The Science of Sexual Development

In this episode, I discuss how hormones such as testosterone and estrogen and their derivatives impact the early development of the brain and body and their maturation. I review published data on environmental factors shown to powerfully alter hormone pathways in animals and humans and the effects of cannabis, alcohol and cell phones on testes, sperm, ovaries and hormones. I describe the predictable relationship between genes, beard growth and balding patterns, and the importance of estrogen for brain development in people of all chromosomal sexes. Finally, I discuss how the hormones we are exposed to in the womb shape the relative length of our finger digits, the sounds our ears make (yes you read that correctly), and how those correlate with people's self-reports of their sexual preferences. As always, basic information and tools are discussed. Access the full show notes, including referenced articles, resources and more at hubermanlab.com. Thank you to our sponsors AG1 (Athletic Greens): https://athleticgreens.com/huberman LMNT: https://drinklmnt.com/huberman Waking Up: https://www.wakingup.com/huberman Momentous: https://www.livemomentous.com/huberman Timestamps (00:00:00) Introduction (00:00:30) AG1, LMNT & Waking Up (00:06:47) Announcement: Mood Meter App Works Again (00:08:00) Maximizing Learning from the Podcast (00:10:00) New Non-Sleep Deep Rest Protocol, Spanish Subtitles (00:11:35) Sexual Differentiation: Hormones, Neurons & Behavior (00:14:15) Hormones Basics (00:15:26) Sperm Meets Egg, Chromosomal Sex, Gonadal Sex, (00:17:50) Y Chromosome Inhibition of Feminization (00:19:00) Placenta Is An Endocrine (Hormone-Producing) Organ, Adrenal Testosterone (00:19:45) Hormonal Sex, Morphological Sex (00:21:04) Hormones Fast & Slow, Sex Steroids Can Turn On Genes (00:23:06) Masculinization, Feminization, Demasculinization, Defeminization (00:23:42) Primary Sexual Characteristics: DHT Drives Penis Development (00:27:03) Secondary Sexual Characteristics (00:27:43) Penis Sprouting: Guevedoces (00:31:25) Estrogen, NOT Testosterone, Masculinizes The Brain (00:33:15) Breast Development In Males: Aromatase; Puberty, & Steroids in Athletes (00:34:50) Estrogen Powerfully Controls Brain Development In All Individuals (00:35:19) Avoiding Hormonal Disruption In Children & Adults: Specific Oils, Creams, Etc. (00:39:00) Environmental Endocrine Disruptors, Sperm Count Decline, Vincloziline (00:44:20) Androgen Insensitivity Syndrome: Hormones Need Receptors, SARMS (00:48:41) Estrogen Establishes “Masculine” Brain Circuits, Testosterone (00:49:42) Cannabis, Alcohol: In Babies, Puberty & Adults (00:56:25) Cell Phone Technology: Effects On Hormones, Ovaries, & Testicles (01:02:33) Beards & Baldness Patterns Around the World, DHT, 5-alpha-reductase (01:06:39) Creatine & DHT/Hair Loss (01:08:20) Predicting Aging Rates By Pubertal Rates (01:10:04) Hyenas, Baseball, & Jumbo Clitorises: Androstenedione (01:14:26) Intersex Moles (01:15:40) Marijuana Plants, Pollens: Plant-To-Animal “Warfare” (01:20:08) Finger Length Ratios, Prenatal Hormone Exposure & Sexual Orientation (01:29:13) Brain Dimorphisms with Sexual Orientation (01:32:00) “Older Brother Effects”: Male Fetuses Might Change Mothers & Subsequent Brothers (01:35:06) The Path Forward & A Warning (01:35:55) Support & Your Questions Title Card Photo Credit: Mike Blabac Disclaimer