Evolution
Life is not Perfect

The Evidence for the Theory of Evolution by Natural Selection

Flatfish


SiteMeter


Vestiges and Redundant Features

Vestiges (or Vestigial structures) are parts of a plant or animal that no longer perform the function for which they evolved. Living organisms abound in vestigial structures and the study of these provides more evidence for evolution.

All flightless birds have vestigial wings.

In some birds like the Kiwi of New Zealand, the wings are useless stubs that perform no function. Other flightless birds include the Ostrich of southern Africa, the Rhea of South America, the Emu of Australia, the Rail in Hawaii, the Kalapo, a flightless parrot from New Zealand, the Flightless Cormorants of the Galapagos and the Wood Rail from Samoa.

These birds have feathered wings that are incapable of flight. These wing remnants can be used for display, sheltering their young, balance and as a threat but all of these wings have lost their original function, that of flight. They are vestiges.

Anatomically these flightless wings have the same bone structure as wings that can be used for flight.

This is very difficult to explain under a creation hypothesis but makes perfect sense under evolution. Flightless birds have evolved from ancestors that could fly and so have inherited all their anatomical structures, including the wings. As flight became less necessary and less used the wings lost their ability to fly.

It is indicative that all flightless birds have evolved on islands with few native predators or in the Southern Hemisphere of continents where there are less of the giant cats and bears.

Talking of the Southern Hemisphere leads us to the most famous of the flightless birds, the penguin. These birds nest on land but hunt in the sea where they are superb swimmers.

Their wings have evolved into flippers. However they still contain the same bone structures as their winged ancestors. And even though penguins never fly and spend much of their time under the sea, they still have feathers.

Penguins make sense only if they evolved from flying bird ancestors.

Many animals have vestigial eyes.

The eastern Mediterranean Blind Mole Rat lives all its life underground. It has eyes but they are covered by skin and never used. They are vestiges and only make sense if the creature evolved from a sighted ancestor.

Burrowing Snakes have eyes that are hidden under scales. In caves there are blind cave fish and spiders with vestigial eyes. There is even a species of blind crayfish that has eyestalks but no eyes on top of them.

All of these creatures with their vestige eyes are evidence of evolution - they evolved from sighted ancestors and were not created with redundant eyes.

Whales have a vestigial pelvis and vestigial hind legs.

The leg bones are present in the whale's body but are not attached to the rest of the skeleton. Instead they are just embedded in the animal's tissue. Again, this makes perfect sense with the fossil record. This shows the evolution of whales from land dwelling ancestors with the consequent loss of the hind limbs and pelvis. All that remains in the modern whale are vestiges of these structures.

Whales

Flightless beetles have vestige wings under their fused wing covers.

Finally, let us look at humans. One of the most famous vestigial structures is the Coccyx. This is a series of fused vertebrae below the pelvis. In other primates (monkeys, lemurs) these bones form part of a tail. The Coccyx is therefore a vestigial tail in humans. Some people even have a rudimentary tail muscle (called the Extensor Coccygis) identical to one that monkeys have. In humans the muscle is useless as the bones to which it is attached do not move.

Another famous vestigial structure is the Appendix.

This is a small piece of gut with a dead-end called the cecal. The same structure is found in other primates. It is larger and more active in primates that eat leaves, like Lemurs, Lorises and Spider Monkeys. In these animals it is used as a fermenting vessel for bacteria that help break down cellulose in plant cells which the animal cannot digest. In Urangutans and Macaques, which eat fewer leaves, the structure is reduced. In humans, who do not eat leaves and cannot digest cellulose, the appendix has nearly disappeared.

The appendix can become inflamed giving rise to appendicitis which can kill if untreated.

In 2013 a study showed that the structure plays a small role in the immune system. This does not mean that the appendix is not a vestigial structure. A vestigial structure is one that has lost its original function, which in humans, it clearly has.

These vestigial structures are proof of evolution. Both the appendix and the coccyx were once in use in ancestor species but no longer perform the function for which they evolved.

The appearance of "goose bumps" in humans is a vestigial trait. They normally occur when we are cold or frightened.

