But it's a very common typo that only creationists seem to make. I'm serious about this: I suspect it reveals a type of brain organization that's different from that of other people.
Now, if creationism really is the more valid conclusion to be gotten from the facts that we all have access to, then this cognitive quirk would be a marker for a superior mind, and not a cognitive deficit as you think I'm assuming it is. I think you can agree with me that keeping singulars & plurals in agreement is the correct way to build a noun/verb phrase, and so if someone has problems keeping them in agreement we'd normally say that they have a cognitive deficiency that they have to work on overcoming. But there are other examples of cognitive deficits being correlated with superior cognitive skills in other areas.
For example: Asperger's syndrome is a "problem" that isn't necessarily a problem overall. "Suffers" of this syndrome may have a hard time interacting with other people, but they are great at focusing their attention on intricate tasks that can require much thought to carry out.
So, since creationism is clearly the superior inference from the facts, and creationists seem to have a higher tendency to exhibit this particular grammatical quirk, it follows that the cognitive "deficit" that causes singular-plural disagreement when they write sentences must be a side-effect of a superior mind. I'm just wondering if those creationists who have this quirk have ever noticed it in their day-to-day lives.