700 thousand year old ancestors of H. floresiensis

Nature 534, 245–248 (09 June 2016) doi:10.1038/nature17999

Homo floresiensis-like fossils from the early Middle Pleistocene of Flores

Gerrit D. van den Bergh, Yousuke Kaifu, Iwan Kurniawan, Reiko T. Kono, Adam Brumm, Erick Setiyabudi, Fachroel Aziz & Michael J. Morwood

The evolutionary origin of Homo floresiensis, a diminutive hominin species previously known only by skeletal remains from Liang Bua in western Flores, Indonesia, has been intensively debated. It is a matter of controversy whether this primitive form, dated to the Late Pleistocene, evolved from early Asian Homo erectus and represents a unique and striking case of evolutionary reversal in hominin body and brain size within an insular environment1, 2, 3, 4. The alternative hypothesis is that H. floresiensis derived from an older, smaller-brained member of our genus, such as Homo habilis, or perhaps even late Australopithecus, signalling a hitherto undocumented dispersal of hominins from Africa into eastern Asia by two million years ago (2 Ma)5, 6. Here we describe hominin fossils excavated in 2014 from an early Middle Pleistocene site (Mata Menge) in the So’a Basin of central Flores. These specimens comprise a mandible fragment and six isolated teeth belonging to at least three small-jawed and small-toothed individuals. Dating to ~0.7 Ma, these fossils now constitute the oldest hominin remains from Flores7. The Mata Menge mandible and teeth are similar in dimensions and morphological characteristics to those of H. floresiensis from Liang Bua. The exception is the mandibular first molar, which retains a more primitive condition. Notably, the Mata Menge mandible and molar are even smaller in size than those of the two existing H. floresiensis individuals from Liang Bua. The Mata Menge fossils are derived compared with Australopithecus and H. habilis, and so tend to support the view that H. floresiensis is a dwarfed descendent of early Asian H. erectus. Our findings suggest that hominins on Flores had acquired extremely small body size and other morphological traits specific to H. floresiensis at an unexpectedly early time.

Link

Nature 534, 249–253 (09 June 2016) doi:10.1038/nature17663

Age and context of the oldest known hominin fossils from Flores

Adam Brumm, Gerrit D. van den Bergh, Michael Storey, Iwan Kurniawan, Brent V. Alloway, Ruly Setiawan, Erick Setiyabudi, Rainer Grün, Mark W. Moore, Dida Yurnaldi, Mika R. Puspaningrum, Unggul P. Wibowo, Halmi Insani, Indra Sutisna, John A. Westgate, Nick J. G. Pearce, Mathieu Duval, Hanneke J. M. Meijer, Fachroel Aziz, Thomas Sutikna, Sander van der Kaars, Stephanie Flude & Michael J. Morwood

Recent excavations at the early Middle Pleistocene site of Mata Menge in the So’a Basin of central Flores, Indonesia, have yielded hominin fossils1 attributed to a population ancestral to Late Pleistocene Homo floresiensis2. Here we describe the age and context of the Mata Menge hominin specimens and associated archaeological findings. The fluvial sandstone layer from which the in situ fossils were excavated in 2014 was deposited in a small valley stream around 700 thousand years ago, as indicated by 40Ar/39Ar and fission track dates on stratigraphically bracketing volcanic ash and pyroclastic density current deposits, in combination with coupled uranium-series and electron spin resonance dating of fossil teeth. Palaeoenvironmental data indicate a relatively dry climate in the So’a Basin during the early Middle Pleistocene, while various lines of evidence suggest the hominins inhabited a savannah-like open grassland habitat with a wetland component. The hominin fossils occur alongside the remains of an insular fauna and a simple stone technology that is markedly similar to that associated with Late Pleistocene H. floresiensis.

Link

D4500 and the unity of early Homo

Science 18 October 2013:

Vol. 342 no. 6156 pp. 326-331

DOI: 10.1126/science.1238484

A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early Homo

David Lordkipanidze et al.



