The timescale for the human Y chromosome family tree has been a source of sharp disagreement within the creation/evolution debate. Recent findings from Y chromosome comparisons between fathers and sons put the origin of global Y chromosome differences around 4,500 years ago. This short timescale predicts that the last few thousand years of human population growth should be reflected in most of the branches of the Y chromosome tree—not just in the tips of the tree. I show that this prediction has been fulfilled in global human Y chromosome data derived from the mainstream evolutionary literature. I also show that this finding revises the root for the Y chromosome tree, and that it independently tests the usefulness of ancient DNA, such as that derived from Neanderthals.