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AiG’s geologist Dr. Andrew A. Snelling weighs in on the radiometric assumptions of the latest (2015) study that assigns an older date to this South African australopithecine that, as we discussed last year, was preserved in a post-Flood cavern collapse. This updated article addresses the latest claims about the age of this australopithecine ape which some evolutionists believe to be one of humanity's oldest ancestors.
Australopithecus prometheus (StW 573)—nicknamed “Little Foot”—began in 2014 to make a bid for the attention accorded to the more well-known australopithecine Lucy. Would Little Foot, from the evolutionary point of view, finally fill the shoes of its mythological promethean namesake by offering humanity an appropriately mythological gift,1 the gift of identifying our oldest hominid ancestor?2
Little Foot’s age has been a matter of great debate since discovery of its nearly complete skeleton buried in a South African cave in the 1990s. Research we reported here one year ago aged Little Foot significantly by showing that the fossil was the same age as the breccia (a kind of conglomerate rock) in which it was buried and not the flowstone insinuated later amongst its pieces.
The new date they report for Little Foot is old enough to keep Little Foot in the running for human ancestor, in the evolutionary view of human history.
Now a new study published in Nature asserts that Little Foot is 3.67 million years old, half a million years older than Lucy and sharing Africa with other earlier examples of her species.3 Evolutionists see great significance in the coexistence of multiple australopithecine species in different parts of Africa, particularly as they try to trace what they believe is the history of human origins. Coauthors Ronald Clarke and Kathleen Kuman explain the discovery “raises the question of how many other species there may have been which have not yet been discovered.” The new date they report for Little Foot is old enough to keep Little Foot in the running for human ancestor, in the evolutionary view of human history.
This South African australopithecine ape, discovered in a Sterkfontein cavern by University of Witwatersrand paleontologist Ronald Clarke, has the distinction of being the most complete australopithecine skeleton yet found. But the brass ring for lasting fame in hominid research demands great age. Even with cute names, contenders for the “oldest human ancestor” need a truly superlative age to achieve lasting fame. Little Foot was once a serious contender using the 3.3 million year paleomagnetic date originally obtained by Clarke and colleagues and an even more impressive date of around 4 million years that was later discarded. Subsequent re-dating to 1.5 to 2.2 million years by other researchers, however, relegated Little Foot to the backbench. In 2014 Clarke and colleagues published a detailed analysis of the bits of sediment tucked in the nooks and crannies of StW 573’s resting place showing that the fossil should be dated in accordance with the breccia, not the flowstone, and thereby asserting that Clarke’s original estimate was correct. Now Clarke and colleagues have published a new paper dating the breccia hosting the fossil yet again and arriving at an even older date for Little Foot’s burial—3.67 +/- 0.16 million years ago.
Little Foot’s saga began in 1994 with the discovery of four australopithecine foot bones in a box of miscellaneous bones from the Sterkfontein limestone cave system 23 miles northwest of Johannesburg, South Africa. They corresponded to a small foot, hence the diminutive moniker. When a fragment of tibia that seemed to match showed up in another box, Clarke sent a team to excavate the cave from which the bones had come. Amid the debris in the Silberberg Grotto, much of which was left from blasting operations, they found matching parts of the broken tibia. The date was July 3, 1997. Excavation of the accumulated rubble eventually yielded a nearly (about 95%) complete australopithecine skeleton with one arm flung over its head and the other by its side.
Though resembling Australopithecus africanus, a hominid commonly identified in South African dig sites, Clarke believes Little Foot has sufficient differences to merit its own species name, Australopithecus prometheus. Though many researchers still consider Little Foot an africanus, Clarke will likely publish additional anatomical details to justify the unique and noble name. Given that this fossil is being distinguished from africanus, Laurent Bruxelles of France’s archaeological research institute INRAP said that one of the two lineages “might have been a close ancestor of the first humans, while the other probably left no descendants.”4
In the evolutionary story—especially the human evolutionary story—age is everything. As London’s Natural History Museum human evolution expert Chris Stringer said regarding a controversial group of Homo fossils, “If we cannot correctly fix the age and identity of the remains then we are in trouble. Getting that wrong even affects how we construct our own evolution.”5 The present study of Little Foot, published in the Journal of Human Evolution with Bruxelles as lead author, therefore, focuses on regaining a more ancient age for the promethean fossil.
