Written by Becca Malizia, MS and Hailey Motooka, BS
It’s a wonderful thing when the mentees teach the mentor. My young and talented team combined what they are learning in school with some of the research we do here, enlightening me in the process. Let us know what you think! – DrBonnie360
– taking a multidisciplinary perspective that is needed in AI diseases –
Have you ever looked at the skulls of past humans and marveled at how straight their teeth were? Ever wondered why we even have wisdom teeth if they just need to be removed? Many of us endured braces and got our wisdom teeth out at some point in our life, but what did our ancestors do before access to dentists and orthodontists? Well it turns out there is a lot we can learn from looking back in time, and diet plays a huge role in our recent evolution, oral health, and overall well-being.
The Introduction of Farming and Dietary Change
Millions of years ago, some of our remote ancestors relied heavily on fruits for the bulk of their diet (1). These were pre-agricultural fruits, and so were smaller, had less fleshy pulp, and therefore had significantly less sugar and more fiber (1). Our ancestors most likely ate the whole fruit as well: casing, pulp and seeds (1). This means that prehistoric humans spent an extreme amount of time chewing their food. Homo sapiens first began farming 10-14 thousand years ago, coined the agricultural revolution (2,3). Moving away from hunting and gathering, farming allowed for stability, sparking the start of cities and civilization as we know it. Farming also radically changed human’s diet, from relying mostly on fibrous foods to relying heavily on softer grains. As a result, time spent chewing decreased dramatically.
For us, 10 thousand years is a long time, but for evolution, this is just a tiny snapshot in ~4.5 billion year old earth. The whole hominid line is just a tiny pin point on the overall life of earth.
Our jaws and teeth evolved for millions of years to chew fibrous foods, and with this recent (in evolutionary time) change in diet, our mouths have suffered some serious consequences.
Dietary Change and Mouth Morphology
Without the intense chewing our ancestors needed to survive, our teeth have become crowded (4), resulting in the need for tooth removal and braces. In comparing hunter-gatherer skulls to that of modern humans, Dr. Kevin Boyd, a pediatric dentist passionate about evolution and oral health, has found that many structural changes have occurred.
We can see here that our hunter-gatherer ancestors had much larger masseter muscles (for chewing), straight teeth, and functional 3rd molars (commonly known as wisdom teeth). On the right is a modern industrial skull showing a smaller masseter muscle, crowded teeth and impacted 3rd molars (the main reason for wisdom teeth removal).
“….there is much circumstantial evidence that jaws and faces do not grow to the same size that they used to precisely because of our softer, more processed diets.” – Daniel Lieberman from The Evolution of the Human Head, 2011.
Dr. Boyd is passionate about Darwinian Dentistry and brings his research to practice in new and preventative therapies. Find him at Dentistry For Children and Families.
Farming and Artificial Selection
With the introduction of farming, the cultivation of many grains as well as the artificial selection for fleshy fruits and vegetables occured. Since farming began, humans have selected for larger and more sugary fruits, vegetables and grains. Here we can see the impact artificial selection has had on our produce. A wild mustard plant has been bred into six different common vegetables, corn of today is strikingly larger than corn of the past, and a peach from 4,000 BC definitely doesn’t look as juicy and delicious as the ones we have today.
This change in our food and our diets over time has had significant impacts- not only on human mouth morphology, but also on the composition of human microbiology.
Going Inside the Mouth
Paleomicrobiology is a field within archaeology that analyzes ancient samples and microbiomes in order to better understand the correlations between human evolution and the emergence of specific diseases (5). Studying ancient microbiome samples allows for further comparison and insight into how changes in diet has affected how the oral and gut microbiome has co-evolved with humans over time.
The loss of fiber
Artificial selection of our fruits, vegetables, grains, and the widespread availability and consumption of processed foods has contributed to a massive decrease in dietary fiber. Fibrous foods play a key role in stimulating chewing, and also have important interactions with our microbiome. Fiber can be soluble (we can digest) and insoluble (we can’t digest, but our microbes can) components that play an important role in digestion and provide the necessary food for our microbes. Explore more about fiber here.
Sugar, carbohydrates and the oral microbiome
Along with a decrease in fiber intake, our modern day diets are composed largely of refined sugars and carbohydrates. While both of these substances help make ketchup taste less like tomato water and more like a dipping sauce, refined sugars and carbohydrates aid in increased plaque formation and gingivitis (6). Foods high in fermentable carbohydrates such as soft drinks and cake, and less obvious foods like bread and cereal, can increase mouth acidity by converting to lactic acid. The presence of both cariogenic bacteria and fermentable dietary carbohydrates are are required for the development of dental caries. In other words, the combination of poor oral hygiene and consumption of fermentable carbohydrates are the perfect ingredients for a tooth decay recipe.
