Lessons of Homo naledi

New discoveries of fossilised hominin remains have to varying degrees helped to shape our ever-morphing interpretation of hominin evolution. Homo naledi is a case in point.

Though many worker in the field of palaeoanthropology were disappointed with the confirmed Middle Pleistocene age of the Dinaledi remains, this news nevertheless fills a void in our understanding of Middle Pleistocene evolution.

H. naledi confirms what we have known since the astonishing discovery of Homo floresiensis, namely that small brained hominins continued to thrive in some part of the planet right up to recent times. H. naledi can now join Homo floresiensis in the small brain Middle to Late Pleistocene club.

Palaeoanthropologist can now exercise a high level of skepticism on dating hominin fossilised remains using morphological stucture and statistics. In 2015, palaeoanthropologist John Francis Thackeray concluded Homo naledi to be over 1.5 Ma, while Mana Dembo and her colleagues concluded an age of 930,000 years of age for the Rising Star remains. Though Dembo et al were closer to actual age of the remains, they were still nearly 600,000 years off.

Finally, H. naledi continues to confirm what we have known since the announcement of Australopithecus sediba that hominin evolution features an ever changing mosasicism. With Australopithecine-like shoulders and cranium, while the lower limbs and foot appears more derived.

Middle Pleistocene Homo naledi

John Hawks discusses the latest news on the Rising Star Project:

Africa’s richest fossil hominin site has revealed more of its treasure. It’s been a year and a half since scientists announced that a new hominin species, which they called Homo naledi, had been discovered in the Rising Star Cave outside Johannesburg.

Now they say they have established and published the age of the original naledi fossils that garnered global headlines in 2015. Homo naledi lived sometime between 335 and 236 thousand years ago, making it relatively young.

They’ve also announced the discovery of a second chamber in the Rising Star cave system, which contained additional Homo naledi specimens. These include a child and the partial skeleton of an adult male with a well-preserved skull. They have named the skeleton “Neo” – a Sesotho word meaning “a gift”.

The Conversation Africa’s Science Editor Natasha Joseph asked Professor John Hawks, a member of the team, to explain the story behind these finds.

To an ordinary person, 236 000 years is a very long time ago. Why does the team suggest that in fact, Homo naledi is a “young” species?

The course of human evolution has taken the last seven million years since our ancestors diverged from those of chimpanzees and bonobos. The first two-thirds of that long history, called australopiths, were apelike creatures who developed the trick of walking upright on two legs.

Around two million years ago some varieties of hominins took the first real steps in a human direction. They’re the earliest clear members of our genus, Homo, and belong to species like Homo habilis, Homo erectus and Homo rudolfensis.

Homo naledi looks in many ways like these first members of Homo. It’s even more primitive than these species in many ways, and has a smaller brain than any of them. People outside our team who have studied the fossils mostly thought they should be around the same age. A few had the radical idea that H. naledi might have lived more recently, maybe around 900,000 years ago.

Nobody thought that these fossils could actually have come from the same recent time interval when modern humans were evolving, a mere 236 to 335 thousand years ago.

How do you figure out a fossil’s age?

We applied six different methods. The most valuable of these were electron spin resonance (ESR) dating, and uranium-thorium (U-Th) dating. ESR relies on the fact that teeth contain tiny crystals, and the electron energy in these crystals is affected by natural radiation in the ground over long periods of time after fossils are buried.

U-Th relies on the fact that water drips into caves and forms layers of calcite, which contain traces of uranium. The radioactive fraction of uranium decays into thorium slowly over time. So the proportion of thorium compared to uranium gives an estimate of the time since the calcite layers formed. One of these calcite deposits, called a flowstone, formed above the H. naledi fossils in the Dinaledi Chamber. That flowstone helps to establish the minimum age: the fossils must be older than the flowstone above them.

For these two methods, our team engaged two separate labs and asked them to process and analyse samples without talking to each other. Their processes produced the same results. This gives us great confidence that the results are reliable.

What does the discovery of Homo naledi’s age mean for our understanding of human history and evolution?

For at least the past 100 years, anthropologists have assumed that most of the evolution of Homo was a story of progress: brains got bigger over time, technology became more sophisticated and teeth got smaller as people relied more upon cleverness to get better food and prepare it by cooking.

We thought that once culture really got started, our evolution was driven by a feedback loop – better food allowed bigger brains, more clever adaptations, more sophisticated communication. That enabled better technology, which yielded more food, and so on like a snowball rolling downhill.

No other hominin species could compete with this human juggernaut. You would never see more than one form of human in a single part of the world, because the competition would be too intense. Other forms, like Neanderthals, existed within regions of the world apart from the mainstream leading to modern humans in Africa. But even they were basically human with large brains.

