That is a lot of pseudoscientific bullshit, if you don’t have the stats to prove it.
How is it bullshit?
There is plenty of science to backup the claim that intelligence is heritable [0]. From there the rest of what I said is basic population genetics statistics.
At least genetically this is unlikely. Several hundred genetic variants explain a good fraction of intelligence and a random mixing of Sarah and James’ variants will include ones that increase and decrease intelligence. Getting a really good random mix of several hundred variants is unlikely. That is, intelligence regresses towards the mean.