Short term neutral.
In the roundworm C. elegans, which is now a very popular animal for testing aging theories, because its genes and cells have been thoroughly "mapped," it was recently found that adding a gene that simply allows it to synthesize cholesterol, rather than depending on food for its sterols, increased its life span by as much as 131% (Lee, et al., 2005). That would be like increasing the human lifespan to about 175 years. These worms are also more resistant than normal to radiation and heat stress.
- Ray Peat