A viking mode for Evo Devo
But, I think the point of the story about Egil's grave was missed: the grave was empty, the interest in it is in validating accounts in the Saga's.
The skeleton was moved and the disinterred, and is thought to have shown clear signs of Paget's disease which explains his symptoms (including rage) and apparent invulnerability to the occasional battle axe to the head.
See Byock's article suggesting this. (see here
What we really want to know is where the two chests of English silver are buried, most think that after he was foiled from sowing dissent at Alþingi by casting the silver to the crowd, he hid the treasure and sacrificed slaves to guard it, before dying (from a self-inflicted wound?).
It would be interesting to do more biological archaeology; I suspect for example that some of the more exceptional "strong men" of history may have been heterozygous mutations for abnormal muscle development (cf superbaby story) - note both the parents of this child were heterozygous for the mutation and were high end athletes or strong people.
The mutation was probably suppressed for several reasons, historically, I'd speculate it has significant metabolic cost and is an unfitness during lean times; that the mother is more likely to die during birth (and therefore the child more likely to die ) pre-modern medicine, and that homozygous children were 100% fatal to mother before cesarean operations were prevalent.
Achilles as a myostatin mutant, anyone?