Elizabeth Mitchell, David Menton and Andrew Snelling Take on the Ledi Jaw

As noted, the promised report from Answers in Genesis about the Ledi jaw (LD 350-1) is out.  Let's see what they say.  This is an interesting group of authors.  Andrew Snelling is the resident geologist, while David Menton is a former anatomist who wrote a truly terrible article on the evidence for human evolution, which I tackled over six long, straggly posts, ending here.  In it he, effectively, revealed that he has little to no knowledge of the fossil record.  I have read little of Elizabeth Mitchell's posts, other than the one in which she championed the evidence for unicorns in the Bible. 

The opening salvo in the “Lucy Connection” contains this:

An extinct knuckle-walking ape, “Lucy” is generally depicted strolling about East Africa 3 million years ago on her two supposedly arched feet with tiny teeth smiling from her gorilla-like face and tiny brain. That image has created an imaginary place for Australopithecus afarensis in the human lineage.

The initial problem with this paragraph is that there is no evidence to back up their depiction of Au. afarensis. The fossil remains that make up Au. afarensis, of which Lucy is a member, clearly indicate a hominin that was bipedal; that much is not debatable.  It carries none of the traits of an ape in this regard.  However, Au. afarensis does have some ape-like characteristics as well.  In fact, there are quite a list of traits that are Hominin and some that are ape-like.  I chronicled those here, in the fourth part of my response to Menton's 2010 article on human origins.  (Aside: It doesn't bother me that Menton didn't read my post, although Ken Ham knows I write for BioLogos because he referenced one of my posts for them.  It does bother me that Menton persistently mischaracterizes the transitional evidence in Au. afarensis, which is pretty hard to miss, if you are paying any attentional, whatsoever.)

Now, on to the jaw, itself, for which they get the account correct (Here is my short post for BioLogos on the jaw).  In fact, they report pretty much exactly what the discoverers and Fred Spoor determined about the jaw and the reconstruction of the related OH 7 skull. 

The the wheels fall off.

They write:

Could the Ledi jaw’s owner have been a transitional form? No. Evolutionists strain to see something ape-like in the array of Homo traits in the Ledi jaw because its position in the fossil record is so “far back” they think it must be their much sought-after transitional form. Since it lacks a protruding chin no one would suggest this fossil belonged to a modern human, but the lack thereof does not demonstrate that it is Australopithecus afarensis or an ape descended from it or even a less-evolved part of the human lineage. The relatively chinless jaw is simply not typical of modern humans. Nothing about this fossil indicates that its owner still had one foot in the ape-camp and was only in the process of evolving into a full-fledged human.

They are correct that the lack of a chin keeps it out of the modern human camp.  They are incorrect that it doesn't have transitional characteristics. Here is the relevant quote from the article¹:

Indeed, in overall dental and mandibular size LD 350-1 matches smaller specimens of A. afarensis (figs. S1 to S4 and tables S1 to S3). In addition, LD 350-1 shares with A. afarensis a primitive anterior corpus, including an inclined symphyseal cross section, a bulbous anterior symphyseal face, and a projecting inferior transverse torus that is only slightly elevated above the corpus base (Fig. 2A).

What then follows in the scholarly article is a long discussion of no fewer than five distinct characteristics that align the Ledi jaw with Homo to the exclusion of Au. afarensis.  Villmoare and colleagues are keenly aware of the differences between australopithecine and human morphology.  This is why they can recognize these traits.  Thus, when Mitchell, Menton and Snelling write that nothing about the Ledi Jaw is transitional, and provide no evidence of their position, one is tempted to not take them seriously.  The next paragraph is no better:

The Ledi jaw’s bid to be Homo or an early transition to Homo rests largely on the fact that its assigned dates place it in the desired gap between the ape Lucy and archaic varieties of humans. Had its host sediment been dated substantially older, its human features would likely have been ignored or explained away. Evolutionists have been known to dismiss fossil evidence of very early Homo, no matter how similar to modern man, if the stratigraphically assigned dates are too old to fit into the evolutionary schema.

This is illogical. Why would evolutionists care how old it is? There are some, in fact, who would relish the idea of our line being pushed back even further.  The human features are there, regardless of how old it is.  That is why it is making waves—because it has the human features.  If it had been found to be older, the human-like features would not have vanished like the snows of yesteryear.  They would still have been there. 

