New Chinese Material Pushes the Exit From Africa to 2.1 mya

Nature is reporting research on new Chinese material that strongly suggests that the Georgian site of Dmanisi is not the earliest location to which migration out of Africa went.  Here is the abstract:

Considerable attention has been paid to dating the earliest appearance of hominins outside Africa. The earliest skeletal and artefactual evidence for the genus Homo in Asia currently comes from Dmanisi, Georgia, and is dated to approximately 1.77–1.85 million years ago (Ma)1. Two incisors that may belong to Homo erectus come from Yuanmou, south China, and are dated to 1.7 Ma2; the next-oldest evidence is an H. erectus cranium from Lantian (Gongwangling)—which has recently been dated to 1.63 Ma3—and the earliest hominin fossils from the Sangiran dome in Java, which are dated to about 1.5–1.6 Ma4. Artefacts from Majuangou III5 and Shangshazui6 in the Nihewan basin, north China, have also been dated to 1.6–1.7 Ma. Here we report an Early Pleistocene and largely continuous artefact sequence from Shangchen, which is a newly discovered Palaeolithic locality of the southern Chinese Loess Plateau, near Gongwangling in Lantian county. The site contains 17 artefact layers that extend from palaeosol S15—dated to approximately 1.26 Ma—to loess L28, which we date to about 2.12 Ma. This discovery implies that hominins left Africa earlier than indicated by the evidence from Dmanisi.

For the new site sequence data, we don't have any hominin remains so we don't know exactly what these folks looked like but the tools are very primitive.  A section from a companion piece reads thus:

The identity of their makers is, for now, unclear: no hominin bones have been recovered at Shangchen. “We would all love to find a hominin — preferably one with a tool in its hand,” says Dennell. Homo erectus is one possibility, because some of the earliest members of this species were found at Dmanisi. But Dennell thinks that the Shangchen toolmakers belonged to an earlier species in the genus Homo.

Petraglia and Rezek both say that the age of the tools — not to mention the possibility that hominins arrived in China even earlier than the 2.12-million-year mark — suggests that the toolmaker was a species such as Homo habilis. This relatively small-brained hominin is thought to have been confined to Africa between around 2.4 million to 1.4 million years ago.

Jungers holds open the possibility that the Shangchen toolmaker was a species of Australopithecus, a group of more ape-like hominins to which the iconic fossil Lucy belongs. So far, all Australopithecus fossils have been discovered in Africa.

Before his death, Grover Krantz argued for the presence of Australopithecus in East Asia but could never get anyone to come on board with him. Everyone was pretty content to label what was coming out of the ground as Homo erectus.I think it would be a stretch if the hominins from Shangchen were australopithecines since we don't see any advanced species of Australopithecus in East or North Africa between 2 and 2.5 mya.  In fact, Au. boisei drops out around 2.1, likely out-competed by early Homo.

Nonetheless, something was making stone tools in China at 2.1 mya and that is “Yuuuuge” news. 

How Intelligent Was Homo naledi?

Discover Magazine (and other outlets) are running a story which questions how important cranial size is to overall intelligence.  The focus of this inquiry is Homo naledi, the small-brained hominin that is now thought to be no more than 200ky old.  Lee Berger, who was on the team that discovered Homo naledi has always argued that, because of the comparative difficulty of navigating the cave, that she was placed in the Rising Star Chamber intentionally.  At issue is the brain size:

When it comes to brain volume, previous research established that Homo naledi‘s was 465-560 milliliters. (In today’s study, the authors acknowledge those earlier numbers, based on virtual reconstructions, but also perform their own physical reconstructions and measure the volume with a water displacement method, arriving at a similar range of 460-555 mL.)

This is very small. As the authors note, contemporary hominins possessed brains well over 1000 cc at this point. It was the complexity of H. naledi's brain that surprised people:

Homo naledi‘s inferior frontal and lateral orbital gyri were organized notably more like that of other members of the genus Homo than that of australopiths. These are parts of the brain associated with complex behaviors, such as communication, planning and tool-making, that are particularly important in our lineage.