The site of Dmanisi, Georgia, has yielded an impressive sample of hominid cranial and postcranial remains, documenting the presence of Homo outside Africa around 1.8 million years ago. Here we report on a new cranium from Dmanisi (D4500) that, together with its mandible (D2600), represents the world's first completely preserved adult hominid skull from the early Pleistocene. D4500/D2600 combines a small braincase (546 cubic centimeters) with a large prognathic face and exhibits close morphological affinities with the earliest known Homo fossils from Africa. 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.

Link

Throwing erectus

Nature 498, 483–486 (27 June 2013) doi:10.1038/nature12267

Elastic energy storage in the shoulder and the evolution of high-speed throwing in Homo

Neil T. Roach et al.

Some primates, including chimpanzees, throw objects occasionally1, 2, but only humans regularly throw projectiles with high speed and accuracy. Darwin noted that the unique throwing abilities of humans, which were made possible when bipedalism emancipated the arms, enabled foragers to hunt effectively using projectiles3. However, there has been little consideration of the evolution of throwing in the years since Darwin made his observations, in part because of a lack of evidence of when, how and why hominins evolved the ability to generate high-speed throws4, 5, 6, 7, 8. Here we use experimental studies of humans throwing projectiles to show that our throwing capabilities largely result from several derived anatomical features that enable elastic energy storage and release at the shoulder. These features first appear together approximately 2 million years ago in the species Homo erectus. Taking into consideration archaeological evidence suggesting that hunting activity intensified around this time9, we conclude that selection for throwing as a means to hunt probably had an important role in the evolution of the genus Homo.

Link

Human-chimp divergence date pushed back in time

I recently wrote:

Actually, we are beginning to get a hold of the mutation rate -thanks to the ability to sequence full genomes- but we have absolutely no clue when human-chimp divergence actually happened, at least not within a few million years.)

The context of that post was to highlight the fact that many aspects of recent human origins research, such as estimates of effective population sizes or mutation rates were inextricably linked to calibration with the date of divergence between humans and chimps. But, that date was obscure: paleontologists didn't always seem to agree on what represented a member of the lineage leading to us or a common human-chimp ancestor; and there were circular arguments a-plenty, where genetic mutation rates calibrated on a particular human-chimp divergence were then used again to "prove" that divergence rate.

Well, at least now, thanks to a new paper by Langergraber et al., we have a better idea. It's clear now that humans and chimps diverged from each other a few million years earlier than previously thought.

And, of course there are implications on every event where calibration based on human-chimp divergence was at play. That has major implications for Neandertal-human divergence, as well as for human-human divergence estimates.

Together with the publication of the two conflicting papers on Neandertal admixture (or not), it appears that August 2012 has proven to be anything but a time for a little quiet vacation.

From Science's coverage of the new work:

Now, after a decade of analyzing the patterns of reproduction in chimpanzees and gorillas in Africa, Vigilant and former postdoc Kevin Langergraber—now a primatologist at Boston University—say they have the data they need. Working with almost 20 collaborators, the duo gathered data recording the age of mothers and fathers at the birth of 226 offspring in eight different chimpanzee communities in the wild, and 105 offspring of mountain gorillas from two different research sites in Africa—and they verified those relationships with DNA paternity tests on coprolites gathered in the field. As they report today in the Proceedings of the National Academy of Sciences, chimpanzee mothers ranged in age from 11.7 to 45.4 years at the birth of their offspring. The average age of reproduction was 25 years for females and 24 years for males, giving them an average generation time of about 25 years. Gorilla females ranged in age from 7.3 to 38 years when they gave birth, and the average generation time for both sexes was about 19.3 years. 

... 

To get the mutation rates, the team divided the number of mutations between parents and their offspring (collected by analyzing DNA from coprolites sent to the lab in Leipzig) by the newly calculated generation times. The researchers got a high and low mutation rate for each species per year—rates that were slower than previously estimated using fossils to calibrate the molecular clock. When they applied the new rates to the history of all three species, they calculated that humans and chimps split earlier than expected—at least 7 million to 8 million years ago and possibly as early as 13 million years ago. They estimate the split between gorillas and the lineage leading to humans and chimpanzees to 8 million to 19 million years ago. Those dates have such wide ranges, Vigilant explains, because they assume the mutation rates seen today have been constant over time in all three lineages. So a key remaining question is whether mutation rates were faster in the past.

