In 1932, anthropologist Louis Leakey, top, and his crew discovered a fossilized jawbone in Kenya with an abnormal-looking growth. At the time, Leakey claimed it was the oldest evidence of early human ancestors. While that view has changed, the fossil is still considered remarkable for the possible tumor it carries on its left side. Now housed at the Natural History Museum in London, the bone is known as the Kanam mandible, named after the fossil bed where it was found. John Reader/Science Source

When Louis Leakey sat down to recount the discovery of what may be the earliest sign of cancer in the genus Homo, the first thing he remembered was the mud. It was March 29, 1932, midway through the Third East African Archaeological Expedition, and it had rained so long and so hard that it took an hour to drive the four miles from the campsite in Kanjera, near the shore of Lake Victoria, to the Kanam West fossil beds. By the time he and his crew had slogged their way through, they were covered with mud, and before long, Leakey, who was just beginning an illustrious career as an anthropologist, was on hands and knees scouring the ground for newly exposed bones.

He was coaxing the remains of an extinct pig from the muck when one of his Kenyan workers, Juma Gitau, walked over with a broken tooth he had just extracted from a cliff side. Deinotherium, Leakey noted, a prehistoric elephantlike creature that roamed Africa long ago.

Gitau went back to look for more, and as he was scratching away at the cliff face, a heavy mass of calcified clay broke loose. He chopped it with his pick to see what was inside: more teeth, but not Deinotherium. These looked like what a dentist might recognize as human premolars, still set in bone, yet they came from a layer of sediment deposited, Leakey believed, in early Pleistocene time, about a million years ago.

The Kanam mandible quickly became a sensation. “Not only the oldest known human fragment from Africa,” Leakey proclaimed, “but the most ancient fragment of true Homo yet discovered anywhere in the world.” It was, he insisted, a direct precursor of us all.

Like many of Leakey’s enthusiasms, this one proved controversial. Anthropologists remain divided over whether Homo kanamensis, as Leakey called it, was as old as he believed. Some of them have come to consider the specimen a more recent jawbone — mid- to late Pleistocene — that had washed into much older surroundings. Whatever its pedigree or precise age, Kanam Man is no longer considered remarkable for its antiquity but for an abnormal growth on the left side of the jaw.

At the time of the discovery, it had seemed like a bother, detracting from Leakey’s find. He was working in his rooms at St. John’s College at the University of Cambridge, carefully cleaning the specimen, when he felt a lump. He thought it was a rock. But as he kept picking, he could see that the lump was part of the fossilized jaw. He sent it to a specialist on mandibular abnormalities at the Royal College of Surgeons of England, who diagnosed it as osteosarcoma — a cancer of the bone.

Others have not been as certain. As recently as 2007, scientists scanning the mandible with an electron microscope concluded that this was indeed a case of “bone run amok” while remaining neutral on the nature of the pathology.

Hands-on History

I first came across a mention of the Kanam jaw in a history-of-cancer timeline somewhere on the web. That sent me digging into Leakey’s old books and papers, and after several email exchanges, I tracked down the fossil at the Natural History Museum in London, where it had been in storage for decades. As far as I could tell, it had never been on display.

On a spring day I arrived, as previously arranged, at the museum’s staff and researcher entrance on Exhibition Road. The man at the guard desk called ahead to Robert Kruszynski, curator of vertebrate paleontology. He came out to greet me and then led me into the museum’s inner sanctum. Waiting for me on a table by a window was a brown cardboard box he had retrieved from museum storage. The handwritten label identified the contents: M 16509, KANAM MANDIBLE.

M stood for mammal. In the upper right-hand corner of the label were two colored stickers — a red sunlike symbol and below that a blue star — indicating that the specimen in the box had been analyzed at various times by radioassay and X-rays. Mr. Kruszynski carefully removed the lid. Inside was a smaller box, fashioned from balsa wood and cardboard and covered with a glass lid, and inside that was the Kanam jaw.

He placed it on a padded mat, to cushion it from the hard surface of the table. “All yours to look at,” he said, and he went off to search for another fossil I hoped to see: a femur retrieved from an early medieval Saxon grave in Standlake, England, with an enormous growth that had also been diagnosed as a cancerous bone tumor.

I had thought I would be content just glimpsing the Kanam jaw. I never expected to be left alone with it and to be able to hold it in my hand. It was dark brown and unexpectedly heavy and dense. That shouldn’t have been surprising. It was a rock really, petrified bone. Once it had been part of a prehistoric man, or a proto-man. Two yellowed teeth were still in place, and there was a deep hole where the root of another tooth had been.

Just below that, on the left inside curve of the jaw, was the tumor. It was bigger than I had expected, reminding me perversely of a type of candy from my childhood called a jawbreaker.

