Unfortunately, they are not going to do controlled studies on red meat causing cancer. #1 it would take too long (cancer takes a long time to develop), and #2, that would be unethical.
Also keep in mind, a million years ago humans lived to about 25, so they didn't have time to develop cancer and CVD and Alzheimer's. They died of starvation, infections, disease, etc.
"Researchers Gurven and Kaplan have estimated that around 57% of hunter-gatherers reach the age of 15. Of those that reach 15 years of age, 64% continue to live to or past the age of 45. This places the life expectancy between 21 and 37 years."
News 
Market Data 
Discover 
