Certain proteins are no digestible by humans, and then they cause gas and bloating in our lower intestines when they are broken down by our ever present bacteria that live inside of us............
Animal proteins are usually totally digestible. Plant proteins may be close to 100%...or below 50%. Fiber is not digested and is the major source of gas and bloating.
https://www.foodunfolded.com/article/bioavailability-of-plant-based-proteins
Dr. Zoë Harcombe - ‘What about fiber?’:
https://www.youtube.com/watch?v=4KrmpK_Lckg
The beans they listed have been staple foods for billions of people over thousands of years. Chickpea, lentils and pinto beans have histories going back 10,000 years in three of the oldest cultures on earth. The Babylonians ate chickpeas, the Indians of every flavor for millennia have eaten lentils. The “new” culture in the group is the Mesoamericans who only have five millennia of eating pinto beans. For most of the history of Latin America there was no domesticated animals the sole protein sources were beans, maize and squash aka the sisters is integral to the culture and history of Mesoamerican civilizations. With those three a human can be completely vegan the B12/6 is in the squash people were vegetarians except for wild turkey, Amarillo,iguana,and some cervids. Chickens, pigs and cattle wouldn’t come to the Americas until the Spaniards came in force in 1512. Bison is a North American species never made it out of South Texas into Mexico let alone Mesoamerica.