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. 

Why Is Homo floresiensis Still Such a Mystery?

Cosmos Magazine has an article by Debbie Argue, biological anthropologist from Australian National University, about Homo floresiensis and why it has been a struggle to accurately and adequately place this hominin within the framework of human evolution.

 Here was the initial assessment:

Peter Brown and colleagues originally proposed two competing hypotheses about the origins of H. floresiensis. One is that the species is an early hominin similar to the earliest identified in the Homo genus. The fossils for these species are known only from Africa and are between one and two million years old. This implies that the ancestors of H. floresiensis could have got to Flores Island in the vicinity of a million years ago and survived there until at least 60,000 years ago.

Their alternative hypothesis was that H. floresiensis is a dwarfed descendant of Homo erectus, which is the only known non-sapiens hominin to once have existed in Indonesia. Its remains have been found on the island of Java. According to this view, the dwarfing of H. erectus was an evolutionary response to being isolated on an island with a limited food supply. Just as the Asian elephant evolved into the dwarfed Flores stegodon after becoming marooned on the island, H. erectus could have met a similar fate.

It was also proposed that this hominin might have expressed microcephaly.  This idea failed to explain other aspects of the skeleton, however, such as its diminutive height (around 3 feet), long arms and feet and primitive skull features. Here is an image of H. floresiensis compared to a modern human, who had been running around the landscape for at least 100k years while H. floresiensis was extant.

This all saw at least some resolution with the discovery and description of some remains  on another areas of the island Flores that were very similar to the H. floresiensis remains but dated to some 600 thousand years earlier than the remains in Liang Bu.  This lent more credence to the idea that H. floresiensis was, in fact, an offshoot of Homo erectus.

So, Argue, along with Colin Groves, Bill Jungers and Mike Lee, performed statistical tests (this story does not say which kind, a peculiar omission) on a number of different hominin species, comparing them to H. floresiensis.  What did they find?

We therefore hypothesise that H. floresiensis shared a common ancestor with H. habilis. We do not know who that ancestor was or when it lived, but it would have to be older than the oldest H. habilis specimen known, so older than 1.75 million years. The implication is that the H. floresiensis ancestor evolved before that time in Africa, dispersed from that continent, and arrived on Flores earlier than 700,000 years ago, judging by the age of the jaw and teeth found at Soa Basin. This represents a hitherto unknown movement of very early hominins out of Africa.

Presently, the earliest evidence for hominins outside of Africa come from Europe, the Near East and Asia, and date to between 1.5 and 1.8 million years ago. Argue's hypothesis would suggest that H. floresiensis appearance in east Asia represents a separate migration out of African sometime either before or after the wave that saw Homo erectus show up in Trinil and Sangiran, in Indonesia.

Questions still abound as to why this species never saw the evolutionary trajectory that other hominins went through in terms of cranial expansion, increase in height and changes in brachial and crural indices. On the other hand, if evolution proceeds through what we have termed systematics, then advanced traits will show up in related species and if the ancestors of H. floresiensis were cut off, they would just go on their merry way.  We know that such a pattern holds for H. naledi, in South Africa, which coexisted with archaic Homo sapiens, in some way, shape or form. 

The article ends on a very peculiar note, in which she suggests the remote possibility that H. floresiensis is still alive out there, somewhere:

Could the Hobbit still exist in the wild mountain forests of Flores? When H. floresiensis was announced, the media picked up on the local folklore that small human-like creatures roam the forests. Descriptions of sightings are well recorded and quite detailed. The similarity to H. floresiensis is intriguing. But most researchers would say ‘show me the bones!’

This reminds one of the stories involving the Yeti/Sasquatch/Abominable Snowman, which likely derive from the finding of the bones of the Miocene ape Gigantopithecus, which was close to ten feet tall, when standing.  Is H. floresiensis still out there?  Probably not, but I am sure that the cryptozoologists haven't given up hope. 

Genetic Model Identifies Paranthropus boisei as Vector For Transmission of Herpes Virus

CNN (usual caveats) reports on a study that identifies Paranthropus boisei as the likely transmission vector of genital HSV-1.  From the story:

Herpes has been around a long time, to say the least.

