Jane Goodall's cause of death has been revealed. According to her death certificate, obtained by TMZ on Monday, the conservationist died from cardiac arrest, also known as cardiopulmonary arrest. The risk of cardiac arrest rises as a person ages, and so with that in mind, the death was considered natural. After all, the beloved primate expert was 91 years old. Related: Did Liam Payne's Sister Ruth Just Shade His Girlfriend?? Jane also had epilepsy, as listed on the certificate, but it is unclear if that played any factor into her death. As we covered, the Chimpanzee expert's death was announced by the Jane Goodall Institute on October 1 after she was found dead in her sleep in Los Angeles, where she was set to speak at UCLA as part of her tour just two days later. According to her longtime personal assistant Mary Lewis, who spoke to People after her passing, Jane worked until the very end. Literally! She was drafting a document up until 10:30 p.m. on the night before her death! Mary told the outlet: "I was actually in bed and I saw this email flash across my phone, and I thought, 'Oh, I'll send a message saying, Jane, I've got to get up at 5 a.m.. I'll get to you tomorrow night.' Then I thought, 'She's terribly busy.' So I went and got my computer and sat in bed and started editing." Jane had such an incredible dedication to her activism work! Our thoughts go out to all of her loved ones. [Image via National Geographic/Netflix/YouTube] The post Jane Goodall's Cause Of Death Revealed After She Was Found Dead In Her Sleep appeared first on Perez Hilton.