Finding Homo naledi‘s brain was structurally similar to that of larger-brained members of the genus tells us two important things. First, it means Homo naledi itself was likely capable of more complex behavior than australopiths with a similar brain volume but different brain structure. Second, it torpedoes the old notion that Homo brains grew steadily in size and complexity until reaching the evolutionary pinnacle that is Homo sapiens (/sarcasm, just a touch).

As we discover that early Homo was behaviorally more complex than we thought, it also forces us to rethink what went on later in hominin evolution and re-evaluate evidence of complexity in H. erectus and archaic H. sapiens. 
 

Australopithecus sediba Voted Off the Island

This does not surprise me.  Science Magazine has a short story which suggests strongly that the characteristics in Au. sediba render it unsuitable for a possible ancestor to the genus Homo. 

With its fossils dated to 1.98 million years ago, Au. sediba is too young to be directly ancestral to all members of the genus Homo. But Berger and his colleagues proposed in 2010, and again in 2013 in six papers in Science, that given the many humanlike traits in Au. sediba’s face, teeth, and body, the Malapa fossils were a better candidate than Lucy or other East African fossils to be ancestral to Homo erectus, a direct human ancestor that appeared 1.8 million years ago.

In a talk here, though, paleoanthropologist Bill Kimbel of Arizona State University in Tempe analyzed the most complete skull of Au. sediba and systematically shot down the features claimed to link it to early Homo. Kimbel noted that the skull was that of a juvenile—a “7th grader”—whose face and skull were still developing. In his analysis, with paleoanthropologist Yoel Rak of Tel Aviv University in Israel, he concluded that the child already showed traits that linked it most closely to the South African australopithecine Au. africanus, a species that lived in South Africa 3 million to 2.3 million years ago. And had it survived to adulthood, its humanlike facial traits would have changed to become even more like those of Au. africanus.

For example, the breadth of the young Au. sediba’s cheekbones appears narrow, as in early Homo. But by studying other australopithecine, ape, and Homo fossils to see how features of the cheekbones change as individuals grow and chewing muscles develop, Kimbel and Rak could predict how the boy’s face and skull would have looked if he’d grown up to be an adult. The resemblance to Au. africanus is so striking, in fact, that Kimbel thinks Au. sediba is a closely related “sister species” of Au. africanus—and not a long-lost human relative. “We don’t believe … that Au. sediba has a unique relationship to the genus Homo,” says Kimbel.

At this point, it is pretty hard to tell where a precursor might be found. We know that there was considerable variability in australopithecines throughout the Plio-Pleistocene but, as of yet, no good candidate has arisen.What seems to be clear, however, is that there is a general trend toward more modern morphology in the pelvis and hands, as exhibited by Au. sediba.  Whether or not these characteristics are present in other specimens of Au. sediba is, however, unknown.  As Kimbel notes, we need an adult one to see for sure. 

Surprising New Information About Homo naledi

The Atlantic (and other outlets) has a story on new information on the date of the Homo naledi fossils from Rising Star Cave and it is...surprising.  As Sarah Zhang writes:

The one thing everyone agrees is that the fossils themselves are spectacular. In 2015, researchers unveiled 1,500 hominin fossils found deep in a South African cave, excavated by six cavers who were all skinny, short, and female. The hominin, a new species the team christened Homo naledi, was an unusual mix of the old and modern. Their heads were small, suggesting an early hominin perhaps more than a million years old. But their feet were stiff for walking upright and their hands adept like modern humans.

So in the media frenzy that followed—a National Geographic cover, a documentary, numerous articles—the question kept coming up: How old are these Homo naledi fossils, really? What do they tell us, if anything, about the origin of Homo sapiens?

To that first question, the researchers now have an answer: 236,000 to 335,000 years old. As for the second question, well, it’s complicated. “You can’t tell simple stories anymore,” says Lee Berger, a paleoanthropologist at the University of the Witwatersrand who led the research. “This is the gigantic message out of Homo naledi.” The age of these fossils puts these strange, small-brained yet human-like hominins in South Africa just before the emergence of the first anatomically modern Homo sapiens.

Holy Liang Bua, Batman!  If the bones really are 236k, then that would put them roughly 40-50 k years before the advent of modernity represented by the Omo 1 cranium.  Admittedly, that skull is fragments “swimming in plaster” but we have a pretty good idea of what it looks like. We certainly have modernity in the Bouri remains from Herto at 160 ky.