The increase in refined sugars and fermentable carbohydrates are only few of the numerous dietary components that arose following the agricultural revolution. Along with these came the introduction of new bacterial species to the mouth, such as P. gingivalis and S. mutans, which are associated with periodontal disease and dental caries respectively. New understanding of the oral microbiome is shaping how we think about caries, periodontal and systemic diseases. While traditional views held that these diseases were caused by a limited number of pathogens, we now think of the oral microbiome as a finely tuned community. An ecosystem that determines the balance between oral health and disease, systemic autoimmune diseases included (7).
Oral health and systemic disease
Periodontal disease refers to inflammatory processes in the tissues surrounding the teeth in response to bacterial accumulations or dental plaque on the teeth. Periodontal disease has been linked to a variety of systemic diseases, including cardiovascular disease, chronic obstructive pulmonary disease, cancer, and many autoimmune diseases such as rheumatoid arthritis, lupus, and Sjogren’s syndrome. More in depth information on this topic can be found here.
More recent human advances
Like the agricultural revolution, the industrial revolution was also a huge turning point for civilization. The technologies and manufacturing techniques it made possible were also applied to our agricultural practices. While the discovery of penicillin by Alexander Fleming in 1928 revolutionized healthcare, it also brought antibiotics to farming. In the past 50 years, antibiotics have steadily become widespread, used in all aspects of our agricultural system from feed to food production, in addition to treating bacterial infections.
Antibiotics work by inhibiting bacterial cell wall production, thus killing off all bacteria. The problem with this is that antibiotics don’t discriminate. They kill all harmful and beneficial bacteria in our bodies. Not only are many of the bacteria within our microbiomes beneficial, but some are actually necessary in maintaining our health. When the oral cavity lacks these beneficial bacteria, dysbiosis can occur, leaving the mouth prone to developing oral diseases. Detection of imbalances in the microbial composition facilitate the early diagnosis of autoimmune diseases, but correction of these microbial imbalances may have potential use as treatments for autoimmune diseases.
All in all, the agricultural revolution started humans on the path towards civilization and modern human life. Because of this, even if you eat “paleo” our diets have drastically changed from prehistoric times. Humans are eating foods that are not in sync with what we evolved to consume. With the recent (in evolutionary terms) changes in our diets and agricultural practices, many serious health consequences have occurred. These dietary changes have also changed our microbiomes and our mouth morphology, which in turn has left us susceptible to oral diseases that can affect the likelihood of developing systemic and autoimmune diseases.
If you have any questions or comments, please do so below!
- Walker, A. “Diet and teeth: Dietary hypotheses and human evolution.” Philosophical Transactions of the Royal Society B. Vol 292(1057). 1981. http://rstb.royalsocietypublishing.org/content/royptb/292/1057/57.full.pdf
- “The Development of Agriculture.” National Geographic. https://genographic.nationalgeographic.com/development-of-agriculture/ . Accessed 6 August 2018.
- “Hunter Gatherers.” History. https://www.history.com/topics/hunter-gatherers . Accessed 6 August 2018.
- Rose, JC, Roblee, RD. “Origins of dental crowding and malocclusions: an anthropological perspective.” Compendium of Continuing Education in Dentistry. Vol 30(5). 2009. 292-300. https://europepmc.org/abstract/med/19514263
- Rivera-Perez, JI, Santiago-Rodriguez, TM, Toranzos, GA. “Paleomicrobiology: a Snapshot of Ancient Microbes and Approaches to Forensic Microbiology.” Microbiology Spectrum. Vol 4(4). 2016. “https://www.ncbi.nlm.nih.gov/pubmed/27726770
- Baumgartner S, Imfeld T, Schicht O, Rath C, Persson RE, Persson GR. 2009. The impact of the stone age diet on gingival conditions in the absence of oral hygiene. J Periodontol 80:759–768. https://www.ncbi.nlm.nih.gov/pubmed/19405829
- Zhang, Xuan, et al. “The Oral and Gut Microbiomes Are Perturbed in Rheumatoid Arthritis and Partly Normalized after Treatment.” Nature Medicine, vol. 21, no. 8, 2015, pp. 895–905., doi:10.1038/nm.3914. https://www.ncbi.nlm.nih.gov/pubmed/26214836