Family Ties

Anton Johnson was born to a family of farmers in  Ärtemark Parish, Sweden in 1859. With his wife Christina he homesteaded a plot of forested land east of Ely, Minnesota. As I think Garrison Keillor has said of other Scandinavian migrants, they left their homeland, with its dark forests, thin rocky soil, cold weather, and short growing seasons, to find a better country. They traveled thousands of miles across the ocean and halfway across America until they reached Minnesota, where they settled down because it reminded them of home: dark forests, thin rocky soil, cold weather, and short growing seasons.

As it turns out, though, Anton got a job working underground in an iron mine, so it didn’t matter so much that the soils were poor and the weather was cold. This was in the early days of Ely’s rapid growth as a mining boom town. He and Christina had one child, Burt, born in 1890. Just over a year later, while Anton was working in the mine, a massive rock fell on his head and killed him. He was not quite 33 years old.

Christina remarried. Burt grew up, married a Norwegian girl, and had two daughters, who had their own families, whose members dispersed across the continent. I knew Burt as Dadda, my great-grandfather: a thin, straight, dignified old man, with thin white hair, thick, black, arched eyebrows, large ears and a long, thin face, serious but kind.

This August, nearly two dozen of his descendants and their families gathered together for a family reunion in a  cabin in the woods in northern Minnesota. In this group, there are some striking family resemblances. Some of my cousins look so much like their mothers that looking at them I feel I’ve become unstuck in time. There are many things that bind us together as a family, including shared memories of gathering in the north woods from time to time over the years. But I am also struck by how different we all are. We are family, but each person is a distinct individual, with different hopes and dreams, likes and dislikes, quirks and foibles. This is obvious, of course, even among siblings; each baby has its own temperament, and grows up to be a unique person.

Uncle Tim now lives out west, but owns the land that Anton and Christina homesteaded. One day we drove to the Ely area and spent two hours searching the woods for the property. Walking through the woods, slapping mosquitoes and gathering raspberries, it was easy to imagine what it must have looked like when those settlers first arrived.

The winters are cold and long. Grandma talked about how winter lasted seven months. I’ve been ice fishing up there in late April. Then once it warms up in the summer there are the mosquitoes, ticks and leeches. As soon as it gets warm enough to bare any skin there’s a crowd of bloodsuckers waiting to take a bite out of you. But the forests grow a bounty of raspberries and blueberries, and the lakes are full of fish. Loons cry their haunting call on the lakes, eagles fly overhead, and in the forests deer, wolves and bears are abundant.

Those northern Minnesota lakes and woods are almost enough to make me believe in ghosts. They vividly bring to mind memories of people who have passed on: sitting with Dadda at his breakfast nook while he explained the town of Virginia’s residential steam heating system; Nana lying in the nursing home bed with her bright blue eyes and wispy white hair;  Poppa scaling a bass after a long day fishing together; Mom orchestrating everyone in previous reunions, making sure that everyone was included and recognized and fed; and Grandma doing the hokey-pokey. I feel a connection to the land and the people. I can’t help wondering, though: if I stumbled back in time and met Anton and Christina in those woods, would we have much in common? Would we recognize each other as kin?

Kinship and lineage are powerful themes in the stories we tell. For example, in Dan Brown’s The Da Vinci Code, a central premise is that Jesus and Mary Magdalene had a child, thereby founding a lineage that continues unbroken to the present. Supposing for the moment that this were true, would people in this lineage be particularly special? Would they be more Christ-like (or Magdalene-like) than the average person?

From a religious point of view, this might be considered a silly question, of course; those who believe in the divinity of Jesus generally attribute this to Jesus having an extraordinary spirit in an ordinary human body. But in the fictional world of the Da Vinci Code, people devoted their lives to the principle that the lineage of Jesus was extra special, worthy of protection (or persecution). And even within the religious tradition, the writers of the Bible show great interest in lineages, describing in detail the generations connecting Jesus to the line of David, Abraham and Adam.

As an exercise focusing just on genetics and not spiritual matters, how many genes would a modern-day member of this lineage have in common with Jesus (or Mary)? We can estimate this using the coefficient of relatedness, r, defined as the probability that any two individuals share a given gene by common descent. (Most genes that we have are very similar to those of every other person on the planet, differing only in minor details, if at all, but the chance that any two genes are identical by descent is estimated by r.) Each sperm or egg that a person produces contains half of that person’s genome. Therefore each generation results in a halving of genetic relatedness: my daughter has half of my genes (r=0.5), and if she has a daughter, that child will have one fourth of my genes (r=0.25).

Estimating r for lots (n) of generations, assuming no inbreeding, r=1/(2n). Assuming human generation time to be about 25 years, about 80 generations have passed since the time of Jesus. The coefficient of relatedness between Jesus and any living descendants of his would thus be 1 over 1.2X1024, which is a really huge number – on the order of the total number of stars in the observable universe. One divided by such a huge number is effectively zero. The coefficient of relatedness between Jesus or Mary and any living descendant of theirs therefore would be r=0.0000000 (with zeros going on and on and on).

