Smart parents breed smart kids. That seems like common sense. And today another study came out reinforcing that claim. By looking at DNA, researchers have linked genes to IQ, according to a study in Molecular Psychology. Scientists found that at least a thousand genes contribute to between 40 and 51 percent of one's intelligence. Now, that doesn't necessarily mean you can predict someone's smarts just from their parents' grades. It just means that genetics make certain kids test the same on a test. And if you stretch the logic, which many have, things can get pretty nasty. So let's set things straight before anyone jumps on the social Darwinism train.

Lots of factors determine what shapes one's intelligence. First of all, intelligence tests are suspect. Some have argued they're biased; don't test for the right characteristics; and some smart people just don't test well. Also the findings only related about half of one's intelligence to their genetic makeup--that leaves another half up to environmental factors and upbringing. 

Understanding the connection between genes and intelligence has spurred heated debates before. Twin studies have shown some connection between IQ variation and genes, explains Slate's William Saletan.

Twin and sibling studies, which can sort genetic from environmental factors, suggest more than half the variation in IQ scores is genetic. A task force report from the American Psychological Association indicates it might be even higher. The report doesn't conclude that genes explain racial gaps in IQ. But the tests on which racial gaps are biggest happen to be the tests on which genes, as measured by comparative sibling performance, exert the biggest influence.

Some interpret these studies as a way to prove that certain races are smarter than others, which could explain socio-economic differences, as 1997 Charles Murray book, The Bell Curve argued.  It can make sense that certain races would develop different types of brains, as Saletan argues. "Everyone agrees that the three populations separated 40,000 to 100,000 years ago. Even critics of racial IQ genetics accept the idea that through natural selection, environmental differences may have caused abilities such as distance running to become more common in some populations than in others."

But of course, as with many scientific studies, others see that research and discount it as unscientific. "Because theorists of intelligence disagree as to what it is, any consideration of its relationships to other constructs must be tentative at best. They further argue that race is a social construction with no scientific definition. Thus, studies of the relationship between race and other constructs may serve social ends but cannot serve scientific ends," argues a study in American Psychologist.

So, science has once again proven genes definitely have something to do with our mind's makeup. But what exactly that means for intelligence...well, the jury is still out.