Surrey, UK — May 7, 2025 — Why do some babies’ first steps start walking at 9 months while others wait until closer to 2 years? New research from the University of Surrey offers a clearer picture—our genes play a big role.

In the largest study of its kind, scientists analyzed the genetic data of more than 70,000 infants and identified 11 specific genetic markers that influence when children take their first steps. The research, published in Nature Human Behaviour, suggests that genetics account for roughly 25 percent of the variation in walking age among children.

“For years, we’ve known that environmental factors—like how much space a baby has to move or how often they’re encouraged to stand—can influence when they start walking,” said the research team. “But now we know that genetics also plays a significant part.”

“Most babies take their first step sometime between ages 8 months and 24 months, so it is a wide window in which this exciting milestone happens. It is a big moment for both parents and baby; it symbolises a new phase in a child’s life,” said Professor Angelica Ronald, Professor of Psychology and Genetics.

The findings also help explain the natural variation in when children reach this milestone. “Until now, we didn’t understand what causes the wide differences between children in when they take their first step. Parents might often worry that walking early or late is a bad sign or that they have done something wrong. We see that genetics play a considerable role in influencing the timing of this milestone,” said Dr Anna Gui, study author and researcher at the University of Rome Tor Vergata and Birkbeck, University of London.

More than just an important developmental step, walking is now shown to be genetically linked with other major aspects of growth and brain function. The study revealed that the genes influencing early walking also relate to brain structure, including the folding and ridges of the cortex. Surprisingly, later walking—still within the normal range—was genetically associated with a lower likelihood of ADHD and shared genetic links with higher educational attainment later in life.

“It is exciting to be able to discover the genes that influence when children learn to walk. Starting to walk independently is a major milestone for young children. We hope these new genetic findings can advance fundamental understanding about the causes of walking and be used to better support children with motor disorders and learning disabilities,” said Professor Ronald.

While these insights are groundbreaking, researchers emphasize that walking later doesn’t necessarily indicate a problem. “While parents should still see their GP if they are concerned, a slightly later start is not always a sign of problems. There is a lot of variety in when children take their first step on their own,” added Ronald.

The study was led by a collaborative team of scientists across the UK, Netherlands, and Norway, supported by international funding, including the Simons Foundation for Autism Research Initiative.