No, Evolution Isn’t “Just a Theory”

It’s crazy right? To think that we, as humans, evolved from apes. From ape, to anthropoid, to humanoid, to hominin to humans. However, no matter how unbelievable this might seem at first, the scientific evidence supporting this claim is irrefutable. And orangutans are our cousins! Well, evolutionarily speaking at least. But questions may remain, for example, how could we have evolved from apes to develop advanced societies with culture and technology? And if we evolved from apes, why are there apes still in existence, shouldn’t they have all become humans? To answer these questions and more, we need to examine the genetic origin of humanity to prove once and for all that when scientists say the “theory of evolution” they are referring to evolution as a set of scientific axioms, not as a hypothetical, unproven idea.

What is a Theory?

You’ve probably heard someone say before that, we can’t trust everything biologists say regarding evolution because it’s still “just a theory”, implying that there is still an element of conjecture in discussing evolution or that it is uncertain whether the principals espoused by evolutionary theory actually apply. However, in academic circles, the term theory often refers to something else entirely, and, especially in the case of evolution, implies a very high degree of certainty while also simultaneously allowing for new evidence to be considered when necessary. For example, a definition provided from Miriam Webster of the word theory that conforms more to how it is used in this context is, “a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena” or “the general or abstract principles of a body of fact, a science, or an art” (Theory Definition & Meaning, n.d.). Thus, in using the term theory, scientists are, in fact, speaking of evolution as a substantiated explanation of the natural world. Examples of other famous theories include the theory of relativity and the theory of gravitation, both of which, like evolution, have a significant amount of evidence supporting them, to the point where they are considered fact. Still, in this methodological framework, when a new piece of evidence is discovered, it can be compared with existing evidence to check for differences. The theory can then be updated or even rejected entirely depending on whether this new evidence is compatible. For example, famed evolutionary biologist Richard Dawkins is most well-known for his contribution that evolution occurs based on the selection of specific genes, in contrast to earlier theories which had previously emphasized group selection (Life, the Universe & Everything: Richard Dawkins, n.d.). This proposal was not something that went against the basic principles of evolution, but instead provided a different interpretation of how evolutionary processes work, ideas that were eventually implemented into evolution’s existing theoretical framework.

The longer a theory holds up to new evidence that is discovered, the more confidence we can have in its accuracy and dependability. Applying this idea to the theory of evolution, if even one intermediate fossil was found to be anachronistic or not in line with existing evolutionary models, it would throw the entire system into doubt. Not only has this not happened, but every single subsequent discovery after Darwin first proposed the idea in his preeminent work On the Origin of Species, with some updates and alterations, has only further supported those initial findings. This holds true as it applies to animals of all kinds, including humans, (or homo sapiens, as they are referred to formally in the field of biology) of which there are detailed fossil records of our development from quadrupedal climbers to bipedal organisms living in grasslands in the Miocene epoch (Background and Beginnings, 2024). Thus, we can see that the term “theory” used in this context in describing evolution as an academic field with substantiated evidence backed by years of peer reviewed research. In this light, the use of this word should not induce doubts regarding the truthfulness of evolutionary science, but instead inspire confidence in the fact that these findings are the byproduct of years of rigorous cross examination, fact checking and collaboration among top scientists.

The Genetic Origins of Humanity

To study the genetic and archaeological origins of humanity, a variety of different scientific techniques are used. These include studies of human anatomy vis a vis other species, studies based on molecular biology, paleoecology, fossil evidence and examination though direct observation (Background and Beginnings, 2024). Initially, through studying human anatomy, scientists can see how certain physical traits may have developed overtime. For example, the (now largely unnecessary) appendix that is still present in the human body is indicative of our past as quadrupedal climbers, during which time it is believed to have been used to digest tougher foods like tree bark. It also provides a stark refutation to the notion of intelligent design. Surely, an intelligent super being wouldn’t have included something which now serves little to no purpose, other than the fact that it can become infected and necessitate surgical removal.

In studying evolutionary relationships, scientists also increasingly examine related genes from different species. Based on these similarities and differences, scientists can determine how closely or distantly related these species are. For example, based on genetics, one can observe that humans are more closely related genetically to chimpanzees than to other species of monkeys, like gorillas (Background and Beginnings, 2024). Another way that scientists can study evolutionary history is through examining biogeographical similarities, also known as paleoecology. For example, during the era of the super continent Pangea, many now disparate continents would have been connected into one gigantic landmass. The historical existence of Pangea is supported by common fossil records for creatures that once lived in a similar location on Pangea in what are now completely different continents (Background and Beginnings, 2024). More generally, by comparing different fossils over time, we can examine how different species develop, such as where there are evolutionary breakages and so forth. Lastly, through direct observation of animals in their natural habitat, we can see how evolution has changed the physiology of different species, allowing them to adapt to their natural environment. For example, we can see how monkeys have evolved to use their tails to balance when climbing trees (Background and Beginnings, 2024). In applying each of these different techniques to study humanity, scientists have come up with a detailed picture as to how we originated as a species.

