What is this person suggesting? I'm assuming that the size of a person's brain is based on two things. First, their genes. Second, the environment including di

What is this person suggesting? I'm assuming that the size of a person's brain is based on two things. First, their genes. Second, the environment including diet. If the researcher is suggesting that diet increases brain size, well that should be easy to measure on living people and will give a fairly definitive answer. If the researcher is suggesting that eating meat changed our genes, well that needs to be explained.