Archaeology thinks a paleo-version of the Atkins Diet made Neanderthals squat and wide-bodied:
“During harsh Ice-Age winters, carbohydrates were scarce and fat was in limited supply. But large game, the typical prey of the Neanderthal, thrived. This situation triggered an evolutionary adaptation to a high-protein diet—an enlarged liver, expanded renal system and their corresponding morphological manifestations. All these contributed to the Neanderthal evolutionary process,” [Tel Aviv University researcher] Miki Ben-Dor said.
There’s more on Neanderthals’ wide pelvises and bell-shaped rib cages at the Tel Aviv University Newsroom.