If you eliminate germline stem cells in flies and nematode worms, they live 20-50% longer. From ScienceDaily, an explanation of the biochemistry: "When reproduction is delayed, animals live longer. Why? Our research suggests that signals from the reproductive system can regulate aging in animals - including, possibly, humans ... speculated that these flies might live longer because they are insensitive to the effects of insulin. ... animals such as flies, worms and mice live longer when they produce or receive less insulin. ... [but] when germline cells were eliminated, and flies lived longer, insulin-producing cells in the fly brain actually make more - not less - insulin. ... How can flies be longer-lived when they're making more of a life-shortening hormone? ... Even though the brains were making more insulin, the bodies were responding as if there was less insulin present. ... In reaction to the flies' brains boosting insulin production, the insects' gonads - their ovaries or testes - produce a protein that acts like a sponge. This protein binds to the insulin and blocks its signals throughout the body. So the flies respond as if there is low, not high, insulin circulation inside their bodies."