These were two completely different vein structures. One was complicated but fragile and the other one was simple yet enduring. The humans had one vein structure and the Yao race had another. The difference in vein structures lead the two different species into two distinct paths.
This difference in vein structures lead the two different species into two distinctive paths. There was no way of knowing which path led to greater success. This became a topic of debate between the races which is still ongoing.