Ancient chimpanzees genetically passed oral herpes (herpes simplex 1, or HSV-1) to the earliest humans millions of years ago when our lineage split. And we almost missed out on catching that other scourge, genital herpes (HSV-2) -- almost. Unlike HSV-1, HSV-2 didn't make the leap to early humans on its own.

Unfortunately for modern humans, millions of years ago, an early human ancestor was in the right place at the right time to catch HSV-2. And it might not have happened if it weren't for that meddling hominin species Paranthropus boisei, according to a new study in the journal Virus Evolution.

Why Paranthropus boisei, you ask? After all, P. boisei was not even on the main line of human evolution, coexisting with all manner of early Homo species at the same time, who likely out-competed them into extinction.  From the article, which is highly technical:

Paranthropus boisei would have been well placed to act as an intermediate host for HSV2. It most likely contracted the infection through hunting or more likely scavenging infected ancestral-chimpanzee meat. Processing (with or without tools) and consumption of raw meat would act as a simple path for ChHV1 to have crossed into P.boisei via open cuts or sores. Tropical refugia during hot dry periods may have driven chimpanzees into higher concentrations in certain areas, driving them into contact and competition with P.boisei and H.habilis as the margins of tropical forest blended into more open savannah-like habitats (Julier et al. 2017). Violent confrontation or hunting/scavenging and butchery practices would have provided a viable path of transmission for HSV2. Homo habilis remains have been recovered from the same layers as stone tools and bones carrying evidence of butchery, supporting a possible transmission–through-hunting/scavenging hypothesis for the initial anc-chimp to H.habilis transmission (Clarke 2012). Paranthropus aethiopicus, P. boisei, and P. robustus are associated with the Oldowan stone tool complex (De Heinzelin et al. 1999), and P.boisei explicitly with butchery (Domínguez-Rodrigo et al. 2013) lending support to the hypothesis that bushmeat hunting/scavenging and butchery may have led to the initial transmission of HSV2 to the hominins.

The entire exercise is very mathematical and relies on somewhat limited evidence of P. boisei behavior. It is, nonetheless, intriguing since it posits considerable interaction between the various hominin groups. 

Here is a mugshot of one of the perpetrators, the Zinj skull from Olduvai Gorge, found in 1959. 

New Study on Homo naledi

Lauren Schroeder and colleagues have published a report on the skull of Homo naledi, in which they address the characteristics and attempt to place them in a taxonomic context, using morphometric analysis.  From the abstract:

Our results indicate that, cranially, H. naledi aligns with members of the genus Homo, with closest affiliations to H. erectus. The mandibular results are less clear; H. naledi closely associates with a number of taxa, including some australopiths. However, results also show that although H. naledi shares similarities with H. erectus, some distances from this taxon – especially small-brained members of this taxon – are extreme. The neighbor joining trees place H. naledi firmly within Homo. The trees based on cranial morphology again indicate a close relationship between H. naledi and H. erectus, whereas the mandibular tree places H. naledi closer to basal Homo, suggesting a deeper antiquity. Altogether, these results emphasize the unique combination of features (H. erectus-like cranium, less derived mandible) defining H. naledi. Our results also highlight the variability within Homo, calling for a greater focus on the cause of this variability, and emphasizing the importance of using the total morphological package for species diagnoses.

Another major finding of the study is that a grouping of H. naledi and specimens of Homo erectus "exceeds, in many instances, what we would expect if this grouping represented a single species."  Recall that we have zero idea how old this find is and, to the extent that this is possible, are trying to place this skull using only taxonomic analysis. Nonetheless, it gives us more information about this stage of hominin evolution and suggests that there was considerable variation of morphs running around during the transition from the australopithecines to early Homo. 

H. floresiensis Not As Young or As Unique As We Thought

In other words, so much for the pathology argument.  Many news outlets, National Geographic being one of them, are reporting on new fossils that closely match those of Homo floresiensis that were found at Liang Bua Cave on the island of Flores in the late 1990s.  Adam Hoffman writes:

The 700,000-year-old human remains are the first found outside Liang Bua cave, the site on Flores that yielded the original hobbit fossils. The much older samples show intriguing similarities to H. floresiensis, including their small size, and so provide the best evidence yet of a potential hobbit ancestor.

