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.

A piece of the elbow from Australopithecus anamensis found in northern Kenya. Image courtesy of Wikicommons

Kenya is a hotspot of human evolution. Birthplace of famed fossil hunter Louis Leakey, the country is home to the remains of at least seven hominid species. Here’s a look at Kenya’s top fossil finds:

1. Orrorin tugenensis: In 2001, a team of researchers reported they had unearthed more than a dozen hominid fossils in the Tugen Hills of western Kenya. The bones date to 5.8 million to 6.2 million years ago, making them some of the oldest hominid fossils. The team, led by Brigitte Senut of the National Museum of Natural History in Paris and Martin Pickford of the Collège de France, determined that they had found a hominid based largely on the species’ thigh, which had telltale features related to walking upright. They named the new species Orrorin tugenensis, meaning “original man in the Tugen region” in the local language. In 2008, an analysis confirmed that the species was indeed capable of walking bipedally. That means Orrorin is in the running for the title of our earliest hominid ancestor.

2. Australopithecus anamensis: A probable direct ancestor of Australopithecus afarensis, A. anamensis lived in East Africa 3.9 million to 4.2 million years ago. The first fossil of this species was uncovered at the site of Kanapoi in northern Kenya in 1965, but the excavators didn’t know what to make of it. Almost 30 years later, in 1994, paleoanthropologist Meave Leakey’s team found similarly aged fossils in the nearby site of Allia Bay. Leakey concluded that the Kanapoi and Allia Bay fossils belonged to a previously unrecognized species that lived a few hundred thousand years before Lucy.

3. Kenyanthropus platyops: Meave Leakey’s team found another new hominid species in 1999. Justus Erus, one of Leakey’s field assistants, found a skull broken in two halves in the West Turkana region. The 3.5-million-year-old skull had many primitive features, including a small brain. But it had several surprisingly modern-looking traits, such as a flat face and small cheek teeth normally associated with the genus Homo. Since then, no other K. platyops specimens have been identified. This has led some researchers to conclude the species isn’t its own species at all. Instead, it may be just a damaged, distorted A. afarensis skull.

4. The Black Skull: In 1985, paleoanthropologists Alan Walker and Richard Leakey discovered a 2.5-million-year-old hominid skull in the Lake Turkana region. Known as the Black Skull, the cranium was darkened by manganese minerals in the soil where it was unearthed. The skull, plus several isolated jaws previously found in the area, resembled the so-called robust hominids—Paranthropus boisei and Paranthropus robustus. The Black Skull had massive molars, flat cheeks and a large jaw. In addition, it had a thick ridge of bone running lengthwise from the top to the base of the skull, called a sagittal crest, where enormous chewing muscles attached. Many researchers think these fossils belong to a species called Paranthropus aethiopicus, a likely ancestor of the later Paranthropus species. Others disagree (PDF) and argue the species’ true name should be Australopithecus aethiopcus. These researchers say the Black Skull is too primitive to be the ancestor of the robust hominids. And their similarities are superficial—an example of parallel evolution, when two closely related species evolve similar characteristics due to similar environmental pressures.

5. The earliest Homo fossil: In 1967, paleoanthropologist Andrew Hill found a bone fragment in the Chemeron Formation of the Tugen Hills. The bone came from the temporal region of a hominid skull, the area near the ear. Comparisons with australopithecines and later species of Homo indicate the bone is probably some early form of Homo. With an age of 2.4 million years, it’s the earliest known Homo specimen.

6. Homo rudolfensis: At the Koobi Fora site in northern Kenya, Bernard Ngeneo found an unusual skull, known as KNM-ER 1470, in 1972. Dating to 1.9 million years ago, the skull’s owner lived at the same time as Homo habilis, the earliest known species of Homo. But the skull’s larger brain size and larger cheek teeth—characteristic of the earlier australopithecines—have led some anthropologists to classify KNM-ER 1470 as a separate species: H. rudolfensis.

7. Turkana Boy: Unearthed in 1984 by prolific fossil hunter Kamoya Kimeu in West Turkana, Turkana Boy is a nearly complete skeleton of an approximately 9-year-old Homo erectus child that lived 1.6 million years ago. The skeleton has helped researchers demonstrate H.erecuts was the first hominid to have a tall body and long legs: Scientists estimate the child was over 5 feet tall when he died and likely would have reached 6 feet had he lived to be an adult.

