About Dirk

As curator of anthropology, Dirk is responsible for the museum’s artifact collection and is involved in its temporary and permanent anthropology exhibits. Dirk is an expert in human cultures; he curates the Museum’s Hall of the Americas and specializes in native American cultures like the Aztec and Maya.

A New Branch: How anthropologists added Homo naledi to our family tree

In a well-deserved world-wide wave of publicity, the existence of a new hominid species was announced recently. Fossil hominins were first recognized in the Dinaledi Chamber in the Rising Star Cave system in October 2013. Now, some two years later, and after exhaustive analysis of more than 1,500 bone fragments, the team decided to go public with this first milestone: the identification of a new human ancestor.

A selection of these bones have been scanned and uploaded to the internet. They also wrote up their findings and published them in an open-access source, eLife, rather than more established channels such as Nature or Science. (A brief side note: as can be seen in this video, one of the thirty specialists involved in the initial evaluation of these remains was Viktor Deak, who was part of the Houston Museum of Natural Science’s team putting together the Lucy’s Legacy exhibit as well as the section on human evolution in the museum’s Morian Hall of Paleontology.)


Fossilized bones discovered in Rising Star Cave in South Africa belong to a new species of hominid.

While social media are currently lit up with all kinds of references to this new species, it might be interesting to address this fundamental question: how does one define a new
hominid species? In other words: “Why is naledi called naledi?“

A starting point in this process is to identify a type specimen. Such a specimen is described in great detail, listing the similarities to and differences from closely related species. There is no central authority that decides on the validity of a species. Rather, this depends on the acceptance of such a designation within the scientific world. New discoveries and more information have given impetus to revisit previous species designations and change them.

As a result, “[i]f two type specimens are later determined to belong to the same species, then the first one named takes priority. For example, when it was decided that the 2nd known australopithecine fossil, assigned to Plesianthropus transvaalensis, actually belonged to the same species as the first that name became invalid and all Plesianthropus fossils were reassigned to Australopithecus africanus.


Skull fragments from the holotype specimen show Homo naledi had a brain about the size of an orange.

If it is decided that the fossils previously assigned to a species actually belong to two different species, then the type specimen and any other specimens belonging to the same species as it keep the old name. The other fossils will take the name of whichever specimen among them is first used as a type specimen for a new species definition. An example is Homo habilis (type specimen OH 7); the species Homo rudolfensis, with type specimen ER 1470, consists of fossils formerly assigned to habilis.”

This new species belongs to the genus Homo. Traditionally, one is a member of that genus if the following criteria are met (Since these are set by human researchers, they are subject to periodic re-evaluation):

  • Brain size: at least 600 cubic cm.
  • Possession of language
  • Opposable thumbs and precision grip
  • Ability to manufacture (stone) tools

We all belong to the genus Homo, species sapiens and subspecies sapiens. We are “Humans, wise, wise” or “very smart humans.” (Since we are the humans investigating ourselves and our ancestors, it should not come as a surprise that we have kept the most honorific label for ourselves.)

If we translate Homo naledi into plain English, we can start with naledi. The species was named Homo naledi; ‘naledi’ means ‘star’ in Sotho (also called Sesotho), one of the languages spoken in South Africa.

According to the research team, the definition of the new species was not “based on a single jaw or skull because the entire body of material has informed our understanding of its biology.”

Interestingly, Homo naledi’s brain size is in the 400 to 600 cubic cm range, yet they are considered to be members of the genus Homo. Here is why: “The shared derived features that connect H. naledi with other members of Homo occupy most regions of the H. naledi skeleton and represent distinct functional systems, including locomotion, manipulation, and mastication.”

Homo naledi - brain size - range

Brain size and tooth size in hominins. (Lee R. Berger et al. eLife Sciences 2015; 4:e09560)

Fossil Dating

One aspect currently left unanswered is when Homo naledi lived; the scientists offer what-if scenarios for dates ranging between one and two million years ago, some even more recent. These are just that: scenarios. They do not provide a date, as none exists at this point.