“Since the hobbit was found, there have been two major hypotheses concerning its ancestry,” says Gerritt van den Bergh, an archaeologist at the University of Wollongong in Australia and a contributor to the work.

According to one theory, H. floresiensis is a dwarfed form of Homo erectus, an ancient human relative that lived in East Asia and parts of Africa until about 143,000 years ago. But other researchers think the hobbits evolved from even earlier, smaller-bodied hominins such as Homo habilis or Australopithecus.

“These new findings suggest that Homo floresiensis is indeed a dwarfed form of Homo erectus from Java, a small group of which must have gotten marooned on Flores and evolved in isolation,” van den Bergh says.

The article goes on to note that the competing argument, that the fossils of Liang Bua represent some kind of pathological condition, and that they maintained this condition for some 700 ky, is now untenable. Clearly this is a side-branch of human evolution.The other key finding is that they also had stone tools, specifically a “straightforward core and flake” technology. Further, the tools show a striking similarity to those found at Liang Bua, suggesting that there was remarkable cognitive "stability" in this population. 

The more we think we know about human evolution, the less, it turns out, that we do.  For now, the entire article is available from Nature for free here. 

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.

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.  

Two Hominin Species Running Around At 1.9 Mya

Meave Leakey and some colleagues¹ have unearthed and described some new fossil hominins from Koobi Fora that seem to confirm that, yes, there were two very different critters running around 1.8 to 1.9 million years ago on the plains of eastern Africa. From the Turkana Basin Institute:

Found within a radius of just over 10 km from 1470’s location, the three new fossils are dated between 1.78 million and 1.95 million years old. The face KNM-ER 62000, discovered by field crew member Elgite Lokorimudang in 2008, is very similar to that of 1470, showing that the latter is not a single “odd one out” individual. Moreover, the face’s well-preserved upper jaw has almost all of its cheek teeth still in place, which for the first time makes it possible to infer the type of lower jaw that would have fitted 1470. A particularly good match can be found in the other two new fossils, the lower jaw KNM-ER 60000, found by Cyprian Nyete in 2009, and part of another lower jaw, KNM-ER 62003, found by Robert Moru in 2007. KNM-ER 60000 stands out as the most complete lower jaw of an early member of the genus Homo yet discovered.

The skull being referenced (heavily throughout the press release) is that of KNM-ER 1470, discovered by Richard Leakey in 1972 and dated to 1.9 million years ago. 1470 has a very flat face and is large, so much so that when it was discovered and compared to the Homo habilis material that Richard's dad, Louis Leakey and Napier and Tobias were pulling out of the ground, it was felt that it represented a new species, Homo rudolfensis.

For a short run-down on the material from this time period, go to my BioLogos post, The Human Fossil Record, Part 7: The Rise of Early Homo.

Anyhow, these new fossils add a new level of what Bernard Wood² calls “complexity.” For quite some time, 1470 existed in its own little world, with no fossil remains being similar to it in size or in shape. Questions began to rise about the veracity of its reconstruction and its provenance. These new fossils fit 1470 to a “T” and it now seems clear the 1470 does, in fact, represent a different form than that represented by skulls like ER 1813, which is small and gracile and gives support to the idea that there were two competing species of hominin on the landscape even before Homo erectus/ergaster arrived on the scene some two hundred thousand years later. Below, on the top is KNM-ER1813 and below it is KNM-ER 1470















As you can see, there is considerable difference in overall size and robusticity between the two and when the new material is compared to the mandible KNM-ER 1802, which is similar to 1813, there is a considerable mismatch. What remains to be seen is where Homo ergaster came from.

¹Leakey, M. G., Spoor, F., Dean, M. C., et al. (2012). New fossils from Koobi Fora in northern Kenya confirm taxonomic diversity in early Homo. [10.1038/nature11322]. Nature, 488(7410), 201-204.
http://www.nature.com/nature/journal/v488/n7410/abs/nature11322.html#supplementary-information

²Wood, B. (2012). Palaeoanthropology: Facing up to complexity. Nature, 488(7410), 162-163.
http://dx.doi.org/10.1038/488162a

New BioLogos Post is Up

My new post on early Homo is up at BioLogos. As always, comments are welcome here and there.