            Based on existing evidence, the genetic origin of humanity can be traced back as late as 16 million years ago, during the middle of the Miocene epoch, though data suggests an ancestry as delayed as the late Miocene, which was about 5 to million years ago (Background and Beginnings, 2024) (See Appendix A). Early hominids (defined generally as primates of the family Hominidae) are speculated to having originated during the subsequent Pliocene Epoch, which occurred some 2.6 to 5.1 million years ago. The most likely possible ancestors to these types of primates include the primate Graecopithecus, believed to have originated in Eurasia and Kenyapithecus, believed to have originated in Africa, specifically Kenya (Background and Beginnings, 2024).  

            In terms of how the first early hominids developed, it is believed that those early ancestors who lived during the Miocene epoch were heavily affected by changing global temperatures during that time. Specifically, forests were gradually being replaced by woodlands, shrublands and grasslands. There were also various mosaic habitats that formed, with forests bordering various bodies of water, including lakes, rivers and oceans. These different environments stimulated different adaptions among wildlife, meaning that there were now more predator and prey options for hominins. As a result of these changes, early hominins strategies for feeding and foraging were also affected, as well as their physiological adaptations to their external environment. Specifically, based on existing fossil evidence, we can see that these ancestors fed on a diet that mainly relied on tough, abrasive vegetation, like seeds and grain. Existing primate remains with large premolar and molar teeth with thick enamel are indicative of how they adapted to this diet. Furthermore, in transitioning from living in trees to in grasslands, they evolved bipedalism, a trait which is believed to have appeared 4 to 5 million years ago (Background and Beginnings).

Evidence regarding the development of human bipedalism can be found throughout various fossil records across the earth. One of the most famous instances is the Laetoli footprints site in Northern Tanzania. Believed to have been made by Au. Afarensis, a pre hominid species, the tracks indicate a form of bipedalism remarkably like modern humans. Existing fossil evidence indicates that other hominins living at the time of the Laetoli track makers were probably obligate bipeds when on the ground, but some of them exhibit features that demonstrate tree climbing capability as well (See Appendix D). However, during the Miocene epoch, for one reason or another, many died out. For example, in the case of hominins living in Africa, the increased variety and shifting distribution of African biomes created a situation in which some hominins survived, and others did not. On the other hand, in Eurasia, hominins largely died out, most likely because of climate exposure. Lastly, in Asia only a few species survived (Background and Beginnings, 2024). Eventually, according to the most popular evolutionary theory, after Homo had developed in Africa, they ventured out into Eurasia, before eventually populating the entire world. There are other, less popular theories that propose an Eurasian lineage as well, through the generally accepted theory remains an African origin of Homo (Castro & Torres, 2022). One piece of evidence that supports this idea is that chimpanzees, our closest living primate relative, still populate much of central and west Africa. Chimpanzees and homo sapiens are believed to share a common ancestor, which likely lived around 6 to 7 million years ago, before an evolutionary breakage occurred. Hence, it is perhaps more accurate to say that humans and apes both evolved from a common ancestor, then that we evolved from apes themselves.

            Along with the physical evolution of homo sapiens, various changes occurred in the cultural framework of these groups over time, including the increased use of tools and language. These changes were often facilitated directly by physical changes. For example, as brain sizes evolved to become larger, human capacity for language and problem solving also changed. This can be measured by the ability of hominid species to display things like art and tool making capability. Thus, the development of human culture and physical evolution were very much associated with one another. This has continued to the point where we have now developed advanced societies with modern technology. However, it is important to understand how this progression began with the development of basic rudimentary tools. Specifically, through using these tools, early homo-sapiens could hunt more effectively and even cook their food, thereby increasing caloric intake. This, in turn, led to the development of increased brain sizes in a positive feedback loop.

            In general, we can see that, based on this article, the evidence supporting evolution is substantial to the point where it is irrefutable. Even now, science continues to make new advancements in this field. With each new fossil properly identified and dated, with each new genome successfully sequenced, our picture of humanity’s evolutionary past only becomes clearer and clearer. Thus, readers should have the utmost confidence that evolution is a substantiated explanation of the natural world, backed by years of rigorous scientific research. In other words, evolution is indeed a theory, but it’s not “just a theory”.

Appendix:

Appendix A:

Appendix B:

References:

“Background and Beginnings in the Miocene.” Encyclopædia Britannica, August 8, 2024. https://www.britannica.com/science/human-evolution/Background-and-beginnings-in-the-Miocene. 

“The Origin of Our Species.” Natural History Museum. Accessed September 4, 2024. https://www.nhm.ac.uk/discover/the-origin-of-our-species.html. 

“Theory Definition & Meaning.” Merriam-Webster. Accessed September 10, 2024. https://www.merriam-webster.com/dictionary/theory. 

“Life, the Universe & Everything: Richard Dawkins.” RSB. Accessed September 10, 2024. https://www.rsb.org.uk/biologist-interviews/richard-dawkins. 

Bermúdez de Castro, J.M., and M. Martinón-Torres. “The Origin of the Homo Sapiens Lineage: When and Where?” Quaternary International 634 (October 2022): 1–13. https://doi.org/10.1016/j.quaint.2022.08.001.