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Evolution of Mermaids

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Transcript of Evolution of Mermaids

Evolution of Forelimbs
Respiration Characteristics
Like all marine mammals, mermaids have physiological adaptations that ensure survival within an aquatic environment
When diving, 'muscular flaps' cover the respiratory tract; ensuring that water does not enter the lung cavity (fig. 1)
Upon surfacing, air is expelled from the nasal cavity and the muscular flap is relaxed.

Physiological Adaptations: Conservation of Oxygen
Red blood cells have high volume which are responsible for the storage of oxygen
When the animal holds its breath, blood supply is diverted to brain and vital organs (blood is removed from low-oxygen tolerant tissue).
A decreased heart rate results in less oxygen consumption.
Mermaids have approximately 2-3 times more blood than humans
Therefore, a higher volume of blood results in increased oxygen conservation; enabling long dives for prey.

The Lungs
Pressure tolerance
Lungs contracted
As fig. 2 demonstrates, mermaids have a large lung capacity; almost double of a human
The evolution of teeth has greatly assisted in the success of vertebrates. Molars are four-cusped teeth found in mammals and have the purpose of grinding food at the back of the mouth. Furthermore, carnassial teeth are classified as the final upper premolar and first lower molar teeth which assist in tearing flesh. The presence or absence of strong teeth determines the type of food that can be consumed by an organism.

The evolution of teeth began with a mutation creating carnivorous-like teeth, which increased the genetic variation in a population.

The individual possessing the mutation was able to grind its food better; therefore, it received greater nutrients, such as protein, which enabled it to grow and develop better than others within the population. This strength allowed it to fend off predators better and also enabled it to be faster at catching its prey, giving it a selective advantage over others in the population.

Through natural selection, the carnivorous teeth phenotype enabled the organism to pass its genes on to the next generation. Similarly, a study by Martin and Pfennig (2012) found that in a population of tadpoles, a carnivore phenotype was present in 80% of sample ponds, providing as evidence of directional selection. “In particular, compared to tadpoles with intermediate phenotypes, omnivores and carnivores are larger, more developmentally advanced, and more likely to survive to metamorphosis”(Martin & Pfennig, 2012). Thus, carnivorous teeth in mermaids evolved as a result of selection pressures such as competition for resources and predation.

Evolution of Carnivorous Teeth
Similarities in Tail Morphology
The muscular system of dolphins is very similar to that of mermaids, which provides as evidence of convergent evolution.

The movement of the tail encompasses the whole body movement.; a sinusoidal wave motion that propels the dolphin through the water. A similarity in muscular skeletal structure indicates that mermaids also used a sinusoidal pattern of tail movement.
Mermaids with prominent
phalanges were able to
hunt and grasp food better,
giving them a better chance
at reaching reproductive age.
source:Bennett, 2012
1. Bennett, S. (2012). Mermaids: The Body Found. America: Discovery Communications Animal Planet.

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3. Janik, V.M., Slater, P.J.B. (1998). Context-specific use suggests that bottlenose dolphin signatures whistles and cohesion calls. Animal Behaviour, 56(4), 829 - 838. Retrieved from http://www.sciencedirect.com/science/article/pii/S0003347298908818

4. Harris, B., Foster, N. (n.d). What is a Mermaid. Retrieved from http://www.wisegeek.com/what-is-a-mermaid.htm

5. Newborn baby birth weight. (n.d). Retrieved September 14, 2013, from http://www.baby2see.com/baby_birth_weight.html

6. Human Body Statistics. (n.d). Retrieved September 14, 2013, from http://www.statisticbrain.com/human-body-statistics/

7. Hurwood, D. (2013). Introduction to the theory of Evolution. BVB102 Evolution Week 4 lecture slides. Queensland University of Technology.

