Somebody: Of course there's variation in innate tendencies - just as there's phenotypic variation in any species. This is as old as Darwin. You find this in spiders, guinea worms, and sea slugs as well. Doesn't mean their behavior is entirely determined by their social structures or the class struggle, or whatever. Of course, somehow humans are magically on a different plane from *all* other species, according to creationists and ideological purists.
Also, if the study had looked at 2 month olds, would that have made any difference to you? Or are vulgar Marxist assumptions about human behavior unfalsifiable? I'm getting the sense that 10, 20, or a 100 studies like this wouldn't breach the ideological fortress some folks have erected.