Summary
Overview
Dr. Chris and Dr. Zandi explore the fascinating science of body odour, from its biological origins to its cultural significance. They're joined by Professor Matthew Cobb, who explains why humans smell the way they do, debunks myths about pheromones and attraction, and reveals how smell can be an early indicator of diseases like Parkinson's. The conversation covers everything from why teenagers suddenly develop BO to whether deodorants are masking important biological signals, ultimately reassuring listeners that managing body odour is a natural part of human culture, not a departure from it.
The Biology and Chemistry of Body Odour
Body odour isn't just about 'bad smells' - humans constantly produce odours from multiple sources including sweat glands, sebaceous glands, and various bodily secretions. Professor Matthew Cobb explains that fresh sweat smells different from stale sweat because our microbiome metabolises the compounds in our sweat, creating the distinctive odour we associate with BO. The smell we produce is influenced by genetics, diet, our microbiome, and environmental factors, making it nearly impossible to define a single 'human smell.'
- Humans produce odours from sebaceous glands, apocrine glands (sweat), urine, feces, saliva, anogenital regions, and feet - basically producing odours 24/7
- Fresh sweat smells different from stale sweat because the microbiome metabolises sweat compounds and produces different byproducts
- Human smell is influenced by genetics, diet, microbiome, and environmental factors - there's no single 'human smell'
" We got sebaceous glands. We got apocrine glands, both which around our hairs, the apocrine is sweat, say sebaceous glands are producing sebum. We've got urine, feces, saliva, various odours from the anogenital region, vaginal secretions, feet, and, you know, belches and farts. So there's an awful lot going on. "
" Your microbiome is going to start metabolizing some of those physiological byproducts. They're going to eat your sweat and they're going to crap out various other products, which we might not find quite so attractive. "
The Myth of Human Pheromones and Attraction
Despite popular belief and urban legends, there's no scientific evidence that humans use pheromones to communicate compatibility or fertility. Professor Cobb debunks the romantic notion that we can 'smell' our ideal partner, explaining that while pheromones work powerfully in animals like pigs, no such genetically-based signals have been reliably identified in humans. What we can recognise is familiar smells through learned association, not hardwired biological programming.
- There is no evidence that humans have genetically-based pheromone signals that communicate fertility or immune system compatibility
- While people can identify familiar individuals by smell (like recognising your children's worn shirts), this is learned, not hardwired
- In pigs, male androstenone can induce ovulation in females - but no equivalent compound exists in humans
" These signals, these pheromones, there is no evidence in humans that we have the genetically based signal that says I'm fertile or I have a particular immune system. People have been studying this for a long, long time, and the evidence is flaky, to say the best. "
" There is no identified compound that changes human behavior in any reliable way at all. "
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