There was also a slight swelling on the outside of the jaw, and I could understand how people might argue endlessly over whether it was the remnant of a modern chin, as Leakey himself believed, or just part of the tumor. I could see where Leakey had sliced through the mass (some of his colleagues considered this sacrilege) to remove a section for further analysis. I could almost picture the rest of the head, its vacant eyes pleading for relief from inexplicable pain.

Mr. Kruszynski returned half an hour later to see how I was doing with the fossil. “Don’t bring it too close to the edge,” he warned. I suddenly realized that the protective pad on the table was sloping toward my lap and how easily a sudden movement might have sent the Kanam mandible dropping onto the linoleum floor.

In the end, he was unable to find the cancerous femur I’d inquired about. “For another time,” he said. He escorted me back across the barrier to the public portion of the museum. Hundreds of visitors of all ages coursed through the hallways. Some of them inevitably would get cancer, or they would love somebody who did. I wondered if anyone had been there for Kanam Man.

Ancient Oncology

Not much has been written about the obscure discipline of paleo-oncology. Although research had gone on sporadically for decades, the word was introduced only in 1983 when a small group of Greek and Egyptian oncologists (from the Greek onkos meaning “mass” or “burden”) began planning a symposium on human cancer in earlier times. The gathering took place the following year on a voyage to the island of Kos, where Hippocrates was born. What emerged was an elegantly published, sparsely printed little book, Palaeo-Oncology. I felt lucky to find a copy on the Internet for $100. Its 58 pages are bound in a blue cover with gilded print, and below the title is a drawing of a crab. Crab in Greek is karkinos, and Hippocrates, in the fifth century B.C., used the word for the affliction whose Latin name is cancer. It became the root of carcinogen and carcinoma.

Some 600 years later, the ancient physician Galen speculated on the etymology in an old text: “As a crab is furnished with claws on both sides of its body, so, in this disease, the veins which extend from the tumour represent with it a figure much like that of a crab.” The story is repeated in almost every history of cancer.

Very few tumors, however, look like crabs. Paul of Aegina, a seventh-century Byzantine Greek, suggested that the metaphor was meant to be taken more abstractly: “Some say that [cancer] is so called because it adheres with such obstinacy to the part it seizes that, like the crab, it cannot be separated from it without great difficulty.” The word karkinoi was also applied to grasping tools, like calipers.

All but forgotten is a very different derivation from Louis Westenra Sambon, a British expert on parasitology who, before his death in 1931, turned his attention to the study of cancer. There is a parasite, Sacculina carcini, that feasts on crabs in a manner eerily similar to the feasting of a cancerous tumor. The process was described in a 1936 report by pathologist Sir Alexander Haddow to the Royal Society of Medicine:

[I]t attaches itself to the body of a young crab, and casts off every part of its economy save a small bundle of all-important cells. These penetrate the body of the host and come to rest on the underside of the latter’s intestine, just beneath the stomach. Here, surrounded by a new cuticle, they shape themselves into the “sacculina interna,” and like a germinating bean-seedling, proceed to throw out delicately branching suckers which, root-like, extend through every portion of the crab’s anatomy to absorb nourishment. Growing in size, the parasite presses upon the underlying walls of the host’s abdomen, causing them to atrophy, so that when the crab moults, a hole is left in this region corresponding in size to the body of the parasite. Through this opening the tumour-like body finally protrudes and becomes the mature “sacculina externa.”

Long before Galen, disciples of Hippocrates, dining on crabs, may have noticed the similarities between the ways the parasite overtakes its host and the invasion of a cancer.

The skeleton of an early medieval Saxon man uncovered in Standlake, England, shows a basketball-size cancerous growth on his left leg. Natural History Museum, London

Whatever the reason for the name, ancient Greek texts describe what sound like cancer of the uterus and the breast. Driven by a belief in sympathetic magic, some physicians would treat a tumor by placing a live crab on top of it. They also recommended powders and ointments (sometimes made from pulverized crabs) or cauterization (burning closed the ulceration). As for patients with internal tumors, Hippocrates warned that they might best be left alone: “With treatment they soon die, whereas without treatment they survive for a long time.” The principle is part of the Hippocratic oath: First do no harm.

There is something comforting about knowing that cancer has always been with us, that it is not all our fault, that you can take every precaution and still something in the genetic coils can become unsprung. Usually it takes decades for the microdamage to accumulate — 77 percent of cancer is diagnosed in people 55 or older. With life spans in past centuries hovering around 30 or 40 years, finding cancer in the fossil record is like sighting a rare bird. People would have died first of something else. Yet in spite of the odds, cases continue to be discovered, some documented so vividly that you can almost imagine the ruined lives.