Incidentally, this might solve Chris Stringer's doubts about the antiquity of the Atapuerca hominins, because it is now possible to reconcile their 600,000-year old age with a genetic date of modern human-Neandertal divergence of 400-800 thousand years.

Any further comments on the paper will be posted in this space after I read it.

UPDATE (Aug 15):

This is a very exciting paper that finally addresses the autosomal mutation rate controversy.

Previously, this rate was assessed by picking a split time for the chimp-human pair, and counting sequence divergence, dividing it by this time. But, this method led to circular reasoning: paleontologists looked at the (very fragmentary and controversial) early fossil record and assigned some arbitrary date to the split.

Then, when new fossils turned up that looked like they belonged to the human lineage but preceded the supposed split, their inclusion in the lineage leading to humans was rejected, on account of them being too old, pre-dating the supposed split!

A different approach is to use the directly observed mutation rate in families. This has been made possible due to the fall in the cost of sequencing. Subsequently, one divides sequence divergence with the mutation rate to obtain generations. But, how does one obtain years, instead of generations? A measure of generation length is needed.

And, this is the exciting and remarkable part: members of the team behind this paper didn't just "guess" the generation length in primates but actually observed primates in the wild, assigning hard parental ages where they could, or intervals where they could not. This was a decades-long process that gave us the best estimates of generation lengths to date.

Armed with this knowledge (directly observed generation lengths + directly observed mutation rates), they were able to go back in time and estimate the human-chimp divergence. Their answer?

As I have said before: this has implications. The authors do not touch on recent human history, except to point out that the Neandertal-human split harmonizes better with paleoanthropology:

analyses of the Neanderthal genome indicated a population split between present-day humans and Neanderthals at 270–440 ka (40). This date appears to conflict with fossil evidence tracing the emergence of Neanderthal morphological characters over the course of the Middle Pleistocene in Europe (41). The earliest evidence for Neanderthal traits was proposed to date to 600 +/- 66 ka at the Sima de Los Huesos (Atapuerca, Spain) (42), thus predating the genetically estimated population divergence times, but this date has been disputed on the basis of both the apparent conflict with the genetic data and on stratigraphic grounds (43). However, even if the early dates for Sima are disregarded, it is clear that fossils from oxygen isotope stage 11 (around 400 ka), such as the Swanscombe cranium, already show clear Neanderthal traits (44). Using the new human– chimpanzee split estimate and assuming generation times between 25 and 29 y would push back the human/Neanderthal split to 423,000–781,000 y, resolving this apparent conflict. 

The authors also propose that:

Whereas the earliest fossil universally accepted to belong to the lineage leading to present-day humans rather than to chimpanzees, Australopithecus anamensis, is 4.2 Ma (31) and thus reconcilable with a molecularly inferred human–chimpanzee split time as recent as 5 Ma, the attribution of late Miocene (5–7 Ma) fossils to the hominin lineage has posed a problem. Our estimates make it possible to reconcile attribution of fossils such as Ardipithecus kaddaba (5.2–5.8 Ma) (32), Orrorin tugenensis (6 Ma) (9), and Sahelanthropus tchadensis (6–7 Ma) (10) to the hominin lineage with speciation times inferred from genetic evidence (Fig. 1). However, our estimates cannot address the controversy of whether specimens such as these truly belong to the lineage leading to present-day humans or to other, closely related lineages (11). 

And, there are calibration points in more recent times that the authors do not consider, but will also support the new mutation rate/speciation time. For example, Gravel et al. obtained a 51ky Out-of-Africa, and sub-30ky dates for the European-Asian split using a mutation rate of 2.38x10^-8. Using the lower mutation rate will bring the European-Asian split up to the 40 thousands (consistent with the first appearance of AMH in both Europe and East Asia), and the OoA event to 100ky, consistent with the appearance of the Nubian Complex in Arabia and the Skhul/Qafzeh hominins in the Levant.

