How Cold Plunge Shaped Human Anatomy
- Thomas P Seager, PhD
- Aug 17, 2024
- 9 min read
Updated: Oct 23
Our ancient Mothers gave birth in cold water
Summary
The most salient aspect of human physiology is our enormous brain. It is composed primarily of the omega-3 fatty acid called DHA that anthropologists think our ancient human ancestors obtained primarily from aquatic animals and plants.
Human bodies are anatomically more similar to aquatic mammals like dolphins, whales, and manatee than they are to apes, suggesting that Homo Sapiens survived near and in the water. For example, bipedalism (walking on two legs instead of four) provides an advantage for wading in the water, but a disadvantage for childbirth.
To ease pain and avoid predators, our ancient Grandmothers likely gave birth in the water, which explains how human babies are born knowing how to swim.
The equatorial glaciers of East Africa suggest that the water in which our ancient grandmother's likely gave birth was cold.
One modern woman in the United Kingdom labored in a cold bath. She reported an easy childbirth and excellent birth outcomes.
Evolution at the water's edge
There are several anatomical features that distinguish human beings from other primates with whom we share more than 95% of our DNA, and these features raise several curious questions. For example:
Why do humans have less hair than chimpanzees, bonobos, and gorillas?
Why are human beings the only primates with subcutaneous fat (just beneath the skin) like dolphins, whales, and seals?
Why do human nostrils point down, while other apes have nostrils that point out?
Why do we humans walk upright on just two legs, instead of on all fours?
A British scientist named Alister Hardy proposed what he called "The Aquatic Ape Hypothesis" (Hardy 1960), to answer each of these questions. In summary, Hardy suggested that our anatomy evolved as an adaptation to aquatic lifestyles. He suggests that early humans lived at the water's edge, and that our ancient ancestors survived by wading, diving, swimming, fishing, and foraging in the streams and shorelines of Africa.
According to Hardy:
Less body hair would streamline the human form for swimming & diving,
Fat just under the skin helps keep the body warm and buoyant in the water.
Downward facing nostrils allow ancient humans to dive without forcing water up their noses.
Walking upright allows wading thru shallow waters with our heads above water, and
Proponents of Hardy's hypothesis point out that many of the unique characteristics of our anatomy are similar to dolphins, whales, and manatee -- i.e., other aquatic mammals (Morgan 2011). Opponents point out that beaver and otters are also streamlined, and they have fur. That is, Hardy's skeptics argue that, although we're the only primates with subcutaneous fat, there are lots of other creatures besides whales that have it, too. And that walking upright would be an advantage for hunters in the African grasslands, not just in foraging for fish.
A 16 minute video (below) provides a lovely summary of the both hypothesis and its detractors.
But none of the opposing arguments to the Aquatic Ape Hypothesis are convincing to me, because no one is really asking, "What makes humans different from beavers?" Moreover, I doubt walking upright is an advantage for hunting on the African savannah, because as far as I can tell, humans are the only predators anywhere in the world that do it.
For me, a much more interesting question is:
Why are human babies born knowing how to swim, but not how to walk?
The answer is that our bodies are adapted to cold water immersion by thousands of years of sexual and reproductive selection pressures.
Human bodies expect cold water immersion
Almost everyone has an experiential understanding of the healing power of the water (e.g., Blue Mind by Nichols, 2015). Even those who do not enjoy swimming almost always appreciate the serenity and beauty of being at the beach.
If cold water is in our genes, so to speak, then that might explain the feeling of deep connection that some people feel to the water. It is sometimes said that Nature (and/or God, depending on your point of view) does not make mistakes. That is, every anatomical feature in the human body must serve some evolutionary purpose that increases chances of survival and sexual reproduction.
If that's the case, then what evolutionary purpose could the aquatic aspects of human anatomy possibly serve?
Allow me to suggest that is our enormous brains.
The principal distinguishing feature of human beings are the large brains that allow them to form complex social networks. Growing such a brain demands nutrient-dense foods rich in omega-3 fatty acids, and aquatic foods are the best source of omega-3's available.
