The remains of a man buried 3,800 years ago in a richly decorated California grave bear some unusual but unmistakable features — a protruding brow, a lantern jaw, thick leg and arm bones, and teeth so crowded together that at one point they erupt in rows three deep.

According to a new study of the ancient skeleton, they are signs of acromegaly, a rare disorder of the endocrine system that’s similar to gigantism.

The California man is among the very few examples of acromegaly ever found in the archaeological record, and it’s the oldest ever identified, according to Dr. Eric Bartelink, a physical anthropologist at California State University, Chico.

“It is the earliest evidence of this condition in humans, the only documented case from prehistoric California, [and] one of the more complete skeletons documented with this condition,” he said in an interview.

Acromegaly has only been identified definitively at two other archaeological sites in North America, Bartelink said: in the remains of a male buried in New Mexico about 600 years ago, and an unsexed 1,100-year-old skull found in Illinois.

The newly found case in California adds to the scant literature of the disorder, he said, potentially improving how acromegaly may be diagnosed in other remains, and also shedding light on the history of the disease, perhaps even how it was interpreted in the ancient past.

The man, believed to have been in his mid-30s at the time of his death, was found in a burial mound with 176 other bodies near the Central Valley town of Elk Grove. [Read about recent research into a grislier mass grave nearby: “Mass Grave of ‘Prodigal Sons’ in California Poses Prehistoric Mystery“]

Labeled as Burial 37, the grave was originally excavated in the 1930s and dated to 3,750 to 3,950 years old.

The man was part of a hunter-gatherer culture known as the Windmiller, one of the earliest sedentary societies in the Central Valley, usually identified by its distinct burial practices, Bartelink said.

Windmillers typically buried their dead laying flat and face-down, rather than in a flexed position, with the heads pointing west. The deceased were also often sent off with a fine complement of grave goods, Bartelink said.

“The mortuary assemblages are rich with projectile points, shell beads, crystal, and charmstones, suggesting a more-or-less egalitarian society compared to groups more recent in time,” he said.

In the case of Burial 37, the body was daubed with red ochre on the head, chest, pelvis, left elbow, and on both hands and feet. The grave was festooned with 48 beads made from the shells of Olivella sea snails, and another 7 ornaments crafted from abalone.

But such artifacts weren’t unique to Burial 37, and the remains give little clue as to the specific cause of the man’s death.

“It is not clear that the condition contributed to death, but it certainly could have,” Bartelink said.

“Acromegalics have a lower life expectancy and many more respiratory and cardiac issues than unaffected people.”

Unlike true gigantism, in which the pituitary gland starts to release excessive amounts of growth hormone in childhood, acromegaly doesn’t begin until early adulthood, after all of the body’s long bones have finished growing.

Typically, a tumor on the pituitary triggers the flood of hormones, stimulating exaggerated growth wherever bone development is still possible — typically in the face, hands, and feet.

So while the Burial 37 man wasn’t exceptionally large for his time — about 170 centimeters, or five feet five inches — his remains bear several signs of hypergrowth in adulthood, Bartelink said.

Comparing the skull with 14 other male skulls from the same mound, Bartelink found it to be both taller and wider than average. [Read about similar recent research: “Infamous Mass Grave of Young Women in Ancient City of Cahokia Also Holds Men: Study“]

And analysis by x-ray revealed several areas of excessive bone formation in the face, including a heavy, prominent brow; bony processes around the sides of the eyes; an elongated chin; and a pronounced nose creating what Bartelink described as a “beak-like” appearance.

More importantly, he said, the bony pocket that holds the pituitary gland — known as the sella turcica because it resembles a Turkish saddle — showed significant signs of enlargement.

“This is a classic finding with acromegaly, because it results from an expanding pituitary tumor,” he said.

In what seems to have been an unrelated condition, the man’s right eyetooth also grew upside down, protruding through the bone of his face just under his nose.

How other Windmillers would have responded to such a distinctive visage is largely a matter of speculation, Bartelink said.

“I would expect that the person would have been treated differently, but it’s hard to say,” he said.

“The physical expression of the disease takes about 10 years to become fully noticeable, so it would have taken a bit for other members of the society to take notice.”

If the ornaments in Burial 37’s grave are any indication, he appears to have been neither revered nor ostracized, Bartelink said.

A few aspects of the burial were “interesting,” however, including the fact that the man was buried face-up, instead of prone, and with his head oriented north rather than the west, like most others interred in the mound.

The head also seems to have been disturbed some time after death, and moved down to the left ankle, where it was originally found.

“This could reflect some aspect of mortuary ritual but could just have been someone digging a grave adjacent to this one and moving bones around,” Bartelink said.

“I am not one to speculate, but there may be something of significance going on here. It’s just not easily testable.”

Bartelink describes his analysis in the International Journal of Paleopathology.

Bartelink, E., Willits, N., & Chelotti, K. (2014). A probable case of acromegaly from the Windmiller culture of prehistoric Central California International Journal of Paleopathology, 4, 37-46 DOI: 10.1016/j.ijpp.2013.11.003