That thinking was wrong.

Africa south of the equator is the core of human evolutionary history. That’s where today’s human populations were most genetically diverse, and that diversity is just a small part of what once existed there. Different lineages of archaic humans once lived in this region. Anthropologists have found a few fossil remnants of these archaic populations. They’ve tried to connect those remnants in a straight line. But the genetic evidence suggests that they were much more complex, with deep divisions that occasionally intertwined.

H. naledi shows a lineage that existed for probably more than a million years, maybe two million years, from the time it branched from our family tree up to the last 300,000 years. During all this time, it lived in Africa with archaic lineages of humans, with the ancestors of modern humans, maybe with early modern humans themselves. It’s strikingly different from any of these other human forms, so primitive in many aspects. It represents a lost hominin community within which our species evolved.

I think we have to reexamine much of what we thought we knew about our shared evolutionary past in Africa. We know a lot of information from a few very tiny geographic areas. But the largest parts of the continent are unknown – they have no fossil record at all.

Explorers Mathabela Tsikoane, Maropeng Ramalepa, Dirk van Rooyen, Steven Tucker (seated), and Rick Hunter (seated) inside the Rising Star cave system. Wits University/Marina Elliott

We’re working to change that, and as our team and others make new discoveries, I’m pretty sure we are going to find more lineages that have been hidden to us. H. naledi will not be the last.

The first Homo naledi discoveries were made in the Dinaledi Chamber. What led researchers to the second chamber? And what did you find there?

The Dinaledi Chamber is one of the most significant fossil finds in history. After excavating only a very tiny part of this chamber, the sample of hominin specimens is already larger than any other single assemblage in Africa.

The explorers who first found these bones, Rick Hunter and Steven Tucker, saw what the team was doing when they were excavating in the chamber. The pair realised that they might have seen a similar occurrence in another part of the cave system. The Rising Star system has more than two kilometres of mapped passages underground. In another deep chamber, accessed again through very tight underground squeezes, there were hominin bones exposed on the surface.

Our team first began systematic survey of this chamber, which we named the Lesedi Chamber, in 2014. For two years Marina Elliott led excavations, joined at times by most of the team’s other experienced underground excavators. They were working in a situation where bones are jammed into a tight blind tunnel. Only one excavator can fit at a time, belly-down, feet sticking out. It is an incredibly challenging excavation circumstance.

Geologist Dr Hannah Hilbert-Wolf studying difficult to reach flowstones in a small side passage in the Dinaledi Chamber. Wits University

The most significant discovery is a partial skeleton of H. naledi, with parts of the arms, legs, a lot of the spine and many other pieces, as well as a beautifully complete skull and jaw. We named this skeleton “Neo”. We also recovered fragments of at least one other adult individual, and one child, although we suspect these bones may come from one or two more individuals.

Is there a way for people to view these discoveries in person?

On May 25 – Africa DayMaropeng at the Cradle of Humankind World Heritage Site outside Johannesburg will open a new exhibit with the discoveries from the Lesedi Chamber and the Dinaledi Chamber together for the first time.

For people outside South Africa, the data from our three-dimensional scans of the new Lesedi fossils are available online.

Anyone can download the 3D models, and people with access to a 3D printer can print their own physical copies of the new fossils, as well as the fossils from the Dinaledi Chamber. It’s a great way for people to see the evidence for themselves.

Reprint from The Conversation

Doctoral student addresses critics of the Cerutti Mastodon Controversary

An anonymous doctoral student associated with the Cerutti Mastodon research addresses critics on Reddit as follows:

First off, my qualifications: My current advisor is the third author on this paper and I worked under (and collaborated with) the second author when I worked at the San Diego Natural History Museum (in fact, I re-prepared some of the material in this paper about 6 years ago). Furthermore, I am a doctoral student in the final months (hopefully) of my PhD. My dissertation work has been on proboscideans (elephants and their relatives), but I have also done a fair amount of work on cetaceans (whales) and other vertebrates.

As far as the dating methods go, this site was dated using multiple types of absolute dating methods, which all resulted in a very similar age. However, the Uranium-series dating (not to be confused with radiocarbon dating, which could not give you an accurate age this old) that was used here got results with a very high confidence. In fact there is essentially no evidence of alteration that might lead to an older date (which really would not be common anyways). The dates recovered are almost unimpeachable (and I don’t say that lightly). I would be very surprised if a geochronologist or any other expert had a major problems with the dates themselves (in fact a geochronologist was a reviewer for this paper for just this reason). Also, to the people that are saying that it is perhaps time to reassess our methods of isotopic dating in general, I strongly suggest you spend more time researching and trying to understand these methods before you make a claim like this…

One other misconception that I keep seeing here are peoples’ interpretation of what is meant by “human” in this paper. “Human” is meant here in the sense of a species of the genus Homo, not necessarily Homo sapiens specifically. In fact, because of the old age it seems fairly unlikely that this would be the modern species of human rather than some other [unknown] species.