That brings up the question: how does one date a fossil? Knowing when a human ancestor lived helps us understand the affiliations of different species and who might have evolved from whom. Scientists have access to a wide array of dating techniques.


Homo naledi had human-like hands, though smaller than our own.

Radiometric Dating

Several techniques measure the amount of radioactive decay of chemical elements. Known as radiometric dating techniques, these include potassium-argon dating, argon-argon dating, carbon-14 (or radiocarbon), and uranium series. This radioactive decay occurs in a consistent manner over long periods of time. A benchmark concept in using this approach is that of a “half life,” defined as “the time it takes for one-half of the atoms of a radioactive material to disintegrate.” Early hominid sites in Eastern Africa have stratigraphic affiliations with volcanic layers. These layers can be dated with the radiometric dating techniques just described. As we will see below, the situation in Southern Africa is different.

Measuring Stored Electrons

Thermoluminescence, optically stimulated luminescence and electron spin resonance measure the amount of electrons that get absorbed and trapped inside a rock or tooth over time. The application of these techniques to date fossils highlights how the study of human origins truly is a multi-disciplinary effort.

Thermoluminescence “(or TL) is a geochronometric technique used for sediment. The technique has an age range of 1,000 to 500,000 years. The technique is used on sediment grains with defects and impurities, which function as natural radiation dosimeters when buried. Part of the radioactive decay from K, U, Th, and Rb in the soil, as well as contributions from cosmic rays, are trapped over time in sediments. The longer the burial, the more absorbed dose is stored in sediment; the dose is proportional to a glow curve of light obtained in response when the sample is heated or exposed to light from LEDs. Greater light doses indicate an older age.”

Luminescence dating is “a form of geochronology that measures the energy of photons being released. In natural settings, ionizing radiation (U, Th, Rb, & K) is absorbed and stored by sediments in the crystal lattice. This stored radiation dose can be evicted with stimulation and released as luminescence. The calculated age is the time since the last exposure to sunlight or intense heat.”


Homo naledi’s feet appear nearly human.

Finally, “electron spin resonance (ESR) measures the number of trapped electrons accumulated, since the time of burial, in the flaws of dental enamel’s crystalline structure. At sites containing human and animal teeth, ESR can be used to determine how long the teeth have been in the ground, but finding teeth at an archaeological site is unusual, so this dating method is not as common as thermoluminescence or radiocarbon dating.”

Another dating technique altogether is paleomagnetism. It compares the direction of the magnetic particles in layers of sediment to the known worldwide shifts in Earth’s magnetic field, which have well-established dates using other dating methods.

Sites in Southern Africa cannot be dated with techniques outlined earlier. A lot of the fossil remains are found in a stone matrix, rather than on the surface. These fossils can be dated using biochronology. Most often – though not always – hominid remains are found in stratigraphic association with animal bones. Quite often, these animal remains belong to animal species that roamed elsewhere in Africa, where absolute dates are available. In this way, sites that do not have radioactive or other materials for dating can still be given a reliable age estimate.

Finally, one can estimate the time that elapsed since two species separated from a common ancestor. This is based on the concept of a molecular clock. This method compares the amount of genetic difference between living organisms and computes an age based on well-tested rates of genetic mutation over time.  Since genetic material (like DNA) decays rapidly, the molecular clock method cannot date very old fossils. The most ancient DNA that has been retrieved thus far dates back to 300,000 to 400,000 years ago.

There is no doubt that more information will be forthcoming from the Rising Star Cave system in South Africa. Over the last two years, the researchers have literally scratched the surface of what is in the cave. As mentioned earlier, the genus Homo is defined by a number of features. One of these used to be that we buried our dead. This appeared to have happened in this case as well. Once the remains are dated, we will know if this fundamentally human trait extended further back in time than we ever imagined. Or not.

