A Centaur’s Life- Mermaids

A Centaur’s Life- Mermaids


The Mermaids, or Merfolk, of A Centaur’s Life, had me laughing as soon as I saw them because that’s not how it works, that is not how any of this works. If you didn’t realize it from the picture, let me spell it out for you, the Mermaids have a thigh gap. No other fictional mermaids have a thigh gap, where the upper legs are separate and the lower legs are fused. Not to mention, that is not how evolution works when real world aquatic mammals adapted to life in the ocean.

Evolution of the dolphin tail

Real world dolphins evolved from an extinct animal called Indohyus, which is about the size of a cat. The animal lived around 50 million years ago, so this process took a very long time, and many species followed, leading up to modern dolphins.

dolphin evolution

The Wikipedia page on the evolution of aquatic mammals found here (https://en.wikipedia.org/wiki/Evolution_of_cetaceans) actually has a nice sequence of pictures where you can see the shrinking of the hind legs and the growth of the tail over time. The legs are eventually lost, and the tail evolves in the flipper we see in whales and dolphins.


However, the animals in A Centaur’s Life have 6 limbs, instead of 4 limbs, which means that the mermaid’s tail would have formed from its legs. As a result, dolphin evolution is not the best real-world example to use. In this case it is seals that become the best example as seen in the image below.

mermaids tail

The seal flipper is not formed from a tail, but actually from its legs which have fused together.
“Ok great, problem solved, the Mermaid thigh gap is actually just a result of evolution and it will slowly close over subsequent generations”

Wrong, very wrong

Let’s think about this logically: dolphins, seals, and our fictional mermaid all evolved from a mammal that lived on land. As the mammal begins to adapt to life in water, it still needs to have some ability to move on land. If the very first part of the legs to begin to fuse together were the feet, the mammal would no longer be able to move around very effectively. Just try and move around with your feet tied together, and you’ll be limited to hopping, and that would get tiring very quickly. However, if your thighs were tied together your walking would be limited, but it would not be impossible. Thus there is no way for a mermaid to have thigh gap, beyond the fan service on a part of the author.


Staying Warm

While A Centaur’s Life clearly failed on the biology of the mermaid’s tail, it does actually get one thing right. All mammals are warm blooded and have to maintain a constant body temperature. This is done through their metabolism and various adaptations to maintain body heat. Some of these adaptations include fur, which is not found on most aquatic mammals that spend all of their time in the water for obvious reasons, such as making it harder to swim. To make up for that aquatic mammals have a layer of fat underneath their skin called blubber, this layer of fat serves as insulation keeping the animals warm in cold waters.

The mermaids clearly do not have any blubber considering their alluring forms, which is believable given that they are shown to live in very warm environments. However, it is possible to get cold even while sitting in warm water given enough time, and given that mermaids live in water this could be a problem. The mermaids are said to have something called counter current circulation as a way to retain body heat in the core of the body. This is a real world physiological feature used by animals that live in cold environments.

When we normally think of blood flow, we think of the artery running out into the limb with warm oxygenated blood, and the vein carrying colder non-oxygenated blood back to the body. This still happens in counter current circulation, but what changes is that the arteries and veins run next to each other as seen below.

mermaids tail

As you can see, the countercurrent is referring to the heat, and not the actual blood or oxygen. Counter current warms the blood as it returns to the body, helping to retain heat as the blood in the veins absorbs the heat from the blood in the arteries as it heads to the limbs. This is because the artery runs down the middle with the veins around it as seen below.

mermaids tail

In this case I have to call A Centaur’s Life use and explanation of counter current circulation confirmed. It might have been useful in the classroom, if the rest of the show wasn’t so problematic.



If the flipper of the Mermaid is evolved from legs, then what happened to their knees, because knees do not bend like that? Also, if their knees are located at the bend in their tails, the femur of a Mermaid must be very, very long.


Outside of fanservice there is just no reason for the mermaids to have a thigh gap, but they did get countercurrent circulation right. I am probably nit picking on the knees, but that’s the science teacher in me. I know it was a bit shorter than usual, but I hope you enjoyed the post and leave any comments or questions below.

FYI- I know I didn’t talk about the mermaids from Daily Life with Monster Girls, but they are based on fish not mammals.

Further Reading



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