The new mutation rate will also affect other dates. Li and Durbin estimated a 100-120ky Yoruba-Eurasian divergence, but only by using a 2.5x10^-8 rate and explicitly rejecting the slower direct rate. We know for a fact that the major part of Yoruba ancestry is shared with Eurasians in the post-70ky time frame (Y-haplogroup E is part of clade CT, and most Yoruba mtDNA belongs to haplogroup L3, of which Eurasian N and M are branches). In order for a 100-120ky (or 200ky+ with the direct rate) divergence to be believable, only one possibility exists: that Yoruba trace their ancestry to a combination of post-70ky E/L3-bearing people who were quite close to Eurasians but also of a group of Palaeoafricans that split off from modern humans well before 200ky. And, I won't even go to the implications about African hunter-gatherers that are divergent from Eurasians by an even greater amount.

Enjoy the calm before the storm: if people start using the slow mutation rate (as they now must), a lot of the old certainties about our origins will be toppled.

PNAS doi: 10.1073/pnas.1211740109

Generation times in wild chimpanzees and gorillas suggest earlier divergence times in great ape and human evolution

Kevin E. Langergraber et al.

Fossils and molecular data are two independent sources of information that should in principle provide consistent inferences of when evolutionary lineages diverged. Here we use an alternative approach to genetic inference of species split times in recent human and ape evolution that is independent of the fossil record. We first use genetic parentage information on a large number of wild chimpanzees and mountain gorillas to directly infer their average generation times. We then compare these generation time estimates with those of humans and apply recent estimates of the human mutation rate per generation to derive estimates of split times of great apes and humans that are independent of fossil calibration. We date the human–chimpanzee split to at least 7–8 million years and the population split between Neanderthals and modern humans to 400,000–800,000 y ago. This suggests that molecular divergence dates may not be in conflict with the attribution of 6- to 7-million-y-old fossils to the human lineage and 400,000-y-old fossils to the Neanderthal lineage.

Link

Multiple species of early Homo

I will point you towards Hominid Hunting, the NY Times, and Nature for coverage of the paper. From the press release:

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.

I'm not competent enough to express an opinion, so I won't. Still, if there were two species living at that time, it would not be surprising; in the recent past where we do have more complete data, it seems that our Homo sapiens ancestors shared the planet with other quite divergent hominins. Perhaps this was the norm for the greater part of human prehistory, until evolution came up with us, and we came up with ideas (whether through love or war) to drive the rest of Homo to non-existence, leaving us as the only living twig of a quite bushy family tree.

Nature 488, 201–204 (09 August 2012) doi:10.1038/nature11322

New fossils from Koobi Fora in northern Kenya confirm taxonomic diversity in early Homo

Meave G. Leakey, Fred Spoor, M. Christopher Dean, Craig S. Feibel, Susan C. Antón, Christopher Kiarie & Louise N. Leakey

Since its discovery in 1972 (ref. 1), the cranium KNM-ER 1470 has been at the centre of the debate over the number of species of early Homo present in the early Pleistocene epoch2 of eastern Africa. KNM-ER 1470 stands out among other specimens attributed to early Homo because of its larger size, and its flat and subnasally orthognathic face with anteriorly placed maxillary zygomatic roots3. This singular morphology and the incomplete preservation of the fossil have led to different views as to whether KNM-ER 1470 can be accommodated within a single species of early Homo that is highly variable because of sexual, geographical and temporal factors4, 5, 6, 7, 8, 9, or whether it provides evidence of species diversity marked by differences in cranial size and facial or masticatory adaptation3, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20. Here we report on three newly discovered fossils, aged between 1.78 and 1.95 million years (Myr) old, that clarify the anatomy and taxonomic status of KNM-ER 1470. KNM-ER 62000, a well-preserved face of a late juvenile hominin, closely resembles KNM-ER 1470 but is notably smaller. It preserves previously unknown morphology, including moderately sized, mesiodistally long postcanine teeth. The nearly complete mandible KNM-ER 60000 and mandibular fragment KNM-ER 62003 have a dental arcade that is short anteroposteriorly and flat across the front, with small incisors; these features are consistent with the arcade morphology of KNM-ER 1470 and KNM-ER 62000. The new fossils confirm the presence of two contemporary species of early Homo, in addition to Homo erectus, in the early Pleistocene of eastern Africa.