Egyptian Nefertiti replica ends in a bust: ‘Ugly’ statue brews social media storm

A mini controversy has just broken out in social media about a rather ugly new rendering of the famous Nefertiti bust. The original bust, currently on display at the Neues Museum in Berlin, is one of the most iconic pieces of Egyptian art, recognized as easily as King Tut’s gold mask. It was not a surprise, therefore, that Egyptian authorities recently decided to erect a larger-than-life replica of the same bust at the entrance to the city of Samalut, to honor her memory.

This effort ended in – pardon the pun – a bust in its own right. The image, which only bears a very superficial resemblance to the original, has caused a storm in Egyptian social media, attracting worldwide attention. While the original bust is very well known, the story of its discovery is perhaps less well known. Nefertiti’s bust was discovered in the ruined workshop of the sculptor Thutmose on December 6, 1912 by a German archaeological team.

Bust being handed over to German archaeologist

Presentation of the Nefertiti bust shortly after discovery in 1912. (Left to right: Hermann Ranke, Paul Hollander and Mohammed es-Senussi)

Although the bust is uninscribed, Ludwig Borchardt, the dig director, immediately realized who was represented: the tall blue crown with uraeus serpent must belong to the queen. “No use describing it, you have to see it” he wrote.


Handwritten note by Ludwig Borchardt on the discovery of the bust. Aside from a quick sketch, it contains the remark “No use describing it, you have to see it.”

The Egyptian government gave the bust, and other finds, to the German expedition at the end of the season, according to a custom of the time, known as “partage.” It was not until ten years later, after World War I, that the bust was put on display in the Egyptian Museum in Berlin. The reaction was immediate: Nefertiti became an icon and the Egyptian government demanded her return, claiming that she had been allowed to leave the country by subterfuge. The matter remains unresolved to this day, and Nefertiti has survived two world wars in Berlin.

Nefertiti was the principal wife of the New Kingdom pharaoh Akhenaten (ca. 1350 – 1335 BC). Akhenaten tried to revolutionize Egypt, outlawing the worship of a host of gods, headed by Amun, the king of the gods. In their place he proposed the worship of the Aten, the sun-disc that gave life to the world. He moved the capital of Egypt from Thebes to a virgin site 250 miles to the north. This new capital he called Akhetaten (“horizon of the sun disc”), the modern site of Tell el-Amarna. Akhenaten’s changes did not find favor, and after his death the site was abandoned by his successor – the more familiar Tutankhamun – as the capital moved back to Thebes. Amun had restored the status quo.

A new religion required a new artistic style to express itself. Set against earlier Egyptian objects, Amarna art can appear more naturalistic, softer and more intimate. Images of Akhenaten, his wife Nefertiti, and their six daughters were the icons of this new creed, and Amarna was filled with sculptor’s workshops producing decoration for the city. The bust of Nefertiti, with its unusual shape, was probably a model used to define and standardize images of the queen.

The latest update on the “controversy” tells us that the Samalut bust is to be replaced with a statue of a peace dove. So all is well that ends well.

The original bust continues to attract huge throngs of tourists in Berlin. A museum quality replica of the same bust, manufactured by highly talented artists at the Neues Museum, has been on display in the Hall of Ancient Egypt at the Houston Museum of Natural Science since 2013. She looks forward to seeing you there.


Her Majesty awaits your visit at the Houston Museum of Natural Science.

News from the trenches: Diggers make significant discoveries at Sanxingdui

Archaeology is a profession that requires patience, persistence, and luck. In fact, a great deal of luck seems to be a prerequisite to make a great discovery; some of these involve kids and dogs. We are fortunate to know about the Lascaux caves because of a boy and his dog. A similar scenario led to the discovery of a new hominid fossil, Australopithecus sediba, near the Malapa cave in South Africa. The famous Chinese terra cotta warriors were found by farmers digging a well. The first artifacts at Sanxingdui were discovered by a farmer, as well.

