3.3 Million Year Old Vertebral Column Confirms Human Pattern of Au. afarensis

The science site PhysOrg has posted a story on a study of the 3.3 million year old fossil from the site of Dikika, in the Afar Triangle.  The fossil, known as Selam, is an almost complete skeleton of a 2 ½ year-old child. From the story:

Many features of the human spinal column and rib cage are shared among primates. But the human spine also reflects our distinctive mode of walking upright on two feet. For instance, humans have fewer rib-bearing vertebrae - bones of the back - than those of our closest primate relatives. Humans also have more vertebrae in the lower back, which allows us to walk effectively. When and how this pattern evolved has been unknown until now because complete sets of vertebrae are rarely preserved in the fossil record.

"For many years we have known of fragmentary remains of early fossil species that suggest that the shift from rib-bearing, or thoracic, vertebrae to lumbar, or lower back, vertebrae was positioned higher in the spinal column than in living humans. But we have not been able to determine how many vertebrae our early ancestors had," said Carol Ward, a Curator's Distinguished Professor of Pathology and Anatomical Sciences in the University of Missouri School of Medicine, and lead author on the study. "Selam has provided us the first glimpse into how our early ancestors' spines were organized."

This gives us much better evidence of how bipedality was practiced in some of the earliest hominins. We know, from the footprints at Laetoli and the hip remains of Lucy, that Au. afarensis was bipedal but now we know that the rib structure had evolved into a more human pattern. 

Human/Gorilla Split at Eight MYA?

Scientific American is running an article, which details work by Gen Suwa and colleagues, in the Afar Triangle, where nine gorilla-sized teeth were found in 2007 that have now been securely dated to around eight million years ago.  The researchers named the species Chororopithecus abyssinicus.  Charles Choi writes: 

The age and location of these fossils strengthen the view that the human and the modern ape lines originated in Africa and not Asia, the researchers said.

"Until now, no mammalian fossils south of the Sahara have been securely dated to 8 million to 9 million years ago," Suwa said. "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."

In addition, 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," Suwa said. "This contradicted the fossil record. 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."

The new findings suggest that Chororapithecus is 8 million years old, so "the actual gorilla-human split must then have been up to several million years before that," Suwa said.

More pieces to the puzzle. The other mystery, of course, is when the last common ancestor of humans and chimpanzees lived.

New Hominin Species Coeval with Au. afarensis

A new hominin has been announced by Haile-Selassie and colleagues.  Here is the abstract from the Nature paper¹:

Middle Pliocene hominin species diversity has been a subject of debate over the past two decades, particularly after the naming of Australopithecus bahrelghazali and Kenyanthropus platyops in addition to the well-known species Australopithecus afarensis. Further analyses continue to support the proposal that several hominin species co-existed during this time period. Here we recognize a new hominin species (Australopithecus deyiremeda sp. nov.) from 3.3–3.5-million-year-old deposits in the Woranso–Mille study area, central Afar, Ethiopia. The new species from Woranso–Mille shows that there were at least two contemporaneous hominin species living in the Afar region of Ethiopia between 3.3 and 3.5million years ago, and further confirms early hominin taxonomic diversity in eastern Africa during the Middle Pliocene epoch. The morphology of Au. deyiremeda also reinforces concerns related to dentognathic (that is, jaws and teeth) homoplasy in Plio–Pleistocene hominins, and shows that some dentognathic features traditionally associated with Paranthropus and Homo appeared in the fossil record earlier than previously thought.

The Washington Post has a write-up of the new find, which they glibly refer to as “An Ethel for Lucy.” Rachel Feltman:

Haile-Selassie and his co-authors believe the find should encourage reexamination of other possible instances of pre-Homo cohabitation.  Two other species have been proposed as living at the same time as Australopithecus afarensis -- Australopithecus bahrelghazali and Kenyanthropus platyops -- but both remain controversial, with some scientists saying they aren't different enough from A. afarensis to constitute a new species. And in a previous expedition, Haile-Selassie himself found a partial foot that he believed was from the same time period -- but not the same species -- as Lucy. Unlike the jaw reported in Nature, the foot didn't provide enough evidence to name a new species.

As noted with the Ledi jaw, there seems to be quite of a bit of morphological variability and experimentation going on at the Plio-Pleistocene boundary.   

¹Haile-Selassie, Y., Gibert, L., Melillo, S.M., Ryan, T.M., Alene, M., Deino, A., Levin, N.E., Scott, G., Saylor, B.Z. (2015) New species from Ethiopia further expands Middle Pliocene hominin diversity. Nature. 521(7553): 483-488.
http://dx.doi.org/10.1038/nature14448

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

New Jawbone Fills Gaps, Raises Questions

A group working in the Afar Triangle has discovered a mandibular fragment with associated teeth that show strong affinities to early Homo.

The catch is that the provisional date for this specimen is 2.8 million years. Writes Pallab Ghosh for the BBC:

The head of the research team told BBC News that the find gives the first insight into "the most important transitions in human evolution".

"This is the most important transition in human evolution”

Prof Brian Villmoare University of Nevada

Prof Brian Villmoare of the University of Nevada in Las Vegas said the discovery makes a clear link between an iconic 3.2 million-year-old hominin (human-like primate) discovered in the same area in 1974, called "Lucy".

Could Lucy's kind - which belonged to the species Australopithecus afarensis - have evolved into the very first primitive humans?

"That's what we are arguing," said Prof Villmoare.

This find in the north of the continent strains, almost to the breaking point, the argument that Australopithecus sediba is the best candidate for being ancestral to early Homo. That find came from a cave in South Africa and, up to this point, all of the respective species of Australopithecus have been fairly tightly geographically restricted in their home ranges. The distinct possibility exists that only A. afarensis is ancestral and ALL other australopithecines went extinct, but we will have to wait for considerably more comparative studies on the morphology of the jaw to make any sort of rudimentary arguments along those lines. 

Smithsonian: Discovering Our Ancestors

The March issue of The Smithsonian Magazine has a large spread on the recent advances in human origins, including a large article on the discovery and identification of Ardipithecus ramidus by Ann Gibbons. One of the striking things about the find is the locale in which it took place: literally a palaeoanthropologist's dream come true. Gibbons writes:

As we wait for the Alisera to arrive, White explains that the team returns to this hostile spot year after year because it’s the only place in the world to yield fossils that span such a long stretch of human evolution, some six million years. In addition to Ardi, a possible direct ancestor, it is possible here to find hominid fossils from as recently as 160,000 years ago—an early Homo sapiens like us—all the way back to Ardipithecus kadabba, one of the earliest known hominids, who lived almost six million years ago. At last count, the Middle Awash project, which takes its name from this patch of the Afar desert and includes 70 scientists from 18 nations, has found 300 specimens from seven different hominid species that lived here one after the other.

It is the palaeoanthropological equivalent of the Liaoning shale fossil beds in China that have yielded so many dinosaur remains. Her description of what the remains of Ardipithecus represent is evocative:

One thing that is clear is that these early fossils belong in a class by themselves. These species did not look or act like other known apes or like Lucy and other members of Australopithecus. They were large-bodied ground dwellers that stood up and walked on two legs. But if you watched them move, you would not mistake them for Lucy’s species. They clung to life in the trees, but were poised to venture into more open country.

Becoming human, one slow step at a time. It is a pity that we do not have any more remains of Ardipithecus kadabba, which preceded A. ramidus by around a million years. What kind of individual would that be? Would he or she walk upright? Would we see any incipient hominid characteristics? At this point, quite literally, only God knows.
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