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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Humans are the most intelligent beings this planet has ever produced. But how is it that we can travel into space, cure diseases and decode the fundamentals of life, and at the same time find ourselves faced with an existential crisis that threatens to overwhelm us? What lies behind this uncharacteristic failure to master the most important challenge of our existence?
In this compelling book, the leading archaeogeneticist Johannes Krause and the journalist Thomas Trappe investigate what DNA can tell us about how we got where we are and what our future might be. They show how the first humans were defeated again and again and suffered fatal setbacks, and how Homo sapiens succeeded in conquering continents, overcoming natural borders, and bringing other species under its control. But the genetic blueprint that enabled us to get to the place where we are today had one flaw: it didn’t factor in planetary boundaries. Now that we are approaching those boundaries for the first time after millions of years of evolution, an urgent question arises: can we learn to live within the available planetary limits, or are we doomed by our DNA to continue to expand, consume, and absorb the resources around us to the point of exhaustion, consigning ourselves and other species to extinction? Has our seemingly unstoppable rise met its ultimate end?
While the looming climate crisis does not augur well for humanity’s capacity to adapt to the new situation in which it finds itself, we are not at the mercy of our DNA – or at least we don’t have to be. But can we harness the lessons of the past to survive the present?
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Table of Contents
Cover
Title Page
Copyright Page
Prologue
1. Lab-Grown Humans
Bring out the Neandertal
The feasible and the impossible
The Frankenstein genome
Humans are predictable
Because we can
Notes
2. Famine
Dining with one’s own kind
Savaged by hyenas
Older than she looks
The desert on chromosome 1
No philosopher’s stone
The shell seekers
Homo sapiens
acquires self-consciousness
Notes
3. Planet of the Apes
Territorial claims in the Middle East
The (very) ancient Greeks
Short, stocky, superior
Udo the upright ape
When the Mediterranean disappeared
The ultimate melting pot
Notes
4. Apocalypse
Off to sunny Spain!
The blackout of 70,000 years ago
An explosive mixture
North Africa, valley of death
Personnel shortages hamper evolution
Burning bridges
Ghost DNA
From dream to illusion
Notes
5. A Clean Sweep
Limited scope for snap dates
Chain-smoking Neandertals?
Sensitive Americans
Champion childbearers
Culture trumps biology
Outclassed
The discovery of America
To the ends of the earth
Last stop Tasmania
Notes
6. Enchanted Forests
A fearsome place
Endless rain
Tough little hobbits
Smashed skulls
An isle of dwarfs and giants
Eurasia a mere sideshow
Deadly Australia
Hunting with wolves
Tameness is also a mutation
An acquired mistrust
Notes
7. Elites
The first bakers
Palefaces
The dominance of the newcomers
The Ancient Egyptians: A closed shop
Learner livestock farmers
Eternal China
Trade-happy Americans
The foragers’ long goodbye
Notes
8. Beyond the Horizon
Cattle trucks on the high seas
Island hopping
Man swapping
A fatal weakness for status symbols
Land of milk and honey
Fifteen canoes head for New Zealand
Sweet potatoes with chicken
Adrift in the Caribbean
The American–Russian axis
Foreign ships loom
Notes
9. The Steppe Highway
Outsider odds
The beautiful mummy and the cheese
On horseback and underground
Invasions
Nothing to inherit, everything to gain
Indian elites
A fateful mutation
If in the East you don’t succeed…
Victory on the Bosporus
Cannons and pathogens
10.
Homo hubris
An armoury of pathogens
The Neandertal: An evolutionary blunder?
The pandemic force of humanity
The vain search for the human self
An intriguing thought
Alone in space
A near-perfect blueprint
Notes
Sources
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
Annex sources
List of Figures
Acknowledgements
Index
End User License Agreement
List of Illustrations
Chapter 1
Figure 1 The human family tree.
Figure 2 A cell culture ‘bred’ from brain cells © Daniel Wolny
Figure 3 Neandertal © Tom Björklund
Figure 4 The great journey north from Africa © Landesamt für Denkmalpflege ...
Chapter 2
Figure 5 Map of Europe during the last Ice Age.
Figure 6 An artist’s impression of a Neandertal woman © Tom Björklun...
Figure 7 Side view of the virtually intact skull of Zlatý kůň ©...
Figure 8 What European hunter-gatherers may have looked like © Tom Björklun...
Figure 9 ‘Lion Man’ © Tom Björklund
Chapter 3
Figure 10 Planet Ape.
Figure 11 Udo the great ape © Velizar Simeonovski
Figure 12
Ardipithecus
,
Australopithecus
,
Homo habilis
, and
Homo erectus
...
Chapter 4
Figure 13 Apocalypse.
Figure 14 The oldest evidence of cosmetics. Image provided courtesy of Christopher Henshil...
Figure 15 Ancient rock paintings by the San people © picture alliance / blickwinkel...
