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 male and female. Whether you agree with Fuentes or not, it’s an argument worth taking seriously.

We had a great conversation, 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.

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 |

Where do we come from? How did we get here? What kind of creature are we?

The science of human origins has made great progress in answering these timeless questions. From carbon isotopes to ancient DNA extraction, we now have unprecedented tools to explore our past. But with all this detail, it’s easy to miss the forest from the trees.

To fill this gap, On Humans has partnered with CARTA — a UC San Diego-based research unit on human origins. Together, we have designed a five-episode journey to dig deep into the new science of the origins of humankind.

Together, these episodes explore the emerging science of how we became the puzzling and wonderful creatures we are today.

The series begins tomorrow. Subscribe now free episode and written summaries at:

Onhumans.Substack.com/Origins

SERIES OVERVIEW

#1 The Big Picture

The series begins with a sweeping take on the history of life on Earth, from the origin of life to the rise of humans.

• Key questions: What is life? Who were our ancestors during the dinosaurs? What led to the rise of primates? And what kind of a primate are we?

• Your guide: Tim Coulson is the Head of the Department of Biology at the University of Oxford. He recently released a breathtaking overview of the history of life and the universe titled A Universal History of Us.

• When: March 25th

#2 An Unusual Ape
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 behind the Stone Age.

• When: April 2nd

  
  

#3 What Is a Human?

The stage has been set. The third episode tackles human evolution head-on, focusing on the new scientific discoveries about the genus Homo.

• Key questions: What is a human? Why did we evolve? And how do modern humans differ from Neanderthals or other extinct humans?

• Your 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

  
  

#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: In 2010, Johannes Krause became the first person to discover a new species of humans by DNA alone. Co-author of Hubris, and A Short History of Humanity, he is the Director of the Max Planck Institute of Evolutionary Anthropology.

• When: March 16th & 23rd

SUBSCRIBE

⁠Onhumans.Substack.com/Origins⁠

India’s history isn’t just the story of one nation—it’s the story of one-sixth of humanity. It’s also a lens for understanding how colonialism, democracy, and globalization shaped the modern world.

This mini-series offers a human-centred perspective on that remarkable story, focusing on how politics and trade impacted the lives of ordinary Indians.

 In Part 1, we explored the decline of the Mughals and the long stretch of British rule. In Part 2, we turn to India's independent journey as the world’s largest democracy.

 To guide us through this complex history, I’m joined again by Bishnupriya Gupta, a professor of economics and the author of the excellent Economic History of India.

In this episode, we discuss:

The legacy of British colonialism in independent India / Why India fell behind the economic miracle of East Asian countries like China / The successes and challenges of India’s democracy in shaping its economic future / What happened to inequality in India during independence?

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

MENTIONS

Following the success of last year’s ⁠What About China ⁠-trilogy, I’m delighted to introduce a two-part series on the economic history of India. This series examines the origins of modern India by focusing on politics, poverty, and the experience of ordinary Indians from 1600 till today.

The first episode covers the decline of the Mughals and the hugely controversial rule of the British East India Company and, later, the British Crown.

One thing is clear: Most Indians lived in poverty when the British left. So, how much of Indian poverty was due to British policies? How much was shaped by deeper trends? And what should we make of those infamous railways?

To tackle these questions, I’m joined by Bishnupriya Gupta, a professor of economics at the University of Warwick and one of the world’s leading historians of the Indian economy. Her new book, ⁠An Economic History of India⁠, provides a uniquely objective and data-driven exploration of India’s history, focusing on the well-being of ordinary people.

In this episode, we discuss:

Indian vs English living standards in 1600 / The impact of British colonialism on India’s economy / The Great Famines of Bengal / What both imperial apologists and Indian nationalists get wrong about the British rule.

In the end, Gupta also explains why Mahatma Gandhi's education might be a clue as to why India lagged behind East Asia in the 20th Century.

Enjoy — and stay tuned for Part II on the era of Independence!

MENTIONS

Why are history books so full of men? Why have so many societies treated women as property?

In short, why is patriarchy so pervasive?

A casual thinker might find an easy answer from biology. Men tend to be bigger and stronger. Hence, they get to run the show. “Just look at chimpanzees!”

But this explanation has obvious problems. Indeed, female chimpanzees don’t have much power in their groups. But female bonobos do. And looking at humans, not all human societies are patriarchal — not nearly to the same extent.

We don’t need to look at modern Scandinavia to get inspiration for women’s empowerment. Quite the contrary, equality between the sexes might have been the norm throughout most of the human story. This might sound surprising given the rates of patriarchy across time and space. However, it is supported by a simple finding: gender equality is relatively common in existing hunter-gatherers. This stands in stark contrast to their agricultural neighbours.

This old finding became part of the scholarly conversation again in late 2024 when a new paper reported high levels of equality between husbands and wives amongst married hunter-gatherers. The levels of equality surprised the scholars themselves. But all this raises an interesting question: why is this? Why would hunting and gathering incline societies towards equality? Or vice versa, why would agriculture nudge societies towards male power? And what should we make of the many outliers from this pattern, like the matriarchal farmers of northeastern India?

To discuss these topics, I invited the lead author of the recent paper to the show.

Angarika Deb is a cognitive anthropologist, soon to earn her PhD from the Central European University. Despite her young career, she has produced tons of interesting articles on gender inequality around the world. A wide-ranging conversation was guaranteed.

LINKS

For links to academic articles and a summary of the conversation, head here (uploaded with a short delay after the episode).

Read more at ⁠⁠OnHumans.Substack.com⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠.

You can also find On Humans on ⁠⁠YouTube⁠⁠ and ⁠⁠BlueSky⁠!

Feeling generous? Join the wonderful group of my patrons at ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠Patreon.com/OnHumans⁠⁠⁠⁠⁠⁠⁠, ⁠⁠⁠⁠⁠or get in touch for other ways to support!

Email: ⁠⁠makela dot ilari at outlook dot com⁠⁠⁠

MENTIONS

Technical terms

Patrilocality | Matrilocality | Virilocatily | Y-chromosome bottleneck

Ethnic groups

Agta | BaYaka | !Kung | Mongols | Garo and Khasi | Inuit

Keywords

Patriarchy | Agriculture | Neolithic | Social evolution | Social complexity | Hunter-gatherers | Sexual division of labor | Human evolution | Anthropology | Archaeology | Evolutionary psychology | Sociology | Social science | Human science