I would have to google such phrases as polyploidy, chromosome evolution, and so forth. When you do this you have to weed through a lot of stuff, but you will find a few nuggets.
My point is not that I have a deep understanding of this subject. It's just that chromosome variation exists, even in humans. Sometimes it results in retardation or sterility, but not always.
If chromosome anomalies were both frequent and inconsequential, the world would be a vastly different place. The fact that anomolies exist at all provides a mechanism required and implied by evolution.
If variation in chromosome count did not exist, or if all hybrids were sterile, that would make common descent impossible.