You Are the Only Animal on Earth That Does This

You are the only animal on Earth that sheds emotional tears. Not chimpanzees, not elephants, not dogs — even though they feel grief. In this video, we go inside the biology and evolutionary history of human crying to find out why. In 1982, biochemist William Frey discovered that emotional tears contain stress hormones not found in reflex tears. In 2011, researchers at the Weizmann Institute found that tears carry a chemical signal that measurably lowers testosterone and aggression in people who encounter them. Crying isn't an overflow valve. It's a broadcast system — and it may be one of the oldest social tools our species ever developed. We also look at what happens neurologically when people lose the ability to cry — and what that reveals about the connection between emotional signaling and the ability to read other people. 00:00 — You're crying at a fictional dog. Why? 01:10 — Three types of tears — and what makes emotional tears different 02:45 — The Weizmann Institute experiment: tears as a chemosignal 05:00 — How crying develops across a human lifespan 06:30 — What happens when people can't cry: Damasio's neurological findings 08:10 — What your tears are actually doing *SOURCES:* Frey, W.H. et al. (1981) — "Crying behavior in the human adult." Integrative Psychiatry. DOI: 10.1016/0020-7489(83)90049-6 Gelstein, S. et al. (2011) — "Human tears contain a chemosignal." Science, 331(6014), 226–230. DOI: 10.1126/science.1198331 Hasson, O. (2009) — "Emotional tears as biological signals." Evolutionary Psychology, 7(3), 363–370. DOI: 10.1177/147470490900700302 Trimble, M. (2012) — "Why Humans Cry: The Science of Tears." Oxford University Press. Damasio, A. (1994) — "Descartes' Error: Emotion, Reason, and the Human Brain." Putnam. why do humans cry, emotional tears, human evolution, are humans the only animals that cry, crying biology, tears science, evolutionary psychology, neuroscience of emotions, ancient humans, anthropology explained, science documentary, William Frey tears, Weizmann Institute tears study, Antonio Damasio, animated documentary, stick figure animation, educational, mind blowing facts, human behavior, psychology explained