a) Fossil Record:

Fossils are the preserved remains or traces of ancient organisms. Fossil records are able to support and be evidences of evolution because some fossils of extinct animals resembled living species. Records of fossils may show similar structures, bones, and other features that may relate to a currently living species, which shows that these species have evolved from the past extinct species. For example, Darwin found a set of fossils belonging to a long extinct species of glyptodonts, which was extremely similar to a living species that lived in the area where this set of fossils were found. This apparently similar species was the: armadillo. Fossil records are an example of indirect evidence of evolution as they are much like puzzle pieces, which must be put together in order to form a bigger picture and serve a greater purpose. Just fossil records cannot be evidence that evolution is possible, but with the help of other fossils as well as the current species that is living, it can then be a part in trying to explain evolution.

A fossil of a fish

b) Recent observable changes in a population of a given species (e.g. bacteria, peppered moths):

Changes in species are observable if the reproduction and adaptation rate of that species is high. During the industrial revolution, peppered moths lived in forests that were close to factories. Most moths were white, however, there were some black ones due to variation. The barks were white and therefore, the favored trait was the color white, as it helped the moths camouflage against its predators. However, factories produced so much soot that it covered the barks of the trees in the forests, turning the barks into a darker color. Now, the black colored peppered moths were favored as they would camouflage better than the white ones. As a result, the number of white moths decreased and the number of black moths increased because more black moths were able to survive and reproduce. In the case of bacteria, they can multiply extremely quickly, making observations in any changes quite easy. When people are infected with a dangerous bacteria, they take antibiotics to help fight the bacteria. However, as there is variation among bacteria, the antibiotics sometimes do not kill ALL of the bacteria and therefore, some are left behind. Those bacteria are obviously immune to antibiotics and they pass off their trait to its offspring, making even more antibiotic-immune bacteria. These observable changes in a population of a given species are an example of direct evidence of evolution because these changes can be seen, noted, and therefore, directly support evolution. It is not something that happened millions of years ago, but something that happens right before our eyes.

A picture of a white and black peppered moth

c) Homologous Structures:

Homologous structures are structures that are shared by related species and that have been inherited from a common ancestor. Homologous structures provide evidence of evolution because evolutionary theory explains the existence of homologous structures adapted to different purposes as the result of descent with modification from a common ancestor. Similarities and differences among homologous structures help determine how recently species shared a common ancestor. These structures show that current species have a specific structure within their body that have constantly been passed down to them from their ancestors and that different organisms have evolved from a recent common ancestor, showing the slow and steady process of evolution. For example, the front limbs of reptiles and birds are more similar to each other than either is to the front limb of an amphibian or mammal. This indicates that the common ancestor of reptiles and birds lived more recently than the common ancestor of reptiles, birds, and mammals. Homologous structures are examples of indirect evidence of evolution because these homologous structures cannot be seen and analyzed in the present, and can also be inferred that they have been inherited by a common ancestor among specific species. These structures can also be seen to be used for different purposes, which are adapted for different environments.

Homologous Structures: structures that are shared by related species that have been inherited

d) Vestigial Structures:

Vestigial Structures are structures that are inherited from ancestors but have lost much or all of their original function due to different selection pressured acting on the descendant. Vestigial structures are evidences of evolution since it clearly shows that descendants have acquired structures from their ancestors, but have been changed to serve different purposes or have lost their main function due to different pressures and environment. This means that as generations passed and changed, so have their structures. For example, the hipbones of the bottle-nose dolphin are vestigial structures because these hipbones played a role in terrestrial locomotion, but are obviously not used anymore. Vestigial structures are an example of indirect evidence of evolution since it cannot be seen that changes occurred on structures that have been directly passed down from ancestors, but only inferred that they were. These changes are noticeable, and most of the time, easy to identify the original function and the reason why it has changed.

The human appendix: A popular example of a vestigial structure

e) Comparative Embryology:

It has become apparent that many animals with backbones look very similar. Observations have made it clear that the same groups of embryonic cells develop in the same order and in similar patterns to produce many homologous tissues and organs in vertebrates. Therefore, this means that embryonic cells in animals with similar structures are created in the same order and similar patterns in order to produce similar homologous organs and tissues. Evolutionary theory explains that similar patterns of embryological development provide further evidence that organisms have descended from a common ancestor. For example, despite the very different adult shapes and functions of the limb bones, all those bones develop from the same clumps of embryonic cells. Embryology is an example of an indirect evidence of evolution since observations cannot be directly made to see and correctly identify the growth of similar embryonic cells and what they actually produce, but again, only inferred.

A picture of different embryos of different species

f) Comparative Biochemistry (biological molecules):

At the molecular level, the universal genetic code and homologous molecules provide evidence of common descent. Universal genetic code is called "universal" because all living cells use information coded in DNA and RNA to carry information from one generation to the next and to direct protein synthesis. This genetic code is nearly identical in almost all organisms, including bacteria, yeasts, plants, fungi, and animals. Also, mutation and the reshuffling of genes during sexual reproduction produces heritable variation, which allows natural selection to occur and later, evolution into different species. The fact that the genetic code is universal is strong evidence that all organisms have evolved from a common ancestor that shared this same code as well. Biological molecules are an example of an indirect evidence of evolution as it is not seen directly observed today that the genetic code is universal and has also been universal for ancestors, which means that the genetic code of present species would quite similar to the genetic code possessed by common ancestors.

The Universal Genetic Code


Evolution is extremely important to understand. Evolution describes how life changes over time, how everything is not fixed, how there is no perfect way of doing something. Evidences of evolution are extremely crucial in today's world, especially in the field of medicine. It is important for doctors to understand how evolution works, just the plain fact that living things change over time has been a great contribution to the science of medicine. This has allowed doctors to realize that harmful living things, such as bacteria, can evolve to become immune to antibiotics. Without the knowledge of how evolution works, doctors would be flabbergasted when faced with a bacterial infection that is basically immune to every antibiotic available. However, because doctors understand how evolution works and how bacterial infections constantly evolve to become immune to specific antibiotics, more are being produced to help in the war against biologically harmful micro organisms.