The introduction of nutrient-dense, bio-available animal foods into the human diet led to a reduction in sexual dimorphism.

“what we see when you start introducing animals into the diet and these incredibly nutrient-dense bio-available foods that our bodies don't have to work that hard to get access to the nutrients in that we start seeing a reduction in sexual dimorphism to the point where female human females yes on average are smaller than human males but nothing like they were in the past”