----------------
Now playing: Emerson, Lake & Palmer - Pictures At An Exhibition: Promenade/The Gnome/Promenade/The Sage/The Hut Of Baba Yaga...
via FoxyTunes

Nature News Story on Au. sediba

Nature News has a story on the Australopithecus sediba skeleton described by Lee Berger and colleagues.  Ewen Callaway writes:

At around 420 cubic centimetres, A. sediba 's puny brain compares to those of other Australopithecus specimens and chimpanzees. But a high-resolution synchrotron scan of the brain's impression on the skull shows enlarged frontal areas that are normally associated with humans and linked to higher cognitive abilities, such as planning. A. sediba's pelvis also looks wider than those of other australopiths, raising doubts about the idea that the human pelvic shape evolved to accommodate large-brained babies. "Whatever is driving a relatively human-like shape of the pelvis, it is not a big brain," says Berger. The orientations of its leg and ankle bones suggest that A. sediba walked upright, and its nearly complete ankle resembles that of a human. But its long arms, and some features of its feet and shin bones, are similar to those of a chimpanzee. Taken together, these features suggest that A. sediba was adapted for both bipedalism and tree-dwelling.

This is a wonderful mosaic. As I wrote yesterday, though, it is not clear where it fits. There are three possibilities: A. africanus gives rise to A. sediba and A. habilis and A. rudolfensis.  Here, the two species of early Homo have been demoted and all three have transitional characteristics that represent a general trend toward modernity (after Walker and Wood).

The second scheme has A. africanus giving rise to A. sediba, which then goes extinct, and H. habilis and H. rudolfensis (in some fashion), one of which then gives rise to H. ergaster.  This posits that the traits present in both early Homo and A. sediba represent a general trend toward modernity. 

 

The third scheme has  A. garhi giving rise to early Homo with A. africanus giving rise to A. sediba, which then goes extinct.  The advantage of this is that A. garhi has modern-like limb proportions and is found in northeast Africa, not far from early Homo, while A. africanus and A. sediba are both found in south Africa.

 

Which one of these is right?  Are any of them right?  Who knows.  What we do know is that these critters have relationships to each other in some way, shape or form.  

Au. sediba Now Considered Possible Ancestor to Homo

New research is suggesting that the overall anatomy of Australopithecus sediba makes it the best candidate for being ancestral to Homo.  The article in Science Daily is quite long and delves into the specific traits that Lee Berger suggests are thought to evolving in the direction of Homo.  They write:

Lee Berger, the project leader from the University of the Witwatersrand in Johannesburg, South Africa, explains what these new findings mean for modern humans. "The many advanced features found in the brain and body, along with the earlier date, make it possibly the best candidate ancestor for our genus -- the genus Homo -- more so than previous discoveries, such as Homo habilis"
The age of the Au. sediba fossils has been constrained to about 1.977 million years, which predates the earliest appearances of Homo-specific traits in the fossil record. Until now, fossils dated to 1.90 million years ago -- and mostly attributed to Homo habilis and Homo rudolfensis -- have been considered ancestral to Homo erectus, the earliest undisputed human ancestor. But, the older age of these Au. sediba fossils raises the possibility of a separate, older lineage from which Homo erectus may have evolved.

This position seemed odd to me at first because there is already evidence of “early Homo” dating back to 2.3 million years ago. Then it occurred to me that this article makes a tacit assumption that is not stated: Homo habilis and Homo rudolfensis are not really Homo, but are Australopithecus. This is an argument that has been made by Alan Walker and Bernard Wood who suggest that, despite the size differential between H. rudolfensis and the late australopithecines, they are more similar than different.This levels the playing field and then Au. sediba simply becomes the branch of Australopithecus from which Homo sprung.

Taxonomy is a black art and we run the risk of tying too much significance to our taxonomic designations.  If we argue that Au. sediba gave rise to H. ergaster, despite the fact that there are already two species of Homo running around, it conjures up ideas of convergent evolution where an earlier australopithecine gave rise to Homo habilis and Au. sediba gave rise to Homo ergaster.  If, however we demote earliest Homo down to australopithecine status, the difficulties vanish “like the snows of yesteryear” as Isaac Asimov would say.  Look for this to be challenged as well. 

