Universal common descent theory postulates that all of the earth's known biota are genealogically related, much in the same way that siblings or cousins are related to one another. Broadly known as macro-evolutionary history, this theory is well supported scientifically and entails the transformation of one species into another, leading to the origin of higher taxa.
Why should I be aware of this?
All living organisms have built-in programmes that force them to evolve. Evolution is the process by which an organism changes, develops and becomes more sophisticated over time and in response to its environment. It is a progression that includes the most advanced animals and plants. These changes are produced at the genetic level as organisms' genes mutate and/or recombine in different ways during reproduction and are passed on to future generations. Many scientists support the Theory of Evolution to explain phenomena in nature. It is currently the most popular concept of how life reached its current state.
All about evolution
Over the last 65 million years, according to the Theory of Evolution, every mammal that we see today (over 4,000 species) evolved from small, four-legged creatures such as the Didelphodon. Through random mutations and natural selection, evolution has produced mammals of striking diversity from that humble starting point:
Evolution has created thousands of different species in different sizes and shapes, from the smallest ant to a 100-ft long whale.
Components in evolution
Evolution has several important components:
- Natural selection: Natural selection drives evolution. This mechanism causes certain organisms to survive an environmental change, which over time, according to the Theory of Evolution, can cause an organism to change into a totally different form of life.
- Micro-evolution: Micro-evolution deals with evolutionary variations within a kind of species. The variations are always in a downward trend and are constrained by the genetic code.
- Macro-evolution: Macro-evolution is transition from one kind of plant or animal into another and involves large or important changes in the basic function of an organism. This cannot happen during a single organism's life, so it can only be the result of a series of genetic mutations.
The basic process of evolution
The basic theory of evolution has three essential parts:
- The DNA of an organism is subject to occasional change, or mutation in a way that affects its offspring, either immediately or several generations down the line.
- There are three types of changes brought about by mutation — beneficial, harmful and neutral. In the case of harmful change, the offspring is unlikely to survive to reproduce. As a result, the mutation dies out and goes nowhere. In a beneficial change, the offspring will do better and will reproduce more. The beneficial mutation spreads through reproduction.
- With mutations occurring and spreading over long periods of time, new species are formed. The species of life that we see in the world today, from the simplest bacteria to humans and everything in between, have been formed over the course of many millions of years.
According to the Theory of Evolution, chemicals randomly organised themselves billions of years ago into a self-replicating molecule, which was the seed of every living thing we see today.
Proof of evolution
The most direct proof of evolution is furnished by the science of paleontology, or the study of life in the past through fossil remains or impressions, usually in rock. Approximately 2 million different species of organisms are now living, but it is estimated that at least 99.9 per cent of species that ever lived are now extinct and that some 2 billion species have evolved during the past 600 million years.
Organisms undergo changes that serve to increase their adaptability, or give greater potential for survival and reproduction, in the face of changing environments. A given kind of organism may evolve only when it occurs in a variety of forms differing in hereditary characteristics, or traits that are passed from parent to offspring.
Common questions on evolution
The theory of evolution states that:
- All life forms (species) have developed from other species.
- All living things are related to one another in varying degrees through common descent (share common ancestors).
- All life on earth has a common origin. In other words, in the distant past there once existed an original life form and that this life form gave rise to all subsequent life forms.
- The process by which one species evolves into another involves random heritable genetic mutations (changes), some of which are more likely to spread and persist in a gene pool than others. Mutations that result in a survival advantage for organisms that possess them are more likely to spread and persist than mutations that do not result in a survival advantage and/or that result in a survival disadvantage.
Some common questions on the Theory of Evolution include the following:
Are all species related?
- Yes. All organisms, both living and extinct, are related and there is a common ancestor shared by these species.
What is a species?
- It is not common for members of one species to inter-breed with members of other species in nature. Though there have been instances of species such as lions and tigers inter-breeding when in captivity together, such closely related species are normally kept apart by geographic locations.
What do genes have to do with evolution?
- Genes, which are the portions of an organism's DNA that carry the code responsible for building that organism in a very specific way, are passed from parent to offspring. Over generations, molecular mechanisms reshuffle, duplicate, and alter genes in a way that produces genetic variation, which is the raw material for evolution.
What role does sex play in evolution?
- Sexual reproduction allows an organism to combine half of its genes with half of another individual's genes. As a result, new combinations of genes are produced every generation.
Is evolution a random process?
- Evolution is not a random process. An individual survives and reproduces depending on the ways its inherited traits function in the context of its local environment.
Are evolution and "survival of the fittest" the same thing?
- They are not the same thing. Evolution refers to the cumulative changes in a population or species through time. "Survival of the fittest" is a popular term wherein individuals who are better adapted to a given set of environmental conditions are given an advantage over those who are not.
Since Charles Darwin proposed the Theory of Evolution more than 150 years ago, nothing has been able to disprove it. On the contrary, many scientific advances have supported, refined and expanded the evolutionary theory far beyond Darwin.
- Human Ancestry
- Becoming Human
- Timeline of Evolutionary Thought
- What is evolution?
- Frequently Asked Questions About Evolution
- Is Evolution Scientific?
- How Evolution Works
If you would like to trace your ancestral origins, visit and register at Family Tree DNA on , which has genetic genealogy databases.