Teeth from two Neanderthal children have provided an astonishing window into life in southeastern France 250,000 years ago, including the local climate and even the fact that children suffered bouts of lead poisoning.

Like tree rings, teeth lay down layers as they grow. Using a sensitive high-resolution ion microprobe, an international team studied the composition of teeth 6,000 years apart at Payre in the Rhone Valley in unprecedented detail.

Periods of high evaporation increase oxygen-18 concentration in liquids, and these become incorporated in the teeth of anyone drinking water. The probe is so sensitive, it can reveal the weather over periods as small as a fortnight.

A paper in Science Advances announces that one of the children was born in spring, although the timing of the other's birth cannot be determined. Mammals frequently give birth as food becomes more abundant, but a sample of one provides little indication as to whether this was a consistent feature of Neanderthal life.

Both the children's teeth show signs of sickness during the winter months, and one was weaned at 2.5 years old, a typical age in pre-Industrial societies.

The most surprising finding was that both children had periods of heavy lead intake, the oldest evidence we have for lead poisoning in a member of the human family.

Lead ingestion, particularly during childhood, damages the development of the brain, lowering intelligence, impeding self-control, and is strongly associated with violence as an adult. The surge in crime experienced in developed nations from the 1960s-80s was probably caused by exposure to leaded petrol and paint. Countries that were slower to phase out the use of lead for these purposes are still suffering the consequences. Lead from water pipes has been controversially proposed as a contributor to the fall of the Roman Empire.

Since Neanderthals were certainly not inhaling car exhausts, and if they used paints at all they probably didn't contain lead, the lead's source is uncertain. However, the fact exposures were predominantly during the coldest parts of winter may provide clues. Two lead mines exist within 25 kilometers (15 miles) of where the teeth were found; nearby caves could have been contaminated. The Neanderthals may have retreated there during cold weather, unaware of the damage to their children.

“At the time they grew up, 250,000 years ago, this region of southeast France was much cooler and more seasonal than it is today,” said lead author Dr Tanya Smith of Griffith University in a statement, so surviving the winters would have been a challenge.

Having demonstrated the power of the technology, the team are keen to apply it to teeth from our direct ancestors, who were still confined to Africa at the time

.