8. Wrenn, E. (2012, May 4). Dolphins help Brazilian fisherman catch their prey, then swim off( (but what’s in it for them?). Mail Online. Retrieved from: http://www.dailymail.co.uk/sciencetech/article-2139619/So-long-thanks-fish-Dolphins-help-Brazilian-fisherman-catch-prey-swim-whats-them.html

1. Frank E. Fish1,Laurens E. Howle† and Mark M. Murray. Integr. Comp. Biol. (2008) 48 (6): 788-800. doi: 10.1093/icb/icn029 First published online: May 6, 2008
2. Aquatic Adaptation and Swimming Mode Inferred from Skeletal Proportions in the Miocene Desmostylian Desmostylus.(2005) Journal of Mammalian Evolution,12, 1-2. doi: 10.1007/s10914-005-5719-1
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4. Janelle.(2012) Dugong Dugon.[image]. Retrieved October 20, 2013, from http://www.rmdrc.com/archives/2528#printpreview
5. Madison Timbrook. (2013) Skeletal and Muscle System. [images]. Retrieved October 20, 2013, from http://wiki.hicksvilleschools.org/groups/hsbiology/wiki/b0c50/


2. Hake, L. (2008). Genetic Mechanisms of Sex Determination. Scitable by Nature Education .

3. Ivanova, O. (2003). Once Again About Mermaids. Letter to the Editor , 131-133.

4. Rui F. Oliveira, A. V. (2000, August 9). Male Sexual Polymorphism, Alternative Reproductive Tactics, and Androgens in Combtooth Blennies (Pisces: Blenniidae). Retrieved March 1, 2001, from http://uiee.ispa.pt/ficheiros/artigos/oliveiraetal2001hba.pdf

5. Tooby, J. (1980, December 3). Pathogens, Polymorphism, and the Evolution of Sex. Retrieved May 27, 1981, from http://www.cep.ucsb.edu/papers/pathogen1.pdf

6. WebMD. (n.d.). Your Guide to the Female Reproductive System. Retrieved from Sex and Relationships: http://www.webmd.com/sex-relationships/guide/your-guide-female-reproductive-system

7. G.L. Kooyman (2009) 'Respiratory Adaptations in Marine Mammals'
Accessed at:http://icb.oxfordjournals.org/content/13/2/457.short

Allele frequencies were altered over time, due to mutations and natural selection. A mutation firstly impacted an individual's phenotype by causing prominent phalanges.

This new phenotype allowed the organism to grasp its prey better than others in the daily struggle for resources. Through natural selection, prominent phalanges were favoured and the frequency of traits was altered within the population; the individual with prominent phalanges was able to survive to reproductive age.

Some of the mutant individual's offspring would show evidence of prominent phalanges protruding from the fin and were also able to catch prey more successfully and survive to reproduce.

The mutation which caused prominent phalanges was passed on through generations and eventually became the dominant phenotype in the population.

A fin is a flat forelimb, evolved for the purpose of maneuvering and propelling an animal through water. A selection pressure must have, however, acted on mermaids for them to form forelimbs similar to humans. Convergent evolution resulted in two species (humans and mermaids) to produce similar characteristics, such as prominent phalanges in the hands, due to similar selection pressures.

If a mutation arose in an individual and produced a phenotype with extremely prominent phalanges, an issue would arise; the individual’s hands would be unable to propel the animal away from its predator fast enough. Thus, the animal would not survive to a reproductive age and the human-like phalanges phenotype would be lost from the population. This stabilizing selection ensured that the intermediate trait (prominent phalanges with a small amount of webbing) was favored; less prominent phalanges withheld the animal’s ability to capture and grasp its prey, but extremely prominent phalanges made the organism unable to propel itself fast enough away from it predators.
-Placental Mammals
-Mermaid has human reproductive system
-Female- small slit in the tail designated to urogenital and anal openings
Male- two slits- one urogenital and one anal opening
-Sexually mature at age 5-13 years (female), 9-14 years (male)
-Mate for emotional as well as reproduction purposes
Sexual Polymorphism
The disadvantages of sexual reproduction, including the costs of meiosis, recombination, and mating are large; while the advantages remain obscure (Tooby, 1981). Males were considered a different species until Charles Darwin discovered sexual selection. As a result of differences in reproductive investment between sexes, individuals (particularly males as their testosterone hormone encourages aggression/competition) will compete for the affection of their potential mate. Females respond by usually choosing the most dominant of males which can be a very selective process. In contrast to males, females produce much larger and more energetic gametes than males which as a result promote lower reproductive rates and consequently less sexual activity in females than males. Therefore, males compete for females and their fitness is dependent on the number of mates in which they breed, whereas the female’s fitness depends purely on the quality of the male. (Rui F. Oliveira, et al. March 1, 2001).