This response is caused by muscles in the base of each hair that can act to raise the hair up. In our hair-covered ancestors, these muscles would act to raise the animal's fur when it was cold. This would help insulate the body. The same muscles would act when the animal was threatened. This time the fur standing up would make the animal look bigger and more threatening.

Atavisms

Vestiges are structures present in most members of a species (like the appendix in humans).

Atavisms are throwbacks. They are rare births with structures that are no longer present in the current species but were once present in the creature's ancestors. Atavisms are not mutations (like a cleft lip or six fingers) but the appearance of a pre-existing ancestral trait.

One of the most dramatic atavisms is human babies born with a tail. Some are soft tails containing only muscle, blood vessels and nerves. Occasionally there is cartilage present and in rare cases up to five vertebrae. These tails can be removed surgically.

Humans carry the same tail making genes as mice but they are normally deactivated. In the embryo stage, humans have a tail that is absorbed back into the body. When an atavism occurs, the tail remains and develops until birth.

Occasionally female humans are born with more than a pair of nipples. This too is an atavism bringing forth ancestral characteristics.

Human Tail
Baby born with an atavistic tail.

One in 500 whales is born with a hind leg that protrudes outside the body. Dolphins have been found with a pair of hind legs. Snakes have been observed with small back legs. All these are traits in the animal's genes because of its evolutionary history.

Horses are occasionally born with three hoofs on a foot instead of one. The modern one-toed horse had ancestors with three toes (Merychippus), so again, the genetic instruction for this feature is present in the modern horse but is normally inactive.

Birds carry the genes for making teeth. They don't normally make them because a single protein is missing during development. If that protein is added to a chicken embryo, the chick develops teeth. This makes sense as birds evolved from reptiles, which had teeth.

Atavisms occur because of inactive genetic material present in all DNA. They are more evidence of evolution.

Bad Design

Supporters of Creation or Intelligent Design often say that living organism are too well designed to have originated by chance.

In fact all evolution is a compromise between a structure that improves survival and the energy required to develop and maintain the structure. In addition, new structures evolve from pre-existing structures. This produces examples of what might be called "bad design". A better name is sub-optimal design.

One of the best examples of sub-optimal design is the Recurrent Laryngeal Nerve in mammals.

It exists in humans. The Recurrent Laryngeal Nerve is a cranial nerve that connects the brain to the larynx where it controls swallowing and speech. If it took the optimum route the nerve would be 30cm long.

In fact the nerve takes a much longer route. It starts from the base of the brain and passes the larynx going down into the chest where it then loops around the dorsal aorta, one of the main blood vessels of the heart. From here it returns upwards to the neck and connects with the larynx. Its actual route is 1m instead of the optimal 30cm.

The same nerve exists in the giraffe. Because of that animal's long neck, the nerve is 5m longer in a giraffe that it should be. Again it travels from the brain, goes to the bottom of that long neck, rounds the dorsal aorta and returns all the way back up the neck to connect with the larynx.

The path of this nerve makes no sense if the mammalian body was intelligently designed. Once the nerve's evolutionary history is understood the path of the nerve makes perfect sense.

The nerve and the structure that would become the dorsal aorta evolved in our fish ancestors. Both were parallel to each other and fed one of the gills. This is still the case in modern fish.

As fish slowly evolved into amphibians, reptiles and mammals, the heart and structures that would become the lungs descended down into the torso. The gills evolved into new structures like the larynx. The nerve remained attached to the larynx but was caught on the wrong side of the heart and was forced down into the torso by the movement of the structure that become the dorsal aorta.

Natural selection lengthened the nerve and took it round the dorsal aorta rather than breaking it and reconnecting by a more direct route. Without the nerve attached to the larynx, the animal cannot swallow and would starve to death.

The Recurrent Laryngeal Nerve can only be understood as a structure developed by evolution. As a designed structure it makes no sense. Many such structures exist in the natural world. Life is certainly not "too perfect to be the result of evolution".

