penis spasmodically jerks up and down. See also erect penis. See video. adolescent Sexually mature but socially immature. Males 915 years old, Females 913 years old. See Fig. 2. Fig. 2 Adolescent: Ten-year-old male of K group, Masisa adolescent infertility Adolescent females usually do not conceive although they copulate often. adolescent sterility See adolescent infertility. adolescent swelling Goodall Adolescent swelling: The first tiny swellings of the sex skin initially involve only the labia. These gradually become larger and more regular over the next 3 years or so until the first adult-sized swelling attracts the attention of the adult males See Fig. 3. adopt 29 A Fig. 3 Adolescent swelling: Nine-year-old female, Abi adopt Long-continuing alloparental care of orphaned infant by single alloparent, sometimes lasting more than a year.