A child’s first steps are an important milestone – and according to a new study, genetics strongly influences when it happens. The research also shows that the timing may be linked genetically to both attention deficit/hyperactivity disorder (ADHD) and body-mass index (BMI) later in life. Parents can do a lot – but they cannot control everything.
A child’s first steps have always felt special, just like their first words, learning to ride a bike and losing that first baby tooth.
A major new study shows that children begin walking as early as eight months or as late as 18 months – and that genetics strongly influences when this happens. The study also links the age at onset of walking to several other traits and conditions, including ADHD and BMI later in life.
According to the lead researcher, the findings may help to reassure parents that they do not fully control when their child begins to walk – and the results also provide new insight into the genes that influence musculoskeletal disorders.
“Parents can provide a good environment – with healthy food and space to practice. But they cannot influence the genetic side. Genes explain some of the variation in when children learn to walk,” says Angelica Ronald, Professor of Psychology and Genetics in the Faculty of Health and Medical Sciences, at the University of Surrey in the United Kingdom.
The first steps say something about the child
The study aimed to find genetic patterns that could explain when children learn to walk by using genome-wide association meta-analysis, which compares DNA with specific characteristics, such as when a child takes their first step.
The researchers gathered data from four large population studies in which parents recorded when the child started walking and DNA samples were collected.
This enabled the researchers to link genetic variation among individual children with the age at which they took their first unassisted step. Genetic variation comprises small differences in genetic material that make people unique – without necessarily being problematic.
“There is currently much research on how genetic variation affects the risk of diseases with onset later in life – such as cardiovascular disease and diabetes. But this study aimed to examine what genes mean very early in life – even before a child learns to walk. A child’s first step is an important milestone and one that can worry many parents,” explains Angelica Ronald.
She emphasises that if a child is not walking by 18 months, parents should consult a doctor to have the child’s development assessed.
Eleven loci behind the first step
The researchers had access to data on 70,560 babies of European ancestry. They found 11 genetic regions – loci – at which small variations in DNA are associated with when children learn to walk.
The study showed that genetic variation explains about 24% of the differences in the timing of the first steps. This means that genes clearly have a role – but that environment and development are also important.
Many of these loci were present in genes that are active in brain development – especially in areas that control motor skills and movement.
“Discovering that genes expressed in the brain are involved in the timing of a child’s first steps is interesting. Some of the same genes also have a role in rare diseases in which children either walk very late or do not learn to walk at all,” says Angelica Ronald.
Early steps linked to the genetics of ADHD
The researchers also investigated whether the timing of a child’s first steps overlaps genetically with other conditions. Some of the genetic variants associated with early walking are also present among people with ADHD.
Conversely, the researchers discovered that the genetic variants linked to starting to walk later overlap with the genetic variants associated with lower BMI in adulthood.
“This does not mean that everyone who walks early gets ADHD – or that walking late causes lower BMI. But there is a genetic link. And it makes sense: a very active child with ADHD may therefore move more and learn to walk earlier. We would like to test this hypothesis further,” explains Angelica Ronald.
The researchers also found a genetic link between late walking and the degree of folding in the brain’s surface (cortex). This suggests that genetics also influence brain development.
Late walking gives insight into the brain
According to Angelica Ronald, the research shows that parents cannot control everything about their child’s development – and realising this can be a relief.
The findings also give researchers deeper insight into what happens in the brain during the early stages of life when a child is learning to walk.
This is important knowledge, because late walking can be linked to various challenges later in life. In the long term, such insight may help provide support for children at an early stage – before problems arise.
“Now we can study genes more closely and find out how they affect brain development – and what consequences this may have later in life. The more we understand about the brain in early childhood, the better we can help children in time,” concludes Angelica Ronald.
