Not "just a theory."
The theory of evolution has been used to describe the natural world for the past 150 years, however, it is extremely misunderstood. For example, comedian Steve Harvey in an interview with Tyra Banks said if we “evolved from monkeys [...] why do we still got monkeys?” Many scientists have tried to determine why evolution is questioned so often by the general public, even though it has been accepted by most scientists.
In contrast to this, there are not many people who question the theory of relativity. Although there is no clear answer as to why, a few common misconceptions might have something to do with it.
1. It’s just a theory
Although scientists call it the “theory of evolution,” this actually means it is a well accepted scientific position. It is the same way that the theory of gravity explains why an apple falls to the ground when it leaves your hand — there is no uncertainty that the apple will fall.
Some people use “theory” in everyday conversation to mean an unproven hypothesis, but this is not what it means in scientific terms. A scientific theory is typically a highly validated explanation that has been tested and retested over and over again.
2. Evolution is not science
There is a misconception that evolution is not science because it is not observable and can’t be tested. However, that statement alone has two incorrect ideas. One, that all science depends on controlled laboratory experiments, and two, that evolution cannot be studied without those experiments.
Many scientific investigations do not involve experiments or direct observations. For example, astronomers cannot hold black holes in their hands (that would end up badly for the astronomer), but they can still learn a lot about them through observation.
3. Humans are descended from monkeys
Now, to Steve Harvey’s question: No, your great-great-great ancestor was not a monkey. Evolution states that we have common ancestors with both monkeys and apes, and that among species that currently exist, they are our closest relatives.
However, this common ancestor was not a monkey or a human, but more of an ape-like creature that liked to use tools.
4. Natural selection is purposeful
There are many, many organisms that are not perfectly adapted to their environment, but this does not disprove the theory of evolution. Natural selection can only favor the best of what is available — this produces advantageous traits, but there are always trade-offs. For example, a cheetah is really fast because of its longer legs, but these legs are quite delicate.
It would also be really useful if humans could photosynthesize. Just think about it… when you’re feeling hungry all you would have to do is go outside and sit in the sun. However, animals still can’t photosynthesize. No species is perfect, but most are well-adapted to their environments.
5. Survival of the fittest
In biology, an organism’s fitness does not indicate health, but instead its ability to pass genes into the next generation, and it is not really “survival of the fittest”, but more like “survival of the fit enough.” What this means is that in most populations, organisms with many different genetic variations survive, reproduce and have offspring which carry those genes to the next generation.
It is not just the two best individuals that mate and have offspring. Other individuals, although they may not be the fittest in the population, are fit enough to pass on their genes.
6. Evolution can’t explain complex organs
Creationists often argue that evolution can’t explain the eye because a half-developed eye would serve no function. However, Darwin suggested that the eye may have originally had origins in organs with different functions, and these organs — which allowed the detection of light — were then favored by natural selection.
This idea was proven correct by researchers studying primitive light-sensing organs in animals. For example, light-sensing cells in molluscs and worms spread across the body and can tell the difference between light and dark.
7. Religion is incompatible with evolution
What a lot of people do not understand is that evolution is not a theory about the origin of life, it is a theory that explains how species change over time — there is really very little conflict between evolution and most common religions.
In fact, people of many different faiths and levels of scientific expertise see no contradiction whatsoever, because science deals with the causes for natural phenomena, where religion deals with beliefs that are beyond the natural world.
Even Pope Francis has said that, “natural selection, as a way of understanding physical evolutionary processes over thousands of years, makes sense. Good religion needs to work constructively with good science” and vice-versa.
Misconceptions about evolution. University of California, Berkeley.