I think your misunderstanding OP's full question. They're asking, if the reproduction is difficult and the offspring are most likely sterile, how did species come to have different chromosomes at all? If we all have a common ancestor when you go back far enough, that must mean a mutation happened that caused one of them to have a different number of chromosomes. Most of the comments are saying how the actual producing offspring isnt difficult, but the fertility of that offspring is rare. But then how could those mutations in the number of chromosomes have become persistent enough that the offspring of them were fertile and able to even pass that down themselves?

Summary: If a member of a species was born with an extra chromosome, or two chromosomes fused, their offspring have a high change of being sterile. How could the increase of decrease of a chromosome become wide spread in a species if that happens?

I think some of the comments are misunderstanding OP's full question. They're asking, if the reproduction is difficult and the offspring are most likely sterile, how did species come to have different chromosomes at all? If we all have a common ancestor when you go back far enough, that must mean a mutation happened that caused one of them to have a different number of chromosomes. Most of the comments are saying how the actual producing offspring isnt difficult, but the fertility of that offspring is rare. But then how could those mutations in the number of chromosomes have become persistent enough that the offspring of them were fertile and able to even pass that down themselves?

Wrong way to look at it. Those people already wanted to kill themselves. Its a 42% increase of people who actually got help, who otherwise wouldn't.

Wait someone explain please. I get that its something about Trunks and Vegeta being inefficent and Gohan and Goku being more efficent and powerful.

You'd be right but technology gets harder to improve the higher you go up. Going from 1mhz to 3ghz was really impressive, but the technological advancements needed to double that even further are insane.

Its like this, the iPhone 1 was released in 2007 and had a 2MP camera. And the iPhone 7 has a 12MP camera and was released in 2014. That's like in another 7 years the iPhone 15 had a 22MP camera. Sure it might *seem* like the same thing, but there's reason the phone's been at 12MP for a while. Your not doing the same thing you did from 1mhz to 3ghz as your doing from 3ghz to 6ghz

Linear progression with exponential technological advancements.