not our ancestor, but simply a relative to the modern gorillas that still live in Africa today. The fact that he was buried in sediment layers below where we find genuine human fossils in Africa is because he and his kind arrived in Africa before man did (see “Lucy Was Buried First”). Whereas the gorillas and other animals obeyed God’s command to leave the Ark and spread all over the earth, man rebelled yet again and chose to stay put at Babel on the Plain of Shinar. So by the time man was forced by God to disperse, the animals had already had about a 100-year head start!

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2016 Volume 11

Footnotes

  1. Shigehiro Katoh et al., “New Geological and Palaeontological Age Constraint for the Gorilla-Human Lineage Split,” Nature, 530 (February 2016): 215–218, doi:10.1038/nature16510.
  2. Charles Q. Choi, “Fossils Shed New Light on Human-Gorilla Split,” Yahoo News, February 11, 2016, http://news.yahoo.com/fossils-shed-light-human-gorilla-split-141205911.html.
  3. The Kenyan gorilla is called Nakalipithecus nakayamai. Like Chororapithecus, only its teeth have been found. They differ slightly but share some characteristics. Nakalipithecus nakayamai’s teethalso resemble some fossilized gorilla teeth from Greece, teeth which were a major source of the claim that ape and human evolutionary ancestry began in Eurasia, not Africa.

    Given that Nakalipithecus nakayamai comes from rock believed to be older than the Chororan Formation, the authors believe the Kenyan gorilla could be a more primitive gorilla or possibly an ancestor of gorillas. In any case, it is apparent that both belonged to great apes, best described as varieties of gorillas, part of the great ape kind.

  4. Choi, “Fossils Shed New Light on Human-Gorilla Split.”
  5. Samantha Mathewson, “Fossil Gorilla and Africa: Humans Likely Evolved Earlier Than Thought, Researchers Say,” Nature World News, February 17, 2016, http://www.natureworldnews.com/articles/19998/20160217/gorilla-fossils-suggest-humans-evolved-earlier-previously-thought-researchers.htm.
  6. Samantha Mathewson, “Fossil Gorilla and Africa: Humans Likely Evolved Earlier Than Thought, Researchers Say.”
  7. Shigehiro Katoh et al., “New Geological and Palaeontological Age Constraint for the Gorilla-Human Lineage Split.”
  8. Choi, “Fossils Shed New Light on Human-Gorilla Split.”
  9. Ibid.
  10. Ibid.
  11. Ibid.
  12. Shigehiro Katoh et al., “New Geological and Palaeontological Age Constraint for the Gorilla-Human Lineage Split.”
  13. Ibid.

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