Peter Ungar: Homo erectus Ate More Diverse Things than Homo habilis

University of Arkansas researcher Peter Ungar has found evidence that the diet of Homo erectus was more variable than that of Homo habilis, its ancestor. The University of Arkansas Newswire reports:

The researchers used a technique developed by Ungar and his colleagues that combines engineering software, scale-sensitive fractal analysis and a scanning confocal microscope to create a reproducible texture analysis for teeth. The researchers looked at both complexity, the roughness at varying scales, and directionality in the teeth they examined. Hard foods like nuts and seeds tend to lead to more complex tooth profiles, while tough foods like leaves or meat lead to more scratches, which corresponds with directionality.

The analysis indicates that Homo habilis ate more plant material, while Homo erectus incorporated more nuts, berries and possibly meat into its diet. Another piece of the puzzle. Yay.

Casey Luskin on The Smithsonian Human Origins Exhibit

Casey Luskin has an article on Evolution, News & Views on the Smithsonian exhibit called "What Does It Mean To Be Human?" Luskin addresses the standard creationist argument that gaps in the fossil record disprove evolution. He quotes from the educator's guide, which reads:

Misconception: Gaps in the fossil record disprove evolution.

Response: Science actually predicts gaps in the fossil record. Many species leave no fossils at all, and the environmental conditions for forming good fossils are not common. The chance of any individual organism becoming fossilized is incredibly small. Nevertheless, new fossils are constantly being discovered. These include many transitional fossils—e.g., intermediary fossils between birds and dinosaurs, and between humans and our primate ancestors. Our lack of knowledge about certain parts of the fossil record does not disprove evolution.

Luskin responds:

Did you get that? Ignoring the fact that transitional fossils are often missing even among taxa whose records are very complete, now Darwin’s defenders argue that their theory “predicts gaps in the fossil record.” How convenient!

This is a semantic trick. It is the same as saying Black Holes don't exist because we cannot see them. Such a statement completely overlooks the fact that there is a very large amount of evidence, based on how astronomical bodies behave under the influence of strong gravimetric forces, that, yes indeed, Black Holes do exist. I would venture to guess that very few professional astronomers doubt the existence of Black Holes.

Because we are missing sections of the fossil record, even large sections of the fossil record overtrivializes the fact that we do have very good fossils to work with and almost unbroken sequences of fossils of many different orders. Luskin, in fact, ignores the second part of the paragraph that he quotes.

That we have gaps is unavoidable. Evolutionary theory doesn't predict gaps. Geology predicts gaps. There is simply no way short of a miracle that we would have completely fossil rich preservation sites for every conceivable depositional environment. Such an expectation misunderstands how geological processes work. Expecting such a fossilized environment misunderstands how taphonomy works. Luskin continues:

What's ironic, however, is that if you ask the question How Do We Know Humans Evolved? the answer you’re given is, “Fossils like the ones shown in our Human Fossils Gallery provide evidence that modern humans evolved from earlier humans.” So whether you find fossils or you don’t, that’s evidence for evolution.

Here's irony for you. The human fossil record, in fact, is replete with transitional forms. Here are a few:

• The recently discovered and described Ardipithecus shows the transition to from a quadupedal gait to bipedalism.
  
• The material from Hadar and Laetoli show more advanced bipedalism relative to Ardipithecus in A. afarensis, which still possesses slightly curved fingers to grasp limbs, indicating that some time was still spent in the trees.
  
• A. afarensis also shows remarkable features in the face that are exactly intermediate between apes and later humans.
• There is a flurry of different australopithecine forms between 3.5 and 2.0 million years ago, some robust, some gracile. All are related and yet are different, showing regional variation and change through time.
  
• The remains attributable Homo habilis, whether they be one species or many, show brain expansion on a basically australopithecine face (this is especially true with KNM-ER1470).
  
• There is a remarkable series of gradations from what is considered Homo habilis to what is considered Homo erectus or Homo ergaster. There is disagreement about how many species are represented because the material is quite variable—and shows considerable change over time. This is also why we are having trouble figuring out which group early Homo came from.
  