When inter-male competition is intense, the undesired male may adopt alternative reproductive tactics (ART) to court and mate. There is one tactic that is considered relevant in this case- average or ‘less competitive’ males invest in masculine behaviour to successfully court the female, such as the colliding of bodies or the extension of the tail.

After the courting process, a sheath located on the pelvic area opens. If copulation is performed successfully, the mermaid will be pregnant for 11 months.
An Extreme Phenotype
Mermaids adopted their behaviour through their surroundings. Similarly, other organisms, such as aquatic mammals, that shared those surroundings were independently capable of evolving similar phenotypic characteristics and behaviours (Hurwood, 2013). For example, mermaids only inhabited warm coastal areas and would migrate when water temperatures decreased; this is similar to the behaviour of manatees.

Considering convergent evolution occurred between mermaids and the sirenia family, calls were a prominent feature in reference to communications. Manatees produce squeaks and chirps to pass on messages ranging from alarm calls to expressions of happiness (The Magnificent Manatee, n.d).

Similarly, dolphins use these chirps and squeaks for echolocation and are known to have complex human-like communications. Certain dolphin whistles are called to identify individuals, similar to humans calling someone by name. Mermaids have analogous calls to dolphins with their human-like complexity in communications, as each mermaid has an individualized call (within their own language) similar to a human voice (Janik & Slater, 1998).

Also, mermaids shared mutual symbiosis with dolphins; where dolphins and mermaids were hunting partners, and each assisted in the communal catching of fish (Bhatt, 2011). This cooperation between species is demonstrated today, where dolphins herd fish towards humans (a similar species to mermaids) and flap their flippers and tails to indicate that nets can be thrown out to haul (Wrenn, 2012).

The similarity in reproductive organs to humans results from convergent evolution.
Thus, the mermaid is more closely associated with dolphins in regards to the birthing process.

Dolphin Reproductive Rate=
3-6yrs (only one calf born)

Human Reproductive Rate=
Individual's time choice (av. 2-3 offspring born in a lifetime)

Mermaid Reproductive Rate=
Likely that mermaids reproduced at a rate to continue its species but this reproductive rate is very slow.
Mermaid's gestation period= 11months
-The female will retreat to shallow water for the birthing process
-Offspring will be born tail first (like a dolphin calf)
-The baby will be aided to the surface where it can take its first breath
-Other mermaids will swim around the mother and the baby to fend off predators
Reproductive System
The relationship between mermaids and humans is polyphyletic; they are of unrelated lineages. Thus, their similar characteristics must have arisen through convergent evolution.
1. Martin, R. A., & Pfennig, D. W. (2012). Widespread disruptive selection in the wild is associated with intense resource competition. BMC Evolutionary Biology, 12(136), 1–11.

Aquatic apes or mermaids are largely compared to marine mammals such as whales and dolphins but a majority of the comparisons are best described by the organisms being apart of the Sirenia family (manatees and dugongs) (Bhatt, 2011).

The upper transverse plane of the mermaid’s body structure resembles a human and the lower transverse plane of their body structure is of marine mammals.

At birth a manatee calf measures around 3-4 feet long and weighs 20 – 30kgs (The Magnificent Manatee, n.d.). The average height of a newborn human baby is 50 cm, approximately 3 – 4kgs.

The West Indian manatee can live to 60+ years which is relatively close to a human’s lifespan.The average length of a mature manatee both male and female is around 10 - 11 feet long and weights around 450 - 680kg, where females are sexually mature at 5 years of age and males at 9 years of age (The Magnificent Manatee, n.d.).

