A 1.7 million-year-old tumor proves that cancer isn't a modern disease.
3D X-Ray cross-sections of the malignant osteosarcoma in a hominin toe bone. Image: Edward J Odes and Patrick Randolph-Quinney
Cancer predates the rise of Homo sapiens some 200,000 years ago. Scientists know that cancer is ancient—evidence of it is found in hadrosaurs alive during the Cretaceous period—but how it evolved alongside human genes has remained a medical mystery.
Now, a study reveals a malignant tumor in the foot of a 1.7 million-year-old hominin, an extinct human species—the oldest known case of human cancer. The new findings, published today in the South African Journal of Science, mark cancer's first appearance in prehistory, and further debunk its inaccurate description as a modern illness.
"Our findings demonstrate, definitively, that pre-modern people also suffered from cancer. That said, today we're exposed to legion carcinogenic—cancer causing—chemicals that simply did not exist in prehistory," the study's co-author Zach Throckmorton, an assistant professor of anatomy at Lincoln Memorial University's DeBusk College of Osteopathic Medicine, told me.
"It's likely modern people suffer from cancer more than did our ancient ancestors, [but] it's more accurate to say that cancer has always been with us. Most likely, our modern lifestyles increase its prevalence."
The international team of researchers from the University of the Witwatersrand's Evolutionary Studies Institute and the South African Centre for Excellence in PalaeoSciences discovered the hominin, whose species is still unclear, in South Africa's Swartkrans Cave. Using 3D imaging technology, scientists observed cancerous patterns in the specimen's toe, and diagnosed the human ancestor with osteosarcoma, an aggressive form of bone cancer. The disease would have been "effectively identical to osteosarcomas that occur in people today," Throckmorton added.
Anthropologists aren't sure when, or how, cancer first emerged in the human lineage. When it comes to ancient diseases, the fossil record can be unforgiving, and most of our evidence comes from written testimonies of cancer's effects.
Sometime around 300 BCE, Hippocrates interpreted cancer as a karkinos, the Latin word for crab. Of a patient's malignant tumor, the Greek physician wrote: it had "veins stretched on all sides, as the animal the crab has its feet".
More than two-thousand years before that, it's believed that ancient Egyptians documented the first record of cancer, in a medical text now called the Edwin Smith Papyrus. Its authors recount eight cases of breast ulcers, for which they say, "There is no treatment." The oldest known occurrence of prostate cancer lies in the mummified remains of a 2,250-year-old Egyptian man.
These historical gaps led some researchers to infer that cancer is a modern affliction, brought on by lifestyle choices, industrialization, and pollution. One controversial study, published in Nature Reviews Cancer, theorized that cancer only recently proliferated, due to its absence in ancient skeletons and Egyptian mummies.
However, a few things can explain why cancer is seemingly missing from ancient history: Cancer tends to afflict older people, and almost all of the mummies analyzed in the study were under 50 years of age. In regard to carcinogens, soot and smoke from fires, along with various fungal toxins, would have been affecting humans for millennia. And childhood cancers, such as bone tumors, were rare enough to be virtually invisible in the fossil records known today.
Fortunately for us, the bony mass that debilitated our hominin relative survived the individual whose life it might have taken. Researchers can't say for sure whether cancer was the ultimate cause of this human's death, but the tumor very likely disrupted its ability to walk comfortably, just like it would today.
"Osteosarcomas are considered among the most painful cancers. It would have been painful at all times, but especially when weight was put on it," said Throckmorton.
The study's authors hope medical technology, such as 3D X-Ray scanners, will make it easier for other scientists to investigate fossilized tumors. And maybe knowing how cancer impacted our history will help us learn how to better deal with it in the future.
"Cancer is, in a sense, simply out of control cell proliferation. Whether it's in a Jurassic-era dinosaur or a living person."