Do Mormons look alike, and if so why? The New York Post published an article on April 15th titled "I’m an ex-Mormon — here’s why members of my former church look alike" to help answer these questions.
The article prominently featured quotes from a minute-long video by Alyssa Grenfell. Grenfell left the Church of Jesus Christ of Latter-day Saints (the Church) in 2017 and now runs a YouTube channel about her experiences in Mormonism.
Grenfell affirmed that Mormons look alike and attributed it to the "very small gene pool" created because members of the Church can only be married in the temple to other members. “The only opportunity to make the gene pool a little larger is to convert people,” she explained. Grenfell did not cite any research to support this claim, however, she flashed a screenshot of an article titled "Genetics in Utah" by Learn Genetics during that section of the video. The article explains how genealogical records, clean living, and high fertility in Utah helps scientists research genetic diseases. No mention is made of a small gene pool brought about by marriage within the faith.
The New York Post article offers another explanation as to why members of the Church might look the same: plastic surgery. The Post referenced a 2017 research snapshot that cited high numbers of plastic surgeons and spending on cosmetics like hair coloring per capita relative to the rest of the nation.
As further evidence, the Post claimed, "the Latter-day Saints church website even offers beauty tutorials." The article links to a fictional story from the September 2001 New Era magazine titled "Beauty Tips." The fictional story is about a young woman who believes she will not get to the Celestial Kingdom because she is not beautiful enough to get married. In the story, the young woman learns that there is more to beauty than good looks. The story does not contain beauty tutorials.
The Church does not have an official teaching on plastic surgery, however, Elder Jeffery Holland of the Quorum of the Twelve Apostles has said, "In too many cases too much is being done to the human body to meet...a fictional (to say nothing of superficial) standard... this is more than social insanity; it is spiritually destructive... And if adults are preoccupied with appearance—tucking and nipping and implanting and remodeling everything that can be remodeled—those pressures and anxieties will certainly seep through to children.”
The New York Post article explains that Mormons do look alike, citing a 2010 research paper that found non-Mormons can properly identify Mormons 60% of the time. A rate researchers said was statistically significant. However, the researchers did not attribute the ability of test subjects to identify "Mormons" to the small gene pool of members of the Church or their plastic surgery rates. Rather they said the skin texture of members of the Church was the giveaway. This difference in skin texture likely resulted from religious observances like not drinking and smoking.