Give me an otherwise healthy infant from Guatemala and let me raise him in Palo Alto with an educated, motivated set of parents. At the same time, give me a kid from wherever you want with your hand-selected lebemsborn genes, and bring him up surrounded with poverty, ignorance, and superstition. I think your eugenics world view would be blown up if we take their IQ tests and look at their station in life when they are adults. Extend that two more generations and you'll be saying that the Guatemalans are naturally more intelligent.
Did some court appointed child welfare work back in the day. I have seen first hand what happens when you do a Trading Places with hispanic foster kids (5 - 8 y.o.'s) when they had literally no education or values. They were pulled out, placed with an academically driven family, and frankly began malnourished with mental functioning of dogs. They couldn't even articulate thoughts very well. In about 3 years both kids became high achievers, and the older one was "the smart kid" in his class if teachers and parents are to be believed.
Children are incredibly plastic, and it appears lots of cognitive "scaffolding" is developed during adolescence and teenage years. There may be a component of THAT that is inherited, as well.... I've read literature that suggests mental stress of momma's childhood impacts even the physiological development of her kids and grandkids. That IQ you're talking about gets turned on its head real fast if you change basic environments and priorities and let that stew for a few years. Even more so if you span it across generations. I don't think you "get" poverty.