An age of 3.3 million years was assigned by Clarke and Tim Partridge on the basis of paleomagnetic analysis of layers of “flowstone,” thin sheets of rock formed by calcium carbonate precipitation from flowing water. As excavation continued, however, Clarke’s team realized that the flowstone had been deposited some time after Little Foot’s death, for the femurs were broken through and displaced. Separate deposits of flowstone had formed over various parts of the skeleton. Subsequent analysis of the flowstone by other researchers yielded a variety of younger dates ranging 1.5 to 2.58 million years.
It was apparent to Clarke’s team that analysis of the carbonate flowstone, because it was deposited some time after Little Foot’s death, was not a valid way to date StW 573. Bruxelles, Clarke, and their coauthors wrote, “Despite this, some investigators have published further dates for the StW 573 skeleton based on U-Pb (uranium-lead) dating of the flowstones, but without taking into account the complexity of the sedimentary record and demonstrably limited applicability of the flowstones.”6 Bruxelles therefore set out to analyze the complex arrangement of flowstone in and around the skeleton.
“The detailed stratigraphic study around StW 573, with supporting observations of thin sections and geochemical analysis, combine to indicate that the collection of stalagmitic flowstones were formed after the deposition and disturbance of the breccia containing the StW 573 skeleton,” Bruxelles, Clarke, and their coauthors write. The illustrations included in this article show some of the many deposits of flowstone and breccia (cemented rubble) surrounding the displaced femurs and pelvis. This suggests that collapse of the cavern and continuing precipitation of flowstone took place some time after the australopithecine died and was buried. They conclude, “that the skeleton was deposited considerably earlier than the adjacent flowstones, and that it is among the most ancient Australopithecus fossils so far known in South Africa. This potentially great age, coupled with the morphological analysis of the skeleton, places StW 573 in a key position for revealing information on the phylogeny of our ancestors.”7
Of course, having discredited the various younger flowstone dates ascribed to Little Foot by other researchers, the question remains, how can scientists determine an age for Little Foot? As Bruxelles, Clarke, and their coauthors in the 2014 study explained, “The question then arises as to whether it is at all possible to establish a reasonably accurate radiometric age for the StW 573 skeleton. Although minimum ages of 2.2 Ma have been determined, it remains difficult to say how much older the skeleton may be. . . . The skeleton is significantly older than the adjacent flowstones and it could be closer in age to that originally estimated by Clarke (1998), i.e., about 3 Ma.”
Unable to rely on the radiometric dates of the rock (the breccia) entombing Little Foot, Clarke’s team needs an alternative dating method. They write, “As we cannot use the flowstones to provide a radiometric age for StW 573, it will be necessary to find other dating methods not focusing in any way on post-depositional modification of the deposit but on its original deposition. Cosmogenic nuclide burial dating [an analysis based on changes induced by exposure to the sun, which yielded an age near 4 million years] has so far not given good results, probably because chert clasts included in breccia have different origins.”
Clarke’s original age estimate, in the wake of the 2014 study, could be viewed by evolutionists as a valid minimum age for StW 573. Little Foot was finally back in the running for oldest hominid fossil in the South African “Cradle of Humankind,”8 having a default age comparable to East Africa’s Australopithecus afarensis’s (Lucy) assigned age of 3.2 million years. But Clarke and Bruxelles, with a Purdue University-based team, kept after the problem and with publication of their work in Nature on April 1st delivered a much older date, one far enough back to clearly make this ancient Prometheus a “person of interest” in evolutionists’ hominid hall of fame.
Like other radiometric dating methods numerous unverifiable assumptions are required for cosmogenic nuclide dating, too.
