October 15, 2001
Miracle or Science?
Identical "Twins" Highlight the Mysteries of Genetics
By Joshua Kors
St. George, UT — Seven-year-old sisters Brooke and Bree Hansen bear a striking resemblance to one another, so striking, in fact, that at the Foster Hills 1st Ward, where they have attended primary for over four years, neither their instructor nor their classmates can tell them apart. At Panorama Elementary, where the girls attend 2nd grade, they routinely face question as to why they look so alike. Most simply assume the Hansens are identical twins.
They are not. In fact Brooke and Bree Hansen are much more than not-twins: They are of no genetic relation whatsoever. Brooke is adopted. And her birthfather is half-black to boot.
Why Brooke and Bree look identical, then, is one of Southern Utah's most intriguing mysteries, an enigma that has piqued not just playground curiosity but is also pressing the state's most accomplished biologists for an explanation. Those scientists insist that having children with an identical appearance but no common bloodlines isn't entirely impossible. But the chances are slim. In Professor Terry Schwaner's words, they are "astronomical."
"We're talking about one out of all the grains of sand on all the beaches in the world," said Schwaner, who studies population genetics at Southern Utah University.
"We're not just talking about a pair of genes leading to two individuals looking alike. We're looking at many many genes that operate to give them these (identical) features. If they were fraternal twins, you might put a reasonable probability on how that might happen. But if we're talking about different lineages, geez, the chances would be ridiculously small."
That's because having identical features requires both girls to share a large number of identical genes. Currently biologists estimate that there are 35,000 to 80,000 genes in the human body. And each of those genes comes in several variations, or alleles. For the Hansen girls to fool the human eye, a significant portion of Brooke's alleles and Bree's alleles would have to match up.
"There are literally billions of combinations that go to make up any individual human being — thousands of combinations of alleles go to make up the face alone," said Professor Duane Jeffery, who teaches genetics at Brigham Young University. "We're talking about thousands of matches here. The chance of that happening I can't even begin to calculate."
It's stiff odds like that that have convinced Kris and Shelly Hansen the likeness between their adopted and natural children is no genetic coincidence. The Hansens are devout members of the Church of Jesus Christ of Latter-day Saints. They say the affinity between their daughters is a sign, an indication Brooke's adoption was of divine inspiration.
"I think the Heavenly Father wanted Brooke to be in our family," said Kris Hansen, the girls' father. "Brooke was the answer to all of our years of prayers."
The Hansen's understanding of their daughters' improbable resemblance is founded on that belief — that Brooke was a divine answer to seven long years of infertility. They see heavenly guidance in the way their lives crossed paths with hers: Moving from California to Layton, Kris and Shelly felt an inexplicable tug toward a run-down apartment in Bountiful. They abandoned a deposit on an upscale flat in Layton and moved into the Bountiful complex, where they met the man who would connect them to Brooke's birthmother.
Shelly got pregnant and gave birth to Bree shortly thereafter. At 90 days, when Bree's face began to mirror her sister's, it only confirmed the Hansens' sense Brooke's adoption was part of a larger plan.
"There are no bloodlines, yet they're the same height, the same shoe size — they do everything alike," Shelly said. "It's a magical thing. To me it means they were supposed to come together."
On their cul de sac in Foster Hills, where the girls skip rope and chase frogs, their likeness has earned them the nickname "the Counterfeit Twins." Rightly so: Almost everyone on the block has been fooled by their resemblance.
That group include Phil Mackert. Mackert has lived next-door to the Hansens for more than a year. In that time he has seen the girls on numerous occasions, including weekly get-togethers with the Hansens and other neighbors. Still Mackert believed Brooke and Bree Hansen were multiples, until just recently, when he was set straight.
"I had no idea one of them was adopted until last weekend," Mackert said. "They look like they're from the same gene pool. I thought they were twins."
Mackert isn't the only one. In primary education at Foster Hills 1st Ward, the Brooke and Bree mix-up is cause for weekly confusion.
"We do singing, and they'll say Brooke or Bree. Whoever they call, one of us will just go up," said Bree. "They don't even know which one's what yet. They'll point to me and call Brooke. And then she goes up and they'll say, 'No, no, I wanted her.'"
Parks, markets and malls are breeding grounds for similar confusion.
"We have people stop us in the store and say, 'How do you tell them apart?' And: 'Isn't it fun to have identical twins?'" said Shelly Hansen, the girls' mother. "I say they're not identical twins and, well, they're not even twins. But people just look at me like, 'What?'"
"Kids their age especially — they don't understand it. So it's easier to just say, 'Yeah, they're twins.'"
Scientific, Religious Explanations
When scientists confront cases as improbable as the Hansen's, their first course of action is to search for mitigating factors, factors that might help explain why the case appears more improbable than it is.
Professor Jeffery notes that Brooke and Bree grew up eating the same food. Nutrition is known to effect bone growth; identical nutrition levels may help explain why the girls' facial structure is so similar. Jeffery also points out that Brooke's having light skin and African heritage is not a complete mystery either: 32 to 33 percent of genes found in today's African-American population comes from Caucasians, a remnant of antebellum sexual practices.
There's also the matter of dressing both girls alike, a practice Professor Schwaner says can make people who aren't identical look so.
In the years she has spent raising the counterfeit twins, Shelly Hansen says she has considered such nurture-over-nature arguments and finds they have merit. But do they explain everything? "Definitely not," she said. She maintains a heavenly influence is at play in the girls' matching identities.
Not everyone in Utah's scientific community dismisses that possibility.
Cheryl Whitelaw, professor of statistics at Southern Utah University, says she often sees divine influence working through science, nudging numbers and guiding events that would otherwise be highly unlikely. In the Hansen case specifically, Whitelaw says the probability of the girls ending up identical is small enough before considering the probability of them ending up in the same home, as sisters.
"You think of all the children being adopted and all the families that want to adopt a child — it becomes a numeric permutation with a very very small probability," Whitelaw said. "That's where a little bit of our Heavenly Father's hand comes in here. Maybe God had that child look a lot like their own to let them know she was sent specially to them."
Others familiar with the case stress there are alternative explanations within the framework of science. For one, Jeffery says, the Hansens highlight all that biologists have yet to learn about genetics. He suggests that in future, when more is known about how genes play out, the case of the Hansens might be much more explainable. Until that time, the professor urges people never to discount the power of chance.
"The improbable does happen," he said. "This is highly unlikely, but so is winning the Lotto. People do win the Lotto. The odds have to happen somewhere."
In happening to the Hansens, Jeffery said, the girls are very lucky. That's precisely how Brooke and Bree feel.
"I know they feel very fortunate to have each other," Shelly said. "Earlier Brooke told me, 'Mom, I don't think I'm adopted. I just think I'm a twin.'"