LessWrong (30+ Karma)

“Who Got Breasts First and How We Got Them” by rba

11 May 2026

Audio

Description

It really is Sydney Sweeney's world, and we’re all just living in it. Human female breasts are an evolutionary mystery along several dimensions. First, breast permanence is unique to humans. All other mammals develop breast prominence during pregnancy or nursing, and the mammary tissue recedes after weaning. This process is called “involution”. In contrast, humans develop breast tissue at puberty before first pregnancies and maintain it permanently after last pregnancies. Second, breasts are costly, both metabolically and potentially from a fitness perspective. Metabolically, because they are fat deposits requiring calories and fitness-wise, because the tissue easily lends itself to malignancy. Breast cancer is apparently rare in captive apes and is overwhelmingly a human disease, often striking women young enough to have children, and so subject to evolutionary selection. Background In Descent of Man, Darwin catalogs human secondary sexual characteristics, but he doesn’t seem to have noted human breast permanence as an issue of interest. Cant, 1981 seems to have been the first to speculate about this systematically and believed breast prominence and permanence might have evolved as a nutritional signal of health to mates indicating potential for maternal investment, a la Robert Trivers. Since then, quite a range of [...] ---Outline:(01:05) Background(04:17) Hypotheses(05:03) Sexual Selection(05:57) Nursing or Thermoregulation(06:34) Camel Hump and fat reserves(07:06) Byproduct or Spandrel.(07:57) Study Design(10:41) Assembling the Genetic Panel(11:14) Subpanel 1: Arrested involution(12:51) Subpanel 2: Pubescent adipose tissue(14:01) Results(17:28) Discussion(20:17) Coda --- First published: May 11th, 2026 Source: https://www.lesswrong.com/posts/XTHa5C6SgGKYopH7o/who-got-breasts-first-and-how-we-got-them --- Narrated by TYPE III AUDIO. ---Images from the article:Apple Podcasts and Spotify do not show images in the episode description. Try Pocket Casts, or another podcast app.

Transcription

This episode hasn't been transcribed yet

Help us prioritize this episode for transcription by upvoting it.

0 upvotes

🗳️ Sign in to Upvote

Popular episodes get transcribed faster

Other recent transcribed episodes

Transcribed and ready to explore now

13:00H | 21 DIC 2025 | Fin de Semana

01 Jan 1970

Fin de Semana

10:00H | 21 DIC 2025 | Fin de Semana

01 Jan 1970

Fin de Semana

12:00H | 20 DIC 2025 | Fin de Semana

01 Jan 1970

Fin de Semana

2ª PARTE | 06 ENE 2026 | EL PARTIDAZO DE COPE

01 Jan 1970

El Partidazo de COPE

3ª PARTE | 22 ENE 2026 | EL PARTIDAZO DE COPE

01 Jan 1970

El Partidazo de COPE

3ª PARTE | 04 MAR 2026 | EL PARTIDAZO DE COPE

01 Jan 1970

El Partidazo de COPE

Comments

There are no comments yet.

Please log in to write the first comment.

Report any issue

LessWrong (30+ Karma)

“Who Got Breasts First and How We Got Them” by rba

This episode hasn't been transcribed yet

Other recent transcribed episodes

13:00H | 21 DIC 2025 | Fin de Semana

10:00H | 21 DIC 2025 | Fin de Semana

12:00H | 20 DIC 2025 | Fin de Semana

2ª PARTE | 06 ENE 2026 | EL PARTIDAZO DE COPE

3ª PARTE | 22 ENE 2026 | EL PARTIDAZO DE COPE

3ª PARTE | 04 MAR 2026 | EL PARTIDAZO DE COPE

Sign in to Audioscrape

Share this moment