Chapter 5
Figure 16 A clean sweep.
Figure 17 The northern mammoth steppe © Tom Björklund
Figure 18 The Tibetan Baishiya Karst Cave © Dongju Zhang / CC BY-SA 4.0
Chapter 6
Figure 19 Enchanted forests.
Figure 20
Homo erectus
in Sundaland © Peter Schouten
Figure 21 Luzon Man © Michael Weis / Alamy Stock Foto
Figure 22
Homo floresiensis
© Peter Schouten
Figure 23 The prehistoric dog © Landesamt für Denkmalpflege und Archä...
Chapter 7
Figure 24 Centres of domestication.
Figure 25 The hunter-gatherers of Europe © Tom Björklund
Figure 26 The transition to an agrarian society © Tom Björklund
Figure 27 The Nile Delta © Planet Observer / UIG / Universal Images Group North Ame...
Figure 28 Comparison between teosinte, a maize–teosinte hybrid, and modern maize ©...
Chapter 8
Figure 29 Beyond the horizon.
Figure 30 Jōmon pottery © Daderot / Wikimedia Commons / CC-BY-SA-3.0
Figure 31 Reconstruction of a boat used by the explorers of the Austronesian expansion in ...
Figure 32 The first farmers in the Caribbean © Tom Björklund
Figure 33 Advancing into the north of Alaska and Canada. © Tom Björklund.
Chapter 9
Figure 34 The Steppe Highway.
Figure 35 Reconstruction of a settlement belonging to the Sintashta culture © Rü...
Figure 36 The beginnings of a patriarchal society © Tom Björklund
Figure 37 Treasure of Nagyszentmiklós © Kunsthistorisches Museum Wien, KHM-M...
Figure 38 A cart of plague victims at Elliant drawn by a woman in rags. Lithograph by Jean...
Chapter 10
Figure 39 Galactic distances.
Figure 40 Hendrik Avercamp,
Winterlandschaft
, c. 1630 © National Galleries o...
Figure 41 The atom bomb © Charles Levy, US National Archives and Records Administra...
Figure 42 Capturing the Milky Way © ESO / B. Tafreshi (twanight.org)
Guide
Cover
Table of Contents
Begin Reading
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HUBRIS
The Rise, Fall, and Future of Humanity
Johannes Krause and Thomas Trappe
Translated by Sharon Howe
polity
Copyright Page
Originally published in German as Hybris. Die Reise der Menschheit: Zwischen Aufbruch and Scheitern © by Ullstein Buchverlage GmbH, Berlin. Published in 2021 by Propyläen Verlag
This English edition © Polity Press, 2025
Polity Press
65 Bridge Street
Cambridge CB2 1UR, UK
Polity Press
111 River Street
Hoboken, NJ 07030, USA
All rights reserved. Except for the quotation of short passages for the purpose of criticism and review, no part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publisher.
ISBN-13: 978-1-5095-6261-9 – hardback
A catalogue record for this book is available from the British Library.
Library of Congress Control Number: 2024938480
by Fakenham Prepress Solutions, Fakenham, Norfolk NR21 8NL
The publisher has used its best endeavours to ensure that the URLs for external websites referred to in this book are correct and active at the time of going to press. However, the publisher has no responsibility for the websites and can make no guarantee that a site will remain live or that the content is or will remain appropriate.
Every effort has been made to trace all copyright holders, but if any have been overlooked the publisher will be pleased to include any necessary credits in any subsequent reprint or edition.
For further information on Polity, visit our website: politybooks.com
Prologue
This is how second decades begin. We know how the twenties turned out last century; what they will bring this time round remains to be seen. In the first three decades of the twentieth century, humanity was wracked by wars, ideologies, revolutions, economic crises, and, not least, a pandemic. A hundred years on, the prospects aren’t much better: at the beginning of the twenty-first century, 9/11 abruptly destroyed the dream harboured in some quarters that we might see an end to geopolitical conflicts, and this was followed by a series of crises, each apparently more dramatic than the last: financial and global economic crisis, years of terror of the Islamic State, global refugee flows and, ultimately, the plight of democracies haunted by self-doubt and by the threat of disintegration. In the late 2010s fear, if not panic, in the face of ‘climate collapse’ galvanized a whole generation. But soon afterwards the feared annihilation of the very basis of our existence faded into the background when a tiny virus, with no will of its own, let alone a higher purpose, succeeded in paralysing the planet for several years and in bringing to a standstill all but the most basic social activities. What a time to be alive – and what a time to fear for your own life and your life support system! Humanity, it seems, has a genuine hangover – only this one can’t be cured by a couple of aspirins.
Climate change, the dawn of the pandemic age, overpopulation, the impending collapse of whole ecosystems, the dangers of global military conflicts: the array of problems facing humanity since the beginning of this new decade is practically endless. But who else can solve them, if not us – this incredible species that can fly helicopters on Mars and even produce oxygen from its atmosphere? A species that manages to feed growing numbers of people, guaranteeing them access to education, clean drinking water, and medical care?
