Evolution – The Absolute Basics

A Guide for Non-Scientists to The Theory of Evolution

Jan 11, 2009
Robert Harrand

Life Is a Struggle For Survival For Most Organisms - Anita Patterson Peppers

Charles Darwin's Theory of Evolution by Natural Selection is the explanation for the variety of life on Earth.

It is a theory supported by millions of pieces of evidence found in fossils, genetics, geology and mathematical models, and it has withstood 150 years of scientific scrutiny. It is, however, frequently misunderstood, and explanations can often be complicated and full of scientific jargon.

Life and Death in Nature

Every second, countless new living organisms come into existence, whether they are Meerkats on the plains of Africa, ants in the Amazon rainforest, or some undiscovered species in the deep Arctic ocean. Many more organisms are born than the environment can support, which leads to competition, struggle, and death. This is the concept of natural selection.

Take, for example, a population of camels. If such a population finds itself in a drought, and one individual can cope with less water than others, it is more likely to survive and reproduce. Its genetic advantage is then passed on to the next generation.

Then, from the next generation, a small number will have some advantage over the rest, and it is these that will reproduce over their rivals. Extend this natural selection over millions of years, and species change and adapt to the pressures of the environment.

This is similar to artificial selection, where humans select desired traits in a species and selectively breed only the chosen animals. This activity has resulted in, for example, today's huge variety of dogs, which all descend from the wolf (Canis lupus).

Evolution and Mutation in Species

The instructions for all life on Earth are carried in DNA. During reproduction, parts of two DNA molecules (one from the male and one from the female) are exchanged to create a single, unique set of instructions. This process is not always perfect, and errors can occur, leading to novel traits in the individual. These new features are almost always either harmful and reduce the chances of survival, or neutral, and have no effect. Some, however, are advantageous, and lead to an increased chance of survival.

The Splitting of Species

A single species, divided in two by geological activity, will evolve separately due to differences in environment. Over millions of years, gradual change results in two related but quite different species, such as Humans and Chimpanzees.

The genetic similarities between, say, Humans and Chimps are overwhelming. Add to that the presence of accurately dated fossils, showing clear transitions between ancestors of the past and species of the present, and the result is far more evidence than at any criminal trial in history.

Is Evolution Only a Theory?

Evolution is a theory, just as there is ‘music theory’ and ‘atomic theory’. Scientific theories explain facts, they do not eventually become facts. In common parlance, the word theory is used when the word ‘hypothesis’ would be more fitting. In science, a theory is the highest level of understanding, a collection of facts and evidence that has withstood every conceivable test and enquiry.

As Richard Dawkins comments, “The theory of evolution by cumulative natural selection is the only theory we know of that is in principle capable of explaining the existence of organized complexity”

The science behind the modern understanding of Evolution is deep and elegant, and further reading is strongly recommended to build upon this brief introduction.