Fairly recently, some eighty-five years after the initial discovery of the site, interesting new finds at Sanxingdui have been announced.


According to recent reports, archaeologists discovered a portion of the northern wall at Sanxingdui. The northern part of the wall would have run along the Jian River, according to this site map. (Image licensed under CC BY-SA 3.0 via Wikimedia Commons).

Archaeologists have discovered what may be a section of the north wall at Sanxingdui. In addition, three tombs were found. A well preserved human skeleton was uncovered in one of these. It was dated to the Neolithic, well before the Sanxingdui site was occupied. As far as we know, human remains dating back to the actual Sanxingdui – Jinsha timeframe have only been discovered at Jinsha.

chinese vice premier

Vice Premier Liu Yongdan, who visited the Houston Museum of Natural Science on June 21 2015. (Image courtesy of the U.S. Department of State from United States)

The complete lack of known written sources at Sanxingdui and Jinsha continues to hamper our understanding of this amazing and sophisticated culture. In her recent visit to the exhibit China’s Lost Civilization: The Mysteries of Sanxingdui at the Houston Museum of Natural Science, Vice Premier Mme. Liu Yongdan said this was indeed the biggest obstacle to our appreciation of the culture. She expressed hope that ongoing research would eventually uncover such information, a development which would bring Sanxingdui out of the shadows of prehistory and into the light of history. Discoveries like these can only strengthen China’s submission of the site as a potential UNESCO World Heritage Site.

Hard currency: Stone money of the Yap Islands

We have all grown accustomed to seeing new forms of payment pop up every day. Cash is used less and less. To be “with the times” now requires making payments electronically, and invisibly. Actual tangible objects, such as coins or bills, are exchanged less and less. Instead, electrons silently move funds from one account to another. Payment is still made, but the way in which it is done has changed dramatically. This blog entry deals with a form of payment that is quite different from what we would consider normal in the Western world. How would you feel about making payments with stone money?

The inhabitants of the island of Yap do exactly that: they pay with stones. They also use shells as currency. Each one of these forms of payment has one thing in common: the exchange medium represents something rare, or something that requires hard work to obtain, thus making it valuable.

We will start out this blog by finding where in the world Yap is located. Then we will see how the Yapese made their stone money, and where they went to get the stone (you will be surprised). Finally, we will answer the question: is this still used today, or is it ancient history?

Micronesia, Federated States of - . Map.

Federated States of Micronesia. The Yap Islands can be found in the far western portion of the Federated States.

Yap Island is part of the Federated States of Micronesia. With a total surface of 271 square miles, the land area of the entire Federated States represents about four times the size of Washington, DC.


The Yap Islands are comprised of several islands, the largest of which is the eponymous Yap Island. (“Yap Islands”. Licensed under CC BY 2.5 via Wikimedia Commons.)

Wikimedia Commons

Yap Islanders use stone and shells as currency, or more specifically, as an “exchange valuable” (Fitzpatrick 2003:67). Yap stone money discs take the shape of a donut. They range in size from small (measuring just a few inches in diameter) to enormous (12 ft in diameter, 1.5 ft thick and weighing 8,800 lbs).

The origin of these stone discs remains murky. Some researchers have suggested that the earliest stones, alleged to have been very small, might have imitated stone or shell beads (Fitzpatrick 2003:68).

The intrinsic value of such a Rai stone, as they are known among the locals, is based on the effort that went into quarrying it, the quality of its finish, and its history. The latter is important, if not a bit morbid. If it is known that a person lost his life while bringing the stone back to Yap, then the value of that stone increased (Fitzpatrick 2002:229; 2003: 77-79). You read this right: they brought the stones back to Yap. The stone used to make these money discs does not come from Yap Island. Rai stones were made from limestone (Fitzpatrick 2003:68, 116-124) from the islands of Palau, located 280 miles southwest of Yap Island. To a lesser degree, the Yapese also traveled in the opposite direction, to Guam, to quarry stone money (Fitzpatrick 2003:70). This was quite a feat. How was this done?

