This is a spin-off exercise of the mind of my Holy mountain TL...
I'm no expert on Chinese prehistory, though, although i'm very interested. So:
What happens to China if pontic-caspian (but not mongolian) horses are extinct before they're domesticated?
The Pod entails that there is no Yamnaya Expansion and the Afanasievo culture never appears on the Altai in th 4th Millennium BCE. Nomadic horse-related culture does not appear, and the steppe remains a barrier instead of becoming a highway of mutual influences.
How does that affect the late Chinese neolithic and bronz Age? Is the yellow river still dominating and unifying? Is Bronze adapted nevertheless? Are Yangze cultures more important then? Or does the Yellow River influence its periphery into a similar direction anyway?