We are, without doubt, the most intelligent being this planet has ever produced. We have come to understand what holds the innermost world together, how it began, and how, together with our sun, it will probably disappear in a giant fireball in a few billion years’ time. We think of ourselves as all-knowing and all-powerful, yet we are effectively powerless to escape the self-destructive urge that seems to be hopelessly entrenched in our DNA: a mechanism that positively compels us to expand, consume, and absorb the resources around us to the point of exhaustion.
This genetic blueprint is what enabled us to get where we are today. There’s just one problem: that brilliant plan has a small flaw. It doesn’t factor in planetary boundaries. Now that we are undeniably approaching those boundaries for the first time after millions of years of evolution, an urgent question arises to which we have yet to find an answer: will our DNA also enable us to live within the available limits, with no further possibility of expansion? Or are we doomed by our genes to keep moving forward until our species runs out of steam?
This book is not one of those that deal with the unstoppable ascent of humankind. But neither is it intended to be one about our inevitable demise. It is the story of an exceptional animal that, thanks to a combination of innumerable coincidences, rose at breakneck speed to the top of the evolutionary tree, eventually conquering every last corner of the planet and harnessing it to its own needs. This unique career began a relatively short time ago, after a whole series of failed attempts. Since the human line split off from the common ancestor we share with chimpanzees and bonobos, countless evolutionary paths have led to a dead end. And only one of them has led to us.
In this book we will look at the first humans and their persistent attempts to colonize the world from Africa. Time and again they were defeated, whether by the climate, by devastating natural disasters, or by other cavemen who held sway in Europe and Asia. We will chart the rapid spread of the modern human – Homo sapiens – to America and Australia and the parallel decline not just of other human-like creatures, but of nearly all megafauna of the time. We will see how humans tamed the wolf and how they became their own worst enemy. We will follow our rapacious ancestors all the way to the remotest spot on earth, Easter Island, where their fate foreshadowed what threatens us all today: the destruction of the resources we depend on. Finally, we will turn again to Eurasia, where a long battle determined who the next world rulers would be; and their worst enemies, disease-inducing pathogens, would later prove to be their deadliest fellow travellers and their mightiest weapons, influencing the course of history time and again. This went on until the twenty-first century, when humans eventually came to believe that they had conquered this scourge too – only to be proved wrong once more.
Humans can do anything and should take nothing for granted: such is the message of this book. It was written by the archaeogeneticist Johannes Krause, director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, and the journalist Thomas Trappe. Krause was one of the key scientists involved in decoding the Neandertal genome in 2010 at the laboratory of Nobel Laureate Svante Pääbo. Shortly afterwards he identified a hitherto unknown species of early human from a 70,000-year-old finger bone found in Siberia: the so-called Denisovan, the Asian cousin of the Neandertal. Krause went on to become one of the founders of the discipline known as archaeogenetics, which is constantly uncovering new details of the history of humankind, as well as groundbreaking new insights into it.* And the more pieces of the puzzle are filled in, the clearer it becomes that our evolution, while it may look like an unstoppable rise, has also been beset by constant setbacks.
It is a declared aim of this book’s authors to add a few darker touches to the rosy picture many people paint of the past of our own species and, by doing so, to bring to the fore the question of how to turn the twenty-first century into a new chapter of success, not of failure. We don’t have the solution either. But we can at least take a closer look at the problem: a problem that is partly rooted in our DNA, and has, not without reason, become part of it. But we are not completely at the mercy of that DNA – or at least we don’t have to be. And in this we differ from all other species.
A book about human evolution can narrate and interpret this story from a new angle, but under no circumstances can it claim exclusivity on that score. The story we unfold here relies heavily on the work of international scholars: these are listed in ‘Sources’ (the bibliography chapter), but as a rule not in the text. We have adopted this mode of presentation simply in the interest of readability; it is not intended to diminish these scholars’ contribution to the body of knowledge in any way. Likewise, it goes without saying that the research conducted by the institutes co-directed by Johannes Krause – the Max Planck Institute (MPI) for Human History in Jena up to 2020 and, since then, the MPI for Evolutionary Anthropology in Leipzig (MPI EVA) – benefitted from key contributions from a large number of colleagues without whom this book would not have been possible. The same goes for all those scholars who have provided fundamental insights into human evolution over the past decades – insights that have stood the test of time and can only be reinforced by occasional new genetic data. We stand on their shoulders, too.
