a.k.a. 'Androgenic alopecia' 'Androgenetic alopecia' and 'Alopecia androgenetica'
A variety of genetic (and possibly environmental) factors probably play a role in causing Male Pattern Hair Loss in humans. Many are documented, but there is no overall agreement (although the link with androgen hormone levels is well established). The syndrome affects around 50% of men over the age of 50 years. Chinese, Japanese, and African American people are less affected than Caucasians. The hair loss is due to miniaturisation of the hair follicles rather than their elimination.
If there are any Darwinian or psychosocial advantages to those having Male Pattern Baldness, they are as yet unproven.
Further reading (comprehensive 2016 report)
Note: A lower percentage of women are affected by severe hair loss, with the name change to Female Pattern Hair Loss (FPHL). The cause(s) are also as yet unclear.