Baby teeth and tree rings have something in common. They both can shed light on how the living organism developed.

Scientists say they have figured out a way to read baby teeth to measure how infants metabolize two key nutrients: zinc and copper. Abnormal fluctuations in these nutrient levels were then used by researchers to predict which children in study groups had autism.

The process to read those teeth is likened by the researchers to reading the growth rings on a tree.

In the womb and during early childhood, children form a new tooth layer every day, with each new layer carrying the fingerprint of the chemicals circulating in their bodies. The baby teeth give scientists a record of the child’s chemical exposure.

Researchers were able to sample the layers in baby teeth — once the teeth had fallen out, of course — with the help of a laser.

Using an algorithm they developed, scientists were then able to predict with up to 90 percent accuracy which of the children had autism, a developmental disorder that impairs a child’s communication skills.

Researchers at the Icahn School of Medicine at Mount Sinai in New York City don’t yet understand the connection between autism and that irregular nutrient cycle. But they say their findings underline the critical importance of nutrient cycles in healthy neurodevelopment.

This testing method can’t yet be used as a diagnostic tool because by the time kids shed their baby teeth, an autism diagnosis is usually apparent. But researchers say these findings nonetheless open the possibility that a diagnostic test might one day be developed for very young children.