How Evolution Works

There are 3 key elements in the process of biological evolution.
Below is an overly simplified explanation of how evolution works followed by more in depth details.

DNA, Life's Blueprints

All of life contains sequences of genes within our DNA known as the genome. The genome is essentially blue prints for how our bodies develop and functions. The slightest changes in our blue prints result in a change of our structure. For example, remove a particular gene and we will be born without eyes, the alteration of a gene in our blue prints and we will grow extra legs.

All embryos start off as a nearly identical cluster of cells before being partitioned into specialized segments that develop into the final form of the animal. Each specific gene segment in our DNA shapes a specific segment of our bodies. Sometimes animals are born with extra limbs or a leg in the wrong place. Insects have been documented to be born with legs in the wrong place, crabs have had a leg grow where a claw should be, pythons have been born with extra ribs, and some people have been born with an extra finger (Polydactyly). These defects in the construction of the body are the result of alterations in the DNA, by natural means or by an outside source such as radiation. The underline blue prints were being disrupted. We know this for certain because we have been able to have such disfigurements reoccur in a controlled lab environment.

By tampering with the Antennapedia gene in a fruit fly they grow legs out of their head in place of antennas instead out of the mid section of the body where legs normally form. The removal of a gene that is appropriately named "the Eyeless Gene" will cause a fruit fly to be born without eyes. What is more interesting is that gene which tells a fly's embryo to "add eyes" is the exact same gene in other creatures. For example, the Eyeless Gene of a fruit fly embryo has been replaced with Eyeless Gene from a mouse's DNA and the fruit fly was still able to grow compound eyes. The fruit fly grew normal fruit fly eyes using a gene from a mouse.

Understanding this mechanism that all animals use during the creation of their bodies is important when trying to understand evolution. Evolution does not tinker with the bodies; it tinkers with the recipe and machinery that builds the bodies, the DNA. When scientists discovered what exactly was the mechanism that caused the changes in evolution they were astonished at how simple the process really was.

Yeast Genome (single celled organism) 12 million base pairs 6,000 genes

Human Genome over 3 billion base pairs 30,000 genes

To the left is an X-ray example of Polydactyly in a human foot and a human hand.

Copy Errors - "Mutations"

During reproduction our DNA blue prints are copied and passed on so our children's cells will develop an offspring that is built in the same way as its parents. However errors occur in the copying process leaving slight changes known as "mutations." The changes in the new DNA blue prints are passed on to that child's offspring along with new mutations. As generations pass the number of changes increase causing the current DNA to differ more and more from the original set of DNA blueprints.

When DNA is copied so it’s information can be passed down to an offspring the DNA strand (double helix) is unwound and split in half into two strands. Each of these strands acts like a template for the reproduction of the opposite strand. Each base is paired with its specific partner, A with T and G with C. That is, Adenine (A) bases are paired up with Thymine (T) and Guanine (G) with Cytosine (C). So if you have an A you know that the other half of the base pair is a T, and vice versa. Well that is how it is suppose to work but the reproduction process is not flawless and errors, known as mutations do occur. The result is usually an ALMOST identical copy of the parent DNA strand.

In nature genetic change by mutation is frequent and completely normal. Most mutations are simply accidental copying mistakes made when the billions of base pairs in the DNA of parents are being combined to produce offspring. Mutations range in size from a single DNA building block to a large segment of a chromosome. Most of these changes are so slight that they have no effect on appearance or bodily functions and go completely unnoticed. These slight changes are passed down from generation to generation. However, as these slight changes are passed down to generation after generation in combination with other mutations originating in each generation that are also passed the overall change can be drastic enough to classify the organism as a new species. Changes through mutations in the genome are responsible for the variety of life on Earth, both past and present.

	You will not find a half-duck half-crocodile like the Crocoduck propaganda by Ray Comfort. Evolution works through small gradual changes that are usually not even noticeable when looking at a direct offspring. The mutations and changes are also random with no set goal in mind. The evolutionary outcome is controlled by the process of Natural Selection.

Natural Selection

Though unique traits are generated randomly by mutations in DNA the selection of what traits get passed on is not random. The evolution of species happens through of a non random, "survival of the fittest" selection process known as Natural selection. If an organism develops a trait that increases its chances of survival or reproduction then those traits are more likely to be passed down to the next generation. Most commonly it is the organism that can survive the best in its environment which passes on its DNA traits. In turn, unfavorable traits become less common or wiped out completely if the organism carrying the traits is less likely to pass on its DNA. This is why species end up being so well adapted to their environment.

Sexual Selection Evolution is all about acquiring features that help you survive to pass on your genes yet some birds are so brightly colored that predators can spot them a mile away. For example, in India where peacocks are native they are on the menu for the ferocious tiger. The last thing a bird living in the wild needs is a handicap like a tale that exposes it to predators and slows down its escape. Why did such traits that increase an animal's chances of being killed get passed on generation after generation? How can natural selection explain this? Even Darwin was puzzled at how the Peacock could have survived long enough to evolve. Later in his research though Darwin realized that evolution was not just about surviving, it was also about sex. He proposed the idea that the female brain played a key role in the course of evolution, and Darwin was right. In nature the flashy and brightly colored birds are all male. Female birds actually prefer males with bright colors and flashy tails. Only the males with the best genes can produce the longest and most colorful tails, by mating with the right males the females ensure that their offspring will also have strong genes and a better chance to reproduce. Because of this males with such vibrant colors are more successful with the girls and thus have more offspring. Over generations their genes for brightly colored feathers have been spread through the population and the genes for dull colored feathers died out.