• There is considerable disagreement about when Homo erectus ends and archaic Homo sapiens begins due to the transitional nature of much of this material. This has led some, such as Milford Wolpoff, to suggest sinking H. erectus into the Homo sapiens line, arguing that it represents one long lineage.
  
• It is also clear that some traits persist in some populations longer than others. Homo antecessor, from Spain, shows incipient archaic Homo sapiens characteristics at 800 000 years ago, while over in Germany, the Mauer mandible from Heidelberg, still shows H. erectus traits.
• Over in China, Homo erectus (Zhoukoudian, Hexian) persists until around 250 000 years ago, while at 200 000, obvious changes have occurred in the face (Dali, Maba) in the Homo sapiens direction.
• Modern human traits do not appear all at once, but rather over a period of 60 to 80 000 years in Africa (Herto, Klasies River Mouth, Border Cave) and the Near East (Mugharet-es Skhul, Jebel Qafzeh). Early "modern" specimens still show a mix of archaic and modern features
  

I could go on for pages and pages. The point is that, despite the fact that we have gaps in the fossil record, what we do have is good enough to make some pretty dang good assessments of what happened in the past. The human fossil record is a wealth of information about our history as a species. To dismiss it out of hand because there are gaps is simplistic at best and ignorant at worst. He ends by quoting the great evolutionary biologist Ernst Mayr, who passed away a few years ago:

But the exhibit gives no evidence of dissent from the official party line, such as an admission from Ernst Mayr in 2004 that "[t]he earliest fossils of Homo, Homo rudolfensis and Homo erectus, are separated from Australopithecus by a large, unbridged gap,” and therefore we’re in a position of “[n]ot having any fossils that can serve as missing links."

Mayr was a brilliant evolutionary biologist but he did not work in the human fossil record. He is incorrect about his assessment. There are fossils of all shapes and sizes between the late australopithecines and Homo erectus. The problem is that there is no agreement about what they represent. It is, nonetheless, not an unbridged gap. Finds like Australopithecus sediba help to bridge that gap. Maybe it is not a direct ancestor to early Homo. It still show the progression toward the Homo line in one of these late australopithecines.

The fact that there are gaps in the fossil record has nothing to do with the fact that evolution has or has not taken place. How does Mr. Luskin explain the areas where there aren't gaps?

----------------
Now playing: Susan Ashton - Summer Solstice
via FoxyTunes

Australopithecus sediba Articles in Science

The Science Magazine articles on A. sediba are out. They are free for the time being. You just have to register at the site. The two articles cover the morphology of the finds as well as the geology of the Malapa Cave, in which they were found.
There is an extensive list of traits listed of both the cranium and face tabulated along with the other australopithecine species and early Homo. According to Berger and his team, it tells us the following:

The closest morphological comparison for Au. sediba is Au. africanus, as these taxa share numerous similarities in the cranial vault, facial skeleton, mandible, and teeth (Table 1). Nevertheless, Au. sediba can be readily differentiated from Au. africanus on both craniodental and postcranial evidence.

The face has the scooped appearance of australopithecines, with nice anterior pillars and the cranium is small, with a size of about 420 cubic centimeters. For reference, our heads are around 1400 cubic centimeters in size. On the Homo side, however, the vault is expanded and the face is considerably narrower than that of your average australopith. Compare it to this front shot of Australopithecus boisei specimen OH5, taken by David Brill. This lateral flaring of the cheeks is characteristic of all australopithecines to one degree or another and is not found in early Homo at all.

From the neck down, the skull has a mix of australopithecine and early Homo traits. The australopithecine traits include comparatively long arms, a somewhat conical-shaped rib cage and a small stature. On the other hand, it has a pelvic structure much more like later Homo, suggesting even better walking and running abilities.

Berger and his team have, I think, correctly placed this critter in the genus Australopithecus, but it clearly does have some characteristics that presage early Homo. What those mean is not yet clear but there was a general shift toward more modern characteristics in all of these hominids at around 2 million years ago.

