In this episode of the Huberman Lab, Dr. Melissa Ilardo discusses her research on genetic adaptations in human populations, focusing on the Bajo people of Indonesia and their extraordinary diving abilities. She explains how certain populations develop genetic variations that help them thrive in specific environments, from enhanced breath-holding capacity to larger spleens that store oxygen-rich blood cells.
The conversation explores how genes, behavior, and environmental factors interact to influence human traits and performance. Huberman and Ilardo examine the role of epigenetics in modifying gene expression across generations, the impact of genetic beliefs on physical performance, and the ethical considerations surrounding gene-editing technologies like CRISPR. They address questions about therapeutic interventions versus genetic enhancements, using real-world examples to illustrate these complex topics.
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Melissa Ilardo studies the Bajo people of Indonesia, traditional sea nomads with remarkable diving abilities who can hold their breath for extended periods and dive to depths of 200 feet. Her research reveals that the Bajo have developed genetic adaptations, including larger spleens that act like biological scuba tanks, storing more oxygen-rich red blood cells. This adaptation, linked to a gene variant affecting thyroid hormone levels, appears in both diving and non-diving Bajo individuals.
Ilardo explains that such adaptations emerge when existing genetic variations become advantageous in specific environments, leading to accelerated evolutionary changes. Andrew Huberman adds that genetic variations can influence cognitive and behavioral traits, citing examples like the correlation between autism and exceptional abilities in focused tasks.
The mammalian dive reflex plays a crucial role in human diving abilities, as Ilardo explains. This reflex optimizes oxygen availability and prioritizes blood flow to critical organs during breath-holding. She notes that sea nomads can hold their breath for up to 13 minutes while actively diving and spearfishing, and their physiological adaptations include slowed heart rates and constricted blood vessels in extremities.
Particularly interesting are the Hanyo women divers of Jeju Island, who dive in cold waters even during pregnancy. Ilardo's research suggests they possess genetic variations that protect them from adverse effects of breath-holding during pregnancy, including protection against hypertensive disorders.
Environmental factors can modify gene expression through epigenetics, with changes sometimes spanning generations. Huberman discusses mate choice, noting that humans prefer partners with different immune systems, potentially providing offspring with more diverse immune protection. Ilardo adds that beliefs about genetic predisposition can influence performance, as demonstrated by studies where participants performed better when told they had beneficial genetic traits.
The emergence of gene-editing technologies like CRISPR raises complex ethical questions. While these tools could prevent genetic diseases, Huberman and Ilardo discuss concerns about unintended consequences and potential misuse, citing the controversial case of a Chinese scientist who modified babies' genomes. They explore the challenging distinction between therapeutic interventions and enhancements, with Ilardo presenting thought-provoking scenarios about what constitutes a genetic "defect" versus normal human variation.
1-Page Summary
Melissa Ilardo studies the Bajo people of Indonesia, traditional sea nomads known for their exceptional diving abilities. The Bajo can hold their breath for extended periods and dive to depths of around 200 feet, with skills reflected in their craftsmanship of jewelry using materials like black coral found at significant depths. These diving skills have a strong cultural value and potentially impact reproductive success within the Bajo population.
Ilardo has found that the Bajo have physiological adaptations, such as larger spleens, which function akin to biological scuba tanks by storing more oxygen-rich red blood cells. This genetic adaptation enables them to dive longer and safer. The presence of larger spleens in both divers and non-divers among the Bajo, compared to individuals from a nearby farming village, suggests a genetic basis for this trait. A gene variant in the Bajo population is associated with higher thyroid hormone levels, resulting in a larger spleen. The phosphodiesterase enzymes, which have evolved in the Bajo, have multiple functions and may impact several systems beyond diving. Ilardo suggests that with proper training, the Bajo could potentially excel in competitive freediving due to their biological advantages.
Ilardo explains that adaptations like those seen in the Bajo arise when "standing variation" (pre-existing genetic diversity) becomes advantageous in specific environments, leading to accelerated evolutionary changes. Dietary needs and pursuit of resources, such as protein and fats, have driven human evolution, sometimes in unexpected ways. She discusses how the adaptation for high-altitude survival in Tibetans likely originated from Denisovans, becoming advantageous as their ancestors moved to high altitudes. This beneficial genetic adaptation spread through the population over time.
