How quickly can gene expression change due to behavior?

Gene expression can change quite rapidly, sometimes within minutes or hours, in response to environmental stimuli. Additionally, epigenetic changes, which are modifications to the genome affecting gene expression, can occur over generations and be passed down, as seen with populations affected by trauma or starvation.

How does mate selection relate to immune system differences in humans?

Studies suggest that humans are drawn to partners with very different immune systems, as evidenced by preferences for odors from individuals with distinct 'major histocompatibility complex' genes. This unconscious selection likely serves to produce offspring with a broader and more resilient immune gene array, better equipping them to combat pathogens.

What is the mammalian dive reflex and how does it affect the body?

The mammalian dive reflex is a physiological response activated by breath-holding and facial immersion in cold water. It causes a slowing of heart rate, constriction of peripheral blood vessels to prioritize organs like the brain, and contraction of the spleen to release oxygen-rich red blood cells into circulation, providing an oxygen boost.

What are the unique adaptations of the Bajau (Sea Nomads) free divers?

The Bajau people, known for their extreme breath-hold diving, have significantly larger spleens (about 50% larger on average) compared to non-divers. This adaptation, likely genetic and linked to higher thyroid hormone levels, allows them to store and release more oxygen-rich red blood cells, enhancing their diving capabilities.

Do the Haenyeo (Korean women divers) have unique cardiovascular adaptations?

Yes, the Haenyeo exhibit two types of adaptations: a physiological training adaptation where their heart rate slows dramatically during dives, and a genetic adaptation that lowers their diastolic blood pressure while diving. This genetic trait is thought to protect them against hypertensive disorders during pregnancy, as they traditionally dive throughout their pregnancies.

How does diet influence human evolution and genetic adaptations?

Diet is a powerful driver of genetic selection, leading to rapid adaptations. Examples include lactase persistence for milk consumption and the Greenlandic Inuit evolving to metabolize high-lipid marine mammal diets to avoid heart disease. This suggests that the pursuit of protein and fat has significantly shaped human species.

How does an individual's mindset impact their physical capabilities?

Mindset plays a significant role in determining physical performance. Studies have shown that individuals told they had a genetic advantage for training (even if false) performed better and showed biological changes. This 'placebo' effect highlights that beliefs about one's genetic predispositions can influence actual outcomes and adaptations.

What are the ethical considerations surrounding genetic engineering in humans?

The use of CRISPR for human gene editing raises complex ethical questions, especially regarding the line between correcting genetic defects and enhancing normal traits. Technological limitations, such as off-target effects, and the debate over who decides what constitutes a 'defect' or 'enhancement,' make widespread application in unborn children a contentious issue.

What is genetic admixture and how does it relate to the definition of human species?

Genetic admixture refers to the mixing of different ancestral populations. While all humans are considered one species, globalized populations are leading to genetic combinations never seen before, creating new forms of resilience and disease. The definition of a distinct species based on genetic diversity requires a significant level of change that is not observed within current human populations.

Behaviors That Alter Your Genes to Improve Your Health & Performance | Dr. Melissa Ilardo

Andrew Huberman

Science & Technology4 min read113 min video

May 26, 2025|295,494 views|7,261|637

andrew huberman huberman lab podcast huberman podcast dr. andrew huberman neuroscience huberman lab andrew huberman podcast the huberman lab podcast science podcast genetics gene expression Dr Melissa Ilardo

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Key Moments

TL;DR

Human behaviors and environment can modify gene expression, impacting health and driving evolution, as seen in diving populations and mate selection.

Key Insights

Gene expression is highly modifiable by environmental factors and behaviors, extending beyond fixed genetic inheritance.

Natural selection can occur over shorter timescales than previously thought, influenced by survival advantages conferred by specific traits.

Mate selection preferences, influenced by immune system compatibility signaled through scent, can drive genetic diversity in offspring.

The mammalian dive reflex, activated by cold-water immersion, enhances oxygen availability through spleen contraction, benefiting breath-hold divers.

Specific human populations, like the Bajau and the Korean Haenyeo, exhibit genetic adaptations for underwater environments, including larger spleens and altered cardiovascular responses.