Recurrent Laryngeal Nerve

In men, the testes are outside the body. They have descended from inside the body where they began as fish gonads. In warm blooded mammals, the production of sperm is enhanced by the testes being outside the body. During development the testes descend from the abdomen though the diaphragm. This leaves weak spots in the human diaphragm that make men susceptible to hernias.

In addition, the Vas Deferens, the tube carrying sperm to the penis, takes a longer route that it needs to. It runs from the testes up over the Ureter (the tube connecting the kidney to the bladder) and down to the penis.

This convoluted route is due to the vas deferens being caught on the wrong side of the Ureter as the testes descend. Natural selection took the longer route as breaking the connection and taking the shorter route was not an option as the male would not have been able to reproduce.

The route of the Vas Deferens is another example that can be explained by the Theory of Evolution but makes no sense under creation or intelligent design.

Vas Deferens

Women have a small gap between the Ovary and the Fallopian Tube which provides a path for a fertilised egg to the womb. Occasionally a fertilised egg will not be able to cross the gap and becomes embedded in the abdomen. This can be fatal to both mother and baby if not treated.

The gap is a remnant from our fish and reptilian ancestors. These animals shed eggs directly from the ovary to the outside of the body. In mammals, Fallopian Tubes evolved later as an add-on.

The gap between the Ovary and Fallopian Tube is another example of sub-optimal design. It makes sense once the evolutionary history of the structures is understood. As a product of intelligent design it does not make sense.

The Koala is a marsupial, a pouched mammal. Even though it lives in trees, the koala's pouch faces downwards. This makes no sense as a created structure. It only makes sense when we realise that the koala is recently evolved from a wombat-like creature. Wombat pouches face to the rear as they dig tunnels - a forward facing pouch would get filled with soil.

And it's not just mammals that show bad design.

Flounders are a bottom dwelling flatfish. There are 500 species including Halibut, Turbot and Dover Sole.

These fish are born swimming upright with an eye on each side of the head like in normal bony fish. One month later a strange transformation occurs. One of the eyes migrates over the skull and joins the other eye. Whether it's left to right or right to left depends on the species. The skull changes shape during the eye movement.

The fish then tips onto its eyeless side and sits hidden on the bottom. In this form flounders are the most asymmetric of vertebrates.

If flounders were being designed, a better model would be a Ray or Skate, both fish that are born flat and have eyes on top of their bodies.

Flounders however are related to and have evolved from normal symmetrical fish. This explains the strange convolutions that natural selection is forced to go through. Evolution explains the strange development of flounders. Intelligent Design or Creation can only rely on the whims of a designer.

Flatfish
Flatfish with two eyes on the same side of its head.

The vertebrate eye has a serious "design fault" when compared to the octopus eye (and the squid - both molluscs) even though the two structures look similar.

In the eye of the octopus, the retina lies above the nerves. That ensures that all the surface of the retina is available to capture light.

In the vertebrate eye (and this includes humans), the retina lies below the nerves. One effect of this is that the optic nerve that transmits information from the eye to the brain has to pass through a small amount of the retina. This leaves a blind spot.

The reason for the differences is because the two structures evolved independently and in a different way as can be seen in the embryonic development of vertebrates and molluscs.

Vertebrate and Octopus Eyes
In the Vertebrate Eye (left): 1 Retina, 2 Nerves, 3 Optic Nerve, 4 Blind Spot.
Octopus Eye: 1 Nerves, 2 Retina, 3 Optic Nerve.

Eyes have evolved many times in the animal kingdom and there are nine distinct types of eyes. Apart from the mollusc and vertebrate eyes there are also the compound eyes of insects.

There are many more examples of bad or sub-optimal design in the natural world. Whatever the whims of a designer, these examples are perfectly explained by the Theory of Evolution. The relatively poor design of the vertebrate eye, shared among thousands of species, provide further evidence of the common descent of these animals.

Continents and Islands   [Evolution in Action]


Books From Amazon.co.uk and Amazon.com


External Evolution Links

These links will open in a separate window

Vestigiality
Studies and examples of vestigiality.

Atavism
Throwbacks or atavisms.

Recurrent Laryngeal Nerve
One of the best examples of "bad design".

Metamorphosis
Metamorphosis is change during the life cycle of a creature.