6 ms·

admittedly i havent read the whole article, only the abstract, but: assuming that children from larger families will partially inherit the trait for having larg

admittedly i havent read the whole article, only the abstract, but: assuming that children from larger families will partially inherit the trait for having larger families themselves seems like a leap to me - arent family sizes in less developed societies generally considered to be either due to religious superstition or because more children = more workers to provide for the family a la victorian times? Once these factors diminish as a society develops, I would argue (from a position of ignorance) that the "traits" governing a bigger family (fertility) are environmental rather than genetic.

Shnooper 7y ago
I agree it's social. In more conservative countries girls receive an unambiguous encouragement to be wives and mothers first.
saagarjha 7y ago
I found this very strange as well, so I skipped down to the section that discussed this: > In countries that have undergone the demographic transition, twin, adoption and family studies have pointed to a substantial genetic effect on fertility (Fisher, 1930; Kirk et al., 2001; Kohler, Rodgers, & Christensen, 1999; Murphy, 1999; Murphy & Knudsen, 2002; Rodgers, Hughes, et al., 2001a; Rodgers, Kohler, et al., 2001b). For example, Fisher (Fisher, 1930) found that a woman could expect 0.21 additional children for each additional child that her mother had, and 0.11 additional children for each additional child that her grandmother had. From this, Fisher suggested that the heritability of fertility at that time was 0.4 (40% of the variation in fertility is explained by genetic factors). Summarising research conducted through to 1999, Murphy (Murphy, 1999) noted that the heritability of fertility averaged around 0.2 in post-demographic transition societies, with the estimates increasing in recent periods. Kohler et al. (Kohler et al., 1999) examined data on Danish twins born in the periods 1870 to 1910 and 1953 to 1964. The first period covers the demographic transition and the second the end of the baby boom. In the first cohort, the heritability of fertility in women varied from close to zero in the pre-transition period to as high as 0.4 to 0.5 during the demographic transition. Estimates of heritability remained strong for the 1953 to 1964 cohort. From an analysis of data for Danish twins from the 1950s, Rodgers et al. (Rodgers, Kohler, et al., 2001b), attributed slightly more than one quarter of the variation in fertility to genetic factors. Rodgers and Doubty (Rodgers & Doughty, 2000) found a median heritability of 0.33 in a contemporary United States population, and heritabilities for underlying desires, ideals and expectations ranging between 0.24 and 0.76. Where measured, the variance attributable to shared environment in low-fertility populations was generally lower than the genetic effects (Kirk et al., 2001; Kohler et al., 1999; Kohler, Rodgers, Miller, Skytthe, & Christensen, 2006; Zietsch, Kuja-Halkola, Walum, & Verweij, 2014). However, the relative balance of genetic and shared environmental factors can change quickly over time (Kohler et al., 1999; Kohler et al., 2006).
- toyg 7y ago
  That is still looking at pre-1970s populations, where the female workforce even in advanced countries was much smaller than today and the religious element was still largely hegemonic.
  - saagarjha 7y ago
    Yeah, I'm not sure that this data is completely relevant, especially given that the birth rate in the US has gone down something like 25% since 1970.
danieltillett 7y ago
In this case it doesn't matter if fertility is genetic or environmental. Parents can pass on the trait either socially or genetically, or as almost is certainly the case as a combination of the two.
- sadris 7y ago
  In almost every case, parents do not pass traits socially. Shared environment impact is roughly zero in nearly every trait ever examined.
deleted 7y ago
[deleted]
lalaland1125 7y ago
Keep in mind that religion is heritable to a certain degree in that parents usually educate their children in their own religion (bring them to church with them, etc). Sure, it might not be as strongly heritable as a genetic trait, but you can certainly see it.

Shnooper 7y ago

I agree it's social. In more conservative countries girls receive an unambiguous encouragement to be wives and mothers first.

saagarjha 7y ago

I found this very strange as well, so I skipped down to the section that discussed this: > In countries that have undergone the demographic transition, twin, adoption and family studies have pointed to a substantial genetic effect on fertility (Fisher, 1930; Kirk et al., 2001; Kohler, Rodgers, & Christensen, 1999; Murphy, 1999; Murphy & Knudsen, 2002; Rodgers, Hughes, et al., 2001a; Rodgers, Kohler, et al., 2001b). For example, Fisher (Fisher, 1930) found that a woman could expect 0.21 additional children for each additional child that her mother had, and 0.11 additional children for each additional child that her grandmother had. From this, Fisher suggested that the heritability of fertility at that time was 0.4 (40% of the variation in fertility is explained by genetic factors). Summarising research conducted through to 1999, Murphy (Murphy, 1999) noted that the heritability of fertility averaged around 0.2 in post-demographic transition societies, with the estimates increasing in recent periods. Kohler et al. (Kohler et al., 1999) examined data on Danish twins born in the periods 1870 to 1910 and 1953 to 1964. The first period covers the demographic transition and the second the end of the baby boom. In the first cohort, the heritability of fertility in women varied from close to zero in the pre-transition period to as high as 0.4 to 0.5 during the demographic transition. Estimates of heritability remained strong for the 1953 to 1964 cohort. From an analysis of data for Danish twins from the 1950s, Rodgers et al. (Rodgers, Kohler, et al., 2001b), attributed slightly more than one quarter of the variation in fertility to genetic factors. Rodgers and Doubty (Rodgers & Doughty, 2000) found a median heritability of 0.33 in a contemporary United States population, and heritabilities for underlying desires, ideals and expectations ranging between 0.24 and 0.76. Where measured, the variance attributable to shared environment in low-fertility populations was generally lower than the genetic effects (Kirk et al., 2001; Kohler et al., 1999; Kohler, Rodgers, Miller, Skytthe, & Christensen, 2006; Zietsch, Kuja-Halkola, Walum, & Verweij, 2014). However, the relative balance of genetic and shared environmental factors can change quickly over time (Kohler et al., 1999; Kohler et al., 2006).

toyg 7y ago
That is still looking at pre-1970s populations, where the female workforce even in advanced countries was much smaller than today and the religious element was still largely hegemonic.
- saagarjha 7y ago
  Yeah, I'm not sure that this data is completely relevant, especially given that the birth rate in the US has gone down something like 25% since 1970.

danieltillett 7y ago

In this case it doesn't matter if fertility is genetic or environmental. Parents can pass on the trait either socially or genetically, or as almost is certainly the case as a combination of the two.

sadris 7y ago
In almost every case, parents do not pass traits socially. Shared environment impact is roughly zero in nearly every trait ever examined.

deleted 7y ago

[deleted]

lalaland1125 7y ago

Keep in mind that religion is heritable to a certain degree in that parents usually educate their children in their own religion (bring them to church with them, etc). Sure, it might not be as strongly heritable as a genetic trait, but you can certainly see it.