How Evolution Shapes Our Health and Disease
The secrets to understanding modern medicine lie buried in our deep past.
Explore the ScienceFor as long as life has existed, so has the potential for disease. From the earliest self-replicating molecules to modern humans, every evolutionary innovation has carried both promise and peril. The same adaptations that gave us larger brains, upright postures, and complex immune systems also left us vulnerable to cancer, back pain, and autoimmune disorders. By exploring our evolutionary history, scientists are now unraveling the mystery of why we get sick—revealing that many modern diseases are deeply rooted in our ancient past.
Evolutionary medicine teaches us that natural selection acts to maximize reproductive fitness, not health or longevity6 . This fundamental principle explains why our bodies are not perfectly designed and why we remain vulnerable to so many diseases.
While enabling complex organisms, this transition created the conditions for cancer when cellular reproduction goes awry1 .
The adaptation of walking on two legs provided survival advantages but led to vulnerabilities including back problems and joint issues9 .
The dramatic growth of the human brain enabled extraordinary cognitive abilities but required trade-offs that potentially increased our susceptibility to psychiatric and neurological conditions9 .
Complex defense mechanisms protected us from pathogens but created the potential for autoimmune diseases when these systems malfunction1 .
"Evolution involves tradeoffs," explains Alex Pollen, PhD, a neuroscientist at UCSF9 . This concept of evolutionary compromise provides a powerful lens through which to view human disease—what benefited our ancestors reproductively may harm our health today.
Perhaps one of the most surprising discoveries in evolutionary medicine is that approximately 8% of human DNA consists of remnants of ancient viruses that infected our ancestors over millions of years. These viral fragments, once dismissed as "junk DNA," are now recognized as playing critical roles in our biology—both beneficial and harmful.
Ancient viral DNA has been co-opted to create new regulatory elements, driving the emergence of unique human characteristics1 .
Some transposable elements play crucial roles in early human development, while others have been linked to cancer, neurological diseases, and aging when they "jump" into essential genes7 .
Recent research has identified previously unknown subfamilies of these elements that strongly influence gene activity in human stem cells and early-stage neural cells.
"Our genome has developed numerous mechanisms to control these ancient viruses, and to eliminate their potential detrimental effects," notes Dr. Lin He, a molecular biologist at UC Berkeley.
The relationship between these ancient viral remnants and our health represents one of the most exciting frontiers in evolutionary medicine.
The transition from hunter-gatherer societies to agricultural communities approximately 10,000 years ago marked a dramatic shift in human disease patterns—a shift we can now trace through ancient DNA.
A 2025 study analyzed DNA from over 1,300 prehistoric individuals, some up to 37,000 years old, identifying 214 ancient pathogens5 .
Zoonotic diseases (transmitted from animals to humans) began spreading around 6,500 years ago.
These infections became more widespread approximately 5,000 years ago, coinciding with human domestication of animals.
The world's oldest genetic trace of the plague bacterium was identified in a 5,500-year-old sample5 .
"We've long suspected that the transition to farming and animal husbandry opened the door to a new era of disease—now DNA shows us that it happened at least 6,500 years ago," says Professor Eske Willerslev of the University of Copenhagen5 .
This research demonstrates how human cultural transformations permanently altered our health landscape, creating new opportunities for pathogens to jump between species and establish themselves in human populations.
When modern humans migrated out of Africa and encountered Neanderthals and Denisovans, these interactions left a permanent mark on our genome—one that continues to influence our health today.
Groundbreaking research comparing modern human DNA with sequenced archaic genomes has revealed that:
| Neanderthal Variant Influence | Effect on Modern Health |
|---|---|
| Immune system | Enhanced adaptation to new pathogens |
| Skin and hair | Lighter pigmentation advantageous at higher latitudes |
| Blood clotting | Increased risk of excessive clotting |
| Mood regulation | Influence on circadian rhythms and depression risk |
| Metabolism | Adaptation to new food sources |
"I think they were a lot sicker than us," observes John "Tony" Capra, PhD, a geneticist at UCSF, noting that Neanderthals likely suffered from an array of ailments that may have contributed to their extinction9 .
This research demonstrates how interbreeding with other hominins shaped our disease risk in ways that continue to affect modern populations.
Modern artificial intelligence is now harnessing evolutionary principles to predict future health trajectories, offering a powerful new application for ancient insights.
In a groundbreaking study published in Nature, researchers modified the GPT architecture to create Delphi-2M—a model that predicts disease progression by analyzing health records through an evolutionary lens3 .
Delphi-2M demonstrated remarkable accuracy in predicting the rates of more than 1,000 diseases based on individual health histories3 . The model's performance highlights how disease progression follows patterns shaped by deep evolutionary constraints.
| Disease Category | Prediction Accuracy (AUC) | Evolutionary Insight |
|---|---|---|
| Chickenpox | High accuracy | Peaks in childhood, reflecting historical exposure patterns |
| Age-related diseases | Variable accuracy | Reflects evolutionary neglect of post-reproductive health |
| Death | Wide prediction spread | Suggests predictable individual differences influenced by evolutionary history |
| Asthma | Narrow prediction spread | Limited predictability beyond population trends |
The research demonstrates that "transformer-based models appear to be well suited for predictive and generative health-related tasks" and provide "insights into temporal dependencies between disease events"3 .
This approach represents a powerful fusion of evolutionary biology and artificial intelligence—using patterns from our past to forecast individual health futures.
Research in evolutionary medicine relies on specialized tools and techniques that allow scientists to extract information from ancient remains and modern genomes alike.
| Research Tool | Function | Key Insight Generated |
|---|---|---|
| Ancient DNA sequencing | Extracts genetic material from archaeological remains | Revealed historical pathogen spread and human migration patterns |
| Genome-wide association studies | Identifies genetic variants linked to diseases | Shows how ancestral adaptations influence modern disease risk |
| Computational genomics | Compares human genomes with those of other species | Identified human accelerated regions (HARs) linked to brain development |
| Paleopathology | Studies ancient skeletal remains for disease evidence | Tracked historical prevalence of conditions like arthritis and dental disease |
| Branching process models | Models pathogen transmission and evolution | Explains how diseases like COVID-19 emerge and spread |
The growing field of evolutionary medicine promises to transform how we prevent, diagnose, and treat disease. By understanding the deep evolutionary roots of our vulnerabilities, we can:
By anticipating how pathogens might mutate based on historical patterns5 .
By understanding the ecological and evolutionary factors that enable pathogens to jump species4 .
"If we understand what happened in the past, it can help us prepare for the future," notes Associate Professor Martin Sikora5 .
This forward-looking application of ancient wisdom represents the most promising aspect of evolutionary medicine.
As Katherine Pollard, PhD, a computational genomicist at UCSF, observes: "Psychiatric research has been laser-focused on genes. There's a growing realization that we need to be looking at regulatory elements, too"9 .
This broader perspective—examining not just our genes but the deep evolutionary history that shapes how they function—may hold the key to addressing some of medicine's most persistent challenges.
In the end, evolutionary medicine teaches us that our bodies are living records of ancient compromises, genetic legacies, and evolutionary innovations. By learning to read this ancient code within, we not only understand why we get sick but also illuminate new pathways to healing.