Why are baby male gibbons sometimes born with an extra testicle?

Answer 1

Extra testicles (termed as POLYORCHIDISM) is a condition that sometimes happens NOT ONLY in BABY MALE GIBBONS but also with other mammals including HUMANS. The extra testicles can be 1 (totaling 3 testes), bilateral duplication makes 2 extra testes, and there was also a reported case of a man with 5 testes (that makes an extra 3).

Theories proposed to explain testicular duplication are all relating it to some alteration in the developmental processes of the testes formation which starts at approximately 8 weeks of fetal gestation. That specifically include the division of the GONADAL RIDGE and degeneration of parts of the MESONEPHRIC DUCT where the EPIDIDYMIS and VAS DEFERENS are formed. Extra testicle can occur when the TESTICULAR FUNDAMENT separates into 2 or more segments.