Thankfully the theory of evolution correctly describes how we got here. When I first started cycling, I had the same worry. My cardiologist said no, you can't hurt your heart by pushing too hard. If you could, your distant ancestors would not have passed on their genes as successfully. We now know that it is possible to overstress the heart by long, extreme efforts, but this mostly by a competitive marathoners and elite Ironman level triathletes.

IOW, don't worry, just ride. Some people naturally have higher HRs than others.