I would disagree, he is not "biologically" impelled to do anything other than rid himself of his superior, Rick. He screwed Rick's wife Lori, not out of love but sheer primal sex drive and the false knowledge that he finally was Rick's superior. And we know how that turned out.....
Shane is a cold blooded psychopath, as evidenced by him bashing his own face into the tree to make it look like he was attacked.
He could care less about Lori's baby, all he wants is Lori and the twisted perceived victory he would gain over his arch rival Rick..........
His hatred of Rick will lead him to betray their own group to the "others"......That will probably be the plot line of next season.
His hatred of Rick will lead him to betray their own group to the “others”......That will probably be the plot line of next season.