A mother’s age can influence the health and development of her offspring, and this effect appears across much of the animal kingdom.
But scientists still do not fully understand how information about a mother’s age is passed to the next generation.
New research involving tiny aquatic animals called rotifers is offering important clues. The findings suggest that the answer may involve changes that control how genes behave rather than permanent changes to DNA itself.
Scientists call these influences “maternal age effects.” They have been observed in animals ranging from small invertebrates to primates, elephants and humans.
In many cases, offspring born to older mothers may have shorter lifespans, reduced reproduction or other disadvantages.
Kristin Gribble, an associate scientist at the Marine Biological Laboratory, studies these effects using rotifers.
These microscopic animals are especially useful because they reproduce quickly, allowing scientists to follow several generations in a relatively short time.
Researchers have often suspected that maternal age effects might result from cellular damage or DNA mutations that gradually build up as a mother gets older. However, experiments from Gribble’s laboratory point toward a different explanation.
The team studied two genetically different strains of the same rotifer species. If accumulated DNA damage were responsible, scientists would expect the negative effects to become progressively worse across generations. Instead, the researchers found that maternal age effects could disappear within just one generation.
That rapid reversal suggests that permanent genetic mutations are unlikely to be the main cause.
Instead, the researchers suspect an epigenetic process may be involved. Epigenetics refers to biological changes that affect whether genes are switched on or off without changing the underlying DNA sequence.
One possible mechanism involves proteins called histones, which help package DNA inside cells. Chemical changes to histones can alter how easily cells access particular genes, changing their activity. Gribble’s team is now investigating whether these histone modifications carry information about maternal age to offspring.
Mitochondrial DNA could also play a role. Mitochondria are structures inside cells that produce energy, and their DNA is usually inherited from the mother.
Genetics may further determine how strongly offspring are affected. Interestingly, one rotifer strain showed the opposite of the usual pattern: offspring of older mothers actually lived longer. This suggests that some genetic variants could protect against, or even reverse, negative maternal age effects.
Another mystery is why these effects remain so common despite their potential disadvantages. Gribble suggests that natural selection may provide part of the answer. In rotifers, most reproduction happens early in life. By the time females become old, they have already produced most of their offspring, so evolutionary pressure against harmful late-life effects may be relatively weak.
Ultimately, the research could help scientists understand how the experiences of mothers—and potentially grandmothers and great-grandmothers—leave biological traces across generations.
For human health, the idea carries an important message: our biology may reflect not only the genes we inherit, but also biological information shaped by the lives and environments of previous generations.