Link

Morphometric analysis of Zuttiyeh (Freidline et al. 2012)

The Zuttiyeh specimen from Israel (unknown date, but between 500-200ka) is extremely important, because it was found in a region of the world in which the earliest co-existence of modern humans and Neandertals is attested. As such, it may be part of a population that led to either (or both) of these species; the population divergence of the Homo sapiens and Homo neandertalensis lineages intersects the 500-200ka range of this specimen.

A recent paper in the Journal of Human Evolution studied Zuttiyeh using geometric morphometric techniques.

Zuttiyeh (Zt) was compared with a wide range of other specimens from various periods, ranging from Homo erectus to modern humans. The PCA analysis is shown on the left. It is clear that Zuttiyeh clusters with Neandertals in Eurasia (open triangles), as well as "transitional" Homo sapiens from Africa (open squares: Florisbad Fl, 290-230ka from South Africa, and Jebel Irhoud 1 I1, 160ka from Morocco).

On the left (filled triangles) are various specimens assigned to Homo heidelbergensis, the presumed common ancestor of modern humans and Neandertals. For more on this, see Chris Stringer's recent overview article. But, this is no simple ancestor species: rather, it encompasses skulls that are very old (Bodo Bd; Ethiopia ca. 600ka), and very young (Dali Dl; China ca. 200ka). Indeed, Zhoukoudian 12 (Zh12; >500ka China) classified as Homo erectus appears quite modern in comparison to many of the heidelbergensis skulls.

On the right (crosses) are the modern humans, including UP Europeans, as well as, intriguingly Liujiang (Ljg), a modern human from China that may be 119-139ka old according to the people who dated it, but at least 68ka old. If the latter date is accepted, this would be within the error bars of the major 70ka Event that may correspond to the earliest colonization of Eurasia. If the former, then Liujiang will join the Qafzeh 9 specimen as an extremely modern pre-100ka find from Asia.

The Mount Carmel specimens (Qafzeh 6 Q6 and Skhul 5 Sk5; Levant 135-100ka) appear intermediate between H. heidelbergensis/H. neanderthalensis and H. sapiens but can usefully be called H. sapiens, since there are modern humans who appear as "left-shifted" as they are.

Intriguingly, Shanidar 5 (Sh5; ca. 50ka) a Neandertal appears to be much closer to H. sapiens than to his Neandertal brethren (including contemporaneous Sh1). This seems to be in line with a recent analysis of shoulder blades in which Shanidar 3 was included, as was a contemporaneous Vindija Neandertal (= the source of the Neandertal genome). It may well appear that late Neandertals were not diverging away from a modern humans, but rather changing from the ancestral heidelbergensis state in the same way that modern humans are.

A neglected possibility is that the late Neandertals, around the time of the apparent modern human Big Bang experienced gene flow from modern humans. This scenario was rejected in the original publication of the Neandertal genome on the basis of the idea that modern human admixture in Neandertals would have been modern non-African-like, because, presumably it was effected by a wave of Proto-Eurasians leaving Africa. But, if the Big Bang of human expansion occurred in Asia, perhaps in Arabia as it dried up post-70ka, as I have suggested, then modern human admixture could have affected late Neandertals.

The discriminant function analysis is also interesting:

The groups were defined a priori according to the population grouping shown in Table 1. Zuttiyeh as well as all transitional (Jebel Irhoud 1 and Florisbad), early (Skhul 5, Qafzeh 6 and Luijiang) and Upper Paleolithic H. sapiens were treated as individuals with unknown group affinities to be classified by posterior probabilities.

 Florisbad appears to be quite distinct here, while Skhul5 and Qafzeh6 are clearly on their way to becoming modern; Zhoukoudian 101 joins this group (13-33ka), but is about 70-100 thousand years younger. Apparently the population of modern humans in Eurasia pre-100ka was widespread. Individuals of regular modern aspect appear post-70ka Event in both West and East Eurasia (Zh102 and Liujiang, assuming the latter is 68ka old). They probably appear in Africa as well probably in Africa as well.

