Genetic diversity is a very interesting topic that’s well worth exploring, but it seems to me that Occam’s razor requires us to consider the possibility they just had a really good, well timed dosage of performance enhancing drugs for Secretariat back in the day.

I think it's surprising that the article predicts the impacts of gene editing to be relatively small.

> Even so, the prospects for exceeding current records through gene editing are slim. Today’s racehorses are already tightly optimized for speed, balancing strength against the cost of carrying additional muscle mass. Adding more muscle is relatively low-hanging fruit, and if this were the key to unlocking greater speed, selective breeding would likely already have brought it about.

It's a whole new tool in the toolbox, and can introduce mutations that didn't first arise by chance in order to be then spread with selective breeding.