Episode sources:
⇢Definition of “mammal” simplified from: Vaughan, Terry A. Mammology. Philadelphia, Pa., Saunders College Publishing, 1986.
⇢The meaning of “mamma” in latin:
1) Burke, Jack. “A Brief History of the Taxonomy of Mammals .” MCV QUARTERLY , vol. 4, no. 2, 1968, pp. 77–80. Department of Anatomy, Medical College of Virginia, scholarscompass.vcu.edu/cgi/viewcontent.cgi?article=1175&context=mcvq. Accessed 15 Jan. 2026.
2) “Mamma, N. Meanings, Etymology and More | Oxford English Dictionary.” Oed.com, 2023, www.oed.com/dictionary/mamma_n?tab=meaning_and_use#38332815, https://doi.org/10.1093//OED//1101233719. Accessed 12 July 2024.
⇢ Cetaceans: Toothed whales (dolphins and more) & baleen whales:
1) Folkens, Pieter A, et al. Guide to Marine Mammals of the World. New York, A.A. Knopf, 2002.
2) Berta, Annalisa, et al. The Rise of Marine Mammals : 50 Million Years of Evolution. Baltimore, Maryland, Johns Hopkins University Press, 2017.
3) Dold, Christopher, and Sam Ridgway. Cetaceans. 25 July 2014, pp. 679–691, https://doi.org/10.1002/9781118792919.ch49. Accessed 25 Oct. 2024.
4) Mead, James, and Robert Brownell Jr. “Order Cetacea.” MAMMAL SPECIES of the WORLD a Taxonomic and Geographic Reference, edited by Don Wilson and DeeAnn Reeder, Baltimore, The Johns Hopkins University Press, 2005, pp. 723–743, repository.si.edu/server/api/core/bitstreams/c9886899-6dc7-4d19-b180-92e4d5189109/content
⇢ Baleen is made of keratin: Rice, Dale. “Baleen.” Encyclopedia of Marine Mammals, edited by William Perrin et al., Academic Press, 2009, pp. 78–80, www.sciencedirect.com/science/chapter/edited-volume/abs/pii/B9780123735539000237
⇢Whale nursing mechanics: I didn’t mention this but they do have nipples! It is just hidden in their mammary slits that protrudes when the baby wants milk. Nursing behavior may differ between species. It is generally described as a mother squeezing milk onto the tongue into the waiting mouth of her calf but a recent paper suggested that sperm whale calves press their tongue against the nipple to actually suckle.
1)“Mother-Calf Relationships.” Baleines En Direct, baleinesendirect.org/en/discover/life-of-whales/behaviour/mother-calf-relationships/.
2) Kera. Aquarium of the Pacific. “How Do Whales Nurse? Let’s Find Out!”. 2009. www.aquariumofpacific.org/blogs/comments/how_do_whales_nurse_lets_find_out.
3) François Sarano, et al. Nursing Behavior in Sperm Whales (Physeter Macrocephalus). Vol. 10, no. 2, 1 May 2023, pp. 105–131, https://doi.org/10.26451/abc.10.02.02.2023.
⇢Whale milk fat content: I do not remember where I learned that the consistency is like cottage cheese, that might need a fact check but the fat content of blue whales is ~40% which 10x thicker than human breastmilk at 4% fat content according to this national geographic articles (all academic articles were only viewable via a paid subscription :/ ): Brian Howard. “Exclusive Video May Show Blue Whale Calf Nursing.” Animals, 2016, www.nationalgeographic.com/animals/article/160302-blue-whale-mother-calf-nursing-video-pygmy-new-zealand. Accessed 16 Jan. 2026.
⇢First life on Earth:
1) Bada, Jeffrey L. “How Life Began on Earth: A Status Report.” Earth and Planetary Science Letters, vol. 226, no. 1-2, Sept. 2004, pp. 1–15, www.sciencedirect.com/science/article/pii/S0012821X04004704, https://doi.org/10.1016/j.epsl.2004.07.036.
2) Martin, William, et al. “Hydrothermal Vents and the Origin of Life.” Nature Reviews Microbiology, vol. 6, no. 11, 29 Sept. 2008, pp. 805–814, earthscience.rice.edu/wp-content/uploads/2015/10/Martin-et-al.-2008-Nature-Reviews-Microbiology-Hydrothermal-vents-and-the-origin-of-life.pdf, https://doi.org/10.1038/nrmicro1991.
3) Sojo, Victor, et al. “The Origin of Life in Alkaline Hydrothermal Vents.” Astrobiology, vol. 16, no. 2, Feb. 2016, pp. 181–197, https://doi.org/10.1089/ast.2015.1406.
4) Dodd, Matthew S., et al. “Evidence for Early Life in Earth’s Oldest Hydrothermal Vent Precipitates.” Nature, vol. 543, no. 7643, Mar. 2017, pp. 60–64, https://doi.org/10.1038/nature21377.
5) Pattison, Kermit. “A Step toward Solving Central Mystery of Life on Earth.” Harvard Gazette, 22 July 2025, news.harvard.edu/gazette/story/2025/07/a-step-toward-solving-central-mystery-of-life-on-earth/
⇢Platypus nursing behavior:
1) San Diego Zoo. “Platypus | San Diego Zoo Animals & Plants.” Animals.sandiegozoo.org, 2024, animals.sandiegozoo.org/animals/platypus.