Sadly, neither Hofmeyr, nor Omo I/II and Herto were included in this analysis. All of the above are often mentioned in connection to modern human origins. So is Kabwe (Broken Hill; Homo rhodesiensis) which is listed here as 700-400ka but may in fact be much younger. Jebel Irhoud 1 a "transitional" Homo sapiens from Morocco seems to have a long way to go to transition to a fully modern shape. Both Amud 1 (Am1; a big-brained late Neandertal from the Levant 50ka) and the aforementioned Shanidar 5 appear just as modern as Irhoud 1.

Can we make any sense of these various facts? I will list some observations:

• Zuttiyeh appears linked to Neandertal and transitional H. sapiens. It is unclear where to place it, except to say that it is an archaic-looking human who is in the process of evolving in the same direction that both Neandertals and modern humans did.
• There does not appear to be any good evidence in this data that H. heidelbergensis underwent a split that led to modern humans and Neandertals. On the contrary, often younger skulls appear more archaic than older ones, and skulls from the same period/region seem to occupy different positions in the archaic/modern range.
• Modern humans appear distinctive, with their closest pre-100ka relatives being the Mt. Carmel hominins from the Levant (Skhul and Qafzeh), as well as, intriguingly, late Near Eastern Neandertals (Amud and Shanidar)

Even during the last 50ky, there seems to have been elevated diversity in modern humans. Zhoukoudian 101 from this study appears to be one example of unusual morphology for so late a specimen; recent discoveries from China and Sub-Saharan Africa point to the same phenomenon.

I continue to think that within the Homo heidelbergensis lineage there was progress towards more modern forms throughout the old world. But, this progress did not replace the older forms; nor did it materialize as obviously divergent lineages. The last few hundred thousand years appear very much like a serious of experiments that lead in some vague way to something akin to us. There probably was a long, drawn-out road to us.

In Africa, the Near East, and Asia, there was a co-existence of quite divergent forms; even Europe, long-considered the exclusive abode of Neandertals, there apparently lived humans  that did not possess the derived Neandertal morphology.

The simple story of our origins is that our common ancestor H. heidelbergensis split into an African and Eurasian lineage that eventually evolved into H. sapiens and H. neanderthalensis, and finally the former replaced the latter, with perhaps a little admixture along the way.

It would appear that aspects of modernity appeared throughout the Old World during the last few hundred thousand years. Perhaps (as the multi-regionalists would have it), this was facilitated by gene flow between distant human groups; alternatively, H. heidelbergensis already had the seeds of his future evolution, and similar solutions were found for similar selective pressures independently.

For the time being, we must probably accept the fact that a great variety of human groups of the last 500,000 years at least have contributed to modern mankind. Only isolated groups like Homo floresiensis who disappeared before having the chance to affect us may have escaped the honor of being our ancestors. But, it also seems that much of our ancestry does come from a unique population emerging somewhere within that broader milieu. Where this population lived and why it became so successful is an open problem, but, until there is evidence to the contrary, I would say that my two deserts theory, as elaborated here, may be a reasonably candidate.

Journal of Human Evolution Volume 62, Issue 2, February 2012, Pages 225–241

A comprehensive morphometric analysis of the frontal and zygomatic bone of the Zuttiyeh fossil from Israel

S.E. Freidline et al.


The Zuttiyeh hominin craniofacial fossil was discovered in Israel in 1925. Radiometric dates and the archaeological context (Acheulo-Yabrudian) bracket the associated cave layers to between 200 and 500 ka (thousands of years ago), making it one of the earliest cranial fossils discovered in the Near East thus far. Its geographic position, at the corridor between Africa and Eurasia, in combination with its probable Middle Pleistocene date make it a crucial specimen for interpreting later human evolution. Since its discovery, qualitative descriptive and traditional morphometric methods have variously suggested affinities to Homo erectus (Zhoukoudian), Homo neanderthalensis (Tabun), and early Homo sapiens (Skhul and Qafzeh). To better determine the taxonomic affinities of the Zuttiyeh fossil, this study uses 3D semilandmark geometric morphometric techniques and multivariate statistical analyses to quantify the frontal and zygomatic region and compare it with other Middle to Late Pleistocene African and Eurasian hominins.

