Savanna Theory Versus Aquatic Ape Theory of Human Evolution
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The evolution of man is constantly in question. While we are reasonably sure that modern humans and primates are both related to the same common ancestor, there is constant debate over what initially caused the two species to split into early hominids and apes. According to some, our longest and most popular theory on the division of man and ape is profoundly wrong. However, those same individuals usually offer an equally controversial theory as a substitute, one that is almost impossible to scientifically test or prove. Both the Savanna Theory and the Aquatic Ape Theory offer solutions to how and why humans evolved into bipedal toolmakers. But with enough questioning, each loses its accountability to rhetorical science.
It was commonly believed that early hominids left the jungle to live on the open plains of Africa. Called the Savannah Theory, it was strongly promoted by Professor Raymond Dart, after he gained recognition for discovering the Taung skull in 1925. The Taung skull was the first admitted link between man and ape, and Prof. Dart based his theory on the modern location of the discovered fossils. However, a report in 2000 by Marc Verhaegen claims that a savanna evolution is extremely improbable. Based on biological and physiological data, he tries to disprove the savanna theory and suggests that our evolution would more likely occur in a humid and wet setting than the dry heat of the grasslands.
Humans have almost nothing in common with any surviving mammals of the savanna. Most mammals of hot, dry climates do not rely heavily on water for survival. They have a high tolerance to heat, and their body temperatures can fluctuate more than 6oC between day and night. They can bear a dehydration of 20%, whereas 10% or more would be fatal to humans. What little they do drink or consume naturally through food, is conserved because they do not sweat. Hair and fur keeps the sun off their direct skin, while humans would have to sweat 10-15 liters of water to physically cool down. (Verhaegen)
Even structurally, humans and African land mammals don’t have much in common.
They will have very high, large, external ears for sensing noise over long distances. A slender build allows them to reach speeds of 30mph, and their feet are designed to put weight on thin hooves or toes. Humans naturally store abundant fat tissues under our skin, and our wide, flat soles are more likely to be cut or hurt on protruding rocks. By using a mixture of fossilized dental records and a modern estimation of prehistoric environments, Verhaegen offers a more hydro-centric theory for man’s evolution.
Verhaegen’s theory is not new. In 1960, a marine biologist by the name of Sir Alister Hardy published an article called “Was Man More Aquatic in the Past?” He offered the basic idea that modern man evolved from his relationship with water bodes, but had very little evidence to support the claim. Many years later, in 1972, then-TV scriptwriter Elaine Morgan grabbed onto the theory and began to be it’s chief promoter. She published several books on the subject, as recent as 1997, and titled it the Aquatic Ape Theory. Since it gained public recognition, the Aquatic Ape Theory (AAT) has been under severe criticism from the scientific community for various reasons, most notably the improper techniques many use when ‘proving’ it. Still, the AAT is interesting to discuss as a solution to the unlikelihood of purely terrestrial evolution.
Those who endorse the AAT are quick to point out the similarities between humans and many types of aquatic life. Many sea mammals are generally hairless, similar to humans. However, on a cellular level, the skin of a seal or dolphin is very different than that of modern human. And most sea mammals are extremely large, retaining heat longer naturally. Having hair would cause them to overheat. (Moore) In addition, we are one of the few mammals that have control of our voluntary breathing. While this can be debated, it is supported by the placement of our nostrils. While many apes have horizontally aligned nostrils, the nose on a human faces downwards. Thus, when we dip our head below water, air pockets are trapped in our nasal passages and prevent water from flowing upwards. Being able to dive underwater would be invaluable for a weak, gathering-based life form.
This evolutionary trait supports the AAT belief that early hominids ate a large portion of aquatic vegetation and wildlife. Verhaegen uses dental studies to suggest that while some australopithecines, the earliest genera of hominids, preferred soft fruits and vegetables, there are examples of hominids, like Australopithecus robustus, who seem to have eaten much harder food items as well. If apes and chimps are still known to eat various shoots and stalks (and even humans eat cereals), it is not too far-fetched to imagine an early hominid surviving the dry season on wetland plants. In addition, the iodine and omega-3 fatty acids used in brain development and growth are plentiful in fish and shellfish. (Westrup) Verhaegen even offers a theory of how the use of tools would evolve from using rocks to break open the hard shells of mollusks.
Because humans are the only mammals to walk upright full-time, there must be extinguishing circumstances for them to solely develop bipedalism. Unfortunately, there are some discrepancies in how the AAT explains this development. The foundation of bipedalism in AAT is centered on water’s buoyancy in supporting the body. As the early hominids constantly hunt and search for food in the water, their muscles would slowly develop for them to stand erect. This would keep their heads above water, allow them quicker travel, and still free their hands for carrying things (such as across the savanna, except in wetlands). Still, whether it was lakes, rivers, oceans, or a combination of any of the above, most experts of AAT agree that early hominids only spent a few hours per day in the water. Any more than that, and there would be considerable risk to predators. For while they may seem safer from land-based hunters (such as lions), there are still many other predators (such as crocodiles) that lurk in the waters. In addition, most large bodies of water would probably attract land predators for drinking, anyway. (Moore)
During my research, I found the notions of AAT just as impossible as the Savanna Theory. While AAT is an interesting concept, there are just as many uncertainties in its structure as in the Savanna Theory. If AAT supporters point out fossilized shells and sea life found alongside hominid remains, then their detractors will snidely reply that most fossilized digs are pre-biased for easiest access and abundance. I was happy to see Marc Verhaegen offer a compromise, that we gradually evolved from, “frugi- and herbivores in gallery or tropical or mangrove forests to ‘short’-legged bipedal waders in forest clearings or mangrove swamps, to omnivores and partial shellfish feeders along seacoasts and rivers, and finally to long-legged bipedalists on land.” The question of human evolution cannot be definitively answered with our current knowledge. Essentially, we are just waiting for more evidence to constantly surface. Until then, it is important to remember there is no prize for guessing the “right” answer, and that only by keeping our minds open to new ideas will we come closer to an understanding of ourselves.
Moore, Jim. “Aquatic Ape Theory: Sink or Swim?” Homepage and various links. <http://www.aquaticape.org/index.html>
Verhaegen, Marc and Pierre-Francois Puech. “Hominid lifestyle and diet reconsidered: paleo-environmental and comparative data.” Human Evolution. pp 151-162; 2000. Found at: <http://allserv.ugent.be/~mvaneech/Fil/Verhaegen_Human_Evolution.html>
Westrup, Hugh. “All Wet?” Current Science. Vol 88, Issue 6. p8; Nov 8, 2002.