Palau Islands

ps_large_locator Palau Islands and their location in the Pacific.

Excavations and radiocarbon dates have revealed that the quarrying activity took place in Palau (Fitzpatrick, 2002: 227, 239) at least several hundred years prior to European contact; it intensified shortly thereafter. About ten quarries in Palau from which the Yap islanders extracted their stone money have been recorded; more remain to be investigated (Fitzpatrick, 2003:8). One of these localities was Omis cave. It contained several unfinished money discs (Fitzpatrick, 2003: 138-160). Radiocarbon dates suggest that work in this cave was carried out during the historic period, going back around two to three centuries ago (Fitzpatrick, 2003: 159).

Work done by archaeologists in 1999 and 2000 identified at least 15 stone money discs in various stages of production in the vicinity of four quarries on the Island of Palau. Shellfish and other faunal remains were also found (Fitzpatrick, 2002: 228; Fitzpatrick, 2003:299).

As far as we know, Palauans never traveled to Yap to participate in trade; instead this was a one-way trade, with Yapese setting out for Palau and returning with the much desired stone money (Fitzpatrick, 2003: 6, 40).

Imagine setting out in your outrigger canoe to travel from Yap Island to Palau to mine stones and shape them into the stone donuts we have come to know. This process involved several stages (Fitzpatrick, 2003: 295-297).

Selecting the quarry: Yapese workers had to obtain permission from Palauan chiefs to quarry. Once they did, they would select a cave or rock shelter along the coast.

Perform carving: upon selecting a suitable deposit of limestone, a general shape was “roughed out.” This was done in situ, meaning the blocks were not hauled off to another area to be transformed.

Detailed carving: Yapese workers used gouges and chisels to create a flat and smooth surface. The disc was probably removed from the limestone deposit during or after this stage.

Abrasion/flattening: after the shape of the disc was complete, the surface was further flattened using a chisel made from shell, stone or iron.

Perforation: the disc was then perforated in the center. Oral traditions tell us this was initially done with coral and a fire drill. Later, iron tools were used.  

Polishing: this represents the final stage of the process. The use of an abrader, such as pumice, mixed with water resulted in a smooth finish of the stone’s surface.

Getting to Palau was one thing, returning with a heavy stone disc must have been quite an experience. First they would have to be brought down to the water’s edge. This is where the hole in the center comes in handy: a sturdy wooden pole would enable porters to lift it and move it to the beach.


Logistics of moving Yap money around. Note the wooden poles sticking through the stones.

At least three modes of transportation were used to get the stone discs from Palau to Yap. The first form of transportation involved the traditional watercraft in this part of the world, a canoe, or two canoes in the case of a large stone. A late 19th century account relates that the stones had “a large hole in the centre through which a log is passed and this, when laid across two canoes, is sufficient to support the stone in transit.” (Le Hunte, 1883:25). Another approach seems to have been to fill the canoes with water, then load the disc and bail out the water (Fitzpatrick, 2003:311).

A second way of moving the stones involved rafts (Fitzpatrick, 2003: 310-311). A late 19th century illustration depicts a set of Rai money discs resting on a raft. Oral traditions on Yap mention how an early Yapese navigator was caught in a typhoon as he was trying to return home with several stones. We learn that the typhoon “[s]plit the canoes into pieces, and some of the rafts carrying the stones sank, and other rafts were separated from the canoes. But Anguman [the navigator] was able to bring some pieces on his rafts trailing after his canoes” (Fitzpatrick, 2003:73-74).