2) “Platypus Facts & Photos.” Bush Heritage Australia, 2022, www.bushheritage.org.au/species/platypus?srsltid=AfmBOoozsW8Nb3ulU7T60s6M0Gsxre3O89zw-t8OKzbF3TRX8JaGAcit. Accessed 16 Jan. 2026.
⇢Human embryo pharyngeal gills to our future jaw structures:
1) Aldhebiani, Amal Y. “Species Concept and Speciation.” Saudi Journal of Biological Sciences, vol. 25, no. 3, Mar. 2018, pp. 437–440, www.sciencedirect.com/science/article/pii/S1319562X17301365, https://doi.org/10.1016/j.sjbs.2017.04.013.
2) “1.7: Pharyngeal Arches.” Medicine LibreTexts, 26 Jan. 2021, med.libretexts.org/Bookshelves/Allied_Health/Histology_and_Embryology_for_Dental_Hygiene_(Sheldahl)/01:_Chapters/1.07:_pharyngeal_arches. Accessed 16 Jan. 2026.
Image sources:
⇢Cetacea family tree: Weiler, Colleen. “Is an Orca (Killer Whale) a Whale or a Dolphin?” Whale & Dolphin Conservation USA, 23 Feb. 2022, us.whales.org/2022/02/23/is-an-orca-killer-whale-a-whale-or-a-dolphin/.
⇢Whale baleen: “Baleen Whales | Center for Coastal Studies.” Coastalstudies.org, coastalstudies.org/connect-learn/stellwagen-bank-national-marine-sanctuary/marine-mammals/cetaceans/baleen-whales/
⇢Baby dolphin whiskers adapted from photo by Natalie Goddard. “A Dolphin’s Whiskers - Mandurah Cruises Dolphin Blog.” SEA WEST, 20 May 2022, www.sea-west.com.au/a-dolphins-whiskers/
⇢Humpback tubercles: “Do Whales and Dolphins Have Hair?” Whale & Dolphin Conservation USA, us.whales.org/do-whales-and-dolphin-have-hair/.
⇢Hydrothermal vent: Lubofsky, Evan. “The Discovery of Hydrothermal Vents.” Woods Hole Oceanographic Institution, 11 June 2018, www.whoi.edu/oceanus/feature/the-discovery-of-hydrothermal-vents/.
⇢Simple tree of life: Tibi Puiu. “Surprising Study Reveals Life on Earth Began Just 400 Million Years after Formation.” ZME Science, 15 July 2024, www.zmescience.com/science/news-science/universal-common-ancestor-timeline/. Accessed 16 Jan. 2026.
⇢Complex tree of life: McMillan, Fiona. “One Big Family: This Beautiful Interactive Diagram Shows How Every Organism Is Related.” Forbes, 30 Dec. 2017, www.forbes.com/sites/fionamcmillan/2017/12/30/one-big-family-this-beautiful-interactive-diagram-shows-how-every-organism-is-related/. Image created by Evogeneao.
⇢Grid of sponge images: Olinger, Lauren K., et al. “Growth Estimates of Caribbean Reef Sponges on a Shipwreck Using 3D Photogrammetry.” Scientific Reports, vol. 9, no. 1, Dec. 2019, https://doi.org/10.1038/s41598-019-54681-2. Accessed 20 Nov. 2020.
⇢Cnidaria examples: “Cnidaria.” Marine Education Society of Australasia, www.mesa.edu.au/cnidaria/.
⇢Monophyletic simple image definition adapted from: Pightling, Arthur W., et al. “Interpreting Whole-Genome Sequence Analyses of Foodborne Bacteria for Regulatory Applications and Outbreak Investigations.” Frontiers in Microbiology, vol. 9, 10 July 2018, https://doi.org/10.3389/fmicb.2018.01482. Accessed 9 Nov. 2021.
⇢First vertebrate phylogenetic tree adapted from: Pascual-Anaya, Juan, et al. “Editorial: New Approaches in Chordate and Vertebrate Evolution and Development.” Frontiers in Cell and Developmental Biology, vol. 10, 12 May 2022, https://doi.org/10.3389/fcell.2022.917101.
⇢Tiktaalik roseae Image: Wood, Matt. “How Fish Fins Evolved Just before the Transition to Land.” University of Chicago News, 2 Jan. 2020, news.uchicago.edu/story/how-fish-fins-evolved-just-transition-land. Illustration by Flick Ford.
⇢Second vertebrate phylogenetic tree adapted from: Meyer, Axel, and Rafael Zardoya. “Recent Advances in the (Molecular) Phylogeny of Vertebrates.” Annual Review of Ecology, Evolution, and Systematics, vol. 34, no. 1, Nov. 2003, pp. 311–338, kops.uni-konstanz.de/handle/123456789/8163, https://doi.org/10.1146/annurev.ecolsys.34.011802.132351.
⇢Three lineages of Mammals: Krubitzer, L, and K Campi. “Neocortical Organization in Monotremes.” Encyclopedia of Neuroscience, edited by Larry Squire, Academic Press, 2009, pp. 51–59, www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/monotreme. Accessed 15 Jan. 2026.
⇢ Human embryo: “Learning about Evolutionary History - Understanding Evolution.” Understanding Evolution, 24 Aug. 2021, evolution.berkeley.edu/evo-devo/learning-about-evolutionary-history/.