How do we know how old the fossil are?  From the eLife article:

Now, Dirks et al. – who include many of the researchers who were involved in the discovery of H. naledi – report that the fossils are most likely between 236,000 and 335,000 years old. These dates are based on measuring the concentration of radioactive elements, and the damage caused by these elements (which accumulates over time), in three fossilized teeth, plus surrounding rock and sediments from the cave chamber. Importantly, the most crucial tests were carried out at independent laboratories around the world, and the scientists conducted the tests without knowing the results of the other laboratories. Dirks et al. took these extra steps to make sure that the results obtained were reproducible and unbiased.

More specifically, they did Electron Spin Resonance (or Electron Paramagnetic Resonance), Uranium-Thorium disequilibrium, Optically Stimulated Resonance and radiocarbon dating.  This is probably not the last word on the dating of the fossils and there are quite a few assumptions that have been made regarding the provenance of the fossils to the cave sediments, but this is the closest thing that we currently have. One of the critical problems in dating much of the South African cave deposits is their relationship to the hominins found there.  Often, the caves opened up at the top and the fossil remains either fell in, were dropped in or they crawled in.  What makes the Rising Star remains so peculiar is that this cave did not form in the traditional way and the bones were so far into the cave. 

Where does this leave us? It leaves us with more questions than answers.  It has been common consensus that, while there was considerable variability in hominin morphology throughout the Pliocene and early to middle Pleistocene, that this "settled down" and that variability diminished as we made the transition to modern humans.  These fossils suggest the opposite: that large amounts of variability were, in fact, present throughout the range of human existence and only recently (200ky to the present) did this variability drop off.

I am quite sure that more studies will be done to elucidate the relationship that these fossils (there are more very similar fossils next door in the Lesedi cave complex) have to other forms in Africa.  There are obviously very peculiar cultural interactions going on, though (or lack, thereof).  With the Liang Bua remains in East Asia, hypotheses of endemic dwarfism and isolation have been put forth to explain why these remains are so diminutive and primitive.  It is more difficult to put forth these same arguments here where there are few to no barriers to migration and interaction between groups. 

Humans and Fire

It had been conventional wisdom that the origin of bipedality occurred in a forest/fringe environment and that a move to the savannah during the dry-out at the end of the Pliocene accelerated the evolution of humans.  That was thrown into turmoil when it was discovered that Ardipithecus ramidus possessed facultative bipedal characteristics at 4.4 million years but lived in an entirely forested environment.

Now, it seems, the savannah is seen as playing a different role in human evolution.  Charles Q. Choi, of Scientific American writes:

A longtime theory holds that early humans discovered how to use fire accidentally—perhaps while making stone tools they found that striking rocks against each other could generate sparks, and then gradually learned fire had many uses.

The problem with such serendipity-based explanations is that they "raise more questions than they answer," says evolutionary anthropologist Christopher Parker at the University of Utah in Salt Lake City. For example, these theories do not address when or where the discovery might have occurred, why it did not happen earlier or why other animals that use stone tools—chimpanzees, capuchin monkeys, crab-eating macaques and sea otters are known to do so—did not also develop fire use, Parker notes.

Parker and his colleagues suggest in a study published in the April Evolutionary Anthropology that humans developed fire use as a natural response to environmental changes. Previous research found that roughly 3.6 million to 1.4 million years ago—as the genus Homo emerged in Africa—the continent regularly experienced bouts of aridity, causing forests to shrink and dry grasslands to spread. Earlier studies suggested these climate shifts may have driven humanity’s ancestors away from a life climbing trees and toward one of walking upright on the ground, Parker says.

Yes, but there have been, as alluded to above, issues with these previous studies. If bipedality originated in the forest, as a response to who-knows-what, then they already possessed it when the drying out began. But this is not the crux of Parker's research:

Parker and his colleagues suggest in the new study that our ancestors not only grew accustomed to fire but learned to exploit it as a naturally occurring resource. This adaptation, called pyrophilia, may have set the stage for more active and deliberate human use of fire.