The last sentence in the quote is, once again, presented without evidence and calls into question the integrity of the scientists involved in this discovery and others like it.  What evidence has been dismissed?  How has it been explained away? To call into question the motives of scientists and call them duplicitous without giving evidence to that effect is worthy of scorn and disrespect.  Put up or shut up.

Next.

The Ledi jaw wouldn’t even be close to being the oldest “Homo” if certain other fossil bones and footprints that are virtually identical to modern man were rightly recognized as Homo sapiens. For example, the Laetoli footprints are claimed to be 3.66 million years old and are virtually identical to modern man’s footprints, but no evolutionist considers them to be human because they are simply too old. The Kanapoi elbow fossil from the Lake Rudolf region of northern Kenya is the distal end of a humerus that is indistinguishable from Homo sapiens, but it is considered to be australopithecine in origin because it is also too old at 4.0–4.5 million years to be considered human. These assigned dates, based on a host of worldview-based unverifiable assumptions, blind evolutionists to the true identity of fossils like these. In truth, humans have been around since the sixth day of the Creation Week, the first two people having been created by God the same day as the land animals.

They are right, the footprints are too old, given that there is no evidence for modern humans until around 190 thousand years ago. The footprints are securely dated by radiometric techniques that the folks from AiG will never accept, despite their robusticity.  Same with the Kanopoi remains.  What this simply means is that, as with many transitional forms at this time, some characteristics were more human-like than others.  What these authors do not mention is that in other fossils from the time period, there are ape-like characteristics as well.  The elbow traits, along with the knee and hip traits are derived in the direction of Homo.  The simian traits are retained from their ancestors.

What these authors do fail to demonstrate is that there are fully modern humans in the same strata as the australopithecines.  That would sink our understanding of human origins once and for all.  Yet, that has never been done. 

They write that this fossil is dated using methods found to have “unverifiable assumptions.”  Curiously, this links to another AiG page on radiometric dating, which, in turn, links to an article authored by Steve Austin, of the ICR, on radiometric dating of Mount St. Helens, rather than actual peer-reviewed scientific articles.

Austin collected dacite samples from around the new St. Helens lava dome, which he knew had been formed around 1986.  He then separated them and sent them to a laboratory for potassium/argon dating.  When the results came back, he declared that radiometric dating was flawed because the results inticated that the dome had been formed around 350 000 years B.P.

In Kevin Henke's response to this report, he addresses how Austin misused the methodology to arrive at his conclusions.  He writes:

Considering that the half-life of potassium-40 (40K) is fairly long (1,250 million years, McDougall and Harrison, 1999, p. 9), the K-Ar method cannot be used to date samples that are much younger than 6,000 years old (Dalrymple, 1991, p. 93). A few thousand years are not enough time for 40Ar to accumulate in a sample at high enough concentrations to be detected and quantified. Furthermore, many geochronology laboratories do not have the expensive state-of-the-art equipment to accurately measure argon in samples that are only a few million years old. Specifically, the laboratory personnel that performed the K-Ar dating for Austin et al. Specifically, personnel at Geochron Laboratories of Cambridge, Massachusetts, USA, performed the K-Ar dating for Austin et al. This laboratory no longer performs K-Ar dating. However, when they did, their website clearly stated in a footnote that their equipment could not accurately date rocks that are younger than about 2 million years old ("We cannot analyze samples expected to be younger than 2 M.Y."; also see discussions by Bartelt et al.). With less advanced equipment, 'memory effects' can be a problem with very young samples (Dalrymple, 1969, p. 48). That is, very tiny amounts of argon contaminants from previous analyses may remain within the equipment, which precludes accurate dates for very young samples. For older samples, which contain more 40Ar, the contamination is diluted and has insignificant effects. Considering the statements at the Geochron website and the lowest age limitations of the K-Ar method, why did Austin submit a recently erupted dacite to this laboratory and expect a reliable answer??? Contrary to Swenson's uninformed claim that ' Dr Austin carefully designed the research to counter all possible objections', Austin clearly demonstrated his inexperience in geochronology when he wasted a lot of money using the K-Ar method on the wrong type of samples.

lawilson200 of Mount St. Helens watch also notes these problems, as does Skeptoid.  If Austin sent the samples to the lab that he knew were produced in 1986, then he either did not know that K/Ar dating requires samples that are at least two million years old to date accurately, or he did know that and submitted them to intentionally get spurious results to publicize the perceived limitations of radiometric dating.  In any event, without the support of Austin's argument, the bad date argument for the Ledi jaw collapses. 

