Den­tal record

Teeth can re­veal ev­i­dence of stress­ful lives and the menopause, study shows

The Guardian - - News Coronaviru­s - Ni­cola Davis

Tell-tale signs of stress­ful life events could be found in our teeth, say re­searchers who have found birth, menopause and even im­pris­on­ment ap­pear to leave their mark in tis­sue that is laid down through­out life.

The phe­nom­e­non is sim­i­lar to the way the thick­ness of an­nual tree rings can tell us about the cli­mate and en­vi­ron­ment in which the tree grew. In teeth, changes to the way the tis­sue in­ter­acts with light of­fer the clues.

“We didn’t know that a por­tion of our or­gan­ism served as such faith­ful bi­o­log­i­cal ar­chive for the en­tirety of life,” said Paola Cer­rito, co-author of the re­search from New York Univer­sity.

Re­searchers be­hind the study say they be­lieve the dis­cov­ery could help shed light on a long­stand­ing co­nun­drum. Hu­mans are un­usual as they are one of only a few mam­mal species that live for many years af­ter they stop be­ing fer­tile. This trait that has led to a num­ber of the­o­ries in­clud­ing the “grand­mother hy­poth­e­sis”, the idea that post-menopausal women sur­vive to help their chil­dren to grow up and re­pro­duce.

The re­searchers say that in or­der to test the the­ory they needed a way to look at pos­si­ble evo­lu­tion­ary links be­tween birth pat­terns and menopause, and changes in the way chil­dren are reared. The new study, they say, may do just that.

The team are now look­ing at the teeth of pri­mates and hu­man rel­a­tives such as Ne­an­derthals to see if they show the same tell-tale clues.

How­ever, Cer­rito said the find­ings could also be use­ful in other fields. “The meth­ods we de­vel­oped can be used by ar­chae­ol­o­gists of the an­cient world to piece to­gether a more com­plete un­der­stand­ing of the lives of past civil­i­sa­tions by in­te­grat­ing writ­ten records of a per­son’s so­cial and pub­lic life to bi­o­log­i­cal data re­gard­ing in­ti­mate de­tails such as fer­til­ity, menopause, or other phys­i­o­log­i­cal stres­sors,” she said.

Writ­ing in the jour­nal Sci­en­tific Re­ports, Cer­rito and col­leagues re­port how they analysed 47 teeth from 15 mod­ern, de­ceased in­di­vid­u­als, look­ing

’These meth­ods can be used by ar­chae­ol­o­gists of the an­cient world’

Paola Cer­rito Co-author of the re­search

at a num­ber of teeth for nine of them.

It has long been known that tooth enamel forms lay­ers over time, but this process stops once the teeth have fin­ished form­ing. As a re­sult, Cer­rito and col­leagues looked at a dif­fer­ent tis­sue, ce­men­tum, that grows through­out an in­di­vid­ual’s life. This tis­sue cov­ers and pro­tects the tooth’s root, and helps con­nect teeth to the jaw.

Look­ing at the teeth us­ing po­larised light mi­croscopy, they found the in­ter­ac­tion of the ce­men­tum with light was not the same through­out the tis­sue.

Tak­ing into ac­count the age of the in­di­vid­ual at death and the thick­ness of the ce­men­tum, the team found that these dis­tinct changes seemed to line up with the tim­ing of known events in the life of the in­di­vid­ual in ques­tion, in­clud­ing giv­ing birth and menopause.

“Sadly, in a num­ber of in­di­vid­u­als that had been im­pris­oned prior to death, we found ev­i­dence of that event,” said Cer­rito.

The ap­proach, at present, does have a num­ber of lim­i­ta­tions, in­clud­ing that the type of change in the ce­men­tum is the same for dif­fer­ent life events, while even within the same in­di­vid­ual, dif­fer­ent teeth of­fer slightly dif­fer­ent tim­ings.

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