Link here (2006 research from U.S. government agency). Interesting, because differences do emerge later in childhood, in particular with East Asians outperforming others. Why is this? Either there are genetic differences that emerge at that point - or culture matters (i.e. it's not just window-dressing) and has an impact on intelligence.
"...there is good and bad speculation, and this is not an unparalleled activity in science...Those scientists who have no taste for this sort of speculative enterprise will just have to stay in the trenches and do without it, while the rest of us risk embarrassing mistakes and have a lot of fun." - Dan Dennett