The skull of Sahelanthropus. What does its body look like? Image courtesy of Wikicommons

Hominid Hunting went on an unexpected hiatus in January. I’m finally back. For my first post, I thought I’d share what I’ve been thinking about for the past couple months: my fantasy fossil finds, or the hominid discoveries I’d most like to see. In no particular order:

1. The skeleton of Sahelanthropus: In 2002, anthropologists announced the discovery of a new hominid (PDF): Sahelanthropus tchadensis. Unearthed in Chad, the find was exciting because it was the first—and still only—hominid found west of Africa’s Rift Valley. And at six million to seven million years old, it was the earliest known hominid. But the species’ place in the hominid family tree is not secure. The original discovery consisted of a skull, jaw and a few isolated teeth. (Since then, researchers have found (PDF) a few additional jaws and teeth.) The position of the skull’s foramen magnum—the hole near the base of the skull where the spinal cord exits—is like that of a hominid, more forward under the skull, indicating an erect posture and upright walking. But to confirm Sahelanthropus‘ hominid status, and convince the skeptics that it’s not a non-hominid ape, scientists need to find the species’ post-cranial bones.

2. The skull of Orrorin: Around the same time that Sahelanthropus was discovered, researchers dug up another new hominid species, Orrorin tugenensis, in Kenya. Like Sahelanthropus, the hominid was very ancient, about six million years old. The discovery consisted of 13 fossils, including thigh bones, finger bones and isolated teeth and jaw fragments. The thigh bones show the telltale signs of walking upright while the rest of the known body looks more apelike, which is expected for a very early hominid. But to get a fuller picture of the species it would be nice to have a complete skull.

3. Hobbit DNA: Almost ten years after Homo floresiensis was discovered on the island of Flores in Indonesia, anthropologists still disagree about whether the hobbit was a distinct species of Homo or a diminutive modern human with a genetic growth disorder, perhaps microcephaly. Extracting DNA from one of the hobbit fossils would help resolve the debate, revealing whether or not its genetic blueprints match our own.

4. Fossils of a Denisovan: The study of the Denisovans has the opposite problem. A couple years ago, researchers discovered a potentially new hominid species based purely on its DNA. The DNA came from an isolated finger bone found in a cave in Siberia. The bone dates to between 30,000 and 48,000 years ago, a time when modern humans and Neanderthals could have lived in the area. But the genetic material didn’t match either species. So now anthropologists know there was a third type of hominid in Eurasia at this time—but they have no idea what it looked like.

5. Australopithecus skin: When researchers stumbled upon Australopithecus sediba in a South African cave, they found more than just a possible link between australopithecines and the genus Homo. Some of the 1.977-million-year-old fossils are covered in a thin layer that might be skin. If so, it would be the first time anyone has ever found fossilized soft tissue from an ancient hominid. To investigate the matter, a pair of scientists has started the open-access Malapa Soft Tissue Project to gather ideas on the best way to analyze the possible skin.

6. More Homo habilis and Homo rudolfensis fossils: Homo habilis is the earliest known member of the genus Homo, living 2.4 million to 1.4 million years ago in East and South Africa. It was given its Homo status largely because its brain was bigger than the Australopithecus brain. The species is somewhat controversial, however, with some researchers believing it really was a species of Australopithecus. The issue became even more confused when scientists decided that at least one Homo habilis fossil was different from all the others. A 1.8-million-year-old skull found in Kenya’s Lake Turkana region had a much larger brain size than any other Homo habilis—nearly 200 cubic centimeters bigger. Now some researchers place this and a few other specimens in the species Homo rudolfensis. But many questions remain. Are the two really different species or part of one variable species? Finding more of the big-brained skulls, with associated post-cranial bones, might help researchers determine how different the two forms really were.

7. The skeleton of Gigantopithecus: The largest ape that ever lived went extinct about 300,000 years ago. All researchers know about Gigantopithecus comes from a few jaws and teeth. Based on that scant evidence, some anthropologists think the ape might have stood 10 feet tall and weighed a whopping 1,200 pounds. But to more accurately determine how gargantuan the ape was, and how it moved, someone needs to find some of its post-cranial parts.

8. More Kenyanthropus fossils: In 1999, anthropologists found the skull of the 3.5-million-year-old Kenyanthropus platyops. Researchers classified the skull as a new hominid species because of its unique mix of apelike and humanlike traits. For example, the species had small earholes like a chimp’s but a much flatter face. Many anthropologists don’t agree with this classification. The skull was in bad condition when it was found, and some researcher think it is just a distorted Australopithecus afarensis skull. The only way to settle the matter is to find more skulls that look like the original, if Kenyanthropus really ever existed.