The method that Purdue geologist Darryl Granger—lead author of the Nature study—along with colleagues at Purdue and South Africa’s University of Witwatersrand used on Little Foot’s host breccia is in essence the same method used to obtain previous advanced ages in excess of three million years for Little Foot, but with a few twists. This dating method exploits the fact that cosmic radiation causes the relatively short-lived isotopes 26Al and 10Be to form in quartz sand when exposed to the sun. Then, if the grains of sand get buried away from the sun, the decay of these aluminum and beryllium isotopes can supposedly be used to determine how long ago the quartz sand was buried. Comparing the ratios of the isotopes in the buried breccia to those in surface sand, the time of burial is calculated.
Despite sounding simple, as Answers in Genesis geologist Dr. Andrew Snelling explains, like other radiometric dating methods numerous unverifiable assumptions are required for cosmogenic nuclide dating, too:
As the authors state in their paper, for this burial dating method to be meaningful and accurate, three criteria must be met. First, the quartz sand grains must be exposed near the ground surface long enough before deep burial to accumulate sufficient 26Al and 10Be atoms. Second, they must then be buried quickly and deeply enough, at least tens of feet deep. Third, they must only be buried deeply once, and then not get re-eroded and reburied, for example, underground in the cave.
Because none of these criteria can possibly be verified through observation, the notion that Little Foot’s new date meets them is highly speculative.
But there are other assumptions inherent in cosmogenic nuclide dating methodology that are clearly not true. It must be assumed that the rate at which sun-exposed quartz sand accumulates 26Al and 10Be has always been the same. However, Earth’s magnetic field affects the influx of cosmic radiation, and Earth’s magnetic field has been observed to decrease substantially! When the magnetic field was stronger, less radioisotope would have formed because less cosmic radiation would have reached the Earth’s surface.9 Therefore, for burial dating purposes, these measurements are meaningless!
Of course, dating methods like this also rely on the constancy of the radioactive decay rate of the isotopes being measured. There is no way that observational science can confirm that the decay rates of these isotopes have always been the same. Furthermore, even the presumably constant half-lives of these isotopes has been substantially changed over the past few years. As mentioned earlier, a previous study in 2003 had determined a much greater burial date of 4.17 ± 0.35 million years for Little Foot. This date was discarded after a reevaluation raised the mean-life of 10Be nearly 4%, from 1.93 million years to 2.005 million years, reducing Little Foot’s burial age based on that one sample to 3.94 ± 0.20 million years. Dr. Snelling points out, “This raises questions as to how well known are the mean-lives of both 10Be and 26Al, and how well can they be known?”
Now, 3.94 ± 0.20 million years is still substantially greater than the 3.67 ± 0.16 million years now being reported by analysis of 11 samples. Because of the error ranges the two “dates” overlap, if there is so much uncertainty and error range, this begs the question as to what the real age is. Dr. Snelling, commenting on the 11 samples cited in the newest study, noted some additional irregularities:
This latest determination used 11 samples, including the sample used in the previous dating study which was re-analyzed, and 9 of the samples plotted on a 10Be versus 26Al isochron or “error-weighted best fit curve” that equated to the new date of 3.67 ± 0.16 million years. However, of these 11 samples, only 5 samples were of fine quartz sand, which had been extracted from the matrix of the breccia hosting the fossil bones of “Little Foot” at different height levels in the cave, with only 2 of those samples being in close proximity to the fossil bones. Then 2 samples consisted of dark and light colored larger fragments hand-picked from 4 of the breccia samples whose sand grains were also being analyzed. The remaining 4 samples were blocks of chert (which is made up of a mass of microscopically fine-grained crystals of quartz) within the host breccia collected from the immediate vicinity of the StW 573 fossil bones.
Thus, this suite of samples contained three different types of samples in terms of the material and the grain size, which it could be argued is like comparing oranges and lemons with apples. Not surprisingly, two of the chert samples did not plot on the isochron curve, one plotting way off in the “forbidden” zone!
Thus, it seems that data from various sample types, different depths, and greatly varying proximity to Little Foot were essentially tossed into the pot to obtain Little Foot’s age. There is no reason to assume that all the sampled parts of the breccia unit formed at the same time much less at the same time as Little Foot was buried. Therefore, even with all the usual worldview-based assumptions attending the millions-of-years interpretation of radiometric dates aside, there is no reason to consider the dates reliable.
