A replica of Piltdown Man. Image: Anrie/Wikicommons

One-hundred years ago, on December 18, 1912, British paleontologist Arthur Smith Woodward introduced the world to a tantalizing fossil: England’s most ancient human ancestor, perhaps one of the world’s oldest hominids. Best known as Piltdown Man, the “discovery” turned out to be the biggest hoax in the history of paleoanthropology. It’s a scientific crime that researchers are still trying to solve.

Piltdown Man consists of five skull fragments, a lower jaw with two teeth and an isolated canine.  The first fossil fragment was allegedly unearthed by a man digging in gravel beds in Piltdown in East Sussex, England. The man gave the skull fragment to Charles Dawson, an amateur archaeologist and fossil collector. In 1911, Dawson did his own digging in the gravel and found additional skull fragments, as well as stone tools and the bones of extinct animals such as hippos and mastodons, which suggested the human-like skull bones were of a great antiquity. In 1912, Dawson wrote to Smith Woodward about his finds. The two of them—along with Pierre Teilhard de Chardin, a Jesuit priest and paleontologist—returned to the Piltdown gravels to continue excavating. They found additional skull fragments and the lower jaw. The following year Teilhard de Chardin discovered the lone canine tooth.

Smith Woodward reconstructed the Piltdown man skull based on the available fossil evidence. His work indicated the hominid had a human-like skull with a big brain but a very primitive ape-like jaw. Smith Woodward named the species Eoanthropus dawsoni (Dawson’s Dawn Man). It was the first hominid found in England, and other anatomists took Piltdown as evidence that the evolution of a big brain was probably one of the first traits that distinguished hominids from other apes.

At the time of the discoveries, the field of paleoanthropology was still in its infancy. The only other hominid fossils that had been found by 1912 were Neanderthals in continental Europe and the even older Homo erectus of Indonesia. As additional fossils were discovered elsewhere, such as Africa and China, it became harder to see how Piltdown fit with the rest of the fossil record. The growing collection of hominid bones suggested upright walking was the first major adaptation to evolve in hominids with increases in brain size coming millions of years later after the emergence of the genus Homo. Finally, in the 1950s, it became clear why Piltdown was so odd: It was a fake.

In 1949, physical anthropologist Kenneth Oakley conducted fluorine tests on the Piltdown Man bones to estimate how old they were. The test measures how much fluoride bones have absorbed from the soil in which they’re buried. By comparing the fluoride levels to those of other buried objects with known ages, scientists can establish a relative age of the bones. With this method, Oakley determined Piltodwn Man wasn’t so ancient; the fossils were less than 50,000 years old. In 1959, anatomist Wilfrid Le Gros Clark and anthropologist Joseph Weiner took a closer look at Piltdown Man’s anatomy and realized the jaw and skull fragments belonged to two different species. The skull was most likely human while the jaw resembled an orangutan. Microscopic scratches on the jaw’s teeth revealed someone had filed them down to make them appear more like human teeth. And all of the bones had been stained to make them look old.

Since the truth about Piltdown Man was revealed, there have been many suspects implicated in the forgery. Dawson was the prime suspect. But he died in 1916, so scientists never had the chance to question his possible role in the hoax. Teilhard de Chardin, who found the isolated canine tooth on his own, is another possibility. One of Smith Woodward’s colleagues, Martin Hinton, may have also played a role. In 1978, workers found an old trunk of Hinton’s at the Natural History Museum in London. The trunk held teeth and bones stained in a similar way as the Piltodwn Man fossils. Despite much interest and speculation, no one has ever definitively tied any of these men to the hoax.

And now, a century after the announcement of Piltdown Man, scientists are still intrigued by the fake hominid’s origins. A team of 15 British researchers are using new methods to investigate the mystery. Radiocarbon dating and DNA testing will help identify exactly how old the bones are and confirm the jaw belongs to an orangutan. Chemical tests will also help the team pinpoint where the bones came from and whether they were all stained in the same way.

It will be several months before the analyses are complete. But if it turns out all the material was stained in the same way, or came from the same location, then it’s more likely that just one person was responsible for the scientific fraud. And that person is likely to be Dawson. It turns out that Dawson was responsible for at least 38 fake finds during his amateur fossil-hunting career, the Telegraph reports. Chris Stringer, an anthropologist at the Natural History Museum in London and one of the scientists investigating Piltdown, speculates in a commentary in Nature that Dawson may have committed such hoaxes in an effort to achieve scientific glory.

Stringer writes that Piltdown Man serves as a good reminder for scientists to “keep their guard up.” I think it also highlights the importance of open science in the field of paleoanthropology. The hoax wasn’t uncovered until scientists unconnected to the discovery analyzed the evidence. Today, numerous hominid species are known based on just a handful of fossils that only a handful of scientists have ever had the chance to study. In no way do I think some of these fossils might be fake. But giving other scientists greater access to the complete hominid fossil record will not only allow more errors to be detected but will also stimulate new interpretations and explanations of how our ancestors evolved.

