They have not shown a causal relationship.
True.
This indicates that if there is a genetic component, it is largely irrelevant as the learning environment has the greater impact.
False. I'm unclear how you came to that conclusion based on the quote you highlighted. It does not say that learning environment has a *greater* impact. It says learning environment has *some* impact. Overall, but it is less than or equal to the importance of genetics.
This result is consistent with other studies on the topic. Unfortunately, this fact pisses people off, especially educators. (Understandably since it is their job to educate everyone equally, and especially to raise the level of the poorest performers). But it is well correlated at this point. Think back to high school: everyone realized this at some point - there were some students who just seemed smarter. Some of them didn't even have to work for it. It sucked if you sat in one of these kids' shadow. It doesn't mean hard work doesn't pay off, it doesn't mean you should not invest in your children, but it does mean that just like in sports, your genes are as big a contributor as the environment.
On that note: why are people willing to accept this in sports, but not in academics? It's totally cool to say something about Nigerian runners having long legs, or say "white men can't jump, hahaha" or "Asians are short" but if you say some people are genetically gifted in intelligence sets off everyone's alarm bells.
Excerpt from Freakanomics:
Eight factors that correlate to higher test scores
Highly educated parents
Parents have high socioeconomic status
Mother was thirty or older at the time of first child's birth
Child had low birth weight
Parents speak English at home
Child is adopted
Parents are involved in the PTA
Child has many books in the home
Eight factors that do NOT correlate with higher test scores:
Family is intact
Family's recent move to a better neighborhood
Mother did not work between birth and kindergarten
Child attended Head Start
Parents bring children to museums regularly
Child is regularly spanked
Child frequently watches television
Parents read to him nearly every day