The problem with your link is that showing an IQ test gap doesn't necessarily prove a "significant difference in mental capacity between humans of different races." Correlation does not necessarily equal causation and all that jazz.
For one, many people have pointed out flaws in IQ tests. Do they really measure "general intelligence"? Are there components they don't track well? And are there aspects of test design that favor some socioeconomic or cultural groups over others?
But let's assume that IQ tests ARE actually a perfect measure of general mental capacity for just a moment. Even if that's true, your own link shows part of the problem -- from your link:
However, even small differences in average IQ at the group level might theoretically have large effects on social outcomes. For example, a randomly selected group of Americans with an average IQ of 103 had a poverty rate 25% lower than a group with an average IQ of 100. Similar substantial correlations in high school drop-out rates, crime rates, and other outcomes have been measured.
Now, one conclusion we might take from this is that the marginally lower IQ of race X leads to greater poverty, high-school drop-out, crime rate, etc. in race X compared to Y.
OR -- the causation could be the opposite. That is, maybe living in a local sub-culture that doesn't complete education as much (or doesn't have access to as high-quality education as others, see most inner city schools) and has greater poverty and other social problems could result in worse education and conditions for raising children, resulting in lower IQ test schools.
It seems that the latter is the larger factor in the explanation, based on a number of studies. If you take poor black kids and raise them in middle-class or upper-class white households, a large percentage of the "IQ gap" magically disappears. If you control for socioeconomic status and parents' education level, a lot of the supposed "gap" disappears. In addition to educational opportunity, a lot of this is also likely related to health and nutrition -- it is well-established in many studies that nutritional deficiencies, particularly at early ages, can cause significant differences in IQ. (And black and hispanic kids in the U.S. are known to have a greater rate of nutritional problems than other races.)
Once you factor in all of this stuff, you're left with MAYBE a few points of IQ difference between races at most. Maybe -- it's still inconclusive, and some adoption studies have suggested there's really no difference at all.
Point being -- at least when it comes to the observed racial differences, a much larger portion is likely based in cultural factors rather than genetics. At least that's what the studies on black and hispanic kids have shown. I haven't seen as many studies looking at whether the asian IQ advantage dissipates when environmental/cultural factors are taken into account, but there have been at least a few which show the effect is diminished in adopted kids or once asian kids are removed from their language or culture.