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Moms and Inheritance: Tracing the Maternal Line

Tuesday, December 04, 2012 - 02:00 PM

Chromosome embroidery. Chromosome embroidery. (Remixed from photo by Hey Paul Studios/flickr/CC-BY-2.0)

When talking to researchers for the genetics portion of our Inheritance show, one thing that consistently came up is that it's difficult for science to study the effects maternal lineage has on offspring.

Some listeners noticed this too, notedly in our segment "You are what your grandpa eats," in which we explored a Swedish study that looked at the effects of food availability on boys between the ages of about 9 and 12 years old, and how those effects showed up in the future sons and grandsons of those boys. Quick recap: for those boys that experienced famine in their tweens, when they grew up to be fathers, they actually passed a health benefit onto their offspring; their kids, and grandkids, were less at risk for heart disease, and diabetes. For those who had lives of plenty, it turns out their kiddos (and grandkiddos) would have a higher frequency of heart attacks and diabetes.

A pretty provocative study. But what about the effect grandmothers, or mothers, have on the offspring? Lars Olov Bygren, the lead researcher on the Swedish study, said that his group did study both the male and female lines but, and it's a big but -- "the maternal influence of this special kind, from availability of food during childhood, is difficult to discern -- probably because there are so many signals between mother and the fetus or child, and this might hide a similar influence as in the male line."

What does Bygren mean by "so many signals"? Well, pregnancy is a very intimate, boundary-smudging process, in which mother and baby share not only genes, but hormones, blood, cells, chemicals, bacteria, and more. If you're trying to isolate the effect that genes -- and only genes -- have on the baby, and isolate that effect over multiple generations... it's a tall order. Like trying to hear a whisper in a room full of crying babies. But if you look for the effect in the paternal line, there's one thing and one thing only to study: sperm. It's more of a clear cut process (as "clear cut" as genetics can be, that is).

That's not to say science isn't extremely interested in what mothers are contributing -- on the contrary, they're doing their best to understand it. In fact, Bygren says that his group sees some kind of "involvement" between a maternal grandmother, her son, and the son's daughter, but they aren't sure exactly what that involvement is. And as for a connection between grandfathers and granddaughters, his team didn't see an influence on cardiovascular or all-cause mortality like they did with grandfathers and grandsons. So the big research results, like the kind of data-driven paternal studies Bygren talked about in our Inheritance show, are still in the making. Hopefully those findings are on their way with future studies -- with larger sample sizes and new techniques, scientists should be better able isolate the whisper in all the noise.

In the meantime, we'll keep our ears perked for any upcoming maternal studies -- and you should too, we'd love to know if you see anything.


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Comments [3]

Maggie from Dubuque, IA

Did anyone pass on the idea of the licking increasing the protein in the brain to the people raising cranes from the other episode?

Dec. 31 2012 10:18 AM
Jim F from Bay Area, CA

Hi, I just love your work…..mostly listen to the podcasts….and donate too :-). I wanted to comment on the last segment of your show entitled ‘Inheritance’ from Nov 2012. I personally have no problem with the payment for birth control strategy and thought your segment was a little one sided. My wife and I adopted 2 kids from birth….both have problems, one significantly enough to never be a productive member of society. My points, in no particular order are:

1) People have the right to make choices, even if some consider them bad choices, as long as they are fully informed. That is, if someone wants to accept money in exchange for having a tubal ligation, that is their right, again, as long as it is a fully informed decision (which is virtually guaranteed by our health care system). This is the counter argument to people who think the pay for birth control is wrong…..who are they to override the informed decision of someone else about what they do with their bodies. This is prevention, not abortion.

2) I think we are incredibly resilient as a species and so there are many kids born addicted who do well when put in an environment that lets them thrive. However, there are many kids who have permanent brain damage from being exposed to drugs/alcohol in the womb. Your segment touted how 7 of the 8 kids born to the mother using drugs are going great…..well, it certainly sounded like those 7 were not raised by the birth mom. So it is not exactly that they are doing great if they stayed with their birth mom. Another counter argument to the people against pay for birth control…. Some of these kids will never be ok, and those that are need a lot of help…..are you willing to pay for them (easy) or be the one to raise them (not so easy)? In listening to the women who were against this program, all I could think was they would sing a very different tune if they adopted a child who was damaged by the drugs their birth mom took.
3) In general, I think there too many people in the world….a side effect of technology. If that is the case, why bring kids into the world who are abused from birth (yes, forcing a newborn to go through withdrawal as an infant is abuse), stand a good chance of being damaged, and need massive support to be ‘normal’? If you accept this view of overpopulation, then why add people who are ill equipped to compete in this world?
4) Last point…..we are talking about preventing pregnancies…..not abortion. I don’t think there are any real moral issues here…..although there are those who strongly value sanctity that will be upset by programs such as this….but I bet if you ask them, they couldn’t really articulate what is morally wrong with a program such as this.

The attitude that we should stop someone from choosing to not have more children because someday they may regret their decision and not give birth to the next Einstein is absurd at best…..and IMHO a bit naive too.


Dec. 11 2012 09:45 PM
David Henderson from Columbia, Missouri

I wonder if it really is "clear-cut" that altered genetics via some degree of starvation/malnutrition (apparently boys only) at the specific ages of 9-12 is passed on only to male offspring and male grandchildren.

I must say I'm skeptical. It seems quite possible that near starvation at an age of 9-12 could have significant impact on one's future behavior (specifically, future diet choices), and perhaps other choices that affect cardiovascular health such as exercise.

I would assume (yet don't know) that his has been considered by the researchers. And even if they have, it is likely they can not account for every variable (likely many are unknown or unknowable).

At best I would say it's plausible vs "clear-cut".

Dec. 05 2012 01:44 PM

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