Summary: New research shows that genetics play a substantial role in determining when infants begin walking, explaining roughly 25% of the variation in this milestone. By analysing genetic data from more than 70,000 babies, researchers identified 11 genomic regions associated with age at first steps, linking this milestone to broader aspects of brain development and neurodevelopmental outcomes.
The findings connect the timing of independent walking with other developmental traits such as brain structure, risk for attention-deficit/hyperactivity disorder (ADHD), and measures related to educational attainment. While environment and caregiving remain important, the study highlights that later walking within the typical range often reflects normal genetic variation rather than parental missteps or immediate cause for alarm.
Key facts
- Genetic contribution: Approximately 24%–25% of the differences in the age infants begin walking are explained by common genetic variation.
- Shared biology: Some of the same genetic factors that influence walking timing also relate to cortical folding in the brain and other neurodevelopmental traits.
- Typical later walking: Genetically later walking within the normal range was associated with a lower genetic correlation with ADHD and with genetic indicators linked to higher educational attainment.
Source: University of Surrey
Study overview
A team led by researchers at the University of Surrey performed the largest genetic analysis to date on age at onset of walking. This genome-wide association meta-analysis included data from 70,560 infants of European ancestry and identified 11 independent loci that reached genome-wide significance. The results were published in Nature Human Behaviour.
Analysis estimated SNP-based heritability for walking age at about 24.13% (95% CI = 21.86–26.40), with roughly 11,900 common variants contributing to about 90% of this genetic signal, indicating a highly polygenic architecture. One notable locus mapped to the gene RBL2 and co-localized with a brain expression quantitative trait locus (eQTL), suggesting a direct link between genetic variation and gene expression in the brain.
The genetic architecture of walking age showed negative genetic correlations with ADHD and body mass index, and a positive genetic correlation with cortical gyrification measured in both infants and adults. A polygenic score constructed from the findings explained 3–5.6% of variance in walking age in independent samples, and sibling-pair analyses supported that much of this predictive power arises from direct genetic effects. The score was also associated with volumes of neonatal brain structures involved in motor control.
Comments from the research team
Professor Angelica Ronald, a senior researcher on the project, noted that most children take their first independent steps between about eight and 24 months, so there is a wide, normal window for this milestone. She emphasized that discovering genes linked to walking helps improve basic understanding of motor development and could inform support for children with motor or learning disorders.
Dr Anna Gui, a study author and researcher at the University of Rome Tor Vergata and Birkbeck, University of London, said parents often worry when milestones fall early or late. The study shows that genetics is a considerable influence on timing, and a slightly later first step within the typical range is frequently part of normal variation rather than an immediate cause for concern.
The study was led from the UK with collaboration from researchers in the Netherlands and Norway and received funding from UK and international sources, including support from the Simons Foundation for Autism Research Initiative.
About this genetics and neurodevelopment research news
Author: Melanie Battolla
Source: University of Surrey
Contact: Melanie Battolla – University of Surrey
Image: The image is credited to Neuroscience News
Original research (open access): “Genome-wide association meta-analysis of age at onset of walking in over 70,000 infants of European ancestry” by Angelica Ronald et al., Nature Human Behaviour.
Abstract
Genome-wide association meta-analysis of age at onset of walking in over 70,000 infants of European ancestry
Age at onset of walking is a widely used early childhood milestone with clinical and public health relevance. In this genome-wide association meta-analysis of walking age (N = 70,560 European-ancestry infants), researchers identified 11 independent, genome-wide significant loci. SNP-based heritability was estimated at 24.13% (95% CI = 21.86–26.40), with about 11,900 variants accounting for the majority of the genetic signal, indicating strong polygenicity. One locus in the gene RBL2 co-localized with a brain eQTL. Genetic correlations showed that later walking age was associated with lower genetic liability for ADHD and lower BMI, and with greater brain gyrification in infant and adult measures. A polygenic score predicted 3–5.6% of variance out of sample, with sibling analyses indicating largely direct genetic effects; this score was also related to neonatal brain volumes in motor-related regions. Overall, the study offers biological insight into a core behavioural marker of neurodevelopment.