Owsley "The Bear" Stanley, the famous LSD manufacturer and Grateful Dead sound engineer, lived very healthily on an all-meat diet for over 50 years. (Note: he did have cancer, though likely due to HPV and years of secondhand cigarette smoke and firsthand marijuana smoke, and his diet probably helped him survive it, and he had a heart attack, but that was likely due to complications from his youth that became noticeable after putting on 30 pounds of muscle weightlifting in his 50s.) He posted all about it on a forum years ago. It's a very interesting read: http://activenocarber.myfreeforum.org/ftopic22-0-0-asc-.php
Traditional Inuit also eat an all-meat diet with lots of fat. See Weston Price's Nutrition and Physical Degeneration (http://gutenberg.net.au/ebooks02/0200251h.html#ch5), as well as the writings of Vilhjalmur Stefansson (http://highsteaks.com/carnivores-creed/vilhjalmur-stefansson... ).
The Plains Indians, as well. See "Guts and Grease: The Diet of the Native Americans" (http://www.westonaprice.org/health-topics/guts-and-grease-th...) and this talk by Stephen Phinney, "The Aboriginal Argument" (https://www.youtube.com/watch?v=ayf4R-y_RYo). Phinney himself has been on a very low carb, ketogenic diet for, I believe, two decades.
Some argue the Inuit were not ketogenic (http://freetheanimal.com/2014/03/reiterate-elevated-ketone.h...), but they tend to overestimate how long glycogen remains in muscles after death, as well as mistaking a lack of elevated ketones as meaning they weren't ketogenic (it's actually because they just use ketone bodies more effectively, which is why urine tests for ketosis only work during keto-adaptation). Dr. Michael Eades had a good article on this: https://proteinpower.com/drmike/2014/04/18/beware-confirmati...
Anyway, there's a lot more out there, but that'll get you started. I tend to believe an all-meat, ketogenic diet is the natural human diet, and I've had great success on it for the past year.
Other sites of note: http://www.ketotic.org/ http://www.empiri.ca/ https://zerocarbzen.com/ (There used to be an interview on this one with a family that has eaten nothing but ribeyes for the past 18 years. The whole family had tremendous health, and it even helped the mother overcome lyme disease. I thought it was fake the first time I read it. They unfortunately had to take it down because they were getting angry mail from angry vegans.)