Jeffrey Dahmer was genetically predisposed to mental illness.

To what extent, I don’t know for sure. My information is obviously limited. But there is evidence that this was the case, particularly on his mother’s side.

Now, I will let the evidence speak for itself. The topic lends itself to discussion, but I will let you do that among your peers. You can debate this into the ground if you like.

Aside from that, I will be providing as much info (with some speculation to help fill in the gaps) about Dahmer’s ancestors on both sides going back to his great-grandparents.

Family tree created with Ancestry.

We’ll start with his mother’s side, which was remarkably easier to research, presumably because their family name is not infamous.

This is Lillian Rundberg, Jeff’s maternal grandmother.

And this is Floyd “Rocky” Flint, Jeff’s maternal grandfather.

Dahmer’s mother was born Joyce Flint. Her parents were Floyd Flint, of Irish descent, and Lillian Rundberg, a “Norwegian housewife” as Joyce described her in The Silent Victims. Floyd was an alcoholic and was physically abusive to both his wife and his children. Joyce recalled being beaten by him at a wedding for dancing with boys; he hit her so hard her head struck and broke a glass window. He was constantly fondling her mother, to the point where she would eventually stop whatever she was doing and make Joyce finish it while they had sex. Joyce complained about growing up with “Irish men” who were sexist and violent, and some people have gone so far as to suggest that Floyd Flint, who was known as “Rocky” sexually abused his daughter. This is extremely iffy, since he was so against her even associating with members of the opposite sex and warned her that they would try to “touch” her. Anyway, Floyd and Lillian eventually divorced.

Lillian’s parents were Ole Rundberg and Inga Kleven. They immigrated from Norway in the 1890’s. Below is a copy of their marriage certificate.

Here is Lottie Mae White, Floyd’s mother. She looks kind of creepy. I think it’s the nose.

Floyd’s parents were Lottie May White and Ernest Humphrey Flint. They also appear to have divorced, as Ernest had another wife, Augusta Bedford.

Posted on Ancestry were two handwritten documents penned by Lottie’s mother Mary E. White, one listed as Lottie’s birth certificate (and signed by a witness of some kind) and the other as Lottie’s mother’s will. The certificate is explained by her saying there was no doctor in attendance at her birth (!), so they must have been poorer than church mice. The will is also very strange in the way that it’s written, as if Mary had reason to suspect no one knew she had a daughter.

Ernest Humphrey Flint, on the other hand, is the missing link. It’s unclear what exactly was wrong with him, but he had a history of mental issues. The 1920 census lists him as an inmate at the Wisconsin State Hospital For the Insane, now known as the Mendota Health Institute. Records at the Institute list his diagnosis as “alcoholism”. Ironically, Dahmer’s neighbor Vernell Bass (author of Across the Hall) theorized that if Jeff Dahmer had been found insane, he would have been sent there.

Here’s Humphrey. All the other photos of him I could find had been poorly colorized, unfortunately. Most of them were taken in nature settings, so I’m assuming he was an outdoorsman.

In Shrine, Brian Masters made the suggestion that Dahmer’s alcoholism came from his maternal grandfather Floyd Flint, who was also an alcoholic. The fact that Floyd’s own father was committed for alcoholism would seem to continue this theme of inherited excessive drinking.

Now, on to Jeff Dahmer’s father’s side of the family.

In A Father’s Story, Lionel mentioned that both of his parents, Herbert Walter Dahmer and Catherine Jemima Hughes, were schoolteachers. They were constantly trying to help him with schoolwork and encouraged him to pursue an education. He did express some resentment toward his mother in particular for making him feel intellectually inferior, although he acknowledged that she was only trying to help. Herbert died in 1971 aged 67, but Catherine of course was still around even while her grandson Jeff was in prison, dying on Christmas Day 1992 at the age of 88.

The surname Dahmer is of German origin; Lionel’s grandparents John and Rosa Dahmer immigrated from Germany at some point in the late 19th/early 20th century. John did not live to be very old—he died at the age of 38 in 1905. His son, Lionel’s father Herbert Walter Dahmer, was only two years old. Rosa likewise died in 1920, when her son was just sixteen. Those who bear the Dahmer name seem to have short lifespans (Lionel notwithstanding).

Catherine Hughes as you can see was one of five children born to Robert Rowland Hughes Sr. and Eunice Adele Spears. Hughes is a Welsh surname, and there is a possibility that Robert’s parents, Rowland and Jane Hughes, were born in Wales and immigrated to Wisconsin. Eunice Adele Spears was actually born in Iowa; I couldn’t find out much more about her, though.