The sacrifices a primate mother must make to support her young literally run deep. A new study in macaques has shown that pregnancy can leave a permanent mark on the skeleton.
After the birth of a child, female macaques show significantly lower concentrations of calcium, phosphorus and magnesium in their bones compared to those that have not experienced pregnancy.
Although this particular study didn’t look at humans, the findings help inform how major life events can leave a signature on the skeletal tissues of primates in general.
Although they may look like concrete pillars on which fleshy bodies grow, primate bones are surprisingly dynamic. Bones grow gradually throughout life, annual variations in growth are often influenced by lifestyle factors.
Most of us know that bone density can be lost with age, especially after menopause, but throughout life, disease, diet, climate and pregnancy can leave a permanent record of calcified tissue. that can be “read” in the afterlife.
During human pregnancy, evidence suggests The mother’s body can actually pull calcium from her bones where insufficient amounts of nutrients are eaten, reducing her skeletal mass, makeup and density for a while.
During lactation, the mother’s bones are “absorbed” into her bloodstream to produce enough calcium-rich milk. Lost minerals are easily restored once lactation stops, but even then, there could be a way for scientists to observe the momentary delay.
In forensics and archaeology, detecting whether someone has become pregnant using only their bones is a controversial task. Signs on the pelvis from childbirth have been called unreliable, and today, methods and interpretations for this work vary widely. Maybe it’s time to look deeper into the bones.
“Our research shows that even before the cessation of fertility the skeleton responds dynamically to changes in reproductive status,” says anthropologist Paola Cerrito of New York University.
“Furthermore, these findings confirm the significant impact that childbirth has on a woman’s organism – quite simply, the elements of reproduction are ‘written in the bones’ for life.”
The study is based on only seven naturally deceased rhesus macaques, four of which were female, but even in this limited group, the femur bones showed relevant changes that could only be explained by pregnancy and lactation.
Compared to males and females that had not been born young, the two macaques that had bred in their lifetime showed relatively different bone composition, including lower calcium, phosphorus and magnesium content.
The observed changes in calcium and phosphate density were associated with parturition, while the decrease in magnesium content coincided with lactation.
The authors suspect that their results are a sign of bone resorption during reproduction, but further studies are needed to say for sure.
“Findings about elemental changes associated with reproduction are important as detection of parturition from mineralized tissues remains a highly unexplored area of research with important implications for evolutionary, conservation and archaeological studies,” the authors write.
More research is needed, preferably using representative wild primate populations, to see if the same can be said for other animals.
It is possible, say the authors, “that the signal of reproductive events and weaning we detected could be masked, in wild populations, by physiological responses to changing diet and environment.”
The study was published in PLOS ONE.