According to a report on 26 July 2017 by BBC corespondent Zaria Gorvett , In a remote region of the US where polygamy is still practised, a town is struggling with a chilling health crisis caused by a recessive gene.
In 1990, a century after polygyny was abandoned, a 10-year-old boy was presented to Theodore Tarby, a doctor specialising in rare childhood diseases from the Barrow Neurological Institute.
The boy had unusual facial features, including a prominent forehead, low-set ears, widely spaced eyes and a small jaw. He was also severely physically and mentally disabled.
After performing all the usual tests, Tarby was stumped. He had never seen a case like it. Eventually he sent a urine sample to a lab that specialises in detecting rare diseases. They diagnosed “fumarase deficiency”, an inherited disorder of the metabolism. With just 13 cases known to medical science (translating into odds of one in 400 million), it was rare indeed.
It turned out his sister, whom the couple believed was suffering from cerebral palsy, had it too. In fact, together with his colleagues, soon Tarby had diagnosed a total of eight new cases, in children ranging from 20 months to 12 years old.
In every case, the child had the same distinctive facial features, the same delayed development – most couldn’t sit up, let alone walk – and, crucially, they were from the same region on the Arizona-Utah border, known as Short Creek,which is polygynous. In this small, isolated community of Fundamentalist Church of Jesus Christ of Latter-Day Saints (FLDS), the likelihood of being born with fumarase deficiency is over a million times above the global average.
“When I moved to Arizona that’s when I realised that my colleagues here were probably the most familiar I’d ever met with this disease,” says Vinodh Narayanan, a neurologist at the Translational Genomics Research Institute, Arizona, who has treated several patients with fumarase deficiency.
The disease is caused by a hiccup in the process that provides energy to our cells. In particular, it’s caused by low levels of an enzyme – fumarase – that helps to drive it. Since it was perfected billions of years ago, the enzyme has become a staple of every living thing on the planet. It’s so important, today the instructions for making it are remarkably similar across all species, from owls to orchids.
For those who inherit a faulty version, the consequences are tragic. Though our brains account for just 2% of the body’s total weight, they are ravenously hungry – using up around 20% of its energy supply. Consequently, metabolic disorders such a fumarase deficiency are particularly devastating to the organ. “It results in structural abnormalities and a syndrome including seizures and delayed development,” says Narayanan.
Faith Bistline has five cousins with the disease, who she used to look after until she left the FLDS in 2011. “They are completely physically and mentally disabled,” she says. The oldest started learning to walk when he was two years old, but stopped after a long bout of seizures. Now that cousin is in his 30s and not even able to crawl.
In fact, only one of her cousins can walk. “She can also make some vocalisations and sometimes you can understand a little bit of what she’s saying, but I wouldn’t call it speaking,” she says. They all have feeding tubes and need care 24 hours a day.
Fumarase deficiency is rare because it’s recessive – it only develops if a person inherits two faulty copies of the gene, one from each parent.
Today in the twin towns of Hildale and Colorado City there are some 7,700 people. It’s the headquarters of the FLDS, which is famous for its conservative way of life and polygyny. “Most families include at least three wives, because that’s the number you need to enter heaven,” says Bistline, who has three mothers and 27 siblings.
In the end, the link to fumarase deficiency is a numbers game. Take Brigham Young. In all, his children begat 204 grandchildren, who, in turn, begat 745 great-grandchildren. By 1982, it was reported that he had at least 5,000 direct descendants.
This sudden explosion is down to exponential growth. Even with just one wife and three children, if every subsequent generation follows suit a man can have 243 descendants after just five generations. In polygynous families this is supercharged. If every generation includes three wives and 30 children, a man can – theoretically – flood a community with over 24 million of his descendants in the space of five generations, or little over 100 years. Of course this isn’t what actually happens. Instead, lineages begin to fold in on themselves as distant (and in the FLDS, not so distant) cousins marry. In polygynous societies, it doesn’t take long before everyone is related.
This is thought to be how one-in-200 men (one in 12.5 in Asia) are descended directly from super-fertile Mongol warrior Genghis Khan, who died nearly eight centuries ago. As Brigham Young said himself: “It is obvious that I could not have been blessed with such a family, if I had been restricted to one wife…”
In Short Creek, just two surnames dominate the local records – Jessop and Barlow.
According to local historian Benjamin Bistline, who spoke to news agency Reuters back in 2007, 75 to 80% of people in Short Creek are blood relatives of the community’s founding patriarchs, Joseph Jessop and John Barlow.
This is all very well, but we now know that most people are walking around with at least one lethal recessive mutation (one that would kill us before we reach reproductive age) in their genome, around the same number as in fruit flies. Humans haven’t gone extinct because, being recessive, they’re only unmasked if we have children with someone who also just so happens to carry a copy of that exact same mutation too.
This is where the system starts to become unstuck. “With polygyny you’re decreasing the overall genetic diversity because a few men are having a disproportionate impact on the next generation,” says Mark Stoneking, a geneticist at the Max Planck Institute for Evolutionary Anthropology, Germany. “Random genetic mutations become more important.”
In isolated communities, the problem is compounded by basic arithmetic: if some men take multiple wives, others can’t have any. In the FLDS, a large proportion of men must be kicked out as teenagers, shrinking the gene pool even further.
“They are driven to the highway by their mothers in the middle of the night and dumped by the side of the road,” says Amos Guiora, a legal expert at the University of Utah who has written a book about religious extremism. Some estimate that there may be up to a thousand so-called “lost boys”. “Often they spend years trying to repent, hoping to get back into the religion,” says Bistline, who has three brothers who were discarded.
Conservationists have known for years that a population’s “mating system” – the fancy word for sexual behaviour – can have a profound impact on its genetics. In wild deer and sage grouse, as in Mormon cults, polygyny is associated with high levels of inbreeding, because it shrinks the number of males contributing to the gene pool and increases the relatedness of the entire community.
The fumarase deficiency gene has been traced to Joseph Jessop and his first wife, Martha Yeates (14 children). Today the number of people carrying the fumarase gene in Short Creek is thought to be in the thousands.
The FLDS are not alone. Today polygyny is more widespread in Africa than any other continent. In March 2014, Kenya's Parliament passed a bill allowing men to marry multiple wives, while in many West African countries it’s been practised for thousands of years.
Intriguingly, it’s associated with rare disease here, too. In Cameroon, scientists recently reported a polygamous community with abnormally high levels of stuttering. By comparing local genomes with those from sub-Saharan Africa, South Asia and North African populations, the researchers identified “exceptionally rare” gene variants among this community, which appear to be responsible – though the authors do not speculate about whether this is a consequence of polygyny.