The research team's models suggest early humans benefited from wildfires in a number of ways: The blazes would have made it easier to find food, much as Martu Aboriginal women in Australia still rely on fire to clear brush for more efficient hunting. The models also indicate that early humans might have combed the charred remains of wildfires to dine on animals, seeds, nuts and tubers cooked in the flames—benefitting from a chemical process that not only makes many foods easier to digest but kills germs and neutralizes some toxins.

This has not been proposed before and it will be interesting to see if more evidence of this is found. Read the whole thing.

Early Homo in South Africa

The New York Times is reporting on a new find out of South Africa, by Lee Berger and his team, that indicates the presence of early Homo there.  John Noble Wilford writes:

The new hominin species was announced on Thursday by an international team of more than 60 scientists led by Lee R. Berger, an American paleoanthropologist who is a professor of human evolution studies at the University of the Witwatersrand in Johannesburg. The species name, H. naledi, refers to the cave where the bones lay undisturbed for so long; “naledi” means “star” in the local Sesotho language.

In two papers published this week in the open-access journal eLife, the researchers said that the more than 1,550 fossil elements documenting the discovery constituted the largest sample for any hominin species in a single African site, and one of the largest anywhere in the world. Further, the scientists said, that sample is probably a small fraction of the fossils yet to be recovered from the chamber. So far the team has recovered parts of at least 15 individuals.

“With almost every bone in the body represented multiple times, Homo naledi is already practically the best-known fossil member of our lineage,” Dr. Berger said.

Here is the link to the first paper, Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa, and here is the link to the taphonomic paper, Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa. Here is the picture from the main paper, as well as the abstract:

Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.

What does this mean?  Well, the principle problem is that we still have no date for these remains, so it is difficult to place them chronologically.  Berger is standing by his contention that early Homo arose from something like Au sediba, despite evidence to the contrary recently uncovered in Northeast Africa.  If the date is late, somewhere on the order of one million years, then a migration model might explain the appearance of such an advanced hominin in this area.  If it turns out to be much older, then other models might have to be entertained.  More thoughts on this find later.

Modern Hand Digit at 1.84 Mya

A story in Lab Equipment has spotlighted new evidence that modern human morphology was present in early hominins at 1.84 million years ago.  From the story:

“The new Olduvai fossil represents the earliest known hominin hand bone with (modern human-like) appearance,” they wrote. “Our results, along with the archaeological record, reveal that instead of following an orderly trend, eventually culminating in the modern human condition, some ‘primitive’ hand bone morphologies persisted side-by-side with (modern human-like) hand bone morphologies well after the first appearance of stone tools and zooarchaeological evidence of their use for butchery by at least (2.6 million years ago).”

This makes sense. Evolution happens at the trait level, not the species level. There are numerous examples of some traits becoming more modern over time, while some retained archaic dimensions.What is not clear is whether or not it is from early Homo or Australopithecus (Paranthropus) boisei.  If it is from Paranthropus, then the modern morphology extends back at least to the point where the later diversification of australopithecines occurred, between 2.5 and 3.0 mya and, perhaps, longer. 

Earliest Stone Tools?

Artifacts have been found near Lake Turkana that are reported to be the earliest stone tools yet produced.  Live Science has this:

Until now, the earliest known tools were about 2.8 million years old, the researchers said. The artifacts are by far the oldest handmade stone tools yet discovered — the previous record-holders, known as Oldowan stone tools, were about 2.6 million years old.

"We were not surprised to find stone tools older than 2.6 million years, because paleoanthropologists have been saying for the last decade that they should be out there somewhere," Harmand said. "But we were surprised that the tools we found are so much older than the Oldowan, at 3.3 million years old."

It remains unknown what species made these stone tools. They could have been created by an as-yet-unknown extinct human species, or by Australopithecus, which is currently the leading contender for the ancestor of the human lineage, or by Kenyanthropus, a 3.3-million-year-old skull of which was discovered in 1999 about a half-mile (1 kilometer) from the newfound tools. It remains uncertain exactly how Kenyanthropus relates to either Homo or Australopithecus.

Part of this is because Kenyanthropus is very badly deformed postmortem and it is very hard to figure out its morphology. In recent years, it has not been seriously included in human lineage models.There is evidence at the site of Gona for the use of tools, around 3.3 million years ago, but no actual tools, themselves.  This represents a more concrete example of early tools.  According to the picture, these are very rudimentary choppers.  More pieces of the puzzle.