I’m sure there will be other questions or comments here throughout the next day or so, and I will try to check in from time to time and update this post. I’m also happy to answer any questions that I can (to the best of my knowledge).

Edit 1: To the folks wondering if this site could have been scavenged by humans (as opposed to hunted), I would say that, that is absolutely possible. In fact there is really no evidence one way or another to argue for hunting over scavenging at this site, and I don’t believe that this paper takes a stance on this either. In fact, I would say that the argument of hunting vs scavenging in association with this mastodon is somewhat irrelevant. What is important is that this extremely old site (relatively speaking, anyways) has fairly clear association with ancient human activity.

Edit 2: Several people have pointed out that the article discusses a lack of evidence of meat stripping on the specimen. This does suggest scavenging, as it likely means the soft tissue was at least somewhat rotted and not usable.

Edit 3: Many people are suggesting that this animal could have been scavenged or had its bones modified many thousands of years after its death (i.e., implying the tools are much younger than the mastodon). To that point 1) the type of breakage seen on these bones is indicative of damage while the bone was still fresh. Fresh bone (sometimes called “green bone”) breaks in a very different “spiral pattern” than older dried out bone; and 2) you have to remember that the sediments that the tools and mastodon are found in represent the context in which they were buried. Therefore since these materials were all found within the same layer they must have been buried at the same time. It is possible that ancient humans exhumed old bones (though I know of no actual evidence of this), but we would see telltale signs of disturbance to the sediment (which was not observed here).
In other words, I don’t think that arguments about this site will come down to whether the material is associated and coeval, but whether folks think that these artifacts are indeed stone tools. Those people who do not agree with this identification will then have to reconcile the crazy taphonomy at this site and attribute it to some other natural process (which will be no small feat, IMHO).

Edit 4: For the people asking why we don’t have any evidence of humans (or human remains) in North America in the time between the age of this site and more generally accepted dates:

First off, I would just like to note that we are almost certainly not talking about a direct lineage of humans between the time of this site and those of Clovis times (in fact, as I’ve stated above, we are likely not even talking about the same species). This was likely a very small population of humans that made it to North America that probably died out long before the modern species of human ever made it over. In that sense, there isn’t necessarily a gap of time to “bridge”.

As for why potential sites might not be preserved: There are a couple of reasons that you might not have evidence of humans found from this time. First off, you may not have rocks of the right age readily exposed in the region where the individuals were living (which is somewhat the case on the west coast, as far as I am aware). Second, the individuals could be living in an environment that is not conducive to preserving fossils (e.g., organisms that live in montane environments tend to not preserve in the fossil record because sediments are not being deposited in those regions). Third, getting preserved in the fossil record (in general) is very rare, and if your study organism has a very small population size or is short lived (as we would expect in the case here) then you have a very very low probability of being preserved (let alone found and collected). Finally, even if these scenarios aren’t the case, there is the possibility that scientists have just been looking in the wrong strata, region, or age.

Three reasons the Cerutti Mastodon was not manipulated by hominins

A team of scientists recently announced an extraordinary claim that the 130,000 Cerutti Mastodon was manipulated by hominins.

“I have read that paper and I was astonished by it,” archaeologist Donald Grayson of the University of Washington. “I was astonished not because it is so good, but because it is so bad. Cracked bones and chipped stones at a fossil site might mean anything”, said Grayson. “It is quite another thing to show that people, and people alone, could have produced those modifications. The study doesn’t take that step, he said, “making this a very easy claim to dismiss.”

Gary Haynes of the University of Nevada Reno had this to say, “The paper states that the bones were being exposed by a backhoe. These pieces of heavy equipment weigh seven to fifteen tons or more, and their weight on the sediments would have crushed bones and rocks against each other.” When asked, Holen, the study leader, said that it “was very easy to tell the difference” between fractures made by stone hammers and those seen in bones crushed by bulldozers. He did not elaborate on how the differences manifest. “He’s pretty much dead wrong — there’s no definable difference,” Haynes said. A similar fossil dispute broke out in 2015 over a 24,000 year old mammoth in Maryland, he noted, shown to be fractured by heavy equipment. Also troubling, the “hammer” and “anvil” stones described in the paper don’t unequivocally look like tools, said Michael Waters of Texas A&M’s Center for the Study of the First Americans.

