Why where humans so short 4 million years?

Humans and their ancestors were relatively short around 4 million years ago due to a combination of evolutionary adaptations and environmental factors. Early hominins like Australopithecus evolved in response to their habitats, which included open savannas where shorter stature may have provided advantages such as energy efficiency and better thermoregulation. Additionally, limited access to nutrient-rich diets and the demands of their environment likely constrained growth, resulting in smaller body sizes compared to modern humans.