Mom of world’s youngest Mensa member reveals the 3 ways they realized they had a mini-genius
“It soon became clear that he was an exceptional little being.”

Joseph Harris-Birtell made history at 2 years old.
There are lots of smart children: ones who potty-train easier than others, pick up reading at a young age, or can play complex instruments before kindergarten. Then, there are genius children. One little boy in the United Kingdom is the latter, who quietly made history by becoming the youngest person admitted to Mensa, the exclusive intellectual organization that only accepts masterminds with an IQ of 132 or above—for those who aren’t in Mensa, that’s less than two percent of the population. So, how old was little Joseph Harris-Birtell when he was admitted to Mensa? A mere two years and 182 days. There are professional sports teams with World Series champion droughts longer than that—much longer.
Born on November 23, 2021, parents Rose and David Harris-Birtell say that Joseph has been extraordinary since birth. “It soon became clear that he was an exceptional little being,” Rose told the Guinness Book of World Records. Perhaps this isn't surprising, considering both his parents are academics: Joseph's father, David, is a Senior Lecturer at the University of St. Andrews and Rose is an Honorary Senior Lecturer at the same institution. “He is very kind and loving, confident and curious, and incredibly determined,” Rose said. “He loves a challenge and is really exhilarated by complexity, whether learning chess or poring over new words and concepts that he hasn’t come across before.”
Beyond intellect, Joseph is kind and loving, too. Guinness World Records
The difference between smart and genius
But when did the Harris-Birtells know they had a prodigy on their hands, that their son wasn't just smart, but a genius? Rose describes three signs that tipped them off:
- He rolled over at five weeks: Rolling over, from belly to back and vice versa, is one of the earliest and most important motor milestones in an infant's development. Think of it as a baby's first step toward taking their first step. According to pediatrician Dr. Lauren Crosby, rolling over is “a crucial gross motor skill essential for building core strength, head control, and weight shifting.” But just because your baby has a penchant for rolling around and started doing it earlier than most doesn't automatically mean they're the next Isaac Newton, or whoever invented Post-Its (that was Dr. Spencer Silver, a true hero). Early physical milestone achievement alone is not a reliable indicator of superior intelligence. But Joseph didn't just start rolling early—he practically did it out of the womb. While most babies typically start rolling over between four and six months of age, Joseph had mastered this skill in a mere five weeks.
- He spoke his first word at seven months: The second sign of Joseph’s extraordinary intelligence came when he was only seven months old, when he said his first word. (For context, the average age for this milestone is between 9 and 15 months.)
- Before two years old, he read his first book out loud: After the first word tumbled out of Joseph, it was off to the races. Reading at this age is extraordinary: research says that from ages three to four, children begin to recognize letters and understand the concept of printed language, but don’t learn how to actually read until much later, around ages six or seven. “By two-and-a-quarter years old, he was reading out loud fluently for 10 minutes at a time,” says Rose. “And he could count to 10 in five languages and could count forwards and backwards to well over 100.”
Joseph loves a challenge.Guinness World Records
And that was only the beginning for young Joseph. Since then, his mother says that the pint-sized genius has also begun to learn morse code, taught himself the Greek alphabet, and is “interested in the periodic table,” adding, “His interests are vast and varied, and he is always keen to learn more and loves a challenge.”
Before Joseph, the youngest member to join Mensa was Isla McNabb, who was two years and 195 days old when she was admitted to the prestigious club in 2023. The Crestwood, Kentucky native scored in the 99th percentile of intelligence for her age on the Stanford-Binet Intelligence Scales, which led to her parents to look into Mensa.
What do you do when a truly gifted child comes along, like Joseph or Isla? Joseph’s achievement highlights a challenge for many parents: supporting a child who has needs that do not fit conventional standards. Whether a child is academically advanced, a creative virtuoso, or has different learning abilities, their parents inevitably struggle to find support and understanding.
Joseph's mom hopes his story can raise awareness for children with different needs. Guinness World Records
“It is a common misconception that everything is super easy for gifted children,” Rose explained to Guinness Book of World Records.
She continues,
"But everyone needs appropriate stimulation and understanding throughout their lives, and highly able learners can sadly have their unique talents dimmed by the pressure to fit into environments that simply haven’t been properly designed for them. Joseph is fortunate enough to attend a brilliant nursery and has an excellent music teacher, and in Mensa we hope to provide him with a community of peers as a source of further support as his formidable intellect continues to grow and develop.”
Yes, Joseph’s story is remarkable, and it’s a joy to marvel at a genius child. But it’s also a reminder that every child is unique, with their own needs and challenges, and they should be celebrated, too. Instead of trying to force them to fit a prescribed mold, or “be like everyone else,” Joseph is a shining example of what can happen when a child is allowed to thrive and dance to the beat of their own drum.