Far from being the stuff of romantic science fiction thrillers like X-Men mutants, everyday mutations are one of nature's most fascinating mysteries. Mutations are responsible for the diversity of life on Earth -- including the existence of humans. They have played a vital role in our past, in our present and in our future. However, while the history of life on Earth has depended upon advantageous mutations, most have no positive effect.

Mutations are “permanent change[s] in the sequence of DNA.” Mutations are caused by external (exogenous), endogenous (native) factors and “errors in cellular machinery.” External factors include environmental factors like sunlight, radiation, or smoking. An example of non-exogenous factors is the fact that errors during DNA replication can lead to genetic changes as can toxic by-products of cellular metabolism.

Mutations have allowed humans to adapt to their environment. For instance, lactose tolerance is a specific external mutation that was advantageous in societies that raised cows and goats. Mutations have been responsible for antibiotic resistance in bacteria, sickle cell resistance to malaria, and immunity to HIV, among others. A rare gene mutation leading to unusual shortness of height has proven to be advantageous for a particular Ecuadorian community. National Public Radio's (NPR) Jon Hamilton writes how the Ecuadorian community with the rare gene mutation known as Laron syndrome are protected against cancer and diabetes.

In 2008, Professor Eiberg from the Department of Cellular and Molecular Biology stated, “Originally, we all had brown eyes but a genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a 'switch,' which literally 'turned off' the ability to produce brown eyes.” He explains that things like “hair color, baldness, freckles, and beauty spots” are all brought about by mutations.

As much as mutations have helped humans, mutations are also the cause of certain diseases. For instance, E! Science News 2008 explains how a particular mutation relatively common on the Indian subcontinent predisposes people to heart disease. Many other diseases, such as cancer, diabetes and asthma, are linked to genetic mutations.

A genetic disorder is a disease that is caused by an abnormality in an individual's DNA. Abnormalities can range from a small mutation in a single gene to the addition or subtraction of an entire chromosome or set of chromosomes.” Non-disjunction is one of the most common types of mutations. Down syndrome is a non-disjunction and a common genetic disorder that has other consequences such as developmental delays.