Humanoid ancestors have been evolving for two million years. Humans migrated to Northern latitudes and became dependent upon animal based foods within the last 50,000 years. From an evolution perspective, humans have been eating meat for a blink of an eye. Humans have been consuming milk and dairy for even less time. Human digestive systems have not evolved significantly over a period of 50,000 years and is better adapted to plant based foods. This is supported by the science supporting a Whole Food, Plant Based (WFPB) diet. Think about how easy it is to find a bird's nest. It would be a rare treat and important if you lacked calories and protein. Our primitive ancestors did not have large eggs fried in oil every morning, and they definitely did not have refined sugars, excess salt and convenience foods. In fact, they lacked calories, protein, and other nutrients. If you wanted to eat like a caveman, you might have to skip one or more days of eating. Cavemen had no choice but to eat meat to survive long winters in Northern latitudes. They lived long enough to procreate, but they had short life expectancy. Eating too much animal based protein has proven to be detrimental to health and life expectancy.
To build muscle, consume dark leafy greens, legumes, and whole grains. Think about how muscular our nearest animal relative is. The great apes grow enormous muscles by eating almost nothing except leafy greens. Sadly, our ad men promote whey protein and other dairy products as muscle builders. The fact is, the excess protein is washed out of your system quickly doing some damage to your kidneys.
For additional information, find the web sites of T. Colin Campbell, Neal Barnard, or Caldwell Esselstyn, Jr.