The predominant theory suggests humans learned to walk on two legs (bipedalism) as an adaptation to life on land, particularly the increasingly common savanna grasslands.
The Savanna Hypothesis and Bipedalism
As forests retreated 4-8 million years ago, giving way to savanna grasslands, early hominids that could walk upright gained significant advantages:
- Easier Foraging and Travel: Walking on two legs made it simpler to find food and move around in the open grasslands.
- Improved Vision: An upright posture allowed for better visibility over tall grasses, helping to spot predators and potential food sources.
Other Contributing Factors
While the savanna hypothesis is widely accepted, other factors likely played a role in the evolution of bipedalism:
- Freeing the Hands: Walking upright freed the hands for carrying food, tools, and infants. This was crucial for survival and development.
- Energy Efficiency: Bipedalism may have been a more energy-efficient way to travel long distances compared to knuckle-walking.
- Thermoregulation: An upright posture reduces the amount of surface area exposed to the sun, potentially helping to regulate body temperature in hot climates.
Summary
In summary, the development of bipedalism in humans was likely driven by a combination of factors, with the adaptation to savanna grasslands being a key element. Walking on two legs provided advantages in foraging, visibility, carrying objects, energy efficiency, and thermoregulation, ultimately contributing to the success of early hominids.