New Dates For Little Foot Push It Back to Au. afarensis Time-Period

On the heels of the Ledi jaw dates for early Homo at 2.8 million years ago, and the corresponding tentative conclusion that only Au. afarensis could emerge as a possible ancestor for early Homo, to the exclusion of any of the other australopithecines, comes a redating of the Australopithecus specimen from the cave of Sterkfontein to 3.67 million years ago.  From the story in Science Daily:

Ronald Clarke, a professor in the Evolutionary Studies Institute at the University of the Witwatersrand who discovered the Little Foot skeleton, said the fossil represents Australopithecus prometheus, a species very different from its contemporary, Australopithecus afarensis, and with more similarities to the Paranthropus lineage.

“It demonstrates that the later hominids, for example, Australopithecus africanus and Paranthropus did not all have to have derived from Australopithecus afarensis,” he said. “We have only a small number of sites and we tend to base our evolutionary scenarios on the few fossils we have from those sites. This new date is a reminder that there could well have been many species of Australopithecus extending over a much wider area of Africa.”

So, what is Au. prometheus, exactly and how does it differ from the other australopithecines in the area?  From the paper by Granger, et al.¹:

This species was named on the basis of a parietooccipital fossil from Makapansgat23. It has been suggested22 that several other Sterkfontein and some Makapansgat specimens also belong in this species making Australopithecus africanus and A. prometheus contemporaries in the assemblages of Makapansgat Member 3 and Sterkfontein Member 4. A. prometheus differs from A. africanus in features including Paranthropus-like larger, bulbous-cusped cheek teeth, a longer, flatter face, incipient supraglabellar hollowing and a more vertical rounded occiput22. (Note that we use the term hominid in the traditional sense to include humans and their ancestral relatives but exclude the great apes.)

One of the raging debates in human palaeontological studies concerns whether or not the robust australopithecines, Au. robustus and Au. boisei, represent their own clade, Paranthropus. This perspective is based on traits that are shared to the exclusion of other australopithecine species.  Opponents of this view argue that quite a few of the traits that make up this clade are functional in nature, involving mostly the chewing complex, and that as such, Au. robustus and Au. boisei are  outgrowths of Au. africanus.

The story continues, quoting Ron Clarke:

“It demonstrates that the later hominids, for example, Australopithecus africanus and Paranthropus did not all have to have derived from Australopithecus afarensis," he said. “We have only a small number of sites and we tend to base our evolutionary scenarios on the few fossils we have from those sites. This new date is a reminder that there could well have been many species of Australopithecus extending over a much wider area of Africa.”

Hope so, because right now, here is how it looks:

• P. robustus (or Au. robustus) only in South Africa
• P. boisei (or Au. boisei) only in East Africa
• Early Homo only in East and Northeast Africa
• Au. africanus only in South Africa
• Ar. ramidus only in North East Africa
• Au. afarensis only in North East Africa

As Slim Pickens would say: “What in the Wide, Wide World of Sports is a-goin' on here?”

All of this sort of leads to the question of who the last common ancestor of humans and modern apes was.  All we have to go on is a badly crushed skull from the Sahel River area in Chad that is purported to be somewhere around 7 mya, but is, in reality, a surface find, and some hominin-looking post-cranial remains from the Tugen Hills, in Kenya that are dated to between 5.6 and 6.1 mya.  By the time we get to Ar. ramidus, at least facultative bipedalism is in place, although there are still quite a few ape-like traits.  What is not clear from the report by Granger et al, is how the morphology compares to earlier hominins.  For example, can the traits observed in Au. prometheus be derived from Ar. ramidus?  If so, then it still represents a possible precursor and something like Ar. ramidus gave rise to both the australopithecines and the paranthropines.  The fact that the discoverers are calling it Australopithecus suggests that it shares enough derived traits with the australopithecines as a whole to be called that.  If the traits cannot be derived from Ar. ramidus, then it raises the possibility that the paranthropines and Ar. ramidus share a common ancestor.  At this point, until some systematic analyses can be done, we simply don't know. 

