Nature and Nurture Both Play Key Roles in When Babies Start Walking, Study Finds

For generations, parents have anxiously watched for the moment their baby takes their first steps — a developmental milestone that signals growing independence and physical progress. But while some babies stride confidently across the room at just nine months, others may not begin walking until closer to 15 months, leaving some parents concerned or even worried.

Now, a groundbreaking new study published in Nature Human Behaviour is shedding light on this variation, showing that both genetics (nature) and environmental factors (nurture) significantly influence when babies start walking. The research suggests that while parents can help support development through a nurturing environment, a substantial portion of the timing is determined by inherited genes.

The Study and Its Surprising Genetic Insights

The study, one of the most comprehensive of its kind, analysed data from nearly 71,000 children across Norway, the Netherlands, and the UK. Researchers identified 11 specific genetic markers that together explain about 25% of the variation in the age at which babies begin walking independently. This is a significant discovery, as it shows a clear genetic influence on a milestone that was previously thought to be largely dependent on upbringing and physical development.

Angelica Ronald, the senior author of the study and a professor of psychology and genetics at the University of Surrey in the UK, explained the importance of these findings. “Parents can provide a constructive environment and support their children, but they're not 100 per cent in control,” she told Euronews Health. “Genes also influence this timing.”

The genetic markers linked to walking age overlap with those associated with brain size and the number of folds in the cerebral cortex — the outer layer of the brain involved in higher-level cognitive processes. Interestingly, these same genes are also connected to conditions such as attention deficit hyperactivity disorder (ADHD), offering insight into how brain development and activity levels might influence when a child starts walking.

A Complex Mix of Factors

While genetics play a crucial role, they are just one piece of a more complex puzzle. The study reaffirms that multiple non-genetic factors still have a significant impact on walking development, including:

• Birth timing: Babies born prematurely often reach motor milestones later than full-term babies.
• Physical size: Smaller or lighter babies may develop balance and strength at different rates.
• Nutrition: Adequate nutrition supports muscle and bone development, which are essential for walking.
• Opportunity to practice: Babies who are encouraged to crawl, stand, and cruise (walk while holding onto objects) may build the confidence and coordination needed to take those first steps.

This interplay between biology and environment reflects the age-old debate of nature versus nurture — and confirms that both are deeply intertwined in shaping child development.

Early Walkers, Later Bloomers, and What It Means

The findings challenge the common perception that earlier is always better. “We put a lot of emphasis on kids who do things quicker than others,” Ronald said. “But there are probably advantages to walking later and walking earlier.”

Some studies have suggested that early walkers may be more physically active, which could support later motor skills. On the other hand, late walkers might be spending more time developing other abilities, such as language or problem-solving.

Additionally, while late walking (beyond 18 months) can sometimes signal developmental delays or intellectual disabilities, it is not always a cause for concern. The new research supports a more nuanced view, suggesting that individual differences are often within the range of normal development and shaped by many interwoven factors.

Implications for Parents and Paediatricians

One of the most important takeaways from the study is its potential to ease the worries of parents who may fear their child is “behind.” By highlighting the significant role of genetics in motor milestones, the research helps shift the focus away from parental performance or pressure to reach developmental targets.

“It’s reassuring to know that parents aren’t solely responsible for when their baby starts walking,” said Ronald. “What matters most is offering a loving, stimulating environment where the child can grow and explore safely.”

What’s Next in Developmental Research?

Looking ahead, the researchers plan to explore how genetic predispositions interact with different environments to influence child development more broadly. By identifying which conditions best support early physical and cognitive development, they hope to provide more tailored recommendations for parents and caregivers.

In the meantime, the message is clear: development is not a race. Whether a baby walks at nine months or 15, their journey is shaped by a unique combination of nature and nurture — and each path is valid.

Are you interested in how other milestones like speech or toilet training are influenced by genes and environment?

Conclusion

The new study offers powerful reassurance to parents: the age at which a baby starts walking is influenced by both genetics and environment. While nurturing a supportive space for practice and play is important, parents should remember they are not entirely in control of this milestone. Genetic factors — including those related to brain development and activity levels — play a significant role in determining when a child takes their first steps.

Rather than fixating on timelines, caregivers are encouraged to focus on fostering healthy, loving environments that support a child’s overall growth. After all, whether walking comes early or a bit later, each baby is developing at their own pace — and that pace is perfectly okay.