What Is Evolution?

The scientific theory of evolution proposes that all species have evolved through a process of molecular change and inheritance of traits involving primary and secondary characteristics of organisms.  In terms of DNA mutations, evolutionary synthesis defines evolution as the change over time in this genetic variation.  Chalres Darwin is said to be the founder or father of the theory, which addresses the evolving of life through a series of genetic mutations, heritant characteristics through migration, horizontal gene transfer, a process of natural selection (often referred to as survival of the fittest in lay terms)and in species that reproduce sexually, through a process called recombination.  The theory is based in both adaptation and in genetic drift, where species experience adaptive change over time to ensure survival and optimize physical existence for the environment.

So evolutionary biology is a predictive theory.  In part it asserts that we may expect specific change to occur throughout species based on the greatest chance of perpetuating the species and its survival as an organism or symbiosis of organisms that co-exist.  This is certainly an over simplification of the theory, but there are many resources on the web or in libraries that can explain it more thoroughly.    Again, in terms of DNA, there is a locus ( which is just a specific location on a particular chromosome), and the sequence of the locus will vary in the individual organism.  This is called an allele.  In evolutionary biology, it has been found that the frequency of one particular allele will fluctuate within individuals of a species, becoming more or less prevalent relative to other forms of that gene.  This is the hingepoint of evolutionary biology, which evolutionary theory derives strongly from.  Here we see that evolutionary  forces act by driving changes in allele frequency in one direction or another. Variation disappears when an allele (DNA reaches the point of fixation, which merely means when it either disappears from the population or replaces the ancestral allele entirely.

Remember that the term 'theory', when postulated as scientific theory, carries a completely different meaning in science than in lay language.  In science, every scientific "truth" is subject to rigorous and continuing replication of results to discover reliability through repetition.  In these terms, a theory is subject to rigorous and constant study and evaluation, and the goal always to DISPROVE the asserted hypothesis by scientific means,,,,,,,,,, not to prove it, so we may expect that scientific study will contain less bias than other methods of study.  Does it help?

Darwinian evolution is based upon natural selection. It is the ability of any organism to adapt to their surroundings. Birds of the same family, evolving in different environments will, based on survival, develop different characteristics. If bird "a" lives on an island where the only source of foods are grubs that live deep in old trees they might develop long beaks so that they can reach in and get the grubs. If bird "b" evolves in a different area and food is plentiful and easy to get to, he would probably have a much shorter beak. How does this happen? Some birds in both environments, at one time, had some long and some short beaks. The birds with shorter beaks had a hard time surviving on the island where long beaks were necessary. They eventually died out leaving only birds with long beaks and the trait is passed on through the generations in the genes. Back on the second island long beaks got in the way of picking up food on the ground and eventually all that were left were the birds with short beaks. Evolution is the passing on of traits from one generation to the next. Another way evolution can occur is called genetic drift. There is a certain amount of randomness in the passing of genetic traits. Black cats might not have all black offspring. If in generation 1 two black cats have two black & white offspring and four all black offspring and the black & white cats were male and female and the all black cats were all female, in the next generation the male black and white cat might be passing more of the black and white genes to the third generations. Genetic drift is a much slower process than is natural selection.

A bunch of men making monkeys out of themselves.

Evolution is a religion.