In an article by Phys.org, they wrote that offspring of older mothers do not fare as well as those born from younger mothers, may it be in humans or animals. These offspring are not as healthy, do not live as long, or have fewer offspring themselves.
Scientists are puzzled why evolution would maintain such maternal effect in many species since these offspring born to older mothers are less fit to survive.
The new study in rotifers tested the evolutionary fitness of older mother-offspring in many real and simulated environments, including the laboratory culture, the threat of predation in the wild, and the reduced food supply.
Offspring From Older Mother Has Reduced Fertility and Evolutionary Fitness
Study lead author Kristin Gribble of the Marine Biological Laboratory and colleague Christina Hernández of Woods Hole Oceanographic Institution published their study this week in Proceedings of the National Academy of Sciences.
Their experiment confirms that the effect of older maternal age, known as maternal effect senescence, can reduce the offspring's evolutionary fitness in all environments. Additionally, it also reduced fertility during the peak of the reproductive period of the rotifer.
Gribble said that their study is unique as it combines laboratory data from prior studies with mathematical modeling to address the evolutionary question: "Why this phenomenon still exist across so many species?"
Using the mathematical models built by Hernández and collaborators, they were able to calculate the strength of natural selection pressure on the survival and fertility of the offspring born from older mothers for the first time. They found that the selection gradient declines with maternal age.
"Because the selection pressure decreases as the mother's age, it may not be strong enough to remove these less-fit [offspring] from the population," says Hernandez.
Gribble added that this explains why maternal effect senescence will persist and continue to evolve in the population, even though it produces offspring who is less healthy and would likely live a shorter life.
The scientists do not fully understand yet what genetic mechanisms cause offspring quality to decrease with maternal age.
The mathematical models can be used in a variety of species to assess the fitness consequences of the maternal effect senescence.
Children From Teenage Parents
Though offspring from older parents may fare less and die at a younger age, children of teenage mothers could also face risks. They could be low in birth weight due to complications of the mother's pregnancy and delivery, and other health problems associated with poor perinatal outcomes.
The impact of teenage pregnancy poses a higher risk to a child, and they could have lower IQ and academic achievement later on, according to research by Sandra L. Hofferth a professor in the Department of Family Science at the University of Maryland, and Director of Maternal and Child Health Program
Many studies find that children of teen parents are at greater risk for a host of health, social and economic problems than children of older parents.
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