Of course, all of this is contingent on the dates holding up.  The article gives a pretty good run-down on how isochron dating works and indicates that the dates are consistent with what would be expected given the deposition.   I am sure that more will come out about this very shortly.  Until then...

¹Darryl E. Granger, Ryan J. Gibbon, Kathleen Kuman, Ronald J. Clarke, Laurent Bruxelles, Marc W. Caffee. New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan. Nature, 2015

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. 

Oldest Footprints Outside of Africa

Fossil footprints have been found in England that are thought to be 800,000 years old.  As Science Daily puts it:

The importance of the Happisburgh footprints is highlighted by the rarity of footprints surviving elsewhere. Only those at Laetoli in Tanzania at about 3.5 million years and at Ileret and Koobi Fora in Kenya at about 1.5 million years are older.

A lecturer in physical geography, and co-director of the Happisburgh project (http://www.ahobproject.org/), Dr Lewis added that the chance of encountering footprints such as this was extremely rare; they survived environmental change and the passage of time.

Timing was also crucial as "their location was revealed just at a moment when researchers were there to see it" during a geophysical survey. "Just two weeks later the tide would have eroded the footprints away."

"At first we weren't sure what we were seeing," explains Dr Nick Ashton of the British Museum "but as we removed any remaining beach sand and sponged off the seawater, it was clear that the hollows resembled prints, and that we needed to record the surface as quickly as possible."

This illustrates the fragility of the fossil record and how incredibly fortunate we are to have anything, let alone what we do have.There isn't a whole heck of a lot in England to begin with.  The boxgrove tibia is around 500 Kya and the Swanscombe skull is around 300 Kya.   We know that early Homo was in southern Europe around 1.2-1.3 Mya and now, in northern Europe by at least 800 Kya. 

HufPo: What We Learned About Human Origins In 2013 Will Blow Your Mind

The Huffington Post has a story on the advances in human origins for the last year.  In the realm of modern human origins:

Recent analyses of fossil DNA have revealed that modern humans occasionally had sex and produced offspring not only with Neanderthals but also with Denisovans, a relatively newfound lineage whose genetic signature apparently extended from Siberia to the Pacific islands of Oceania.

This year, hints began emerging that another mystery human lineage was part of this genetic mix as well. Now, the first high-quality genome sequence from a Neanderthal has confirmed those suspicions.

These findings come from Denisova Cave in southern Siberia, where the first evidence of Denisovans was discovered in 2008. To learn more about the Denisovans, scientists examined DNA from a toe bone unearthed there in 2010.

The researchers found that the fossil belonged to a Neanderthal woman. Her DNA helped refine the human family tree, as it revealed that about 1.5 to 2.1 percent of the DNA of modern people outside Africa is Neanderthal in origin, whereas about 0.2 percent of DNA of mainland Asians and Native Americans is Denisovan in origin. [Top 10 Mysteries of the First Humans]

As Dennis Venema points out, modern humans appear to come from a population of around 150,000, which likely arose in North Africa.  I would still suggest two possibilities that might explain the hybridization.  One, that from around this time to 50 thousand years ago, humans existed as a generally polytypic species and that interbreeding, until the demise of the Neandertals and the Denisovans was, perhaps, widespread.  In the 50 thousand years since then, these genes have stochastically dropped out of the population.

The other possible model that would explain the variation between Neandertals, Denisovans and early moderns might be a syngameon, in which there are three definable species that, at their peripheries, hybridize.  At some point, then, the modern humans simply swamped the other two genomes. This would be the model of modern-day dogs and wolves which can mate but ordinarily do not. 

Another finding?  That early Homo may have been one highly-variable species, rather than a bush of species:

The level of variation seen in Homo fossils is typically used to define separate species. However, analysis of 1.8-million-year-old skulls excavated from the Republic of Georgia revealed the level of variation seen among those skulls was about the same as that seen among ancient African Homo fossils. As such, researchers suggest the earliest Homo fossils may not be multiple human species, but rather variants of a single lineage that emerged from Africa.