We will begin our ride through human history with the oldest decoded genome of a modern human; its DNA was published by a team at the MPI EVA in spring 2021. But before we accompany our ancestors on the incredible journey that began in Africa and led meteorically to the present day, let us peep over the shoulders of the scientists to whom we owe our new knowledge in the first place. What brought us to this summit, from which we now survey the world, not knowing whether we will eventually fall from it? Why were we, and not other great apes, the ones to establish a civilization? These are questions that researchers in the field of archaeogenetics are attempting to answer using a unique approach: not by looking into human brains, but by building miniature new ones. These brains are based on those of an old acquaintance who, a few thousand years ago, came a thankless second in the contest for the crown of creation: the Neandertal.
Notes
*
This is the only point in the book where the authors are mentioned by name. From here on, as a general rule, wherever Johannes Krause’s research work is discussed, his involvement is not explicitly mentioned.
1Lab-Grown Humans
A brief excursion into the weird and wonderful world of archaeogenetics: in order to better understand our own brain, we are reconstructing a Neandertal’s.a And, while we’re at it, why not a whole Neandertal, or a Homo erectus?
Bring out the Neandertal
One of the places where we are gaining a closer understanding of the extinct Neandertal by bringing parts of him/her back to life is the Max Plank Institute for Evolutionary Anthropology (MPI EVA). This institute is a world leader in genetic research into Neandertals, our closest extinct relatives. In 2010, after years of DNA sequencing and research work, a team led by one of the institute’s directors, Svante Pääbo, published the genome of female Neandertals who last walked the earth around 40,000 years ago (all genomes decoded to date are from female specimens). This work won Pääbo the Nobel Prize in Physiology or Medicine in 2022. One of the most important discoveries made at the time was that Neandertals had not really died out, in fact all modern humans outside sub-Saharan Africa still carry genes of these early hominins. Hence early modern humans must have interbred with them when they emerged from Africa to colonize the entire world.
Figure 1The human family tree.
Since then, the MPI EVA has consolidated its lead in early human research by proceeding not just to sequence other whole Neandertal genomes, but also to analyse the DNA of Denisovans. This archaic human species split off from the Neandertal lineage at a very early stage and lived in Asia, in some cases alongside Neandertals and modern humans, up until around 50,000 years ago. It, too, left genetic traces in some modern human groups, namely the Indigenous populations of the Philippines, Papua New Guinea, and Australia, which carry an average of 5 per cent Denisovan DNA in their genomes. Crucial to the discovery of this hitherto unknown hominin was an approximately 70,000-year-old finger bone found at the Denisova Cave in the Russian Altai Mountains in southern Siberia whose DNA was decoded at the MPI EVA in 2010. No Denisovan skulls, let alone skeletons, have been identified to date: all we have is DNA from tiny new bone fragments that are periodically unearthed in the same cave in Siberia.
Far more bones – a large number of well-preserved skulls and, occasionally, whole sections of skeletons – have been found in the case of Neandertals: their genome is, next to ours, the best researched of all prehistoric human forms. The fact that the Leipzig team has been able to grow archaic human brain cells – and even miniature organs, ‘organoids’ – is the result of this comprehensive sequencing work and of a strong similarity to the blueprint of a modern human: the differences amount to a tiny fraction of a thousandth in an otherwise identical genome. Even our nearest non-human relatives, the chimpanzee and the bonobo, differ from us in genome by little more than 1 per cent, although the last common ancestor of these three great apes lived some 7 million years ago.
It wasn’t until around 600,000 years ago that modern humans parted company with the Neandertal and Denisovan lineages. Although the genetic differences are marginal, they produce very clear contrasts between Neandertals and modern humans in physiognomy and physique. There are about 30,000 fixed differences – positions where the DNA of all modern humans differs from that of the Neandertal women analysed at the MPI EVA, who resemble chimpanzees at these points in their genome. But most of these differences do not lie in the genes, as these make up only about 2 per cent of our genome. Indeed, there are only ninety genetic differences that actually encode different proteins in the genomes of Neandertals and modern humans and hence are responsible for potentially divergent physical features.
In the past few years, genetic engineering has made it possible to reset a human cell, at certain locations in its genome, to its ‘original state’ from before the split between modern humans and Neandertals. In other words, it has made it possible to take the genome of a modern human and reverse the evolutionary steps it followed after branching off the line that led to the Neandertals. This is, if you like, a ‘neandertalization’ of those genomic locations. The process is extremely fiddly and involves introducing into the genetic information of a human cell some of the genetic differences vis-à-vis the Neandertal women. Once this task is completed, the modified cell can grow in a culture into a small clump of brain cells, for example. Such hybrid cells and cell clumps can already be seen in the Leipzig laboratory. The hope is that this would be the next step in the science of evolutionary genetics: we would no longer read DNA differences between archaic and modern humans only from fossilized bones but would observe them directly, in living human cells. This way we would be able to identify the genetic variants that define us as modern humans and are missing from Neandertals. Not all body cells are suitable as a base for neandertalizing human cells.1 For this operation we need stem cells, which can now be easily produced in the laboratory. At the MPI EVA, this is currently being done using human blood cells, which are then genetically modified with CRISPR/Cas9 ‘genetic scissors’.2
The feasible and the impossible
When it comes to the manipulation of human DNA and the production of hybrid cell structures, the moral implications, though obvious, are by no means entirely predictable, not even for scientists. In 2018, as if to prove that there is also a dark side to our power over our genes, the Chinese researcher He Jiankui, who has since vanished from the academic radar, claimed to have used genetic scissors on human embryos. He justified this molecular biological intervention as an attempt to protect the resulting babies against HIV by modifying one of their genes. He Jiankui never published a paper on his intervention, however. All that the (largely horrified) scientific community got to see was a publicity stunt at an international congress. A year later, the Russian biologist Denis Rebrivok wrote in the journal Nature of a plan to edit the genes of human embryos in order to prevent congenital deafness in newborns, albeit with the assurance that he would only do so subject to approval by the relevant authorities. Nothing has been heard of the experiment since.