Andrew Huberman discusses the potential of genetic variations influencing cognitive and behavioral traits. For example, there appears to be a correlation between autism and exceptional ability in focused tasks, w ...
Genetic Variations and Adaptations in Specific Human Populations
The ability of certain human populations to dive exceptionally well is largely attributed to physiological adaptations akin to the mammalian dive reflex, as well as potential genetic variations that protect divers from the impacts of this behavior.
Dr. Melissa Ilardo elaborates on the mammalian dive reflex, illustrating how the physiology of the spleen adjusts to cold water breath-holding, optimizing oxygen availability and red blood cell count. She links this ability to traditional sea nomads, like the Bajo, who have larger spleens believed to enhance this reflex for prolonged and deeper dives. These adaptations allow their body to prioritize oxygen to the critical organs like the brain and heart.
Ilardo also discusses how breath-holding can lead to a dangerous lack of oxygen since humans do not have a sensor for low oxygen levels, but rather an urge to breathe triggered by carbon dioxide buildup. She highlights this risk by mentioning free divers like Andrew Huberman, who explains that exceeding one's breath-hold limitation can result in a sudden and fatal blackout underwater.
Further, Ilardo notes that sea nomads claiming to hold their breath underwater for 13 minutes are able to do this while actively diving and spearfishing, unlike static breath-hold record breakers. She comments on the dive reflex aspects such as a slowed heart rate, constricted blood vessels in extremities, and contracting spleens enhancing oxygen-rich red blood cell circulation.
Ilardo points out the possibility of physiological and genetic adaptations in diving populations like the Bajo and Hanyo women divers of Jeju Island, who dive in cold waters without wetsuits, sometimes during pregnancy.
She suggests that the longstanding diving practice of the Bajo and Hanyo, along with large spleens, could imply a correlation with robust general health. This practice even extends into pregnancy for Hanyo women, who dive up until and shortly after giving birth, hinting at genetic variations that may shield the ...
Mechanisms Behind Exceptional Human Diving Abilities
Dr. Melissa Alardo and Andrew Huberman discuss the dynamic interaction between genes and environment, highlighting the role of epigenetics in human evolution and traits.
Melissa Ilardo notes that genes respond dynamically to environmental stimuli, sometimes with changes that span generations. She mentions how epigenetic changes, which involve modifications caused by molecules attaching to the genome, can be inherited. Instances such as refugee populations inheriting epigenetic changes related to trauma and historical famine-induced epigenetic modifications illustrate this phenomenon, despite no specific mentions in the provided transcript.
Andrew Huberman brings up the concept of hybrid vigor and the preference of both mice and humans for mates with a dissimilar major histocompatibility complex (MHC). This preference likely offers a genetic advantage by producing offspring with diverse immune systems. Melissa Ilardo references a study where individuals were more attracted to the scent of those with very different immune systems than their own. She and Huberman discuss how the globalization of human populations leads to unique genetic combinations that can impart both resilience and susceptibility to new diseases.
Huberman and Ilardo address the concept of genetic determinism, emphasiz ...
Genes, Epigenetics, and Behavior in Human Traits and Evolution
As the potential of gene editing unfolds, Huberman and Dr. Alardo dive into the ethical questions raised by technologies such as CRISPR, which allows for human genome modification.
The conversation addresses the promise and peril of gene editing in humans, where the ability to prevent certain genetic diseases comes packaged with substantial caution regarding unintended consequences, misuse, or societal discrimination.
Huberman and Dr. Alardo consider the possibilities offered by gene editing technologies like CRISPR. While these technologies have potential to eradicate genetic disease, there is trepidation surrounding their misuse and the unforeseen outcomes of altering the human genome. An incident is cited where a scientist in China was imprisoned after using CRISPR to genetically modify the genomes of babies, purportedly to make them resistant to HIV but also potentially affecting human memory. Such actions have incited worldwide condemnation from a community of genetic ethicists and scientists. Huberman suggests that parents with harmful mutations could desire to use CRISPR to prevent transmitting conditions like Huntington's disease to their offspring, underscoring the ethical complexities likely to feature prominently in future discussions.
The debate differentiates between "therapeutic" interventions aimed at treating recognized diseases and "enhancement" modifications that could lead to socioeconomical disparities or philosophical concerns.
Ilardo highlights the challenging discussion of setting boundaries in gene editing between corrective measures and ...
Ethical Issues in Human Genetics and Gene Editing
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