The four different blood types and samples found on him along with the arrowhead in his back suggests he had a rough last few minutes. Some one or some number wanted him dead.
The blood samples were found on his clothing. "Scientists" have no way of determining when they got there? These people hunted to live. With stone weapons. And they typically owned one outfit. It would be suprising if he DIDN'T have multiple blood samples on his clothing.
“The four different blood types”
Sounds like he took a few with him, to me, and ran off.