‘Pregnancy test’ for skeletons could help reveal ancient mothers

Scientists are looking into a pregnancy test intended for women who lived hundreds or even thousands of years ago.

For the first time, researchers have detected levels of estrogen, progesterone and testosterone in the skeletal remains of women from the 1st to 19th centuries AD – some of whom were buried with fetuses. The results show that ancient bones and teeth retain clear traces of certain sex hormones, which could help identify which people at archaeological sites were pregnant or had just given birth at the time of their death, says Aimée Barlow of the University of Sheffield in the United Kingdom.

“The physiological and emotional experience of pregnancy, miscarriage and childbirth is very profound for women, but until now they have remained largely invisible in the archaeological record,” she says. “This method has the potential to revolutionize the way we study the breeding histories of past populations. I’m excited, to be honest.”

Pregnancy is difficult to see in ancient individuals, especially if the fetus did not yet have a visible skeleton. Even second and third trimester fetuses can be overlooked since their bones may resemble those of the mother’s hands – which are often placed on their abdomen for burial.

Modern pregnancy tests measure levels of hormones like hCG in blood or urine. But hCG breaks down quickly, leaving little trace of its presence in the body.

However, progesterone, estrogen and testosterone can persist longer in tissues. Recent research shows that these steroid hormones can be found in human blood, saliva and hair – even in the long-buried locks of Egyptian mummies.

To assess the potential for detecting ancient pregnancies, Barlow and colleagues sampled rib fragments and a neck bone from two men and seven women buried in four English cemeteries. They also sampled the people’s teeth, as well as those of a third man.

Two of the women had confirmed fetal remains in their abdomens and two others were buried with newborns. The sexes of the other people had been determined by DNA analysis.

The team ground each sample into powder and used chemicals and other techniques to isolate the steroid hormones. Laboratory tests then determined the amount of estrogen, progesterone and testosterone contained in each of the 74 samples.

Estrogen only appeared in four samples, with no clear trend – perhaps because it breaks down more quickly than progesterone and testosterone and might not be stored well in tissues.

Progesterone, however, was particularly high in the vertebra of a young woman who died with a full-term fetus between the 11th and 14th centuries. The other third trimester woman, buried in the 18th or 19th century, had high progesterone levels in her rib. Moderate levels of progesterone also appeared in the dental plaque of the two women buried with their babies in the 5th or 6th century.

Notably, these four women had no trace of testosterone in their bones, nor in any part of their teeth – although the one buried with a premature baby had a small amount in her dental plaque. In contrast, the three women unrelated to fetuses or infants, buried in an 8th-12th century cemetery and in a Roman-era tomb, had testosterone in their ribs and in all layers of their teeth.

Testosterone at low levels plays an important role in women’s health, so its presence in these samples is not surprising, says Barlow. “But perhaps the absence of testosterone indicates a recent or ongoing pregnancy at the time of death,” she says.

“This is an exciting and unexpected intersection between archeology and hormonal science,” says Alexander Comninos of Imperial College London. “These techniques could be used to more reliably detect pregnancy in skeletal remains and thus give us more accurate information about ancient pregnancies.”

Even so, while the results are promising, further research needs to iron out the details, Barlow says. Men’s bones and inner teeth often had moderate levels of progesterone, for example, for reasons still unknown, she says. “Interpretations are very cautious at the moment.”

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