Of course, this is assuming that no inbreeding occurred. If (as is common in royal lineages) efforts were made to ensure marriages among members of the lineage, such as cousins, then r would be higher. But even so, with even a modest amount of marrying outside the lineage, the disruptive effects of sexual reproduction would rapidly erode much of the genetic similarity between the founders of the lineage and their remote descendants. Insofar as anything special about Jesus or Mary Magdalene was contained in the particular combinations of their genes, after a few generations of mixing and matching genes with people from other lineages, the descendants would have no more in common with Jesus or Mary than most other people in that population.

The same goes for any lineage. The “royal blood” of Queen Victoria, for example, is seven generations removed from the youngest heir to the throne, Prince George (r=1/27=0.0078). Thus, from a genetic point of view, Prince George is not particularly similar to Queen Victoria, despite being a relatively recent direct descendant of hers.

This calculation of r, though, doesn’t work for all genes. Some genes are passed down in packages rather than individually. We inherit our mitochondrial genome intact from our mothers. Mitochondrial genomes thus change only slowly, through the accumulation of mutations. In the same way, boys inherit their Y-chromosomes intact from their fathers. Prince George thus has the same Y-chromosome as his paternal grandfather Prince Charles.

Back in 2003, Tatiana Zerjal and colleagues published a paper showing that some 8% of men in Central Asia shared nearly identical versions of the Y-chromosome (Zerjal et al., 2003). Based on mutation rates and geographic patterns, they estimated that the family tree of this lineage originated in Mongolia roughly ~1,000 years ago. The most likely explanation of the wide spread of this chromosome was thus the historically well-attested reproductive success of Genghis Khan and his descendants.

There’s not very much on the Y-chromosome, though; just over 200 genes. Just because a man happens to have inherited a slightly mutated version of Genghis Khan’s Y-chromosome doesn’t mean that he shares anything more in common with Genghis Khan’s personality than any other man on the planet.

Personality and appearance both have strong genetic components, but because of sexual reproduction, similarities between lineage founders and descendants rapidly erode over time. So one might ask: given this erosion in similarity across the generations, why do we care so much about kinship and lineages? And more specifically, if there are only 200 or so functional genes on the Y-chromosome, why do patriarchs invest so much effort in ensuring that their particular Y-chromosome is perpetuated?

I suppose a major part of the answer must be that lineage survival is a pretty good proxy of fitness. If organisms are designed by natural selection to do whatever they can to promote the survival of their lineage, such organisms will leave more descendants, and thus more copies of their genes, than organisms that are indifferent to their lineage. If your lineage goes extinct, you won’t leave any copies of genes in the population. But if your lineage survives for two or three generations, and the number of individuals per generation grows rather than declines, then your genes have a good chance of surviving far into the future. Thus the particular satisfaction and happiness that grandparents and great-grandparents experience in seeing their descendants makes good evolutionary sense.

As for patriarchs, the focus on the patriline is less to do with the Y-chromosome itself, but with the greater potential variance in reproductive success between the sexes. The reproductive success of female mammals is limited by the number of babies they can have, whereas the reproductive success of male mammals is limited by their mating success. A Genghis Kahn or King David thus can have many more offspring than a Börte or Bathsheba.

Anton Johnson had just the one wife, though, rather than a harem, and he had only a single child before his life was cut short by a falling rock. Nonetheless, his lineage has carried on and grown.

The particular combinations of genes that Anton and Christina carried, though, have long since been mixed up with the genes of other lineages from varied parts of the world. That is, of course, the whole point of sexual reproduction. But whether due to genes, family experience, mate choice, or just the basic heritage of humanity, many members of this family do share an enjoyment in being outdoors, tramping around in the woods, and looking at living things.

White pine on Anton and Christina's homestead.
White pine on Anton and Christina’s homestead.

As we searched the woods, my son was the first to find the pipe in the ground that marked the southeast corner of the land that Anton and Christina homesteaded. After finding the corner marking, we could discern a cut line along the eastern boundary of the property: a straight path devoid of trees, brambled over in raspberries. Off the property, much of the land has been logged and is now covered with secondary growth: white-barked birches and poplar, thin trees crowded together, straining for the sky. But the family land has older growth, including a grand old white pine that already must have been a tall tree a century ago.

I don’t know what Anton Johnson was like as a person. If I could wander back to this same land 130 years ago, would I recognize any more kinship with him than with any of the other immigrant miners in the area? All the same, I still very much like the thought of him walking in the shadow of that same white pine, and perhaps admiring the flight of an eagle passing overhead.


Zerjal, T., Y. Xue, G. Bertorelle, R. S. Wells, W. Bao, S. Zhu, R. Qamar, Q. Ayub, A. Mohyuddin, S. Fu, P. Li, N. Yuldasheva, R. Ruzibakiev, J. Xu, Q. Shu, R. Du, H. Yang, M. E. Hurles, E. Robinson, T. Gerelsaikhan, B. Dashnyam, S. Q. Mehdi and C. Tyler-Smith (2003). “The genetic legacy of the Mongols.” American Journal of Human Genetics 72: 717-721.

4 thoughts on “Family Ties”

  1. Very nicely done, although I doubt Anton and Christina would give a wit about the coefficient of relatedness.

  2. Thanks, Tim! While they might well not give a wit about coefficient of relatedness, I imagine that like for most of us, on an unconscious level, an intuitive understanding of r would affect a wide range of behaviors, from national pride to incest avoidance.

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