On Humans is back from the break!

To mark the summer heat, here is a two-part series on how climate has shaped the human story. In next week's episodes, we will explore the role of water and weather in the origins of European colonialism. But today, we start by crawling deeper into the past: to the origins of humanity itself.

In this episode, Yale professor Jessica Thompson helps us navigate one of the most influential ideas in human evolution: that an ancient climate change pushed our ancestors out of the jungle, onto the savanna, and eventually toward big brains, meat-eating, and tool use.

This is a captivating story. It has been mentioned many times on the show. But do the details hold up?

What follows is a sweeping account of human origins, which nuances — but does not reject — the grand arc explored in The Origins of Humankind series. This is a story about a climate that has never remained steady. It serves as a poignant reminder of the weather's power to shape human destiny. But it’s also a story about human resilience and our capacity, from the very beginning, to defy the iron laws of ecology. Enjoy!

Thoughts about the episode? Share them at OnHumans.Substack.com⁠. You'll also find a bunch of links to dig deeper.

SUPPORT THE SHOW

You can pledge your support at Patreon.com/OnHumans⁠

MENTIONED SCHOLARS

Richard Wrangham (guest in summer 2023)

Sarah Blaffer Hrdy (guest in Spring 2024)

KEYWORDS

Human evolution | Human origins | Paleoanthropology | Human biology | Climate change | Miocene | Pleistocene | Brain evolution | Brain energetics | Deep history | Anthropology | Archaeology | Austrolopithecins | Genus homo | Bipedalism | Evolution of apes | Missing link | Tsetse flies |

Binary thinking is out of fashion. But what about biological sex?

Whatever we might say about diversity and fluidity, the ideas of “male” and “female” seem essential in biology. I’ve taught the subject. I’ve drawn bees and flowers, with arrows from anthers to ovaries. I’ve used the terms “dad cell” and “mother cell” while doing so. I don’t know how I could have done it any differently.

And maybe that’s just fine. Human sex cells are binary: sperm and egg. But here’s the twist: humans aren’t sex cells. Humans are animals. And animals aren’t so easily grouped. XY chromosomes don’t always produce a penis. And when we turn to hormones, brains, and behaviours, the picture gets even messier.

Or so argues Princeton Professor Agustín Fuentes, a leading expert on human biology. His new book, Sex Is a Spectrum, came out this week. It makes the case that biology no longer supports a sharp separation between the male and the female.

I approached this topic with a mix of curiosity and scepticism. And while I'm still unsure of what to make of the conclusion, I do not regret the conversation one bit. We had a great chat, ranging from hermaphroditic worms to sex-changing fish, and from gender stereotypes to intersex humans. At times, I pushed back. But I learned a lot throughout the conversation. I hope you do, too.

Thoughts about Fuentes’s argument? Or my takes? Share them at onhumans.substack.com. You'll also find more links to dig deeper.

Support the show: patreon.com/onhumans

MENTIONS

Agustín Fuentes: Sex is a Spectrum; Creative Spark; Race, Monogamy, and Other Lies They Told You

Yuval Noah Harari: Sapiens, A Brief History of Humankind

Jared Diamond: Guns, Germs, and Steel

Steven Pinker: How the Mind Works

Sara Blaffer Hrdy: Father Time (see episode in April 2023)

KEYWORDS

Biological sex | gametes | chromosomes | intersex | hermaphrodite | sex determination | sexual dimorphism | sex-changing fish | clownfish biology | evolutionary biology | human evolution | Agustín Fuentes | anthropology of sex | reproductive biology | nonbinary biology | developmental biology | sex differences | male and female | sex in animals | sex in humans | genetics of sex | human biology | science of sex | sex vs gender | c. elegans sex | 5-alpha-reductase type 2 deficiency (5α-R2D) | PCOS (Polycystic Ovary Syndrome) |

And so it ends! In the final episode of The Origins of Humankind, we explore the aftermath of the story so far—the story of how one peculiar species, Homo sapiens, evolved, spread, and outlived its relatives.

Guiding us through this final chapter is Johannes Krause once again. Together, we uncover the emerging picture of the global spread of farming, pastoralism, and other key ingredients of modernity. Along the way, we explore some of the central questions of history—from the origins of inequality to the surprisingly pivotal role played by the peoples of the Eurasian steppe. (Yes, Mongols will make an appearance! But the story of the steppe goes much deeper...)

As always, we end with my guest’s reflections on humanity.

Enjoy!