According to University of Sherbrooke Professor Stephen Cunnane PhD, in a human infant, two-thirds of total energetic throughput of is consumed inside the brain. Most of that energy is dedicated to rapid growth of new neural cells composed primarily of DHA.
In his book Survival of the Fattest (Cunnane 2005) he makes clear that ancient humans who were adapted to the water would secure more of the essential fatty acids necessary to construct healthy brains. For example, a human walking upright is better able to wade in the water to spear or trap fish.
The problem is that the demands of walking upright limits the width of the human female pelvis, complicating giving birth to human babies with enormous skulls. The risks in childbirth, both to Mother and baby, of passing such a large brain through the birth canal must have put tremendous negative selective pressure on the first Homo Sapiens. Even though the bones of the newborn skull are flexible and the human baby brain is highly underdeveloped (small) relative to how much it still needs to grow, the baby's enormous head is still difficult to birth. For our ancient grandmothers, the remedy for the unique difficulties of human childbirth was likely also found in the water. For example, experience with modern water births have demonstrated reduced pain, greater maternal satisfaction, and fewer medical interventions (Simkin & Bolding 2004), compared to births outside the bath (Young & Kruske 2013).
The Aquatic Ape Hypothesis suggests that our ancestral Mothers would have sought out in water births the same relief from childbirth pain that modern Mothers do, which would explain why baby's born with instinctive knowledge of how to swim would have an evolutionary advantage.
If an ancient practice of water births made it feasible for human beings to birth larger brains, then it was water births that allowed us to become uniquely human.
The idea that our ancient ancestors gave birth in the water was resurrected by author Elaine Morgan, who often described the advantages of water birthing (Morgan 1972, Morgan 1994). More recently, others like obstetrician Michel Odent MD have reinforced her argument, writing
Taking into account the physiological perspective, and also the strong attraction to water expressed by many laboring women, I eventually bought a blue inflatable garden wading pool. Thus began the history of birthing pools in hospitals. As soon as the birthing pool was installed, new strategies became possible. When a woman in hard labor was demanding painkillers, we had something else to offer than the injection of an analgesic drug (this was before the age of epidural analgesia). We could introduce the mother-to-be to the aquatic birthing room, so that she could observe and hear beautiful blue water filling the pool. The room was painted blue, with dolphins on the walls. From that time the question was no longer: “When will you give me a painkiller?” but rather: “How long does it take to fill the pool?” The first lesson concerned the importance of the time when the woman in labor is anticipating the bath: the dilation of the cervix can already progress dramatically before water immersion – if the aquatic environment is associated with privacy. It is like the sudden release of brakes. We witnessed one of the many magic effects of water on human beings, a profound power that cannot be easily explained with the language of physiologists. At the time of the plastic pool (before we installed a solid pool), women were not influenced by the media or by what they read in books about childbirth. Their behavior was spontaneous, and thus we learned about the genuine effects of a water environment. One day, a mother-to-be had not been in water for long when suddenly she had two irresistible contractions, and the baby was born before she felt any need to get out of the pool. While giving birth, this woman was really on another planet. Clearly, in that altered state of consciousness associated with hard labor, she intuitively knew that her baby could be born safely under water. There was no panic. It is as if a deep-rooted knowing could express itself as soon as the intellect and its knowledge were set aside. - Dr Michel Odent (2019)
How cold was the water?
Even though we all remember that it was Mount Kilamanjaro in Tanzania that Wim Hof chose for his record-breaking, frigid hiking expeditions, it's easy to forget that there are three mountain-top glaciers near the Equator in East Africa, where the oldest human fossils have been found. So despite our expectation that human beings must've evolved in a hot place that was without winter, it must also be true that during recent Ice Ages, there was no shortage of streams and river beds fed by melting snow.
