My husband realized that if such hypothesis was true, then the most archaic way of killing known to man --applying a blow to the head-- might have imprinted a gene of the collective unconscious, thus becoming inheritable as a component archetype.
Man had afterward learned to kill from a distance by hurling stones and shooting arrows; he also learned the sophisticated use of sharp-edged weapons and eventually abandoned the crude --primitive-- original way of killing.
However, under given circumstances of intense rage related to primitive narcissism hurt, the archaic way of killing might surface --especially if an appropriate instrument were at hand. And an ax is quite such instrument. Would the splitting of the head symbolize a personality split by ambivalence, such as Jake's patient was suffering? Did Dostoyevsky suffer such a psychic schism? Did he undergo the personal experience of seeing an ax while enraged, and feeling a titillating murderous desire to use it? Are the Karamazov brothers his split personalities, and parricide the central theme? Why did the attacks make him so blissful, what did he dream?

Jake opened the encyclopedia and found that the Russian author had indeed suffered in his adult years from convulsive seizures; he had been strongly ambivalent and had written stories about the "double." No mention of axes or aggressive tendencies, only compulsive gambling. Was gambling and resulting ruin the way of expressing and expiating murderous repressed urges?
But I'm not interested in pursuing such leads, nor was Jake. I expressly have not told how the anthropologist's theory about ancient man suddenly becoming a killer cared to explain the dramatic suddenness of such a fateful change. I've withheld such information because it came to Jake's attention after he himself had reached a conclusion that tallied with the anthropologist's theory, although from another angle. To wit, Jake's own personal belief about the sudden appearance of a creature called Man --as contrasted with the existing Manwomen-- and about the eventual emergence of Woman. And Jake had held the "proof" of that belief for thirty years! It took him that length of time before he tied tails and was enabled to reconstruct the history of how it happened!