Here's a headline that just sounds awesome: Better Identification of Viking Corpses Reveals: Half of the Warriors Were Female.
A lot of people have sent us this link these past two days. It raised my "Really?" flag, so I got the original source paper, "Warriors and women: the sex ratio of Norse migrants to eastern England up to 900 ad" by Shane McLeod, published in the journal Early Medieval Europe in 2011. Then I read it all the way through. And, unfortunately (meaning I really hate to ruin everyone's fun here): That's not what it says at all.
This paper looks at the history of using grave goods and other methods to determine the sex of remains, rather than using the bones themselves. Using grave goods to determine sex really isn't very accurate. (How do we know only women wore a brooch like that? How do we know it wasn't pinned there, affectionately, by a grieving spouse or friend before the body was buried? Answer: We really don't.)
(And if the question is "Why should we conclude that this body was a man because it has a spear and a shield?" The answer is: We shouldn't.)
The paper then looks at grave sites at which the sex of the remains was determined using the bones themselves. This method, while still not foolproof, is much more accurate at determining sex than using other, non-human-remains stuff that was buried in the grave along with the body. A really clear pattern emerged when comparing the male/female ratios at the sites that used grave goods against the ratios at the sites that used bones to determine sex. When the bones made the determination, more of the remains were identified as female.
So, based on a very small number of skeletons, the proportion of women present at the time of Norse invasions was probably higher than previously thought. I say "probably" because we're extrapolating a greater trend from a tiny number of skeletons.
However, this paper absolutely does not conclude that these women were warriors, or that the army had an even split of male and female fighters:
Note the use of the word "migrants," not "warriors" or "fighters." And:
There's all kinds of other research that really is about gender in Norse society and about women fighters in armies. And there is plenty of evidence that, yes, there were female Norse warriors (and neither I nor the source am saying there were not). But, this paper essentially uses the presence of six female migrants and seven male as evidence that women and children most likely accompanied the Norse armies with the intent of settling the land once it was conquered, rather than migrating in a second wave once the fighting was over. It is, sadly, not at all about female Viking warriors, and not some Earth-shattering evidence that Norse armies were evenly split among women and men.
I'm as disappointed as you are.
Here also is How the Vikings Worked.
Updated to add: The original post has now been updated with a link to a comment that clarifies a number of things, but the original post still has the same headline and the same misrepresentations of the source text.