Michael Waters of Texas A&M’s Center for the Study of the First Americans noted that the “hammer” and “anvil” stones described in the paper don’t unequivocally look like tools. The study also runs afoul of the mounting genetic evidence, which indicates that the first people to reach the Americas and eventually give rise to modern Native Americans arrived no earlier than 25,000 years ago.”

National History Symposium of North Korea 2016

On the 28th of November 1976, Eternal Leader of North Korea, Kim Il Sung, ordered the Kim Il Sung University to investigate the origins of the Korean people. Since then, both Kim Il Sung and his son Kim Jong Il have proposed hypotheses to explain the origin of the Korean people and their history. On the 28th of November 2016, exactly 40 years later, a National History Symposium was held in Kim Il Sung University to take account of all the research that had been conducted within the country until now.

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Kim Il Sung University, Pyongyang, North Korea

The outside world has not been informed of these advances to a very clear level, but what we do know is that there is evidence that the Korean peninsula featured hominins by about the Upper Palaeolithic. According to the Pyongyang Times, Korean ancestors had settled down in the Taedong Basin around the present day capital Pyongyang “at the dawn of human history”.

palaeolithic-of-north-korea
State of Korean Palaeoanthropology in the year 2000. List of 45 Palaeolithic sites on the Korean Peninsula (Norton, 2000)

University President, Thae Hyong Chol and Minister of Higher Education, Ri Hye Jong both attended, but the current Leader of North Korea, Kim Jong Un was not present.

A number of people spoke at the Symposium, including:

  • University Dean: Choe Su Nam,
  • Laboratory Technician: Han Kum Sik and
  • Deputy Director of the National Authority for the Protection of Cultural Heritage: Ro Chol Su,
  • Director of the Academy of Social Sciences: Son Su Ho
  • Kim Hyong Jik University Lecturer: Jon Ryong Ho.
    5-1
    A glimpse into the National History Symposium held at Kim Il Sung University

     

     

The First Human Epidemic: Late Pleistocene Origin?

Current models of infectious disease in the Pleistocene tell us little about the pathogens that would have infected Neanderthals (Homo neanderthalensis). High quality Altai Neanderthal and Denisovan genomes are revealing which regions of archaic hominin DNA have persisted in the modern human genome. A number of these regions are associated with response to infection and immunity, with a suggestion that derived Neanderthal alleles found in modern Europeans and East Asians may be associated with autoimmunity. Independent sources of DNA-based evidence allow a re-evaluation of the nature and timing of the first epidemiologic transition. The paradigm of the first epidemiologic transmission, the hypothesis that epidemic disease did not occur until the transition to agriculture, with larger, denser and more sedentary populations, has been essentially unchallenged since the 1970s. Our views of the infectious disease environment of the Pleistocene period are heavily influenced by skeletal data and studies of contemporary hunter-gatherers. New genetic data – encompassing both hosts and pathogens – has the power to transform our view of the infectious disease landscape experienced by Neanderthals in Europe, and the anatomically modern humans (AMH) with whom they came into contact. The Pleistocene hominin environment cannot be thought of as free from infectious disease. It seems likely that the first epidemiologic transition, envisaged as part of the package of the Holocene farming lifestyle, may be fundamentally different in pace or scope than has previously been suggested. This paper demonstrates how high quality genomic data sets can be used to address questions arisingfrom the ecological context that shaped the co-evolutionary relationship we share with infectious diseases. We analyse the evidence for infectious disease in Neanderthals, beginning with that of infection-related skeletal pathologies in the archaeological record, and then consider the role of infection in hominin evolution. We have synthesised current models on the chronology of emergence of notable European disease packages and analyse what implications this evidence has for the classical model of the first epidemiologic transition. Using emerging data from Neanderthal palaeogenomics and combining this with fossil and archaeological information we re-examine the impact of infectious diseases on human populations from an evolutionary context. These palaeogeneticists argue that the first epidemiologic transition in Eurasia was not as tightly tied to the onset of the Holocene as has previously been assumed. There is clear evidence to suggest that this transition began before the appearance of agriculture and occurred over a timescale of tens of thousands of years. We suggest that the epidemiological transition was not, as has been thought since the 1970s, a phenomenon of the human shift to sedentary agriculture during the Holocene but a much older and more complex process that involved at least two species of humans. The origin of resistance to infectious disease has a much deeper timeframe and is highlighted by the ingression of Neanderthal DNA into modern human lineages. The transfer of pathogens between human species may also have played a role in the extinction of the Neanderthals. Our analysis of the genomes of archaic hominins provides evidence of pathogens acting as a population-level selection pressure, causing changes in genomes that were passed on to descendants and preserved in the genomes of modern Eurasians. the analysis of ancient genomes demonstrates that human behavioural patterns (in this case a shift to agricultural subsistence) should not be used as an ecological proxy to explain shifting trends in the co-evolutionary relationship between pathogens and human populations.