LINKS

More material: ⁠⁠⁠⁠OnHumans.Substack.com/Origins⁠⁠⁠⁠

Support the show: ⁠⁠⁠⁠Patreon.com/OnHumans⁠⁠⁠⁠

Free lectures on human origins: ⁠⁠⁠⁠CARTA⁠⁠⁠⁠

Krause's books: ⁠⁠A Short History of Humanity⁠⁠; ⁠⁠Hubris: The Rise and Fall of Humanity⁠⁠

ABOUT THE SERIES

The ⁠⁠Origins of Humankind ⁠⁠is produced by On Humans and UC San Diego's Centre for Academic Research and Training in Anthropogeny (⁠⁠CARTA⁠⁠). Other guests include Chris Stringer, Dean Falk, and Tim Coulson.

KEYWORDS

Anthropology | Biology | Human evolution | Human origins | Homo sapiens | Agriculture | Ancient DNA | Climate changes | Pleistocene | Holocene | Archaeology | Neolithic | Yamnaya | Bell Beakers | Proto Indo-Europeans | Ötzi Ice Man | Gunpowder Empires | Bantu-expansion | Austranesian expansion | Sami poeple | Y-chromosome bottleneck |

The time has come! This is where our story truly begins.

In Episode 4 of The Origins of Humankind, we finally turn the spotlight on Homo sapiens. Guiding us through this journey is Johannes Krause, director of the Max Planck Institute for Evolutionary Anthropology and a pioneer of one of the greatest scientific revolutions of our time: the science of ancient DNA.This ability to extract DNA from fossils has transformed our understanding of the human past—giving us tools to tell a genuinely global history of our species.

In this episode, we use the magic of ancient DNA to explore the world our species was born into: a weird, wild Ice Age planet teeming with other human species, from Flores Hobbits to Neanderthal Giants. We touch on big questions, such as:

• How did Homo sapiens spread around the world?

• Why were our ancestors so successful?
• How did climate changes shape their story?
• What was palaeolithic life like?
• What happened to the Neanderthals? (Be prepared for a plot twist!)

We end at the dawn of the Holocene—the warm, wet period that would give rise to farming, cities, and everything we call “history.” That’s the story we’ll tackle in the final episode of The Origins of Humankind. Stay tuned. And enjoy this episode!

LINKS

More material: ⁠⁠⁠OnHumans.Substack.com/Origins⁠⁠⁠

Support the show: ⁠⁠⁠Patreon.com/OnHumans⁠⁠⁠

Free lectures on human origins: ⁠⁠⁠CARTA⁠⁠⁠

Krause's books: ⁠A Short History of Humanity⁠; ⁠Hubris: The Rise and Fall of Humanity⁠

ABOUT THE SERIES

The ⁠Origins of Humankind ⁠is produced by On Humans and UC San Diego's Centre for Academic Research and Training in Anthropogeny (⁠CARTA⁠). Other guests include Chris Stringer, Dean Falk, and Tim Coulson.

KEYWORDS

Anthropology | Biology | Human evolution | Human origins | Homo Erectus | Australopithecines | Brain evolution | Paleoneurology | Hominins | DNA | Homo sapiens | Climate changes | Pleistocene | Cognitive evolution | Cognitive archaeology | Stone tools | Palaeolithic | Neanderthals | Homo floresiensis | Denisovans | Homo longi | Sima de los Huesos | Gravettian | Cannibalism | Aurignacian | Svante Pääbo |

Things are about to get personal... In episode 3 of The Origins of Humankind, we zoom into the birth and spread of humanity itself.

Our guide is the iconic Chris Stringer, one of the most influential paleoanthropologists alive. Together, we trace the origins of our genus and the emergence of Homo sapiens as the last surviving human species. While doing this, we meet many oddities, such as rhino hunting along the River Thames, but we also explore some of the biggest questions in human evolution:

• What is a human?
• Why did we evolve big brains?
• Why do we have such long childhoods?
• Is Homo sapiens truly unique — or just one human among many?

As always, we finish with my guest's reflections on humanity.

MORE LINKS

More material: ⁠⁠OnHumans.Substack.com/Origins⁠⁠

Support the show: ⁠⁠Patreon.com/OnHumans⁠⁠

Free lectures on human origins: ⁠⁠CARTA⁠⁠

Stringer's books: Lone Survivors; Our Human Story

WHAT'S NEXT

#4-5: The Story of Sapiens, in Two Parts

The series finishes with two episodes on the story of Homo sapiens, using the magic of ancient DNA to tell a genuinely global history of our species.

• Key question: How did migrations shape the human story? Why are we the only humans left? And how did humans spread worldwide, first as hunters and gatherers, then as farmers and shepherds?

• Your guide: Johannes Krause was the first scholar to discover a new species of humans by DNA alone. Co-author of Hubris, and A Short History of Humanity, he is now the Director of the Max Planck Institute of Evolutionary Anthropology.

