One could easily presume that such a cure would probably reduce fertility. It might even require medical treatment to enable childbirth.
There's a downside to everything. On the good side, every child would be wanted.
As for Clark's progeny...well, the Cure never worked on him. How much it would work for his children is up in the air. They might be more fertile than the average human. Undoubtedly the Kent family be a special case compared to everyone else.
And I can easily see a world where humanity is leaving, expanding to other planets and stars despite lower fertility.
By the time HG Wells arrived, the planet might have a much lower population than we have now.
Thanks for the comments Terry and Karen.
