An ancient bone from a 1.7-million-year-old human ancestor shows evidence of cancer. The cancer is now the oldest-known malignant tumor found in a human ancestor.

The fossilized foot bone belonged to a hominin, a now extinct relative of modern humans. The fossil was excavated from South Africa's Swartkrans cave between 1960 and 1980 but the tumor was not immediately identified.

In a new study, which was published in the South African Journal of Science on July 28, researchers scanned the ancient bone in sections and assembled them into a detailed 3D image. They found the mass in the fossil's metatarsal, one of the bones that connect to the bones.

The 3D cross-section revealed that the mass, which was earlier suspected to be a benign bone tumor called osteoid osteoma, was actually a malignant cancer. The researchers guessed that the cancer is some form of aggressive bone cancer called osteosarcoma.

According to the American Cancer Society, osteosarcoma is the most common type of cancer that develops in the bones. Although the condition can happen at any age, it often occurs in young individuals with teens being the most commonly affected.

Children who suffer from osteosarcoma are often tall for their age suggesting that the condition is related to rapid bone growth. If left untreated, this aggressive cancer, which usually develops in areas where the bone grows quickly, can lead to early death.

Study researcher Bernhard Zipfel, from University of the Witwatersrand, who is an expert on early humans' feet and locomotion said that the cancer would have been painful and it likely affected the sufferer's ability to walk or run.

Nonetheless, he said that the members of the research team are not sure if the cancerous foot bone caused the death of the individual and whether the bone belonged to an adult or child.

Although cancer is often associated with the toxicities of modern-day living such as poor diets and polluted environments, the findings affirm that the disease is an ancient health problem, just as suggested by earlier discoveries of ancient Egyptian mummies that were found to have prostate cancer.

"The expression of malignant osteosarcoma in the Swartkrans specimen indicates that whilst the upsurge in malignancy incidence is correlated with modern lifestyles, there is no reason to suspect that primary bone tumours would have been any less frequent in ancient specimens," the researchers wrote in their study.

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