Bipedal Threat Display Theory is the concept that being bipedal allowed these hominins to hold a weapon and appear threatening. This is a behavior that could have prompted some groups of apes to adopt the bipedal posture more as it allowed them to appear threatening to predators. It allowed greater vigilance against predators due to the increased height and increased visual range that bipedalism would have given them

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- Postural Feeding Hypothesis
- Man the Hunter-Scavenger 
- Environmental Food Distribution Theory
- Thermoregulation Theory
- Aquatic Ape Theory
- Bipedal Threat Display Theory

Theories on Bipedalism

HubPages. “The Many Theories Behind Human Bipedalism.” HubPages, 6 June 2011, https://discover.hubpages.com/education/The-Many-Theories-Behind-Human-Bipedalism. Accessed 28 September 2022.

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The Postural Feeding Hypothesis theory suggests that bipedalism developed as a feeding technique. This theory suggests that human ancestors started to stand on their hind legs to reach food that was higher in trees and bushes. In finding that this was an effective stance, early hominins may have then adopted this and later locomotion.

Postural Feeding Hypothesis

Man the hunter-scavenger is a theory based on the idea that at a slower pace, bipedalism allowed for greater stamina. This advantage would have allowed early hominins to track and kill their prey by endurance chases, meaning that they could follow migrating herds in order to obtain a greater amount of prey at the back of the herd (weaker prey). The problem with this theory is that when bipedal features started to appear in our history, around 4.2 – 3.9 million years ago, there is no evidence of stone tools and there is no widespread evidence of meat eating amongst the specimens.

Man the Hunter-Scavenger Theory

The Environmental Food Distribution Theory was developed by Rodman and McHenry (1980). This is the environmental food distribution theory, which states that food became more dispersed due to the changing environment around the world requiring further travel. These periods of heating and cooling led to the drying out and thinning of the forests, producing patches of grassland. For humans, bipedalism was the easiest to develop, as it allowed for quicker transport between patches of forest and the ability to carry food home. The problem with this theory is that ‘cheaper’ evolutionary changes would have been to change the group size or to alter the main hominin diet into something that was more readily available in the changing environment.

Environmental Food Distribution Theory

Thermoregulation Theory was developed by Wheeler in 1984, suggesting that bipedal posture developed as hominids had to forage in the newly created savannahs, when the sun was overhead. Therefore, being bipedal would have meant that they would not have had to stop their foraging to look for shade as bipeds show 60% less body surface to the sun. Therefore, bipedalism would have meant that early humans had to deal with less thermal stress and the possibility of overheating was greatly reduced. Another advantage would be that there would have been less need for water. However, the problem is this theory only works when the sun is directly overhead. Also, bipedalism is proved to have evolved predominantly in the woodlands, not the savannah, and there is no evidence in the Australopithecine skeletons found that would prove this theory.

Thermoregulation Theory

Aquatic Ape Theory states that around 5 – 1.5 million years ago, there was prolonged flooding across the world due to climate change that drove the human ancestors that were not equipped to deal with the new environment out of the forests and into the sea. Bipedalism would have allowed these hominins to wade through the water, and efficiently swim and dive for food. This theory is widely rejected and has only recently begun to be reconsidered, however, there are still many flaws, including there is no supporting evidence from any flora or fauna found with bipedal fossils and the body proportions most ideal to swimming did not appear till the Homo genus evolved.

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