First of all let's clarify something:
Theory of Evolution - what does it do
- It explains how life forms develop and diversify over generations.
- It's based on scientific facts, can be verified.
- starts with some well known facts (physical traits of parent life) and see which forms are inherited by the next generation (through artificial process or natural selection)
Theory of Evolution - what doesn't do
- doesn't explain how the Universe was born, our species beginning.
- doesn't say anything about GOD's existence, aliens, if religion is good or bad, true or false.
Second a scientific theory is not just a theory = a personal opinion.
A scientific theory is
- a well-confirmed type of explanation of nature, made in a way
consistent with scientific method, and fulfilling the criteria
required by modern science.
- contains a body of well substantiated facts that can be verified.
The evolution can be done
- by artificial process (selective breeding). Ex: species of dogs, cats, horses, etc.
- natural selection.
By mating together individuals that exhibit those traits most strongly and repeating this process with successive generations.
Breed only from horses with good competition records and their offspring will tend to perform well.
Breed only from aggressive dogs and their offspring will tend to be aggressive.
Artificial evolution and natural selection are similar
If a greyhound breeder selects only the fastest dogs for breeding stock and in the wild only the fastest gazelles outrun their predators and survive to reproduce, then both nature and the greyhound breeder are favoring certain individuals for reproducing offspring and passing on
their genetic information to the next generation.
Mutation is not good or bad. It's extremely simple and ordinary.
Mutation is not about dramatic malformations like animals with 2 heads.
Mutation is everywhere and is natural.
Mutations are simply changes in genetic variation within a population brought about by insertions, deletions and recombinations of the DNA sequence.
But mutation isn't the only cause of variation because it's not only the DNA sequence that's important to evolution.
Epigenetics studies for example show the genes can be switched on or off and that this genetic activation or inhibition can be inherited and expressed in later generations.
Genetic changes are harmless, mostly.
Most variations are neutral and have no impact on an organism survival, accumulating naturally over successive generations in what's known as genetic drift.
A variation in color for example could have a major impact.
Example: for some insect,
If genetic variation make some of its offspring less
conspicuous to predators they'll have a greater chance of surviving
and reproducing and in the course of time the insects with this
variation may become more abundant.
If the variation makes other offspring more conspicuous to predators they may not survive to reproduce and the variation may vanish or become suppressed because of natural selection.
Evolution is an accident ?
Camouflage capabilities, hooves, petals, antennae, fins, wings, eyes and roots have evolved in the natural world. Not in the laboratory.
All these physical traits have served specific functions in contributing towards different organisms' reproductive success. Clearly if the organisms that have these traits manage to reproduce they perpetuate their genetic information. Including the information for the traits. For the next generation.
But this is a game ... a game of genes, traits
Not quite a game but similar.
For example, traits that give no particular advantage can still be favoured if they're associated with other traits that do.
Bulk may be a great advantage for a walrus (he dominates its rivals). but it would be a distinct disadvantage for a small monkey (that lives in the trees).
But it's not an accident that walruses are bulky and small monkeys are agile. These physical attributes have helped them survive and improve in their respective environments.
And to compete for reproduction.
This is not luck. Like the probability of winning the jackpot. Miraculous accidents are the opposite of what evolution is about.
Dramatic change can be achieved one small step at a time. This is what does the evolution mean.
countless mostly minute changes have accumulated over millions of years.
But evolution it's more than variation. Much more. And interesting.
If members of a given species become geographically isolated from each other, each group may end up having to respond to different environments and predators.
And adapt to very different ways of gathering the food.
And genetic variations will no longer be shared throughout the whole population, but only within each group.
In this way, genetic drift and natural selection can lead to the emergence of two distinct populations which, after a given period of time are no longer related closely enough to interbreed.
A catch. Little attention, please.
The Theory of Evolution doesn't say that organisms from one species suddenly produce organisms from another. Dogs don't produce cats.
Nor does it say that individual organisms change species. Individual apes don't morph into humans.
If humans evolved from apes, why are there still apes ?
- Humans didn't evolve from the apes we see today. We and modern apes have a common ancestor. Different from both.
- When one life form evolves into another that doesn't mean the first life form has to stop existing.
We have a monkey population. It changes very little from one generation to another.
A part of this population goes to a new environment. A bad one. The new group changes dramatically because of the environment. The first group remains much the same.
After many generations there are 2 very different populations. The second population can not look the same. It's not a demand, to look the same after generations and generations.
Nature doesn't reward just any random combination of features. Even highly specialized animals are being driven to extinction all the time.
Nature rewards only whatever is efficient at reproducing itself.
Why we bother understanding the evolution ? Why should we care ?
Not only because is essential to our understanding of biology.
You know, viruses that quickly evolve to be resistant to our defences can be a problem. A major one.
Not only for the curiosity of generations of dedicated scientists. Not for them. No.
It' because many reasons. The most important, in my humble opinion:
we finally get some answers to our biggest questions about life on this planet.
This is the scientific inheritance we pass on to new generations. This is a legacy that is important: will refine our/their education.