Siren Spotlight: biological atavism December 1, 2015 06:00

From Jess: 

The first book in the "Rescue Sirens" series is subtitled "The Search for the Atavist"... but what is an Atavist, anyway?

According to our unique mermaid mythology, merfolk existed before human beings — in fact, they represent our species' very origin. From the beginning of time, mermaids and mermen were able to "make legs" indistinguishable from our own and walk around on shore, where they bred, gave birth in special birthing coves, and simply explored the vast expanses of wild land.

There was a catch, though (isn't there always?): after more than a day away from the ocean, legged merfolk would start to feel ill, and if they went for three full days without "turning tail" and submerging in water from head to fin-tip, their specialized lungs would dry up and they would lose their ability to change from legs to tail. Forever.

In other words, they became human.

Across the globe, merfolk were trapped on land often enough — due to losing their way, natural disasters, illness or injury, and even treachery — that the resulting small bands of human beings were able to sustain and eventually grow their population (although the offspring of human/human pairings lacked from birth the capacities to "turn tail" and breathe underwater). These humans were watched over when they went near the water by the mermaids and mermen still living in the ocean, and merfolk observe that ancient vow to protect their landbound brethren to this day; that's the role of a Rescue Siren.

But sometimes, once in a very long while, a human being is born with the ability locked within them to change their legs into a tail (and back again) as well as to breathe water, just like humankind's merfolk ancestors. This genetic throwback is known amongst merfolk as an Atavist.

The concept might sound like fantasy, but it has its roots in science. Courtesy of, an atavism is defined as follows:

[at-uh-viz-uh m]
1. Biology.
a. the reappearance in an individual of characteristics of some remote ancestor that have been absent in intervening generations.
b. an individual embodying such a reversion.
2. reversion to an earlier type; throwback.

Origin of atavism
1825-35; < Latin atav (us) remote ancestor (at-, akin to atta familiar name for a grandfather + avus grandfather, forefather) + -ism

Related forms
atavist, noun

Since humans came from merfolk, the lower body's ability to metamorphosize between a legged and tailed form as well as the specialized lungs that allow breathing above and below water are biological atavisms. If the genes governing those features get "switched on" in the womb, that person will have the potential to regain the traits of his or her merfolk ancestors. (Successfully activating those traits if they're present is another matter entirely, however; you'll have to read the book to find out how that happens!)

Some of the most compelling examples of a biological atavism come from the sea, as well, but in reverse: wild whales and dolphins have been photographed with floppy little vestigial legs! Because cetaceans' origins are thought to lie in land-dwelling creatures like Pakicetus, today’s whales and dolphins still retain small bones in their lower bodies that resemble a reduced pelvic bone and hind limbs. Most of the time, these limb structures remain internal, but, when the genetic switch for longer legs gets flipped to the "on" position, you get—well, this: 

Read the "National Geographic" article from 2006.

Crazy, right? I hope the other dolphins don’t make fun of them.

In addition to dolphins with hind legs like the one pictured above, scientists have also recorded cases of snakes with limbs and chickens with teeth, hearkening back to these animals' earlier forms as they existed millions of years ago.

You may even have heard about (or read — I haven't, yet) paleontologist Jack Horner's 2009 book, "How to Build a Dinosaur: The New Science of Reverse Evolution," in which he "predicted that scientists would someday be able to turn chickens into dinosaur-like forms" ("Reverse Engineering Birds' Beaks into Dinosaur Bones,", 2015). That would involve "switching on" the genes that code for teeth and long tails, which the humble chicken possesses as relics passed down from its dinosaurian ancestors. It's an attempt at turning back the evolutionary clock that might yield very... interesting... results.

Since birds are the only surviving members of the family tree of the dinosaurs, why can't we flip some switches in the genetic code and return a chicken back to its former glory as a dinosaur?
Source: LiveScience

So, there you have it: the answer to the question "What is an Atavist?" In "Rescue Sirens"' lore, the Atavist is a genetic throwback  a human with his or her "mer-gene" turned on — in the same vein as other biological atavisms, like dolphins with wee squiggly legs or hens with teeth. Oh, I love science.