Slightly off topic, but I just had to check: Shanghai to SF is around 9873.51 km. Some internet counter estimates China's population at 1,389,221,780. Assuming 50/50 split (can't find a better one now), average height in China is 161.45 cm. That gives us a possible human chain 2 242 898.56 km long. That's more then enough to reach from China to SF.