Our results show that the frontal and zygomatic morphology of Zuttiyeh is most similar to Shanidar 5, a Near East Neanderthal, Arago 21, a European Middle Pleistocene hominin, and Skhul 5, an early H. sapiens. The shape differences between archaic hominins (i.e., Homo heidelbergensis and H. neanderthalensis) in this anatomical region are very subtle.

We conclude that Zuttiyeh exhibits a generalized frontal and zygomatic morphology, possibly indicative of the population that gave rise to modern humans and Neanderthals. However, given that it most likely postdates the split between these two lineages, Zuttiyeh might also be an early representative of the Neanderthal lineage. Neanderthals largely retained this generalized overall morphology, whereas recent modern humans depart from this presumably ancestral morphology.


Link (pdf)

Gilbert on erectus, Klein on sapiens

This is a very interesting and information-rich talk by Henry Gilbert on Homo erectus and the Acheulean. A must-watch.

 

A second talk by Richard Klein on Homo sapiens and Out-of-Africa. Klein has featured in a mini-controversy regarding the recent evidence for archaic admixture in Africans, so it is interesting to get a concise overview of his opinions. I absolutely agree with him that "something big" happened at around 50,000 years ago, and I share his skepticism about signs of earlier behavioral modernity in Europe and Africa alike. I also agree with him that this "something" involved a migration of people. Where we part ways is that I do not share his conviction that this was an Out-of-Africa event. For several reasons:

• Eurasian mtDNA mega-haplogroups coalesce before 50ky
• Y-haplogroup CT coaelesces before 50ky, although some suggest (wrongly in my opinion) that it is of African origin
• Genetic divergence times between West Africans and Eurasians exceed 100ky; with hunter-gatherers they are even higher
• There is clear evidence of archaic admixture not only in Eurasians but also in Africans
• There does not seem to be clear temporal priority in any region with respect to the appearance of the 50ky Event

 

Homo floresiensis: dramatically dwarfed Homo erectus descendant

Journal of Human Evolution doi:10.1016/j.jhevol.2011.08.008

Craniofacial morphology of Homo floresiensis: Description, taxonomic affinities, and evolutionary implication

Yousuke Kaifu et al.

This paper describes in detail the external morphology of LB1/1, the nearly complete and only known cranium of Homo floresiensis. Comparisons were made with a large sample of early groups of the genus Homo to assess primitive, derived, and unique craniofacial traits of LB1 and discuss its evolution. Principal cranial shape differences between H. floresiensis and Homo sapiens are also explored metrically.

The LB1 specimen exhibits a marked reductive trend in its facial skeleton, which is comparable to the H. sapiens condition and is probably associated with reduced masticatory stresses. However, LB1 is craniometrically different from H. sapiens showing an extremely small overall cranial size, and the combination of a primitive low and anteriorly narrow vault shape, a relatively prognathic face, a rounded oval foramen that is greatly separated anteriorly from the carotid canal/jugular foramen, and a unique, tall orbital shape. Whereas the neurocranium of LB1 is as small as that of some Homo habilis specimens, it exhibits laterally expanded parietals, a weak suprameatal crest, a moderately flexed occipital, a marked facial reduction, and many other derived features that characterize post-habilis Homo. Other craniofacial characteristics of LB1 include, for example, a relatively narrow frontal squama with flattened right and left sides, a marked frontal keel, posteriorly divergent temporal lines, a posteriorly flexed anteromedial corner of the mandibular fossa, a bulbous lateral end of the supraorbital torus, and a forward protruding maxillary body with a distinct infraorbital sulcus. LB1 is most similar to early Javanese Homo erectus from Sangiran and Trinil in these and other aspects. We conclude that the craniofacial morphology of LB1 is consistent with the hypothesis that H. floresiensis evolved from early Javanese H. erectus with dramatic island dwarfism. However, further field discoveries of early hominin skeletal remains from Flores and detailed analyses of the finds are needed to understand the evolutionary history of this endemic hominin species.

