This 2015 UK bird study found that older mothers had female children who had fewer offspring than did the rest of the house sparrow population. The finding applied also to older fathers and their male children.
In general, if a study didn’t directly demonstrate cause and effect, it isn’t appropriate to force the use of epigenetics to explain everything. That’s what this study did with epigenetic inheritance.
Did the study:
“Demonstrate that this parental age effect..potentially is epigenetically inherited.”
by analyzing DNA across generations?
The researchers ran some numbers that tested the effect of older foster parents where the model’s only other possible explanation was epigenetic inheritance.
Several other things about this study were off:
- The researchers used the term “fitness” 28 times as shorthand to mean the number of offspring, but only twice was it explained as “reproductive fitness.” This was potentially misleading in some of the contexts of the term’s other uses. For example, several of the cited references used “fitness” in a different context.
- The researchers went into a long exposition of telomeres, punctuated by citing 11 references, only to say:
“However it is unclear how telomere dynamics could affect fitness.”
The next sentence was:
“An alternative explanation might be the accumulation of deleterious mutations as individuals age.”
which was additionally irritating because “alternative” assumed that telomeres presented a factual explanation of the study’s findings in the first place. Was this section an artifact of a struggle with the reviewer?
After forcing epigenetic inheritance as an explanatory factor and potentially misleading readers about reproductive fitness and telomeres, the researchers had little basis to conclude that their research had “important implications.”
http://www.pnas.org/content/112/13/4021.full “Reduced fitness in progeny from old parents in a natural population”