From birth to 90: The five big turning points that rewire the human brain

Scientists studying around 4,000 brain scans have found that the human brain grows and changes in five major stages, with key shifts around ages nine, 32, 66 and 83

Researchers have uncovered five key “epochs” in human brain development, offering one of the clearest pictures yet of how our neural wiring changes from birth to old age. The research by the University of Cambridge comes from a study of 3,802 brain scans of people aged from infancy to 90 years.

 

The team analysed how different regions of the brain communicate and how these connections shift over time. Their work revealed five broad developmental phases, each separated by a major turning point around the ages of nine, 32, 66 and 83.

 

“Looking back, many of us feel our lives have been characterised by different phases. It turns out that brains also go through these eras,” said Prof Duncan Astle of Cambridge University, the study’s senior author. He added, “Understanding that the brain’s structural journey is not a question of steady progression, but rather one of a few major turning points, will help us identify when and how its wiring is vulnerable to disruption.”

 

Epoch one: Birth to age nine

 

The first phase stretches from infancy through childhood. During these years, the brain is shaped by what scientists call “network consolidation”. Babies are born with an enormous number of synapses, the tiny links between neurons. As they grow, these connections are gradually refined -- busy, useful links are strengthened, while others fade away.

 

The study found that the efficiency of the brain’s wiring actually decreases during this period because the system is reorganising itself. Meanwhile, both grey and white matter grow rapidly.   

 

Epoch two: Adolescence to early 30s

 

At around nine years old, the brain transitions into the adolescent era, which continues until about 32. This period is marked by increasing efficiency in communication across brain networks. White matter continues to expand, making information transfer faster and more reliable.

 

“We’re definitely not saying that people in their late 20s are going to be acting like teenagers, or even that their brain looks like that of a teenager,” said Alexa Mousley, who led the study. She added that this era may offer clues to why mental health disorders often emerge during adolescence.

 

Epoch three: The long adult phase

 

The next major turning point occurs at about 32 years, when the brain’s wiring shifts into what the researchers call an adult mode. This epoch is the longest, lasting more than three decades. Brain architecture becomes more stable, with fewer dramatic changes than seen in childhood or adolescence.

 

This stage also aligns with what other studies describe as a “plateau in intelligence and personality". Researchers suggest that life events such as parenthood may influence some of the structural shifts seen around this age, though the study did not directly examine this.   

 

Epochs four and five: Early and late ageing

 

After about 66 years, the brain enters an early ageing phase, followed by a late ageing phase beginning at around 83. Both stages are associated with decreasing connectivity, likely linked to white matter degeneration. These changes reflect the natural processes of ageing, which gradually impact how efficiently different brain regions communicate.