• When: March 16th & 23rd, 2025

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  KEYWORDS

  Anthropology | Biology | Human evolution | Human origins | Homo Erectus | Australopithecines | Brain evolution | Paleoneurology | Hominins | Cave art | Homo sapiens | Climate changes | Pleistocene | Cognitive evolution | Cognitive archaeology | Stone tools | Palaeolithic | Neanderthals | Alloparenting | Expensive tissue -hypothesis | Radiator theory | Brain growth | Palaeoanthropology |

  
  

  
  

  
  

The story continues! In part 2 of the Origins of Humankind, we trace the first steps of our ancestors after they left the chimpanzee lineage.

To get humanity going, our ancestors had to wander through millions of years of what anthropologist Dean Falk has called the Botanic Age. It's a time shrouded in mist, yet it may hold the key to some of humanity’s most defining traits — from language and music to our clumsy toes and our large brains.

On this walk through the mysteries of the Botanic Age, our guide is Dean Falk herself. She is a Distinguished Professor of Anthropology and the world's leading expert on human brain evolution. Together, we try to make sense of topics such as:

• The common ancestor between humans and chimpanzees
• Against “Man the Toolmaker”: Tool use in other apes
• The walking ape: how bipedalism shaped our ancestors
• Origins of language
• Origins of music
• Size matters, but… The early evolution of the human brain

As always, we finish with the guest’s reflections on humanity.

MORE LINKS

• More stuff (including written highlights): ⁠OnHumans.Substack.com/Origins⁠
• Support the show: ⁠Patreon.com/OnHumans⁠
• Free lectures on human origins: ⁠CARTA⁠
• Dean Falk’s book: ⁠The Botanic Age

WHAT'S NEXT

Origins of Humankind #3: What Is a Human?

The stage has been set. It is time for humanity to enter. But what is a human? What makes a skeleton fall into the Genus "Homo"? And why did this puzzling genus evolve?

Key questions: Why did humans evolve? And how do modern humans differ from Neanderthals or other extinct humans?

Our guide: Chris Stringer is an iconic figure in the field, best known for his groundbreaking work towards the widely accepted Out of Africa -theory of human evolution. His career at London’s Natural History Museum stretches across five decades.

When: April 9th, 2025

KEYWORDS

Anthropology | Primatology | Human evolution | Human origins | Homo Erectus | Australopithecine | Australopithecus africanus | Brain evolution | Paleoneurology | Apes | Great apes | Chimpanzees | Bonobos | Gorillas | LSA | Cognitive evolution | Cognitive archaeology | Baby slings | Motherse | Parentese | Baby talk | Putting the baby down -hypothesis | Radiator theory | Biology | Honinins | Hominoids | Palaeolithic Palaeoanthropology |

Welcome to the first episode of the Origins of Humankind!

In this sweeping pilot, we cover the entire planetary backstory of human existence – from the origins of life to the climate change that kickstarted human evolution. Our expert guide on this journey is Tim Coulson, the Head of Biology at the University of Oxford and the author of A Universal History of Us.

The episode explores questions such as:

• What is "life”? How did it begin?
• The surprising role of meteors (even before dinosaurs)
• Why animals?
• “Ediacaran Garden” and the dawn of predators
• Blood, bones, and the dawn of “terrestrial fish” (yup, that’s us!)
• Our ancestors amongst the dinosaurs
• Fruits and snakes in primate evolution
• The climate change that made humanity
• The rise and spread of humans

As always, we finish with the guest’s reflections on humanity.

MORE LINKS

• More stuff: OnHumans.Substack.com/Origins

• Support the show: Patreon.com/OnHumans

• Free lectures on human origins: CARTA

• Tim Coulson’s book: A Universal History of Us

NEXT EPISODE

#2 An Unusual Ape (Tuesday 2nd of April)

In episode two, we follow the first steps on the human line, exploring how abandoning life in the trees paved the way for many of our human oddities.

Key questions: Why was upright posture so important? What did it do to parents and children? When did the brains of our ancestors start to show human oddities?

Your guide: Dean Falk, a leading expert on brain evolution at the University of Florida. She recently published a book titled A Botanic Age, looking at human evolution before the Stone Age.

Stay tuned. And subscribe to On Humans.

KEYWORDS

Evolution | Human evolution | Human origins | Origin of life | Emergence of life | Abiogenesis | Natural history | History of life | Meteors | Organic chemistry | Vertebrate evolution | Tetrapods | Dinosaurs | Pleistocene | Predators | Early humans | Austrolopithecins | Lucy | Homo erectus | Homo ergaster | Homo sapiens | Megafauna extinction | Humanity | Carl Sagan | Ediacaran Garden | Cambrian Explosion | Mesozoic | Jurassic | Triassic | Cretaceous | The Great Oxigenation Event | Sauropsids | Synapsids |