----------------
Now playing: Anthony Phillips - It's All Greek to Me
via FoxyTunes

CNN Story on Australopithecus sediba

CNN has a story on the new hominid, complete with picture, which is now tentatively being called Australopithecus sediba. It is truly remarkable, with obvious characteristics of early Homo and yet what appear to be some nifty-looking anterior pillars. Here is the image that appears on the CNN site. Until we get a full description, what this find appears to represent is a very primitive Homo with some australopithecine facial characteristics and some Homo facial characteristics along with a slightly expanded cranium. This pattern is later seen in specimens like KNM ER-1470, Richard Leakey's famous find in 1972.

Here's the problem. As I mentioned in the first post about this find, if you are familiar with the facial skeleton of the gracile australopithecines, you can see those characteristics in this specimen. If you are familiar with the facial skeletons of the specimens attributed to Homo habilis, you can see some of those characteristics as well. The fact that this specimen has both is a big deal. That Anika Smith can dismiss it out of hand strongly suggests that she doesn't have the background to understand what she is looking at.

----------------
Now playing: Yes - And You and I (I. Cord of Life, II. Eclipse, III. the Preacher the Teacher, IV. Apocalypse) (Remastered)
via FoxyTunes

More on the Hominid Discovery

The Telegraph has a larger, more in-depth article on the discovery in South Africa of the early Homo remains. Richard Gray writes:

Experts who have seen the skeleton say it shares characteristics with Homo habilis, whose emergence 2.5 million years ago is seen as a key stage in the evolution of our species.

The new discovery could help to rewrite the history of human evolution by filling in crucial gaps in the scientific knowledge.

Most fossilised hominid remains are little more than scattered fragments of bone, so the discovery of an almost-complete skeleton will allow scientists to answer key questions about what our early ancestors looked like and when they began walking upright on two legs.

This discovery was hinted at months ago but no details had been forthcoming. One of the problems that continually plagues palaeoanthropology research is sections for which the fossil record is not as good as we would like it. There are a number of Homo habilis fossils that show a clear evolution of Homo but only a few instances in which it appears as though there is a clear transition between australopithecines and Homo habilis. This may change that.

----------------
Now playing: Yes - Siberian Khatru (Remastered)
via FoxyTunes

New Hominid from South Africa Fills Gap

Lee Burger has discovered a hominid specimen that fills some of the holes between australopithecines and early Homo. The article by Christopher Szabo, in Digital Journal notes:

The near complete skeleton was found by Professor Lee Burger of the University of the Witwatersrand (known locally as ”Wits”) in Johannesburg. He was exploring cave systems in the Sterkfontein region near Johannesburg in an area dubbed the ”Cradle of Humanity” for all the finds originating there.

More in a bit, I am sure.



----------------
Now playing: Anderson, Bruford, Wakeman, Howe - Quartet - i) I Wanna Learn, ii) She Gives Me Love, iii) Who Was The First, iv) I'm Alive
via FoxyTunes

Anika Smith Comments on Hominid Discovery

Anika Smith of the Discovery Institute has written a comment on the hominid find that could help bridge the gap between the australopithecines and early Homo. It is silly. She writes:

Another year, another fossil with some serious media backing. This week it's a Homo habilis said to be "almost-complete" — of course, the report from the Telegraph also claims that Homo habilis was "previously unknown," so you might want to take that with a grain of salt.

In fact, you might want to read a bit more before you throw that OMG Missing Link Found! party I know you were planning. (Squatch is going to take it hard when you cancel his first music gig since the Sonics left town.) This is the same species that was reported in an AP article from 2007 which disowned Homo habilis as a human ancestor. As far back as 1999, a paper in Science explained that this species should not even be considered a member of the Homo genus.

These statements suggest a complete lack of familiarity with the fossil record of these hominids. The reason that there is disagreement with the designation of Homo habilis is because there is considerable morphological variability within the specimens that make up Homo habilis as well as disagreement about how much the earliest specimens differ from the late australopithecines.

The article referenced from the NYT suggests that Homo habilis and Homo erectus lived on the same landscape for c. 500ky or so and thus, one was not unilineally descended from the other. So? That doesn't mean they didn't both have a common ancestor or that Homo habilis survived after Homo erectus split off. There are plenty of examples of descendant species coexisting with their progenitors. More silliness from the Discovery Institute.

----------------
Now playing: The Buggles - Kid Dynamo
via FoxyTunes