This is really just a curiosity, but I'm looking more for either studies/surveys or at least strong anecdata from birth professionals with a LOT of experience.
It's always been my instinct/understanding (but not truly based on hard data) that baby size is primarily dependent on the following, to varying degrees:
-"Age" at birth (30 weeks, 35 weeks, 40 weeks, etc.)
-Nutrition (maybe less so than currently emphasized)
-Interventions (both procedures and drugs- medical and other)
-Certain diseases and anatomical issues (such as what might lead to IUGR, twin pregnancy, etc.)
Of course it's still an inexact science, but what I am curious about is whether Dad's genes really come into play all that much?
Intuitively, I'd actually guess they didn't? Especially since size at birth does not correlate much at all to size at 1 year or 5 years (unless I'm grossly misinformed), not to mention size at adulthood.
Obviously, we are talking about at least two things here (if not many more). 1) How big Dad and Dad's genetic relatives were at birth, and 2) How big Dad and his relatives are as people/adults.
At the very least, I'd guess #2 would be really minimally important, and #1 might not be that important either? One would guess that evolutionarily it would make sense for women's bodies (almost always) to grow baby to whatever size ideal for them as individuals. Doesn't matter if the baby grows up to be a 4'11" woman or a 6'5" man.
I know this would be super-hard to narrow down in any decent study! Especially considering how "messed-around-with" (inductions, etc.) so many women's births are, and not just in the US-- and every individual birth and pregnancy is so different anyway.
And... let's say Dad was 11 pounds at birth, and all his siblings were 10+ lbs... We don't know if that was something genetic that could even be passed down to his sperm or if it was for some other reason related to his mom's nutrition or any other number of things.
But of course, ideally, one would track the babies of women who had children by more than one bio father, preferably more than one by each father...
My guess would be that the babies would be fairly close in length/weight to each other when other factors were minimized.
What say you?
I ask in part because it seems people just assume that if a small woman is impregnated by a big man, she's going to explode.
This is especially true when the man comes from "stock" considered big in general, and the woman does not. Say, a woman of Cambodian descent with a man of Swedish descent.
I have heard that if you can get a Chihuahua pregnant by a Great Dane or whatever, there will be problems. But domestic dogs are SO much more diverse than people because humans have interfered so severely and artificially with their "evolution" for thousands of years. Still, if it is true, it seems to imply that dad's genes come into play somehow... But to what extent? Is it really significant or even determinable in humans, who are much more genetically similar to one another than dogs (esp. considering race as a social construct, etc.)?
Just thinking "out loud!" Any input is appreciated.