After my visit to London, I received from the Natural History Museum photographs of the Saxon skeleton whose tumorous femur I had hoped to examine. I had read that the growth was large — 10 inches by 11 inches — but I was astonished to see what looked like a basketball grafted onto the young man’s leg. The tumor shows a sunburst pattern that pathologists recognize as a sign of osteosarcoma, a cancer so rare that one would have to comb through the bones of tens of thousands of people to find a single example.

Yet ancient cases continue to turn up. There were signs of the cancer in an Iron Age man in Switzerland and a fifth-century Visigoth from Spain. An osteosarcoma from a medieval cemetery in the Black Forest mountains of southern Germany destroyed the top of a young child’s leg and ate into the hip joint. Bony growths inside the roof of the eye sockets indicated anemia, which may have been an effect of the cancer. The authors of the report speculated on the cause: contamination from a nearby lead and silver mine.

Maybe it helped to believe there was a reason. But no one knows what causes osteosarcoma. Then, as now, a few cases probably were hereditary, traced to chromosomal abnormalities. In modern times, speculation turned for a while to fluoride-treated water and, more plausibly, radiation — therapeutic treatments for other diseases or exposure to radioactive isotopes like strontium-90, which is spread by nuclear fallout. Strontium sits just below calcium in the periodic table of the elements and imitates its behavior, incorporating itself tightly into bone. But most often, osteosarcoma strikes for no apparent reason, leaving parents grasping to understand what remains as inexplicable as a meteor strike.

Another malignancy, nasopharyngeal carcinoma, which affects the mucous membrane in the nose, can scar adjacent bone. Signs of it have been found in skeletons from ancient Egypt. One woman’s face had been all but obliterated, and I tried to imagine her stumbling through life. “The large size of the tumor, which caused such extensive destruction, suggests a relatively long-lasting process,” observed Eugen Strouhal, the Czech anthropologist who documented the case. “Survival would be impossible without the help and care of the patient’s fellow-men.” Here was another case where the horrors of cancer punched through the flat veneer of scientific prose.

Osteosarcoma and nasopharyngeal carcinoma — these are primary cancers, those found at the site of origin. They are debilitating enough. Most skeletal cancers by far come from metastases, tumors that migrate from elsewhere. They also show up with greater frequency in the fossil record, leaving a distinctive signature. Metastatic bone cancer has been discovered in Egyptian tombs, in a Portuguese necropolis, in a prehistoric grave in the Tennessee River Valley and in a leper skeleton from a medieval cemetery in England. Buried near the Tower of London, the skeleton of a 31-year-old woman was marked with metastatic lesions. We even know her name from a lead coffin plate: Ann Sumpter. She died May 25, 1794.

In 2001, archaeologists excavated a 2,700-year-old burial mound in the Russian Republic of Tuva, where nomadic horsemen called the Scythians once thundered across the Eurasian steppes, their leaders exquisitely dressed in gold. Digging down through two wooden ceilings, the scientists came upon a subterranean chamber. Its floor, covered with a black felt blanket, cushioned two skeletons. Crouched together like lovers, both man and woman wore what remained of their royal vestments. Around the man’s neck was a heavy band of twisted gold decorated with a frieze of panthers, ibex, camels and other beasts. Near his head lay pieces of a headdress: four gold horses and a deer. Golden panthers, more than 2,500 of them, bedecked his cape.

His riches couldn’t save him. When he died — he appeared to have been in his 40s — his skeleton was infested with tumors. A pathological analysis, including a close look with a scanning electron microscope, concluded that the nature of the lesions and the pattern of their spread were characteristic of metastatic prostate cancer. Biochemical tests revealed high levels of prostate-specific antigen, or PSA. For all the false positives these tests can produce, this one was apparently genuine.

While prostate cancer tends to be osteoblastic, adding unwanted mass to the skeleton, breast cancer is osteolytic, gnawing mothlike at the bone. A middle-aged woman with osteolytic lesions was excavated from the northern Chilean Andes where she died around A.D. 750. Her body was buried in a mummy pack along with her possessions: three woolen shirts, some feathers, corncobs, a wooden spoon, a gourd container and a metal crucible. She was no Scythian queen. Her hair reached down her back in a long braid tied with a green cord. There were lesions in her spine, sternum and pelvis. On top of her skull, cancer had chomped a ragged hole 35 millimeters across. Cancer had feasted on her right femur, shortening her leg.

Counting Cancers

Altogether I counted about 200 suspected cancer sightings in the archaeological record. I was left to wonder how big an iceberg lay floating beneath the tip.