9. A chimp relative: Almost nothing is known about the evolution of chimpanzees after they split away from the human lineage. The lack of fossil evidence may be due to where chimpanzee ancestors likely lived—warm, wet forests where fossils are not often preserved. But in 2005, a pair of anthropologists reported they had found three isolated chimp teeth dated to 500,000 years ago. Whether these teeth belonged to modern chimpanzees (which would imply they are a very long-lived species) or a chimpanzee ancestor is unknown. But what’s interesting about the teeth is where they were found: the Rift Valley of Kenya. Half a million years ago this part of Africa was largely a savannah, indicating ancient chimps were not restricted to forests. Still, even with this discovery, next to nothing is known about chimp ancestry. More fossils, from an even older period, would be a great find.

10. Something unexpected: Of course, the most exciting fossil discoveries are the ones you don’t anticipate and make scientists rethink some aspect of human evolution.

This is just my personal wish list. What’s on yours?

A reconstruction of Gigantopithecus. Image courtesy of Flickr user Sam_Wise

Bigfoot. Sasquatch. Yeti. The Abominable Snowman. Whatever you want to call it, such a giant, mythical ape is not real—at least, not anymore. But more than a million years ago, an ape as big as a polar bear lived in South Asia, until going extinct 300,000 years ago.

Scientists first learned of Gigantopithecus in 1935, when Ralph von Koenigswald, a German paleoanthropologist, walked into a pharmacy in Hong Kong and found an unusually large primate molar for sale. Since then, researchers have collected hundreds of Gigantopithecus teeth and several jaws in China, Vietnam and India. Based on these fossils, it appears Gigantopithecus was closely related to modern orangutans and Sivapithecus, an ape that lived in Asia about 12 to 8 million years ago. With only dentition to go on, it’s hard to piece together what this animal was like. But based on comparisons with gorillas and other modern apes, researchers estimate Gigantopithecus stood more than 10 feet tall and weighed 1,200 pounds (at most, gorillas only weigh 400 pounds). Given their size, they probably lived on the ground, walking on their fists like modern orangutans.

Fortunately, fossil teeth do have a lot to say about an animal’s diet. And the teeth of Gigantopithecus also provide clues to why the ape disappeared.

The features of the dentition—large, flat molars, thick dental enamel, a deep, massive jaw—indicate Gigantopithecus probably ate tough, fibrous plants (similar to Paranthropus). More evidence came in 1990, when Russell Ciochon, a biological anthropologist at the University of Iowa, and colleagues (PDF) placed samples of the ape’s teeth under a scanning electron microscope to look for opal phytoliths, microscopic silica structures that form in plant cells. Based on the types of phyoliths the researchers found stuck to the teeth, they concluded Gigantopithecus had a mixed diet of fruits and seeds from the fig family Moraceae and some kind of grasses, probably bamboo. The combination of tough and sugary foods helps explain why so many of the giant ape’s teeth were riddled with cavities. And numerous pits on Gigantopithecus‘s teeth—a sign of incomplete dental development caused by malnuntrition or food shortages—corroborate the bamboo diet. Ciochon’s team noted bamboo species today periodically experience mass die-offs, which affect the health of pandas. The same thing could have happened to Gigantopithecus.

A Gigantopithecus jaw. Image courtesy of Wikicommons

Further evidence of Gigantopithecus‘ food preferences and habitat was published last November. Zhao LingXia of the Chinese Academy of Sciences and colleagues analyzed carbon isotopes in a sample of Gigantopithecus teeth. Plants have different forms of carbon based on their type of photosynthesis; this carbon footprint is then recorded in the teeth of animals that eat plants. The team determined Gigantopithecus—and the animals living alongside it, such as deer, horses and bears—ate only C3 plants, evidence the ape lived in a forested environment. This work also supports the proposed bamboo diet, as bamboo is a C3 plant.

So what happened to this Pleistocene Yeti? Zhang’s team suggested the rise of the Tibetan plateau 1.6 million to 800,000 years ago altered the climate of South Asia, ushering in a colder, drier period when forests shrank. Other factors could have exacerbated this crisis. Gigantopithecus‘s neighbor, Homo erectus, may have over-hunted and/or outcompeted their larger ape cousin. And at least one dental study indicates Gigantopithecus developed and matured very slowly—a sign they probably had low reproductive rates, which can elevate a species’ risk of going extinct.

Some Bigfoot hunters say Gigantopithecus is alive and well, hiding out in the forests of the Pacific Northwest. Other Sasquatch enthusiasts, however, point out this is unlikely, as Bigfoot is reported to be a swift, agile, upright walker—not a lumbering, 1,200-pound quadruped.