Never trust the headline. From the article:

> And comparing DNA and archaeology at individual sites suggests that for some in the Viking bands, "Viking" was a job description, not a matter of heredity.

The article is just really confused in its terminology. But historically, vikingr meant raider or pirate. It was only hereditary in the sense it might be a family tradition to go viking. But if you dont go raiding you are not a vikingr whatever your ancestry.