* Hair growth rate varies greatly between individuals and body parts. Some people's scalp hair grows faster than others, and the same is true for facial hair.
* Beard hair can grow relatively quickly compared to some other areas. This is often attributed to hormonal influences, especially testosterone.
* However, scalp hair generally has the potential to grow longer than beard hair. This suggests that while beard hair *might* have a faster growth rate initially, scalp hair may have a longer growth cycle.
* Eyebrows and eyelashes have a very slow growth rate
Conclusion:
It's not definitively true that beard hair is always the fastest growing hair on a human body. It really depends on the individual and a number of factors, but beard hair usually grows faster compared to other body parts, except for scalp hair, which typically grows longer.