Whether individuals can grow a full beard is a matter of common knowledge and biological observation determined by genetics and hormones, requiring no formal citation.
The claim states that some individuals are genetically incapable of growing a full beard. This is a matter of straightforward biological observation and common knowledge regarding human variation in secondary sex characteristics, genetics, and androgen response. None of the retrieved papers specifically test or evaluate beard growth capabilities in the general population, making them tangential. Per instructions, trivial or everyday observational facts are classified as COMMON_KNOWLEDGE without attaching citation receipts.