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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.