"At age 15, chimpanzee life

expectancy is an additional 15 years,

as compared to 39 more years for human foragers."

So prehistoric adults may mostly have lived to be around 55. That's right around where menopause starts (45-55).

https://www.unm.edu/~hkaplan/KaplanHillLancasterHurtado_2000_LHEvolution.pdf