In short, the waters in the East African Garden of Eden must have been cold, given the hydrogeography of that region during the Ice Ages, when advancing glaciers forced the entire global human population into communities that were squeezed between the ice and the ocean. It was in those cold waters that our ancient Grandfathers must've fished, and our ancient Grandmothers must've given birth.
The analgesic effects of cold water immersion have been well known, so it stands to reason that a cold water birth will relieve labor pains. To date, I've only found one woman who is documented as having tried it. She lived in the United Kingdom and practiced cold water swimming during her pregnancy, so it was probably natural for her to have a cold water birth. She reported that she used a cold outdoor pool "while in early labour and had a very easy and quick birth" (Cool Swimming, Buckley 2022, p16).
While most women won't try a cold bath, more than one study has demonstrated that ice massage during birth labor is effective for reducing childbirth pain. For example, a group of researchers from Iran compared ice massage, acupuncture, and placebo for pain relief in a group of 90 pregnant women. They found ice massage to be most effective during labor (Hajiamini et al. 2012).
Moreover, when two nurses studied the effects of ice massage on 49 laboring women in New Mexico, they discovered that...
... the results suggest that ice massage is a safe, noninvasive, nonpharmacological method of reducing labor pain. -- Waters & Raisler (2003)
Feeling called to the water
I had a phone conversation with Dean Hall, the trauma therapist who cured his leukemia with cold water swimming. He asked me why he felt such a strong emotional release when he emerges from his ice bath.
I told him, "I don't know for a fact, but I will share with you my speculation."
This is what I told him:
One of the things that has been very difficult to explain about cold plunge therapy is "Why is an ice bath so important to human health, when you know our species emerged in the hot, equatorial climate of East Africa?" It's a particularly vexing problem, to explain why the benefits of cold water are not exclusive to those human beings who descend (more recently) from cold climates. The Aquatic Ape Hypothesis probably holds important clues.
That is, no matter whether your ancestors hailed from the North Sea (as mine did) or from the equator, the early evolutionary experiences shared by all human ancestors likely shaped our anatomy to need cold water immersion on a regular basis. Just like our bodies are evolved to expect exercise and we get sick if we're not getting enough of it, it is likely that we will experience less-than-optimal health if we don't get enough cold water immersion.
Whole-body, cold water immersion is in our ancient DNA.
As I told Dean Hall:
The fact that our ancient ancestors were all born into the cold water probably means that something about the experience of the cold brings up the original trauma of childbirth for us. It's no wonder that you feel an emotional unburdening after an ice bath. Something in your ancestral, evolutionary history is calling you to the ice bath, where you can relive your birth trauma, and resolve it from a position of control.
Dean told me that after swimming the entire length of the Willamette River in Oregon, he referred to the Willamette as "Mother River." Perhaps it is no accident that the Christian tradition of baptism in the water is sometimes characterized as being "born again."
References
Buckley JPD. Cool Swimming: A survey of cold water swimming and physical and mental well-being. 2015.
Cunnane SC. Survival of the fattest: the key to human brain evolution. 2005.
Hajiamini Z, Masoud SN, Ebadi A, Mahboubh A, Matin AA. Comparing the effects of ice massage and acupressure on labor pain reduction. Complementary Therapies in Clinical Practice. 2012 Aug 1;18(3):169-72.
Morgan E. The descent of woman: The classic study of evolution. 1972.
Morgan E. The descent of the child: Human evolution from a new perspective. 1994.
Morgan E. The aquatic ape hypothesis: the most credible theory of human evolution. 2011.
Odent M. Obstetrical implications of the aquatic ape hypothesis. Was Man More Aquatic in the Past? Fifty Years after Alister Hardy Waterside Hypotheses of Human Evolution. 2019:156.
Waters BL, Raisler J. Ice massage for the reduction of labor pain. Journal of midwifery & women's Health. 2003 Sep 1;48(5):317-21.
About the Author
Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University. Seager co-founded the Morozko Forge ice bath company and is an expert in the use of ice baths for building metabolic and psychological resilience.