Cases like these illustrate what a fine line genetic research is currently treading: it is of course easy to conceive of genetic scissors being used to ‘neandertalize’ a human embryo. In ten years’ time at the latest, scientists will have reached the point where they are able to modify numerous genomic locations at once, even without a high-tech laboratory. Unscrupulous researchers wouldn’t even need much imagination to achieve a scientific breakthrough of an extremely dubious kind.
At the MPI EVA, the genetic scissors are used to neandertalize human cells, but emphatically not embryos. The aim is not to breed Neandertals or archaic humans – or even whole organs – but merely cell clusters (see Figure 2). For these, too, can be used to observe biological processes such as the contractions of a heart muscle or the growth and interactions of brain cells.
Figure 2 A cell culture ‘bred’ from brain cells © Daniel Wolny
This already produces biochemical processes that can be observed in the laboratory, although such cell clusters are still a far cry from real organs.
So far, eight genetic differences between humans and Neandertals have been introduced into the cell cultures grown at the MPI EVA. But it will be a few more years before a cell culture can be grown with all ninety genetic variants. That said, the exponential acceleration we have seen since the turn of the millennium in the field of genetics and, by extension, archaeogenetics is likely to continue. By the end of the twenties it should thus be perfectly possible to incorporate into a human cell not just the ninety genetic differences that separate us from the Neandertals but all 30,000 genetic locations where all humans differ from the Neandertal genome. That would include those bases in the genome that don’t encode any proteins but may still fulfil a function.3
The Frankenstein genome
For the record, the ninety genetic differences are not the only differences between humans and Neandertals, but they are the only ones between all humans and all Neandertals. In other words, none of the million decoded genomes of modern-day humans looks like that of a Neandertal in any of those ninety locations. This means that they cannot have developed anywhere but in modern humans, and must have asserted themselves when our ancestors interbred a second time with the Neandertals. So clearly these variants, or at least some of them, must be integral to being human. Nevertheless, there are other segments of the female Neandertal genome that we still carry to this day: all humans outside Africa have an average of 2 per cent Neandertal DNA.4 In some people, the Neandertal genes are responsible for a particular skin texture, in others for an immune response, and in others for nothing at all – or at least nothing that we can identify.
When the successful decoding of the Neandertal genome was announced in Leipzig in 2010, it was based on a kind of Frankenstein genome, concocted from a mixture of female Neandertal specimens found in a cave in Croatia. What was justifiably celebrated as a big breakthrough back then would hardly make it into a major scientific journal today, given the crude database, which effectively involved throwing into a pot the DNA extracted from three Neandertals and looking to see how far it differed from the modern human genome, decoded barely ten years earlier.5
Nevertheless, that was enough for the anthropologically groundbreaking discovery that all modern humans outside Africa carry Neandertal genes, meaning that our ancestors had sex – and evidently plenty of it – with this early hominin. The Leipzig team was only at the beginning of its journey, however, and could do no more than shine a spotlight on an era that could hold the key to a deeper understanding of our own species. By this we mean an understanding of why it was modern humans – and not Neandertals or Denisovans – who went on to colonize the entire world and subjugate or destroy all other life on Earth.
In the meantime, dozens of Neandertal genomes have been decoded, all of them at the MPI EVA. New publications are constantly appearing that discuss evidence not just that Neandertals mated with modern humans, but that modern humans mated with Denisovans and Denisovans with Neandertals. Over the past few years, there have been some impressive discoveries regarding both of these early human species; but such discoveries can only hint at the secrets that lurk in the genome. We may have the blueprint of the Neandertal, with all its bases, but it is still only a blueprint – not a living, breathing individual. To gain an even better understanding of the Neandertal, we would need a real-life one.