This will rattle those that hold to more cladistically-driven models of human origins like Ian Tattersall who supports a model more like the phylogenetic species concept, in which  single trait difference might confer species-level taxonomy.  This takes care of this issue of why there are two very different morphs on the landscape in East Africa at this time, represented by ER 1813 and ER 1470.  The dimorphism is quite large, but, as we discovered, is not beyond what would be expected in any species of large-bodied hominoid but larger than what would be found in any living population of humans in the last several hundred thousand years. 

A good run-down.  Read the whole thing. 

"Single Evolving Lineage of Early Homo"

This was reported a month or so back.  A new fossil has been described from the site of Dmanisi, the 1.8 million year-old site in the Russian republic of Georgia.  The skull is almost totally complete and, with associated jaw, is one of the best examples of early Homo in existence.  From the abstract of the Lordkipanidze et al¹ article:

The Dmanisi sample, which now comprises five crania, provides direct evidence for wide morphological variation within and among early Homo paleodemes. This implies the existence of a single evolving lineage of early Homo, with phylogeographic continuity across continents.

The idea of a single, evolving lineage is the closest you will get to someone admitting that there might be anagenetic speciation going on here. It also suggests a wide range for early Homo that extended from eastern Africa, across the upper coast, and across the strait of Gibraltar. There is evidence of early Homo at Orce, in Spain and Pirro Nord, in Italy from around 1.6 to 1.3 million years ago. No actual hominin remains exist at these sites but the stone tools that have been found found match, generally, those found at Dmanisi. Not a smoking gun but close.

What is intriguing about this is that it is not a huge intellectual leap that is making these hominins move.  The newly-described Dmanisi skull has a cranial capacity of 546 cubic centimeters, barely 100 more than the late australopithecines.  The morphological diversity also has people interested.  From the Science Daily story:

According to [Christophe] Zollikofer, the reason why Skull 5 is so important is that it unites features that have been used previously as an argument for defining different African "species." In other words: "Had the braincase and the face of the Dmanisi sample been found as separate fossils, they very probably would have been attributed to two different species." Ponce de León adds: "It is also decisive that we have five well-preserved individuals in Dmanisi whom we know to have lived in the same place and at the same time." These unique circumstances of the find make it possible to compare variation in Dmanisi with variation in modern human and chimpanzee populations. Zollikofer summarizes the result of the statistical analyses as follows: "Firstly, the Dmanisi individuals all belong to a population of a single early Homo species. Secondly, the five Dmanisi individuals are conspicuously different from each other, but not more different than any five modern human individuals, or five chimpanzee individuals from a given population."

the differences between the East African and Eurasian fossils then could be just regional variation in an evolving polytypic species. This kind of explanation certainly gives the "lumpers" a leg up and, if this explanation is the best one going, calls into our question the splitting that we have applied to other species. Is it, instead, appropriate to sink such taxonomic forms such as Homo heidelbergensis, Homo ergaster, Homo rudolfensis and Homo habilis, all of which exhibit considerable size and shape dimorphism, into one species: Homo erectus which now has taxonomic precedence?

¹A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early Homo David Lordkipanidze, Marcia S. Ponce de León, Ann Margvelashvili, Yoel Rak, G. Philip Rightmire, Abesalom Vekua, and Christoph P. E. Zollikofer Science 18 October 2013: 342 (6156), 326-331.

Environment Highly Variable For Early Humans

The Telegraph is reporting a story out of PNAS that suggest that the environment was highly variable during a critical point in our evolution.  They write:

The early landscape shifted between woodland to grassland half a dozen times over 200,000 years, meaning man had to adapt to survive.

Experts from Penn State university say that this may have set the tone for the rapid evolution which then took place.

Writing in the Proceedings of the National Academy of Sciences, Clayton Magill said: "The landscape early humans were inhabiting transitioned rapidly back and forth between a closed woodland and an open grassland about five to six times during a period of 200,000 years.

"These changes happened very abruptly, with each transition occurring over hundreds to just a few thousand years."

The findings appear to contradict previous theories which suggest evolutionary changes were gradual, and in response to either long and steady climate change or one drastic change.

The general consensus is that that there was a gradual drying out of the environment that led to the hominins taking over the savanna.  It is not clear that these hypervariable changes will correspond to abrupt changes in hominin form but it could partially explain the somewhat sudden appearance on early Homo.  We shall see.