Ninety percent of human cancers are carcinomas, which arise in the epithelial tissues that line the organs and cavities of the body and envelop us with skin. As the layers are worn by the passage of food and waste or exposure to the elements, the outer cells are constantly dying. The cells beneath must divide to form replacements. And with every division there will be mistakes in the copying of genes — spontaneous mutations, or ones caused by carcinogens in food, water and air. For children, who are just beginning to withstand life’s wear and tear, only a fraction of cancers are carcinomas.

When it comes to hunting ancient cancer, primary carcinomas would almost always be lost with the decomposing tissues. And those that had metastasized would have often spread first to the lung or liver, killing the victim before a record was left in bone. Egyptian medical papyruses make ambiguous references to “swellings” and “eatings,” and some evidence has survived in mummies. A rectal carcinoma in a 1,600-year-old mummy was confirmed with a cellular analysis of the tissue. Another mummy was diagnosed with bladder cancer.

Other evidence of ancient cancer may have been destroyed by the invasive nature of Egyptian embalming rituals. To prepare a pharaoh for passage to the afterlife, the first step was removing most of his organs. The brain was pulled out though the nostrils. The torso was sliced open to take out the abdominal and chest organs (except for the heart, which was believed necessary for the ethereal voyage). To slow the process of decay, a turpentine-like solution was sometimes injected as an enema to dissolve the digestive tract.

Mummies are a curiosity, and most skeletal evidence is stumbled on by chance. Only recently have anthropologists really begun looking for cancer — with CT scans, X-rays, biochemical assays and their own eyes. What they will never see, even in bone, are clues lost through what anthropologists call taphonomic changes.

In digging and transporting skeletal remains, markings can inadvertently be erased. Bone-eating osteolytic lesions can cause a specimen to crumble and disappear. Through erosion, decomposition and the gnawing of rodents, taphonomic changes might also create the illusion of metastasis — pseudopathology — a possibility that must be taken into account along with alternative diagnoses like osteoporosis and infectious disease.

But on balance, it seems likely that the evidence of ancient cancer is significantly underreported. Most skeletons, after all, are incomplete. Metastases are more likely to appear in certain bones like the vertebrae, pelvis, femur and skull. Others rarely are affected. No one can know if a missing bone happened to be the one that was cancerous.

Hoping to cut through the uncertainty, Tony Waldron, a paleopathologist at University College London, tried to get a feel for how much cancer archaeologists should expect to find. First he had to come up with an estimate, no matter how imperfect, of the frequency with which primary tumors might have occurred in earlier times. There wasn’t much to go on. The oldest records that seemed at all reliable came from the Registrar General of Britain for causes of death between the years 1901 and 1905.

Using that as his baseline, he took into account the likelihood that various cancers would come to roost in the skeleton where they might be identified. The numbers, a range of approximations, came from modern autopsy reports. For colorectal cancer, the odds were very low, 6 to 11 percent, as they were for stomach cancer, 2 to 18 percent. On the high side were cancer of the breast (57 to 73 percent) and prostate (57 to 84 percent).

From these and other considerations, Waldron calculated that (depending on age at death) the proportion of cancers in a collection of old bones would be between zero and 2 percent for males and 4 and 7 percent for females. (The numbers were higher for women because of gynecological cancer. In the next century, cancer in men would come to dominate because of smoking.)

No matter how hard you looked, cases of ancient cancer would be sparse — even if the rate had been as high as that of industrial Britain. To test if his numbers were plausible, he tried them out on the remains of 623 people from a crypt at Christ Church, Spitalfields in the East End of London between 1729 and 1857. Relying solely on visual inspection, Waldron found one case of carcinoma among the women and none among the men.

That was within the range of his formula, encouragement that it was not wildly wrong. The next step was to try the predictions on much older and larger populations: 905 well-preserved skeletons buried at two sites in Egypt between 3200 and 500 B.C., and 2,547 skeletons placed in a southern German ossuary between A.D. 1400 and 1800. (The church cemetery was so small and crowded that remains, once they had decomposed, were periodically removed and put into storage.)

Using X-rays and CT scans to confirm the diagnoses, pathologists in Munich found five cancers in the Egyptian skeletons and 13 in the German ones — about what Waldron’s formula predicted. For all the differences between life in ancient Egypt, Reformation Germany and early 20th century Britain, the frequency of cancer appeared to be about the same.

Since then, the world has grown more complex. Longevity has soared along with the manufacture of cigarettes. Diets have changed drastically, and the world is awash with synthetic substances. The medical system has gotten better at detecting cancer. Epidemiologists are still trying to untangle all the threads.

Yet running beneath the surface there has been a core rate of cancer, the legacy of being multicellular creatures in an imperfect world. There is no compelling evidence that this baseline is much different now than it was in ancient times.

[This article originally appeared in print as "Cancer: The Long Shadow."]