Humans are predictable
So far, the idea of bringing our extinct relatives back to life is no more than idle speculation, though this doesn’t rule out the possibility of such experiments in future. Still, such a venture wouldn’t be an advance in stem cell research but rather a perversion of it. Although the cell clusters cultivated at the MPI EVA are a kind of minuscule forerunner of organs with Neandertal DNA, they wouldn’t be able to develop into anything like a whole organ, let alone become part of an organism through transplantation.6 Nevertheless, such cell cultures are incredibly valuable for archaeogenetic research and could lead to the next big breakthrough in Neandertal research – one whereby cellular processes in these early humans no longer have to be theoretically deduced, but can be directly observed.
Ten for the price of one
As in the early days of archaeogenetics, it was thanks to relatively small technical innovations that scientists in the 2010s were able to delve ever deeper into early human DNA, and hence into the past. Most of the progress achieved in archaeogenetics depends on apparently very simple tricks. Thus the team at the MPI EVA developed a technique that allows for information to be obtained not just from the DNA double helix but also from individual single strands that have survived over the millennia. This way the extracted quantity of DNA can be increased tenfold, so that we can now sequence even the most ancient bones, from which most of the genetic information has already been lost. This is how researchers managed, for example, to sequence the oldest decoded Neandertals to date, who lived in the Sima de los Huesos (Pit of Bones) cave in Spain some 420,000 years ago. And the same technique allowed the reconstruction of a high-quality genome that belonged to a roughly twelve-year-old Denisovan girl from something as tiny as a 70,000-year-old finger bone.
Another achievement of archaeogenetics in recent years was the ability to calculate lines of descent. By comparing early human DNA with the genetic material of modern humans, we are gaining an increasing understanding of which human lineages diverged or split off from each other and when. We simply need to look at the number of genetic mutations in a sequenced genome using a ‘gene clock’ or ‘molecular clock’. The more of these genetic differences we find, the earlier the split occurred.7 Thus the genetic differences between chimpanzees and all hominins suggest that our last common ancestor lived around 7 million years ago. The common forefathers of modern humans, Neandertals and Denisovans, lived roughly 600,000 years ago; Neandertals and Denisovans parted company some 500,000 years ago. Similarly, we would probably never have been able to study the interbreeding between the different hominins by using the techniques of classical palaeoanthropology alone. Thanks to archaeogenetics, we can now track it in the genome of every human being.
How efficient is a Neandertal heart by comparison with a human one? What metabolic processes can a human liver perform that a Neandertal one can’t? Can a Neandertal tolerate alcohol? Or – and this is of course the really big question – are our brain processes different from those of this extinct hominin? Do we form neural networks more quickly, for example? The assumption underlying these questions is obvious: namely that, at some point after the split between humans and Neandertals, changes occurred in our ancestors’ brains that led us to turn the world into the place it is today. What is clear is that sheer size is not a factor: the average Neandertal brain weighs 250 grams more than that of a modern human.
That the idea of resurrecting Neandertals for research purposes is not purely theoretical and is undoubtedly at least discussed in many a laboratory (though probably over a second glass of wine rather than the first cup of coffee) was proved a few years ago by George Church. A pioneer of DNA sequencing, Church was a key contributor to the Human Genome Project and in 2006 launched the Personal Genome Project, whose aim was to sequence the genomes of as many individuals as possible, for medical research purposes. In short, he is regarded as an authority among geneticists.
For this reason alone, it is worth considering the other big idea that Church outlined (among other things) in his 2012 book Regenesis: that of breeding Neandertals. The main foundation had already been laid, he claimed at the time, with the sequencing of the Neandertal genome. A possible next step would be to break down the genome into thousands of components in order to gradually transfer more and more Neandertal genes into a human stem cell line. The end result, according to Church, would be a ‘Neandertal clone’, although he was careful to state that such a procedure would require a society-wide debate. The benefit, he argued, was at any rate clear: a greater ‘diversity’ of the human community that would be conducive to the survival of all species, including humans.
Church did not assume that modern humans were necessarily more intelligent than Neandertals: indeed, the latter’s larger brains could equally well indicate the opposite. His point – as he explained in an interview with Der Spiegel – was that, if humankind one day had to ‘deal with an epidemic, quit the planet, or whatever’, the Neandertal ‘mentality’ might be ‘an advantage’. So then: had Neandertals not drawn the short straw in the evolutionary contest, would they have become the better scientists? Instead of contenting themselves with reconstructing the cells of extinct hominins, would they have gone on to conquer global epidemics, antibiotic resistance, and climate change? Or would they have avoided the path that led to all these problems in the first place? These would be questions best put to the Neandertals themselves, were we to follow through Church’s vision.
Even today, cloning a Neandertal is still a matter of science fiction, and there is little to suggest that the situation will change (see Figure 3). As a Plan B, Church floated the idea of producing a hybrid by introducing into the human genome specific mutations that distinguish Neandertals from modern humans. The advantage of this method is that it would be selective in terms of the implanted genes, allowing us to cherry-pick the most useful characteristics of the Neandertal. According to Church, the same procedure would apply not just to Neandertals but to any other hominin whose genome was decoded. This way we could travel up to a million years back in time, theoretically bringing the humans of that era – or at least parts of their DNA – back to life: a shopping tour, you might say, in the department store of human evolution.