Mitchell, Menton and Snelling write that the geologists studying the area around where the Ledi jaw was found cannot be sure how many stratigraphic layers are missing between the Gurumaha tuff beds and the Lee Adoyta tuff beds, so we cannot know for sure what the total thickness was.  Yes, but we know where the jaw was found and the authors are clear about what the maximum and minimum ages for the fossil can be, based on the dates.  The AiG writers then make an argument that the tuffs could have been formed in hours because of the nature of volcanic eruptions.  This fails to account for the depositional environment between the tuffs, to wit:

Ecological community structure analysis based on mammalian fauna recovered from the Gurumaha fault block indicates a more open habitat (mostly mixed grass-lands/shrublands with gallery forest) that likely experienced less rainfall than any of those reconstructed for the Members of the Hadar Formation (6). The landscape was similar to modern African open habitats, such as the Serengeti Plains, Kalahari, and other African open grasslands, given the abundance of grazing species and lack of arboreal taxa, although the presence of Deinotherium bozasi and tragelphins likely indicate a gallery forest (fig. S6). The existence of Kobus sigmoidalis, aff. Hippopotamus afarensis, crocodiles, and fish in this package reflect the presence of rivers and/or lakes. Approximately one-third of the mammalian taxa present are shared with the youngest Hadar Formation (~3 Ma), while one-third are first appearances of these taxa in the LAV (Table 1). The remaining one-third of mammals recovered can only be identified to the genus level.

How would these landscapes have formed in hours? They reflect hundreds, if not thousands of years of development, and they certainly could not have formed in the middle of a world-wide flood.

The argument presented by AiG also points to a peculiarity of the young earth argument: arguing against a proposition using uniformitarian principles, while at the same time taking no stock in those principles, whatsoever, since they have to be thrown out the window in any flood model. 

They continue:

The evolutionary determination to subdivide varieties of humans into various species is based on evolutionary claims, when in reality all humans would best be called Homo sapiens regardless of their variations. Nevertheless, we are stuck with the terminology that calls the descendants of various people descended like us from Adam and from Noah via the dispersion from Babel by names that imply they are unrelated. Truly, however, when it comes to a fossil like this one, the real question should not be “where in the evolutionary history of humans does it fit?” but rather “does it fit within the norms for human beings or not?” Though limited by its incompleteness, analysis of LD 350-1 suggests it belonged to a person.

Once again, how, then, do you explain the traits that link it to Au. afarensis? Those are clearly non-human. To sweep them under the rug is simply not tenable. These traits are outside the known variation of all modern humans.  No one has them.  Further, they don't even track with traits seen in later hominin forms such as Homo ergaster, Homo erectus or archaic Homo sapiens.  They are clearly australopithecine.

In summary, then, this article written by Mitchell, Menton and Snelling suffers from three principle problems:

1. A failure to correctly describe the fossil material related to the Ledi jaw (Describing Au. afarensis as “An extinct knuckle-walking ape,” for example)
2. A failure to correctly assess the human and non-human morphology of the Ledi jaw, itself, instead simply denying that the non-human traits exist, when in fact, they clearly link it to the preceding australopithecine fossil remains in many ways.
3. Reliance on a single article for rejection of modern radiometric dating assumptions that has been heavily criticized for its misuse of proper methodology. (See this Davis Young article on radiometric dating for a good primer on how reliable it is).

These problems completely sink the AiG's analysis and conclusions of the Ledi jaw.  


¹Villmoare, B., Kimbel, W. H., Seyoum, C., Campisano, C. J., DiMaggio, E., Rowan, J., Braun, D. R., Arrowsmith, J. R., & Reed, K. E. (2015). Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia. Science. doi: 10.1126/science.aaa1343