[quote=Magic Magnum]
Impact in terms of Religious Wars or Crusades perhaps.But it has a rather big impact on education and scientific knowledge.Quite a lot, it's basically going "What difference does it make if we believe in Gravity, but say it doesn't apply to humans?".
[/quote]

Let the record reflect, that Magic believes Young earth creationism caused the Crusades. 

And as for gravity, that would suggest that Intelligent-design advocates believe humans are not currently effected by Natural selection, which is not so.

Better analogy: "What if a small segment of the population believed gravity didn't apply to humans until 6,000 years ago?"

No effect.