Figure 3 Neandertal © Tom Björklund
Also thanks to archaeogenetics, we now have a fairly accurate idea of what Neandertals looked like, although not much is known so far of their social behaviour. These hominins probably lived in close family units too – much like us.
From an archaeogenetic perspective, however, such a projection is a bold one to say the least. The fact that we have now managed to sequence almost all the Neandertal genome is due to a rich fund of well-preserved bone finds from which the DNA could be extracted, the oldest sample being just over 420,000 years old. And, even though countless remains of Homo erectus – the most likely common ancestor to us, to Neandertals, and to Denisovans – have been found all over the world, so far they have been only of anthropological, not archaeogenetic, use. If we wanted to reconstruct the genome using the same method as the one used for Neandertals, we would need not just any old bones, but ones from which DNA can be extracted – something that is not available to date.
A much more realistic option, and one that actually takes Church’s ideas from 2012 a step further, would be to calculate the genome of Homo erectus on a computer. This could be done by considering three genomes: that of a chimpanzee, that of a modern human, and that of a Neandertal – all of which are known to derive from a common ancestor. On the basis of the differences between the great ape on one hand and the two hominins on the other, we could first determine which specific mutations occurred after the common lineage of modern humans branched off from Neandertals. In the gene positions where we are identical with chimpanzees but not with Neandertals, only the Neandertal DNA will have changed – and the same applies the other way round, that is, in gene positions that differ only in modern humans from their counterparts in chimpanzees.
Given this, all positions in the genome of a modern human could then be restored to the ‘original state’ using gene scissors. The result, however, would not be a pure Homo erectus as it existed in Africa a million years ago, but a Homo sapiens/erectus hybrid in which the genes of modern humans have been reset. From a medical ethics perspective, the very idea of this is outrageous, but this is precisely why it cannot be brushed aside. Nowadays such a hybrid genome could be calculated on a standard Notebook.
Because we can
The re-creation of a Neandertal in Church’s laboratory – or at the MPI EVA, for that matter – is certainly not on the cards, either now or in future. But apart from all the ethical issues, there is also a much more mundane argument against such an experiment. For one thing, if we really wanted to resurrect an archaic species of humans at population level, we would have to create not just one, but hundreds of Neandertals. Since there could be no justification for excluding them from modern human society, or indeed for locking them up, they would sooner or later begin – as they did 50,000 years ago – to interact with us sexually (and we with them), and this would result in hybrid children. Within a few generations, probably in less than a hundred years, the gene pool of this tiny number of Neandertals would sink into that of the billions of modern humans, before presumably disappearing without a trace – apart from the 2 per cent of Neandertal genes that people outside Africa already carry (see Figure 4).
Figure 4 The great journey north from Africa © Landesamt für Denkmalpflege und Archäologie Sachsen-Anhalt / Karol Schauer
When modern humans first set out on their great journey north from Africa, they encountered the mostly bitter cold mammoth steppe – a vast hunting ground that laid the foundations for our ancestors’ subsequent expansion.
In the end, we would probably be looking at decades of ethical debate and runaway costs, without the benefit of any real groundbreaking discoveries – apart from the fact that the modern human is positively incapable of refraining from doing something just because s/he can. But this hardly needed proving.
In our quest to solve the great riddle of Homo sapiens, the neandertalized cell cultures in our laboratories can be only a tool that, with a bit of luck, we can use to identify the single genetic change that gave modern humans their decisive advantage. Was it our culture-building capacity that led to complex, collaborative societies and enabled an increasing specialization of the individual for the benefit of the community? Or was it rather our cruelty towards fellow humans, and even more towards those who didn’t belong? The willingness to risk our own life in order to enhance it in unimagined ways? Was it all just a weird coincidence that modern humans ended up on the right evolutionary path, while Neandertals and Denisovans did not? Or is it ultimately the wrong track, a dead end towards which we are currently heading at full speed? And what is it in us that makes us think it would be a good idea to have a Neandertal clone in the passenger seat on that final spurt?
So, for now, let us consider the genetic reconstruction work with neandertalized cells that is currently going on at the MPI EVA as a valuable technological tool that may one day help us to answer these questions. And, in the meantime, let us take a journey far back in history, in the spirit of classic archaeogenetics: a journey to a time when large areas of the northern hemisphere were covered in ice and this part of the world was dominated by Neandertals and Denisovans. And somewhere in the Bohemian Forest, not far from present-day Prague, a woman was laid to rest – a woman who, according to prevailing archaeological doctrine, shouldn’t have been there at all, and who was an early harbinger of the Neandertals’ and the Denisovans’ demise. It was this woman – Zlatý kůň – who yielded the oldest genome of a modern human ever to be sequenced.