This work is available on BioRxiv: http://dx.doi.org/10.1101/017343

Acknowledgements: Rob Foley, Marta Lahr and the members of the Human Evolutionary Science Discussion Group at the University
of Cambridge. Funding for this research was provided by King’s College Cambridge and UCL.

The 1,000,000 year old child of Ngrejeng, Indonesia

NG 8503
Date Found: March 1985
Found By: Ngrejeng Villager
Locality: Near Ngrejeng Village, Indonesia
Announced: 1994
Fossil: Partial mandible (Right side), with M1 and M2. The latter had not yet erupted at time of death.
Age: 1.02 – 1.51 million years of age

Papers to check out:

1994 – Aziz et al – Preliminary report on recent
discoveries of fossil hominids from the Sangiran area, Java.

2005 – Kaifu et al – Hominid mandibular remains from Sangiran (1952-1986) Collection

2006 – Kaifu – Advanced dental reduction in Javanese Homo erectus

2011 – Wood – Encyclopedia of Human Evolution

Returning Kabwe Man To Zambia: Renewed Efforts for 2015

Everybody has heard of the Elgin Marbles and the debate surrounding the right’s of countries to those artefacts. These marbles are famous the world over but this story is repeated many more times not just in archaeology, but palaeoanthropology also.  Zambia was once a colony of the British Empire and it was during that time that a certain hominin skull E 686 was uncovered. This skull Mr-Kabimba-with-Hon.-Susan-Kawandami-in-Kaoma-for-the-Kazanga-ceremony-is now lies in the vaults of the South Kensington Museum, London. In Zambia, Deputy Minister Susan Kawandami (pictured) recently reported before the Zambian Parliament that years of talks failed to secure the return of E 686 to Zambia with the Natural History Museum, London prepared to make copies of the skull instead. Kawandami will now establish new discussions through UNESCO, while Minister of Chiefs and Traditional Affairs, Nkandu Luo will visit London to establish a dialogue with the Trustees of the Museum.

E 686

If the Natural History Museum is ever to return the fossil, one thing is for sure, Zambia will have to convince the London Museum, that it is proactive in heritage (particularly palaeoanthropological) promotion and will ensure great care for the priceless skull. Which is currently not the case. The famed locality has no interpretative centre, no sign, no indication that two pivotal hominin bones – E 686 (Skull) and E 691 (tibia), were uncovered there. On the 17th of June 1921, A. S. Armstrong and A. W. Whittington uncovered those remains at Mutwe wa Nsofu, Mulungushi Road, Kabwe, Zambia. That same year, the fossils were given a new human species name – Homo rhodesiensis. This species has, thus far, only ever been found in Africa and it is a species that is seldom used by palaeoanthropologists. Most consider it a variation of Homo heidelbergensis. A key species that diverged into Homo sapiens (in Africa) and Homo neanderthalensis (in Europe). From about 1.5 million to 500,000 years ago, is a time that palaeoanthropologists have difficulty understanding due to the particularly patchy fossil record. So, what I have described is quite simplistic and many would argue over the exact details. The two fossils represent two adults males, that lived around 1 million years ago. Sadly, given they were found in the 1920’s, excavations in the field of human evolution were in their infancy and so, grossly inaccurate. The only way to date the site was through biostratigraphy. By looking at the animals that were found in the layers in which the fossils were found, later palaeoanthropologists compared those assemblages to strata at other sites which were radiometrically dated. The Kabwe stratigraphy was quite similar to Bed IV at the Oldupai Gorge which was dated to between 780,000 years to 1.3 million years.

homo_heidel_655_fs
E 686 (Kabwe 1) fleshed out in this hyper-realistic reconstruction by John Gurche (http://www.gurche.com)

Zambia’s National Heritage and Conservation Commission (NHCC) is now in the process of rehabilitating the site. Chief executive officer of the commission, Collins Chipote warned that though the site was intact, it needs to be secured and developed. A Kabwe Mining museum was commissioned by Nkandu-LuoMinster Nkandu Luo (pictured), which will be run by the Lead-Zinc Mining company Enviro-Processing Ltd. a subsidary of the giant Berkeley Mineral Resources PLC. More effort is required on the part of Zambia to show that they have the determination to celebrate their priceless heritage and right now, there seems to be no action, but plenty of talking.