Investigations close to Omis Cave have revealed the presence a dock at the entrance to the cave. At high tide, the dock is almost fully submerged; at low tide, it is fully exposed. This would have “facilitated the loading of stone money onto watercraft. Rafts could be placed on or adjacent to the dock at low tide and discs moved or rolled on top and secured. At high tide the raft could then be maneuvered out of the shallow lagoon into the deeper channel for eventual transport back to Yap” (Fitzpatrick, 2003:146).

Not all stone discs made it to their destination. Some found a watery resting place. Modern divers have encountered many sunken stone discs in the waters of these islands; there must be many more resting on the bottom of the ocean.

Yap harbor

Yap harbor, showing a raft supporting two stone discs. (From Hernsheim, Franz, 1883. Südsee-Erinnerungen (1875-1880). Berlin : A. Hofmann, p. 125.)

A third form of hauling the stone money was with European ships (Fitzpatrick, 2002: 228; 2003:311-312). This form of transportation allowed many more stones to be shipped safely to Yap. By the late 1800s Yap was inundated with stone money. The Yap islanders paid for these stones with copra (Fitzpatrick 2003:101). The Japanese counted over 13,000 disks during their administration in the 1930s. Typhoons, flooding, and the use of these stones as anchors and construction materials during WWII cut this number in half (Fitzpatrick 2002:229; 2003:111).

Transport by canoe and rafts depended on prevailing trade winds and open ocean currents. The best time to transport discs from Palau to Yap would have been between late April and the beginning of October. The ideal time for Yapese workers to come to Palau to prepare a load of money discs would therefore have been from September to February (Fitzpatrick, 2003:311 – 312).

Just in case you are wondering, the US dollar is now the common currency in Yap. The last stone disc was carved and brought to Yap in 1931 (Fitzpatrick 2003:111-112). From that moment on, the US dollar replaced it as commonly used currency. However, stone money is still used to this day for major transactions like payment of dowry or purchase of land. Moreover, small pre-contact discs are considered more valuable than larger post-contact discs (Fitzpatrick, 2003:302).

Because of their size and weight, the largest stones have not moved since the day they were brought ashore in Yap. We find them lining roads, propped up in front of a house, or standing in someone’s backyard. When transactions involving Rai money occur, ownership of the stone is transferred, but the stone itself does not move. People just know that someone else now owns it.

Yap license plate

Old currency proudly remembered on modern license plate on Yap Island.

More prevalent and much easier to transport are the images of Rai money. As a symbol of Yap Island, they can be found on the island’s license plates.

Speaking of the stone money being a national symbol, one stone disc was presented on the inauguration of the Federated States of Micronesia (July 12, 1978).


Yapese stone money for FSM

Presentation of Yapese stone money for FSM (Federated States of Micronesia) inauguration.

Today they help draw and entertain tourists. On Yap Day, March 1st and 2nd (sic), strong island men carry “small change” around, much to the delight of assembled tourists.  Speaking of small change, the Houston Museum of Natural Science also has a small (but still heavy) example of this Rai money.

HMNS stone money

Stone money disc, Yap Island. (HMNS collection.)

Much smaller and rarer than Rai money is Yapese shell currency. In earlier days, shell money served as small change. Two kinds of shell money existed: the mother-of-pearl (yar) and non-native Spondylus shell (gau) (Fitzpatrick, 2002: 228; 2003:7).

Fitzpatrick, Scott M., 2002. A Radiocarbon Chronology of Yapese Stone Money Quarries in Palau. Micronesica 34(2):227-242. [link].

2003. Stones of the Butterfly: An Archaeological Investigation of Yapese Stony Money Quarries in Palau, Western Caroline Islands, Micronesia. Ph.D. Dissertation, Department of Anthropology, University of Oregon. [link].

Le Hunte, J.R., 1883. Report of HMS Espiegle to Sir G.W. Des Voeux, Acting High Commissioner for the Western Pacific, 10 October 1883. General Proceedings (1-83). Central Archives of Fiji and the Western Pacific, Suva: Fiji.