The acceptance of this new ‘burial date’ is ultimately agenda driven—the need to find an age for this fossil that best fits the desired evolutionary story.
If an accountant played as fast and loose with his employer’s money as the authors of the current study seemed to play with Little Foot’s dates, he might well find his employer audited and himself unemployed. But perhaps the rules differ when in pursuit of a good fit for the human evolutionary story. Commenting on the study, Dr. Snelling writes, “The acceptance of this new ‘burial date’ is ultimately agenda driven—the need to find an age for this fossil that best fits the desired evolutionary story.”
Australopithecines are not human ancestors but only extinct apes.
Before considering the implications of Bruxelle et al.’s stratigraphic analysis, we should reiterate, as we have discussed in many other articles, that australopithecines are not human ancestors but only extinct apes. Future papers discussing Australopithecus prometheus will doubtless give us the opportunity to address specific claims about Little Foot’s identity. For now, read more about the distinctions between human fossils—like Homo erectus, Homo neanderthalensis, Homo antecessor, Homo heidelbergensis, and Homo sapiens—and extinct apes like Ardipithecus ramidus (aka “Ardi,” currently sporting the impressive age of 4.4 million years but having trouble meeting the evolutionary demands of bipedality) and the well-known, allegedly bipedal australopithecine apes like Australopithecus afarensis (“Lucy”), Australopithecus sediba (“Karabo”), and Australopithecus africanus.
There are, incidentally, a lot of similarities among the australopithecines, and some researchers maintain that Australopithecus sediba is really just another example of Australopithecus africanus. The subtle distinctions that distinguish species from one another can often be sorted out in living creatures because their ability to interbreed can be assessed. Fossils divulge far less information to scientists, but the distinctions between different created kinds—like between apes and humans—are far more apparent when sufficiently complete specimens are available. (You can learn more about the distinctions between fossilized extinct apes and fossilized human varieties in Dr. David Menton’s video presentation Three Ways to Make an Ape-Man and Dr. Terry Mortenson’s Ape-Men: The Grand Illusion.)
We know from God’s Word that humans (Adam and Eve) and land animals—including apes—were made on the same day about 6,000 years ago as separate creations, humans alone being made in the image of God. Humans are also anatomically and intellectually distinct from apes. The fossil record shows diversity of apes and even diversity among humans but a distinct absence of “missing links” because, as biology demonstrates, animals reproduce and vary within their created kinds but do not evolve into new, more complex kinds of creatures.
Bruxelles, Clarke, and their coauthors showed in 2014 that the dates assigned by other researchers were invalid. They admitted that they really had no way, even with the usual evolutionary assumptions, to determine the age of Little Foot. They fell back on the ~3 million year date, however, because that was the age assigned to an associated “index fossil”—a fossil of “known” age by which other fossils in comparable strata can be dated.
Answers in Genesis geologist Dr. Andrew Snelling, commenting on their analysis, says,
This study very carefully shows the relative sequence of deposits in the cave. The authors have very successfully demonstrated that the Australopithecus skeleton StW 573 is older than the flowstone deposits that were previously dated by the U-Pb radiometric method; at supposedly 2.2 million years old. The skeleton is entombed in a breccia which has been locally eroded to create voids, which were later infilled with the flowstones, though not before part of the skeleton was broken and shifted by subsidence.
The details provided by this study also discount the previous attempt to date the breccia enclosing the fossil at supposedly about 4 million years old using the 26Al and 10Be cosmogenic burial method. So they conclude the fossil may be as old as about supposedly 3 million years, based on the original determination of the fossil's discoverer at the time of discovery in 1997 using an associated index fossil.
The only conclusion that is certain is that the fossil is as old as the breccia it is buried in and older than the flowstone associated with it. But that's where the certainty ends.
