Children could live in a world without wild apes unless something urgent is done about it, says a Nature journal study.
It's thought they're being hunted for meat, but they are also being killed by the deadly Ebola virus.
The number of apes living in Gabon and the Republic of Congo has dropped to more than half in 20 years, says the study.
Ape populations there were thought to be safer than in other African areas because the jungles weren't disappearing as much.
Meat business
Cutting down jungle areas where they live has been the cause of their falling numbers in the past.
And their meat used to be hunted just for local people, but now the meat business has increased.
Ebola too has spread to a major national park with a huge gorilla population.
Ape experts are really worried because about 80% of the world's chimps and gorillas live in the Congo and Gabon.
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