A Saskatchewan bio-archeologist led the discovery of a nearly 8,000-year-old skeleton belonging to a mother and those of her twin fetuses, which are the earliest confirmed set of human multiples.

The incredibly rare skeletons were exhumed from a graveyard at a New Stone Age lakeside community in southern Siberia. Experts believe they died from complications during delivery, according to research published this month in the journal Antiquity.

"Inside the tragedy is a compelling story and very personal window into life and death almost 8,000 years ago," co-author Angela Lieverse said in a statement. "It's a remarkable find."

Death during labour was quite common in prehistoric societies, but evidence of this, especially involving twins, is very rare because of the delicacy of infant bones and because women and their children were rarely buried together, the researchers wrote.

One study of mummies in Chile found 14% of mothers died during childbirth.

The skeletons were exhumed from a hunter-gatherer cemetery in 1997, but Lieverse, the University of Alberta's Andrzej Weber and Vladimir Bazaliiskii of Russia's Irkutsk State University didn't examine them until 15 years later.

The researchers estimate the mother was in her early 20s when she died, and the fetuses were full-term. They couldn't say for sure exactly how the woman died, but one of the fetuses appeared to have been partially delivered breech, feet first, obstructing the second, which likely contributed to the tragic outcome, the researchers wrote.

"Obstructed labour accounted for as many as 70% of maternal deaths, even in the late 20th century," Lieverse said. "Without the skills, experience and technology of modern medical practitioners, it would have been a virtual death sentence for all three individuals."