Charles Darwin’s theory of evolution postulates that organisms change over time as a result of changes in heritable physical or behavioral traits. Beneficial changes that better enable an organism to adapt help it survive and produce offspring that might carry the same traits.

Since Darwin released his book On The Origin of Species in 1859, evolution by natural selection has been supported by evidence from geology, paleontology, biology, and genetics; now it’s one of the best substantiated theories in the whole history of science. But despite the overwhelming confirmation, a 2014 Gallup Poll showed that a whopping 73 percent of Americans still subscribed to one form of creationism or another. So to help those people understand that humans didn’t just magically arrive in their present form 10,000 years ago, here’s a list of seven ways that science has validated the theory of evolution.

7. The Examination of Embryo Development

If you take a look at the growth of a human mbryo and compare it with other species such as fish and reptiles, it becomes apparent that they all look similar at certain stages in their development. This is because, even though their evolutionary paths diverged millions of years ago, they still all have some ancient genes in common. These genes date back all the way to the origins of cellular life and they’re the reason why early human embryos feature tails and have a lot in common with fish embryos.

6. Observing Evolution in Adaptive Species

An animal’s color can determine whether it lives or dies in the wild. If it’s too noticeable, it’s likely to become an easy meal for predators. But if it blends in nicely with its surroundings, it’s much more likely to survive and pass on its genes to the next generation.

Back in the 1950’s, coal smoke had blackened England’s trees, so that light pepper moths, which once blended nicely against the tree bark, now stood out against the darker background. During this time, a dark form of peppered moths, once rare, became much more common. Researchers suspected that natural selection was the reason behind the changing moth population, and they tested that idea by putting dark and light moth models on trees. Birds quickly attacked the mismatched ones, just as predicted.

This type of fast moving, adaptive evolution happens with other species as well. In the case of bacteria, the over-use of antibiotics in healthcare has led to the evolution of certain antibiotic-resistant strains of bacteria that are now becoming some of the most difficult pathogens to treat.

5. Studying Computer Simulated Evolution

Since large-scale evolution and speciation generally happens gradually over thousands and millions of years, it can be quite difficult to study in a natural setting. Fortunately, evolutionary biologists can now take advantage of computers to create virtual models of species populations that can be subjected to all sorts of changing environmental factors. Of course, the time scales of these models can be greatly accelerated to see how a given species is able to cope with changes over a long period. The simulations can also be run hundreds of times to verify consistent results. In the past, computer simulated evolution has been used to show that limited life spans are an evolutionary adaptation, that mass extinctions can speed up the evolutionary process,  and that humans likely evolved bigger brains as a means of dealing with large, complex social groups.

4. Linking Attributes to a Common Ancestor

One of the ways biologists identify common ancestry is by looking for similar attributes that are present in both ancient and modern day species. Identifying such features not only demonstrates evolution at work, but can also give insight into the various ways that speciation can occur. Many species of birds, for instance, share very similar appearances and behaviours due to the process of their DNA being passed down from the same common ancestor. By discovering common attributes in species (both living and extinct) scientists are able to track the ways in which certain animals have changed over time in order to adapt to their environment.

3. Identifying Vestigial Physical Traits and Imperfect Characteristics

Many organisms alive today, including humans, contain organs and other physical traits that were once functional in our evolutionary past, but have since become useless or seen their function significantly reduced. In Darwin’s book The Descent of Man, he claimed that roughly a dozen of our own anatomical features were now mostly useless including wisdom teeth, the appendix, the tailbone, the muscles of the ear, and body hair. Traits like these that are no longer needed for our day-to-day survival don’t just disappear over night though, rather, they tend to slowly fade because there’s no pressure for the gene or genes in question to be either disposed of or retained. This results in lingering physical traits that still exhibit a slight resemblance to their original form. To Darwin, this was strong evidence that man had evolved from primitive ancestors.

A close inspection of our anatomy also reveals that human bodies, while nice is some respects, certainly aren’t perfectly formed for all the life-sustaining functions they need to carry out. The fact that thousands of people die every year from choking on their food probably suggests that, in terms of an organisms overall design, putting the food hole in the same place as the breathing hole should generally be considered a bad idea. Nevertheless, since evolution’s primary concerned is adaptation and not perfection, we’ll just have to remember to chew all our food carefully before swallowing.

2. Fossil Discovery and Analysis

Fossil records serve as key pieces of evidence for evolution and species’ gradual change over time. For example, if dinosaurs really did evolve into birds, there should be some clues pointing to the existence of transitional creatures which resemble an intermediate species, having skeletal and other body features in common with both dinosaurs and birds. As it happens, paleontologists have uncovered a number of these transitional fossils. One of the most famous is Archaeopteryx, which combines feathers and bone structures that are specific to birds with features found in dinosaurs. The discovery of fossils like this demonstrate how different species are interrelated though time and give scientists a more comprehensive understanding of the ever expanding tree of life.

1. The Discovery of DNA

In the late nineteenth century, a German biochemist discerned that nucleic acids, long-chain polymers of nucleotides, were composed of sugar, phosphoric acid, and several nitrogen-containing bases. When it was later revealed that the sugar component of nucleic acid could be either ribose or deoxyribose, RNA and DNA had officially come the scene. However DNA wouldn’t gain remarkable recognition until 1943, when Oswald Avery proved that it was actually the means by which genetic information was transferred. Since then, the field of genetics has led us to the conclusion that DNA is universal to all of life of Earth and points to the idea that every living thing on the planet evolved from a common ancestor. In the end, the discovery and study of DNA provided the first insights into the mechanisms behind evolution, as DNA copying errors (genetic mutation) combined with the process of natural selection provided a sound explanation as to why species are able to change over time.