Humans vs Marine Mammals - what do we have in common?
At first glance when comparing an average human and a 50 tonne Humpback whale there is no real similarity between the two. When diving deeper, research shows that us humans share more characteristics than we think with the deep diving mammals - the most notable comparison being the Mammalian Dive Response.
The mammalian dive response is a set of physiological responses to immersion that overrides the basic homeostatic response and is found in all mammals studied to date. These sets of responses can be primarily activated by apnea and immersion in cool water. After submersion the strongest receptors are found around the eyes, nose and mouth. From there the response flows to the brain stem.
The tenth cranial nerve called the vagus nerve, which is part of the autonomic nervous system, carries the impulse from the brainstem to the heart. When it reaches the heart the major changes in the body will start to occur.
The most notable change that occurs will be bradycardia, which is the slowing of the heart rate. After scientific testing it is seen to allow for a 10–30% slowing of the heart rate in water and up to 50% in trained athletes.
The 2nd notable response is peripheral vasoconstriction, which is the narrowing of the blood vessels in the extremities. That allows for reduced blood flow to the limbs, ensuring that oxygen sensitive organs like the brain and heart receive oxygen throughout apnea. With this blood shift it also allows sensitive organs to be protected by the increase in hydrostatic pressure as the marine mammal or human preforms a deep dive. A newly found response occurring in mammals is spleen contractions. This response allows for a higher amount of red bloods cells to enter the blood stream. The higher count of available red blood cells enables the body to bind more oxygen in the blood and thus enhances the breath hold capacity.
Humans vs Marine mammals So what gives marine mammals that extra edge against other mammals/humans when comparing times and depths? The two main points would be a physical and a biological advantage. When looking at the deepest and longest diving marine mammals you can see a strong physical trait shining through. Those traits being slick fur or skin, extreme body control and incredible hydrodynamic movements in the water with absolute efficiency.
During dives most marine mammals such as sperm- and beaked whales make use of their flipper pockets, a special adaptation to make their bodies more streamlined in the water. When delving beyond the physical adaptions you will notice an amazing biological difference. The key factor being a protein called myoglobin. Myoglobin is an iron and oxygen-binding protein found in muscle tissue of vertebrates, and it is closely related to haemoglobin found in blood. Recent studies have found that diving mammals including whales, seals, otters and even beavers have positively charged myoglobin proteins. These positive characteristics allow the animals to pack much more myoglobin into their muscles than other mammals/humans.
This positive charge avoids these proteins from clumping together in the muscles, and allow for maximum storage of myoglobin and oxygen. This clumping allows diving mammals to have 10 times more myoglobin in their muscle systems and it gives the muscles a purple/brown texture.
The mammalian dive response in humans is strongly seen during water-based activities such as freediving, spearfishing and scuba diving. With theories stating that humans evolved from marine mammals, we can't help but think that we should still have this forgotten response somewhere within us when entering the water, and with intensive training there can be a strong improvement of this response. Starting to freedive can be compared to trying to find the buttons of this forgotten mechanism. By repetition, the response will become stronger, quicker and easier to activate.
When comparing the worlds best marine mammals and freediving athletes there is a huge gap in performance. The deepest diving mammals on the planet are Cuiver’s Beaked Whales.
This diving mammal has been documented diving to -2992m and having a breath hold of around 2 hours and 17 minutes. The species being one most widely spread of the beaked whale family, usually preferring water deeper than -1000m, research of them is extremely difficult. These deep diving mammals hunt mainly on several species of squid and invertebrates in the deep ocean.
Coming in second place as the deepest diving human on the planet would be Herbert Nitsch. Herbert is a multiple world champion and has the title of the Deepest Man on Earth. This title was given to him when he set the world record diving -214m using No Limits.
The deepest No Fins diving human is an incredible -102m by William Trubidge, showing the rawest and most closely related form of freediving to our fellow marine mammals.
When standing back and looking at the different statistics you can see a massive gap between marine mammals and humans. Showcasing how well these animals have evolved over 1000´s of years, and how weak our mammalian dive response is compared to marine mammals. With an ever-changing environment and ocean basin our time might be running out to learn more from these amazing deep diving animals. By eliminating their major threats such as poor fishing practices, water pollution, sound pollution and climate change, we could see these species thriving once more. All those factors may seem like massive tasks but every bottle, straw, non-fish food item, non-C02 emitting option counts. There is also no better way to make people around you aware of the on-going problem than sharing the love for the ocean and its habitants.