Dr. Snelling points out that every date in the 2014 and 2015 studies and the associated earlier studies of Australopithecus prometheus and the minerals entombing it are steeped in unverifiable, worldview-based assumptions. Describing some of these, he says,
All their postulated dates are dependent on the unprovable assumptions on which the uniformitarian (slow-and-gradual) worldview depends. These include constant radioisotope decay rates (at today's measured rates) and a closed system during the presumed millions of years without the possibilities of contamination.
The latter assumption is problematic given the recognized intermittent water flows in the cave and the solution saturation necessary for flowstone deposition capable of moving trace elements with such solutions. The rate of acquisition of cosmogenic isotopes is based on assuming constant geologic process rates in the past, which cannot be tested by observation because the past is gone.
The index fossil method relies on assuming both the reliability of radioisotope dating of deposits associated with such fossils where they are found elsewhere, and that the same animals evolved and lived at the same time in widely scattered geographic locations across the globe, both of which again cannot be verified in the unobserved past.
The researchers investigating Little Foot have made a valiant effort to discover its age, resorting to assumptions that even within their own worldview seem unreasonable. In truth, however, because the assumptions governing their entire analysis are rooted in a worldview that rejects God’s eyewitness account of humanity’s origins, the age of the Earth inferred from the Bible, and the history of the global Flood documented in God’s Word, they have missed the lessons that could be gleaned from this extinct ape’s burial.
To accurately estimate Little Foot’s age, we need to compare the analysis of the Sterkfontein cave with an eyewitness account of a relevant time in Earth’s geological history. We know from God’s Word that the global Flood about 4,350 years ago remodeled the Earth’s surface. Flood-based geological models help Bible-believing scientists understand the most likely geological changes that occurred not only during but also in the aftermath of the Flood. Dr. Snelling explains the findings in StW 573’s naturally formed tomb in terms of a post-Flood catastrophe:
In the end, we can say with certainty that nothing so far claimed about this fossil's age is incompatible with the biblical framework and its chronology for earth history. The cave, like so many others around the globe, is a product of early post-Flood dissolution (chemical erosion) of limestone and dolomite layers (deposited during the Flood about 4,350 years ago) when there were much higher precipitation rates due to huge storms dumping torrential rainfalls on the continents because of the warmer ocean waters (a result of the release of enormous volumes of volcanic waters during the Flood).
Those wetter conditions would also have caused the breccias in the cave to accumulate rapidly from ceiling rock-falls, which makes sense of the full skeleton of the Australopithecine (a post-Flood ape whose relatives migrated within decades to Africa from the Ark) being rapidly buried and preserved intact. The subsequent erosion of voids and their infilling with flowstones need not have taken more than hundreds of years, due to the changing and variable climatic conditions.
Viewing the evidence in light of biblical history, we can safely say that Little Foot is an ape that most likely died in the years soon after the global Flood. Extinct ape fossils in Africa are typically found deeper in the fossil record than human fossils. Following the global Flood, animals disembarked and began to move away, reproduce, and replenish the earth. Despite God’s command, however, the descendants of Noah’s family delayed moving out to replenish the earth until forced to by the confusion at the tower of Babel. The history in the Bible thus makes sense of apes’ placement in the fossil record, which has nothing to do with evolution.
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The terms hominin and hominid are both words whose definitions embody the evolutionary assumptions 1) that humans evolved from an ape-like ancestor through a series of pre-human and extinct human species and 2) that humans and modern Great Apes (chimpanzees, gorillas, orangutans) share a common ancestor.
Hominid (as it is currently used by most writers) refers to all these individuals—modern humans, modern Great Apes, and all the presumed ancestors of both, back to the common ape-like ancestor.
Hominin refers only to the human side of the evolutionary lineage after it branched off from the common ancestor supposedly shared with apes. Hominins are thus modern and extinct humans and all their immediate ancestors, back to the common ape-like ancestor.
Thus, in current usage, the word hominid includes all hominins plus all the Great Apes and their ancestors.
Answers in Genesis is an apologetics ministry, dedicated to helping Christians defend their faith and proclaim the gospel of Jesus Christ effectively. We focus on providing answers to questions about the Bible—particularly the book of Genesis—regarding key issues such as creation, evolution, science, and the age of the earth.