And with that sentiment, I end my last Hominid Hunting post as I head off to a new job with Science News. I’ve enjoyed sharing my love of all things hominid with my readers, and I’ve appreciated all of the spirited feedback.

Ed. Note: Thanks, Erin, for all of your blogging the past couple of years! It’s been a thrill and best of luck to you going forward. — BW

This X-ray of a human skull highlights the main nasal cavity (orange) and the sinuses: frontal (pink), ethmoid (yellow), maxillary (green) and sphenoid (purple). Asian apes do not have frontal or ethmoid sinuses. Image: Hellerhoff/Wikicommons

I was sick this weekend. The kind of sick where your nose runs so much that you begin to question how the human body can produce so much mucus. My throat hurt. I was coughing. But the worst part was the headache: My head felt like it was being continuously squeezed by a vise, or maybe some sort of medieval torture device. The pain was so bad even my teeth hurt. As I was lying in bed next to my half-empty box of Kleenex, I thought, “This wouldn’t be happening if we had descended from Asian, not African, apes.” (Yes, I was really thinking that.)

But before I explain what apes have to do with my cold, let’s cover some basic biology. When the cold virus (or bacteria or an allergen like ragweed) enters the body, the nose produces mucus to prevent an infection from spreading to the lungs. This results in a runny nose. All of the extra snot can also plug up passages that connect the nose to air-filled pockets in the bones of the skull, called sinuses. Sinuses produce their own mucus and are thought to help humidify air, as well as stabilize and strengthen the skull. But when the passageways between the head’s sinuses and nasal cavity get blocked, the sinuses’ mucus can’t drain and the air pockets fill, causing pressure to build . Sometimes the lining of the sinuses swell, which results in the further production of mucus and build-up of pressure. That pressure hurts.

Humans have four types of sinuses that play a role in sinus headaches: the frontal sinus in the forehead, the maxillary sinus in the cheeks, the ethmoid sinus between the eyes and the sphenoid sinus behind the nose. The African apes, gorillas and chimpanzees, have all four of these sinuses. The Asian apes, orangutans and gibbons (the so-called lesser apes because of their smaller size), have just two, lacking the ethmoid and frontal sinuses.

The ethmoid and frontal sinuses can be traced back at least 33 million years ago to a primate called Aegyptopithecus that lived in Africa before the ape and Old World monkey lineages originated. (Old World monkeys are those that live in Africa and Asia.) These sinuses have also been found in some of the earliest known apes, such as the roughly 20-million-year-old Morotopithecus and 18-million-year-old Afropithecus, both from Africa. Chimpanzees, gorillas and humans inherited these sinuses from the most ancient apes. Gibbons and orangutans, however, each lost these sinuses independently after they diverged from the rest of the apes; gibbons evolved about 18 million years ago while orangutans split from the other great apes roughly 15 million years ago.

It’s not clear why the Asian apes lost the ethmoid and frontal sinuses. In the case of the orangutan, the animal has a much more narrow space between its eyes and a more severely sloped, concave forehead than the African great apes. So there just may not be room for these air pockets to form.

But gibbons and orangutans do still have the maxillary and sphenoid sinuses, which are enough to cause annoying pain and headaches. So I should really apologize to my African ape ancestors. Clearly, I had some misdirected anger. I should have been mad at the virus that invaded my body.

Some fossil evidence indicates the common ancestor of gorillas (shown), chimpanzees and humans came from Europe. Image courtesy of Flickr user Jenny Varley

Europe is not where most people would search for the common ancestor of chimpanzees, gorillas and humans. But that’s exactly where one team of anthropologists thinks the grandfather of the African apes came from.

But before we explore the origins of African apes, it helps to know how to identify a paleo-ape in the fossil record. The most distinct physical traits that all living apes share are the ones that help the animals swing through trees: long arms; a broad, flat chest; a short, stiff lower back; and long, curved fingers and toes. They also lack a tail. These traits didn’t evolve all at once, however. The world’s earliest known ape—the 20-million-year-old Proconsul from East Africa—had a monkey-like body, but aspects of the wrist and the absence of a tail indicate Proconsul did indeed sit at the base of the ape family tree.

By about 17 million years ago, apes appear in Europe’s fossil record. In a recent issue of Evolutionary Anthropology, David Begun and Mariam Nargolwall, both of the University of Toronto, and László Kordos of the Geological Institute of Hungary describe Europe’s fossil apes and why they think Europe was, in a sense, the motherland of African apes.

The ancestors of European apes probably came from Africa as part of a wave of mammals that were attracted to the continent’s subtropical forests. During the early part of the Miocene, the epoch that spans roughly 23 million to 5 million years ago, the two land masses were connected by land bridges that crossed the ancient Tethys Sea (a more expansive version of the Mediterranean). The first European apes, which lived 17 million to 13.5 million years ago, were Griphopithecus (found in Germany and Turkey) and Austriacopithecus (found in Austria). Both apes are known mainly from teeth and jaws, so we don’t know what their bodies looked like. But they did have thick dental enamel, another ape-like characteristic.

