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## The DNA Finding: XX and No Y
The central finding of the 2017 paper was expressed in the language of genomics but its implication was clear.
The individual in grave Bj 581 had two X chromosomes and no Y chromosome. This is the chromosomal pattern associated with biological female sex. The analysis was conducted on samples from two different skeletal elements, and both produced the same result. The finding was described in the paper as establishing biological female sex for the occupant of the grave.
The mitochondrial DNA haplogroup was T2b — a lineage found in England, Iceland, and Scandinavia, consistent with geographic origins within the region of Viking cultural influence.
Strontium isotope analysis added another dimension. Strontium absorbed from food and water during childhood becomes embedded in tooth enamel, and its isotopic ratios reflect the local geology of where a person grew up. The isotope values from the Bj 581 individual were lower than those typical of most Birka inhabitants, placing her outside the regional baseline. Comparison of values from different molars — which form at different points in childhood — suggested she had moved during early childhood, possibly before the age of three. She was not a local, and she was highly mobile — a pattern the researchers associated with elite status in the Viking Age.
The finding of biological female sex did not resolve the question of how to interpret the grave’s meaning. That question was already contested before the DNA result and became more contested after it.
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## 130 Years of Male Assumption: Why It Held