How did the modern human come about? Why do we have certain features in our physiology and our anatomy? When looking at the various evolutionary theories that involve human development, one that is beginning to gain traction today is called the Aquatic Ape Theory.
The Aquatic Ape Theory suggests that at some point in the evolutionary chain for humanity, there was a period of time when there was an aquatic or a semi-aquatic stage. Through the process of convergent evolution, an aquatic environment offers an alternative hypothesis for certain features that humans have compared to other primates.
The Aquatic Ape Theory was first proposed by Max Westenhofer in 1942, then once again in 1960 through the independent research of Alister Hardy. An early proponent of the theory, Elaine Morgan, was a documentary writer and composed a series of books on the topic that helped to raise more awareness for it beginning in 1972.
Despite the proposals, the Aquatic Ape Theory is generally not accepted within the scientific community, though it does generate some interest within certain paleoanthropologist communities. There may be evidence that the Aquatic Ape Theory is closer to reality than many may realize.
What Is the Evidence for the Aquatic Ape Theory?
The primary piece of evidence that is cited for the Aquatic Ape Theory is the bipedal nature of humans. It is believed that humans developed the process of being able to stand on two legs as a way to be able to get out of the waters that covered the ancient world. Over time, the legs could then support more strength so that early humans could be able to spend time on the shore outside of the water.
There are these additional pieces of evidence that are cited by proponents of the theory as supportive for the idea that humans had an aquatic ancestor at some point in their evolutionary history.
- Subcutaneous Fat. Humans have an extended fat layer that other primates do not have. This fat layer is seen, however, in aquatic mammals such as whales. This was one of the original ideas that spurred the Aquatic Ape Theory in the first place. The layer of fat is also believed to help humans cope with varying air temperatures, allowing for a greater distribution to various habitats.
- Hairlessness. The relatively hairless skin of humans is believed to be an adaption that is comparable to what aquatic mammals have as well, which is clear difference from land-based mammals. What body hair that a human does have tends to follow the flow of water that occurs across the body. It is an advantage to dolphins and whales for fast swimming speeds, diving, and migration, which is a similar advantage that humans can also use to some extent.
- Larynx. The human larynx is in the throat instead of in the nasal cavity, which is another characteristic that is shared with some aquatic mammals. Humans have a lot of control over their breathing, which is another trait that sea mammals have in common, as some aquatic animals use their descended larynx to close off their trachea while they dive.
- Brain Size. Humans have the highest encephalization quotient known in nature. It compares the size and complexity of the brain to body size. Just behind humans are aquatic mammals, such as whales and dolphins. Apes and elephants are in the top list, but so are squid and even some birds. The idea here is that aquatic mammals developed larger brains, while land-based mammals had a more stagnant lifestyle, which restricted brain development.
There is also evidence to suggest that humans are more adaptable to water as infants than other land-based mammals. Babies come equipped with a dive reflex, increased insulation, and increased buoyancy, which allows infants to learn how to swim at very young ages when supported by adults.
Many babies can actually swim before they have developed the strength to be able to walk, which is completely unknown with other simian offspring. Even childbirth in water may be safer for the mother with no observed additional drowning risks compared to traditional common practices today.
From bathing behaviors to the wrinkling of the skin to habitat adaptation, there are several pieces of potential evidence that may show that the Aquatic Ape Theory has some merit. Though critics may point to some inconsistencies offered within the theory, it is a possibility that humans did have an aquatic or semi-aquatic stage in their evolution and that means we may have many more relatives than we first realized.