By about 12.5 million years ago, the first apes that really resemble modern great apes emerged in Europe and Asia. Those in Asia gave rise to that continent’s sole living great ape, the orangutan.

A drawing of Dryopithecus. Image courtesy of Wikicommons

And those in Europe might have given rise to today’s African apes. A good candidate is Dryopithecus, first unearthed in France. Features of the ancient ape’s arms indicate it could probably swing through the trees like modern apes do. It also had a large frontal sinus, an air pocket in the forehead that produces mucus (also the site of dreadful sinus infections). This trait ties Dryopithecus to African apes. Gorillas, chimpanzees and humans all have a frontal sinus; orangutans, found only in Asia, do not.

Other European apes from around this time also shared characteristics with today’s African apes. For instance, Rudapithecus, an ape that lived in Hungary about 10 million years ago, also had a frontal sinus as well as a bevy of other characteristics seen in African apes, such as brow ridges and a downwardly bent face.

Begun and his colleagues think an ape like Dryopithecus or Rudapithecus returned to Africa and established the lineage of modern African apes. They point out the timing makes sense. The features that characterize gorillas and chimpanzees today evolved first in Europe, two million years before they appear in the African fossil record.

Apes may have left Europe in the later Miocene as climate change made Europe uninhabitable. The rise of the Himalayas made the continent much cooler and drier. Starting 9.5 million years ago, deciduous woodland replaced subtropical forests, and many tropical animals died out.

Luckily for us, at least some escaped before it was too late.

Adult male orangutans have large cheek pads and a big throat pouch, but it can take decades to develop such traits. Image courtesy of Flickr user nebarnix

In Interview with the Vampire, Claudia, portrayed by Kirsten Dunst in the movie version, becomes a vampire at age 6. Six decades later, she still has the body of a child but the thoughts and desires of a grown woman.

In this way, orangutans are kind of like vampires. They have their own form of arrested development.

When male orangutans hit puberty, they develop distinct traits known as secondary sex characteristics that separate them from females. In addition to being much bigger, males grow longer, shaggier hair on their arms and back and sport giant cheek pads. They also have throat pouches that resemble large double chins, allowing males to beckon females with loud long calls.

Some males are late bloomers, not acquiring these traits until as late as age 30. But looks can be deceiving. Even though these males appear to be youngsters, they are sexually mature and capable of siring offspring.

Scientists think the two different types of adult males—those with secondary sex characteristics and those without—are two alternative mating strategies that evolved in orangutans. A new study published online in the American Journal of Physical Anthropology tries to pinpoint the circumstances under which orangutan arrested development emerges.

To do this, Gauri Pradhan of the University of South Florida and Maria van Noordwijk and Carel van Schaik, both of the University of Zurich, considered the differences between orangutans living in Borneo and those in Sumatra. These Indonesian islands are the only two places in the world where orangutans are still found in the wild. But arrested development is largely limited to Sumatra.

Orangutans in both locations are mostly solitary. They roam the treetops alone, but they live in home ranges that overlap with those of other orangutans. In Sumatra, a female prefers to mate with the dominant male that lives in her neck of the woods. This male always has his full set of male features. A female finds the dominant male by following the sound of his long call, and when she’s ready to be pregnant, the two enjoy a sort of honeymoon—traveling and mating together for up to three weeks. Other adult-looking males may live in the same area, but females actively avoid their calls and stay hidden from them.

Because the dominant male is so popular, he can be choosy about mates. These males tend to pass over inexperienced females who haven’t yet had a baby. With younger adult females, it’s hard to tell if they are truly ready to become mothers, so it’s a better bet to stick with females who are already moms.

Yet some males are interested in these naïve females: the sexually mature males lacking adult traits. Unlike the other male orangutans, these guys don’t wait for females to come to them. They search the forest for receptive females, and Pradhan and his colleagues speculate that these males might father a lot of the children of first-time orangutan moms.

The sex lives of orangutans on Borneo are quite different. Here, no single adult-looking male is dominant. Many full-fledged males mate with an area’s females. Orangutan honeymoons are much shorter, and males may fight with each over a potential mate. Because the competition is so fierce, males aren’t choosy about who they mate with—and sometimes, even if a female’s not in the mood for mating, a male might force her to copulate.

Pradhan’s team incorporated these differences, as well as some assumptions about male growth, into a mathematical model. Their equations allowed them to determine which factors best explain the presence of immature-looking adult males in a population. The most important variable, they conclude, is the ability for one male to dominate an area. When this happens, as in Sumatra, it becomes beneficial for other males to have a covert mating strategy.

But if there is a lot of direct competition among males, as in Borneo, then it’s better to be a full-fledged male, who will always beat out immature males. No one male can monopolize females in Borneo because males tend to travel more on the ground there, the researchers say. That improves their mobility and makes it easier to quickly find females, even those who may not want to be found.

Thousands of years ago, orangutans once lived throughout much of Southeast Asia, even on the mainland. I wonder how pervasive arrested development was back then. Even if we had large bone samples, would anthropologists ever be able to detect such behavior in the fossil record?