The average height of a human is approximately 5”7 (although this varies due to genetic variation between males and females and ancestral genotypes and phenotypes). The average weight of the human is 88kgs (Human Body Statistics, n.d.).

Figure 1: Muscular flap
The Evolution of Mermaids
Figure 2: Air and Lung Capacity
Over hundreds of thousands of years apes became increasingly adapted to a marine environment, due to better food sources in the ocean. Iodide, iron and calcium found in the crustaceans and fish that the apes were consuming increased their intelligence and strategizing ability. Furthermore, genetic variation arose in the population predominantly through mutations. Aquatic apes with phenotypes which allowed them a better chance at survival, such as when hunting, allowed them to pass these ‘successful’ genes on to the next generation. Some of these changes in phenotypes include the shedding of fur/hair, to decrease the organism’s weight to make movement through water more smooth and effortless. In addition, partial hand webbing increased the aquatic ape’s speed through water.
Evolution of the Digestive System
➢ The configuration of the mermaid’s digestive system is considerably similar to that of dolphins, humans and manatees, therefore suggesting a common ancestor between the organisms.

➢ The adaptations of highly functional digestive features have allowed mermaids to thrive in environmental conditions requiring prolonged exposure to deep submersion. Like most mammals, digestion in mermaids begins with a single oral orifice and terminates with the anal sphincter.

➢ Similar to the complex digestive structure of dolphins, the mermaid stomach also consists of three compartments where mechanical and chemical digestive processes take place to breakdown food. In addition, mermaids have adapted the ability from the dolphin family to ingest food into the fore-stomach where it can be stored or regurgitated at will.

Adaptation: Digestive Features of Mermaids

➢ The digestive system of the mermaid through evolutionary processes has adapted a range of compensatory mechanisms making it notably more resilient than most related species. For instance, through natural selection mermaids that had the ability to secrete thicker and greater quantities of mucous (3 times the average human daily) were able to better protect their internal systems and organs from damage caused by infectious agents to enhance relative fitness.

➢ In addition, most mermaid species also have specially developed kidneys that aid in removing excess salt, by-products of cellular activity and other waste to maintain optimal salinity levels. This adaptation is likely to have been caused by the mermaid's need to absorb fresh water for survival. Access to fresh water sources can often be limited when mermaids are in the ocean or brackish coastal areas, although it is not a permanent solution, many mermaid species have gained this ability to counter inadvertently ingesting irregular quantities of salt or when forced to rely on seawater for hydration. This is a prime example of convergent evolution acting as a generator of morphological diversity when phenotypes are derived from selection for similar function.

➢ One other special feature, although still very uncommon, is present in a few species of mermaids that have evolved to become polyphyodonts; the ability to continually replace their teeth throughout their lives, similar to manatees. This is most likely due to selection pressures related to having to rely upon more abrasives diets that often are mixed in with sand or dirt due to high volume intraspecific competition or environmental conditions acting as a central driver of viability selection.

According to Frank E. Fish et al,(2008), “...the morphology of the appendages provides hydrodynamic advantages with respect to drag, lift, thrust, and stall.”

The tail structure of the dolphin and dugong are incredibly alike, due to possessing a common ancestor. This excludes the split at the end of the dugong tail that is also found in some whale skeletal systems.
Skeletal structure
Evolution of the tail:
Mermaids with the strongest tail and most proficient hydrodynamics were able to evade predators, such as sharks (Megalodon), and were thus able to survive to reproduce. Through natural selection, those featuring the phenotype allowing for successful hydrodynamics was selected for and was passed on to the next generation.
1. Convergent evolution- Prominent phalanges, carnivorous teeth and a similar digestive system to humans resulted from similar selection pressures acting on both humans and mermaids.
2. Sexual selection resulted in male-to-male competition for females.
3. Directional selection- teeth promoting omnivory were favoured, as they allowed for a diverse range of nutrients to be received (which in turn increased fitness).
4. Natural selection ensured that only the most suited phenotype for the environment was passed on through generations.
5. Stabilizing selection- The intermediate trait for slightly protruding phalanges was favoured, allowing for prey to be caught, but also for the mermaid to escape from its predators.
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