The University of Alaska Fairbank's Ben Potter explains the significance of finding burial sites for infants during the Ice Age. (University of Alaska Fairbanks)

Scientists have found two infants buried under an ancient dwelling, sitting beneath a previously discovered set of toddler remains. At 11,500 years old, this Alaskan grave isn't the oldest in North America -- but it's the oldest to show such elaborate burial practices, indicating that Native Americans put more care into burying their kin than we had thought. But because we have so little knowledge of life at that time, the remains present as many questions as they do answers.

The burials of these children, who died around the same time (probably even within the same season, the researchers report) showed an unprecedented level of care. But even though the researchers believe that one cultural group buried all three children, they weren't all buried in the same way.

Two of the children (one of whom died around six to 12 weeks after birth, and the other who was stillborn) were swaddled and buried with grave offerings -- intricately carved and pounded hunting tools made from elk antlers and stones. They were buried in a pit dug into the hearth of a residential dwelling, with a new hearth created on top. Later, the three-year-old was cremated in that hearth, which was then filled with dirt -- probably right as the nomadic Native Americans were leaving the settlement.

The researchers, led by Ben Potter of the University of Alaska Fairbanks, published their work Monday in the Proceedings of the Natural Academy of Sciences. They can't be sure why the toddler was treated differently from the infants, but they don't believe that gender was an issue -- while their results on the sex of the remains aren't definitive, they're fairly sure that all three children were female. They're also pretty sure that this nomadic group was only around for one summer, so it's not likely that they had seasonal variation in burial practices.

It could be that the group had specific burial requirements depending on age, based on when they thought children gained souls. The researchers also suggest that ceremonial burials might only have taken place if certain family members were present to oversee them. Whoever was meant to carry out the burial rites might not have been present at the time the toddler died. Or maybe, given the timing of the cremation, the tribe was just in too much of a hurry to bury the last child.

It's frustrating to have so few answers about these lost children, but the archaeological finding is nonetheless an impressive one. "We are so often limited to comparing stone artifacts, often with questionable context, in our understanding of the early peopling of North America," Brian Robinson, a University of Maine anthropologist who wasn't involved in the study, told The Verge. "Burial ritual provides insights to human belief and organization that are largely unobtainable in other ways."