Here's Steve Levitt:
In my work with Fryer, we analyzed a newly available nationally representative survey of children ages two and under, done by the Department of Education. Included in this study are tests of mental ability around a child’s first birthday. While you might think it would be impossible to capture anything meaningful at such a young age, it turns out that these measures of one-year-olds’ intelligence are somewhat highly correlated with IQ scores at later ages, as well as with parental IQ scores.The striking result we find is that there are no racial differences in mental functioning at age one, although a racial gap begins to emerge over the next few years of life.
So what does this mean for the genetics vs. environment debate? Quoting from our abstract, "the observed patterns are broadly consistent with large racial differences in environmental factors that grow in importance as children age. Our findings are not consistent with the simplest models of large genetic differences across races in intelligence, although we cannot rule out the possibility that intelligence has multiple dimensions and racial differences are present only in those dimensions that emerge later in life." [With bold emphasis added by me]