"Though IQ is heritable, there seems to be no good reason to assume genetic differences in intelligence at the population level: the populations we're talking about here (African-Americans and white Americans) are so heterogeneous that polygenic traits are unlikely to differ meaningfully across groups. "
The average is what matters for average differences in IQ, not whether there's heterogeneity. African-Americans have an average of 80% recent Sub-Saharan admixture, whites about 0%. Differ in plenty of polygenic traits like skin color, eye color, hair color.
"Moreover, the IQ gap between Black and white Americans has decreased substantially in recent years"
"Moreover, this also doesn't work for the same reason as above: we see variation in cognitive scores by socioeconomic status, but the groups at each SES level are extremely diverse. Hypothetical differences in IQ by race, ethnicity, or national origin don't make sense as an explanation here, since these characteristics are spread across different SES levels."
It makes perfect sense: IQs are distributed on a bell curve. Different racial means still means there's people of every race in every IQ category.
"I think there are compelling .............................................................................. That is to say, adoption into a high-SES household raises cognitive test scores." Your source/evidence ???
"Though IQ is heritable, there seems to be no good reason to assume genetic differences in intelligence at the population level: the populations we're talking about here (African-Americans and white Americans) are so heterogeneous that polygenic traits are unlikely to differ meaningfully across groups. "
The average is what matters for average differences in IQ, not whether there's heterogeneity. African-Americans have an average of 80% recent Sub-Saharan admixture, whites about 0%. Differ in plenty of polygenic traits like skin color, eye color, hair color.
"Moreover, the IQ gap between Black and white Americans has decreased substantially in recent years"
https://ideasanddata.wordpress.com/2021/07/06/critiquing-charles-murray-on-changing-iq-gaps/
"Moreover, this also doesn't work for the same reason as above: we see variation in cognitive scores by socioeconomic status, but the groups at each SES level are extremely diverse. Hypothetical differences in IQ by race, ethnicity, or national origin don't make sense as an explanation here, since these characteristics are spread across different SES levels."
It makes perfect sense: IQs are distributed on a bell curve. Different racial means still means there's people of every race in every IQ category.
If IQ differences were caused by low-SES, then comparing within SES would eliminate racial gaps, which is not remotely the case: https://preview.redd.it/82mujmdjpp461.jpg?auto=webp&s=ababc75d2a5637b32426872888519559a157fa2a
Effects of adoption on IQ fade out by adulthood, when the effect of shared environment on IQ is basically 0.
Please read some HBDers who have long since debunked these environmental explanations.
"I think there are compelling .............................................................................. That is to say, adoption into a high-SES household raises cognitive test scores." Your source/evidence ???