Link

Homo erectus soloensis fades into the past...

Every year or so there seems to be a redating of a key fossil in human evolution. It's nice to see scientific self-correction in action, and soon after Neandertals got a little older, casting doubt on their supposedly long co-existence with modern humans, we now have a redating of Homo erectus soloensis from Java to about 150-550 thousand years ago, but certainly long before there were any anatomically modern humans in the area.

PLoS ONE 6(6): e21562. doi:10.1371/journal.pone.0021562

The Age of the 20 Meter Solo River Terrace, Java, Indonesia and the Survival of Homo erectus in Asia

Etty Indriati et al.

Homo erectus was the first human lineage to disperse widely throughout the Old World, the only hominin in Asia through much of the Pleistocene, and was likely ancestral to H. sapiens. The demise of this taxon remains obscure because of uncertainties regarding the geological age of its youngest populations. In 1996, some of us co-published electron spin resonance (ESR) and uranium series (U-series) results indicating an age as young as 35–50 ka for the late H. erectus sites of Ngandong and Sambungmacan and the faunal site of Jigar (Indonesia). If correct, these ages favor an African origin for recent humans who would overlap with H. erectus in time and space. Here, we report 40Ar/39Ar incremental heating analyses and new ESR/U-series age estimates from the “20 m terrace" at Ngandong and Jigar. Both data sets are internally consistent and provide no evidence for reworking, yet they are inconsistent with one another. The 40Ar/39Ar analyses give an average age of 546±12 ka (sd±5 se) for both sites, the first reliable radiometric indications of a middle Pleistocene component for the terrace. Given the technical accuracy and consistency of the analyses, the argon ages represent either the actual age or the maximum age for the terrace and are significantly older than previous estimates. Most of the ESR/U-series results are older as well, but the oldest that meets all modeling criteria is 143 ka+20/−17. Most samples indicated leaching of uranium and likely represent either the actual or the minimum age of the terrace. Given known sources of error, the U-series results could be consistent with a middle Pleistocene age. However, the ESR and 40Ar/39Ar ages preclude one another. Regardless, the age of the sites and hominins is at least bracketed between these estimates and is older than currently accepted.

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Erectus out of Georgia?

From a Nature News story on the article:

The presence of a tool-using population on the edge of Europe so early hints that the northern continent, rather than Africa, may have been the evolutionary birthplace of H. erectus. Unfortunately, the fossils of the hominins responsible for making the tools are not proving very helpful to the debate.

Fossilized bone fragments found in the same sedimentary layers as the Dmanisi artefacts are too weathered to be identified as belonging to any one species, so it is impossible to say for sure whether the tools were made by H. erectus.

Neither do fossil skulls previously retrieved from later sediments at the site help to resolve the controversy. These fossils, dating from 1.77 million years ago, had brains between 600 and 775 cubic centimetres in volume, whereas H. erectus is generally thought to have had an average brain size of around 900 cubic centimetres. For comparison, modern humans have a brain capacity of around 1,350 cubic centimetres. "Many people call those Dmanisi fossils the earliest H. erectus, but there is still frequent debate about this," explains Ferring.

PNAS doi: 0.1073/pnas.1106638108

Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85–1.78 Ma

Reid Ferring et al.

The early Pleistocene colonization of temperate Eurasia by Homo erectus was not only a significant biogeographic event but also a major evolutionary threshold. Dmanisi's rich collection of hominin fossils, revealing a population that was small-brained with both primitive and derived skeletal traits, has been dated to the earliest Upper Matuyama chron (ca. 1.77 Ma). Here we present archaeological and geologic evidence that push back Dmanisi's first occupations to shortly after 1.85 Ma and document repeated use of the site over the last half of the Olduvai subchron, 1.85–1.78 Ma. These discoveries show that the southern Caucasus was occupied repeatedly before Dmanisi's hominin fossil assemblage accumulated, strengthening the probability that this was part of a core area for the colonization of Eurasia. The secure age for Dmanisi's first occupations reveals that Eurasia was probably occupied before Homo erectus appears in the East African fossil record.

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