“...that their genitals are retracting into their bodies.”
Tree of Life Sickness...??
Per Wiki...
“The transition from Breeder to Protector involves reconfiguration of the anatomy. Skin thickens becoming similar to leather armor, strong enough to turn a copper knife. Joints swell until the creature becomes “a parody of the human form done in cantaloupes and coconuts”. This increases leverage available to muscles by increasing the moment arm: the result being that a protector can lift 10 times its own weight.
Genitalia vanish, and a second two-chambered heart forms in the groin at the fusion of the femoral veins.
The arms lengthen. Fingernails turn into retractile claws. Teeth fall out, and the lips and gums fuse, the mouth forming a horny beak (flat in human protectors, non-flat in Pak protectors). All the breeder’s hair falls out and the head acquires a bony ridge to protect the newly-expanded cranium The expanded skull allows the brain to grow to an enormous size; the resulting mind, even starting from something as “unintelligent” as a chimp, becomes far more intelligent than a human mind. Pak Protectors also acquire an extended lifespan, and can live tens of thousands of earth years (a common element in Niven’s stories).”
Then again, he could be describing Harry Reid...
LOL! Good grief!