That depends on what land you're talking about. Beans can only grow well in certain places. Ungulates such as cattle have a particular ability to convert low quality plant matter into high quality protein which almost exactly matches human needs.
Beans are great, but the amino acid ratios aren't ideal for humans and they are deficient in certain essential amino acids which we can't synthesize. It's certainly possible to get near optimal ratios and quantities with a mix of plants but this takes a bit of planning.
https://en.wikipedia.org/wiki/Digestible_Indispensable_Amino...
Beans are great, but the amino acid ratios aren't ideal for humans and they are deficient in certain essential amino acids which we can't synthesize. It's certainly possible to get near optimal ratios and quantities with a mix of plants but this takes a bit of planning.