Dietary adaptations and cultural practices significantly influence human evolution and can confer survival advantages, such as lactase persistence and lipid metabolism.

THE DYNAMIC NATURE OF GENE EXPRESSION

Contrary to the idea of our genes being entirely fixed, Dr. Melissa Ilardo emphasizes that gene expression is significantly modifiable by our environment and behaviors. While core genetic blueprints exist, epigenetic modifications and other mechanisms allow for dynamic changes in how genes function. This understanding opens up possibilities for influencing our health and physiology through deliberate actions, moving beyond a purely predetermined genetic destiny.

RAPID EVOLUTION AND NATURAL SELECTION

The concept of natural selection is often associated with very long evolutionary timescales. However, Dr. Ilardo highlights that significant genetic changes can occur more rapidly than anticipated. Behaviors that confer a direct survival advantage, such as those essential for obtaining food or navigating hazardous environments, can drive rapid adaptation within populations over generations, demonstrating that evolution is an ongoing process.

THE ROLE OF BEHAVIOR IN MATE SELECTION

Our preferences in selecting mates are influenced by unconscious biological signals, particularly scent, which can indicate immune system compatibility. Humans, like other mammals, are often drawn to individuals with immune systems different from their own, a mechanism believed to promote greater genetic diversity and resilience in offspring against a wider range of pathogens. This highlights a sophisticated, non-conscious layer of genetic selection in human reproduction.

ADAPTATIONS FOR UNDERWATER LIFE: THE BAJAJ DIVERS

The Bajau people of Southeast Asia, known for their extensive freediving, exhibit remarkable adaptations. Studies show they have significantly larger spleens, which act as a biological scuba tank by releasing more oxygenated red blood cells during dives. This, along with potential genetic variations related to thyroid hormone, enhances their oxygen utilization and diving capacity, demonstrating a clear example of selective pressure favoring specific physiological traits.

THE KOREAN HAE NYEO AND PREGNANCY ADAPTATIONS

The Haenyeo, female divers in Korea, showcase adaptations to cold-water diving, even during pregnancy. Their training leads to a remarkable reduction in heart rate during dives. Furthermore, a genetic adaptation appears to lower diastolic blood pressure during dives, potentially protecting against hypertensive disorders of pregnancy, a condition that can arise from hypoxic episodes similar to unintentional diving. This suggests evolutionary pressures acting on reproductive health.

DIET AS A DRIVER OF HUMAN EVOLUTION

Diet plays a profound role in shaping human evolution. The ability to digest lactose past infancy (lactase persistence) and the specialized metabolism of marine mammal lipids in populations like the Greenlandic Inuit are prime examples. These adaptations arose relatively quickly in response to dietary changes, illustrating how food availability and composition can exert strong selective pressures on the human genome.

PERFORMANCE, GENETICS, AND POTENTIAL

Exceptional human performance, whether in endurance running or specialized skills, often involves a complex interplay of genetic predispositions and rigorous training. While specific genetic variants may confer advantages, environmental factors and training are crucial for realizing full potential. The concept of 'human super-performance' often arises from the synergy of these elements, as seen in elite athletes from genetically predisposed regions and specialized populations.

GENETIC ENGINEERING AND ETHICAL CONSIDERATIONS

The advent of gene editing technologies like CRISPR presents both incredible potential for preventing genetic diseases and significant ethical challenges. Questions arise about where to draw the line between correcting defects and enhancing traits, and who decides these boundaries. The precision of these tools is rapidly improving, making the discussion around responsible application and potential misuse increasingly critical for future human health and evolution.

ADMIXTURE AND THE CONCEPT OF SPECIES

Human populations exhibit significant genetic variation, leading to the concept of admixture – the mixing of different ancestral populations. While this variation is extensive, Dr. Ilardo suggests that it does not currently support the classification of distinct human species. Instead, differences often stem from single gene variants or combinations thereof, underscoring the interconnectedness and single-species status of Homo sapiens, albeit with rich diversity.

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Common Questions

The extent to which our DNA is modifiable by behavior and environment is still being understood, but new fields like epigenetics reveal there's much more room for change than previously thought. While some traits are genetically written, many aspects of gene expression can be altered by our choices and environmental stimuli.