Notes
a
This name comes from a German toponym: the Neandertal valley along the river Düssel. Hence we prefer the vernacular spelling ‘Neandertal’ to the Latinized ‘Neanderthal’, which derives from the taxonomic formula
Homo neanderthalensis
. The form ‘Neandertal’ is increasingly adopted in German.
Notes
1
There are embryonic stem cells that can form whole organisms, but these are no longer used for the reproduction of cell tissue for ethical reasons. On the other hand, the use of so-called pluripotent stem cells is ethically and legally acceptable. Unlike totipotent embryonic stem cells, these cannot be used to grow whole organisms, but only parts of them – such as liver, heart or brain cells. As early as 2006, the Japanese researcher Shin’ya Yamanaka developed a technique for producing pluripotent stem cells from any body cell, through the induction of a few genes. This discovery won Yamanaka the Nobel Prize in Physiology or Medicine in 2012, not least because it made stem cell research possible without the need to use embryos.
2
The CRISPR/Cas9 method, better known as ‘gene scissors’, was developed in 2021 by a team headed by the French researcher Emmanuelle Charpentier and the American molecular biologist Jennifer Doudna. Both women were awarded the Nobel Prize for Chemistry in 2020. Their discovery ushered in a new age of molecular biological medicine and genetic research. Gene scissors exploit a mechanism that is present in about half of all known bacterial organisms. The CRISPR/Cas9 system allows bacteria to store in their cell structure some of the genetic information from the viruses that attack them and thus to build up an immune response that can then be passed on to the next generation. If at a later stage the same type of virus re-encounters the modified bacterial cell, it will activate its immune memory. Bacterial RNA molecules will then attack the basal combinations recognized by the bacteria from the previous infection. Finally, the cas enzyme released by the bacteria as a rearguard action sets to work, cutting out the piece of virus marked by the RNA. The virus is, as it were, dissected with the gene scissors and thus rendered harmless. The CRISPR/Cas9 technique, which was copied from the bacteria themselves, is now part of the standard toolkit of genetic research. In November 2019, the US–Swiss company CRISPR Therapeutics, of which Emmanuelle Charpentier is a co-founder, announced success in two patients with the inherited blood disorders beta thalassemia and sickle cell anaemia; this success was soon followed by promising progress in the treatment of cancer patients. Both cases involved cutting out, from the DNA of the body’s own immune cells, information that normally serves to inhibit the immune response.
3
Although we know the ninety genes that distinguish us from the Neandertals, it is not genes alone that are responsible for different phenotypes (the physical characteristics of cells). Rather it is the combination of different genetic variants, the number of modifications in the genes, and their interaction with other bases in the genome: all these factors determine which proteins and how many of them are produced in the various cells. This is also the reason why geneticists can easily decode the function of individual genes in single-cell organisms, yet are still none the wiser when it comes to humans.
4
However, this is not the same 2 per cent but a large pool of genetic information, from which each receives a small handful. Thus around 40 per cent of the genetic information of the Neandertal and more than half of the Denisovan’s is still floating around in the great ocean that constitutes the human genome; the rest has disappeared without trace.
5
This task can be imagined as a giant Neandertal jigsaw, very similar to a modern human jigsaw. From the Neandertals’ pool of genetic information, pieces are fished out that are identical in colour and shape with those of the master template, in other words with our genetic code. Bit by bit, a picture appears, but there are still many gaps. In the Neandertal puzzle we can find a piece with the right shape to fit the gap, but a completely different colour; thus one of the fixed differences is rendered visible. As mentioned, back then the Neandertal jigsaw was one with many missing pieces, and by the end of five years of work only about a half of the genome was in sight.
6
We are already able to transplant organs across different species. Doctors and researchers hope that such xenotransplantations will soon offer a solution to the undersupply of organs in human medicine.
7
Not every mutation results in changed inherited characteristics, far from it; only a very few do. This is because only 2 per cent of the genome actually contains genes – the rest serves to control the genes, and more than half has no known function. This part is also referred to as ‘junk DNA’.
2Famine
We enter the bitter cold Ice Age. Our ancestors didn’t stand a chance in the north: here it was their cousins, with their rough table manners, who held sway. We meet Zlatý kůň. Our ancestors find a way of coping with the depressing notion of their own mortality. In the background, hyenas prowl.
Dining with one’s own kind
Other than in caves, the Europe of the Ice Age (see Figure 5), which only ended around 11,500 years ago, was barely habitable without a good fire. And this applies to all human species who lived here. Caves were the centre of human life at that time, and it is no coincidence that they, along with graves, are the most fruitful sites for archaeologists. The finger bone that opened our eyes to the Denisovans came from Denisova Cave; Chauvet Cave in France contains impressive portraits of aurochs and horses thought to have been painted by our ancestors over 32,000 years ago; and the world’s oldest flutes, made from bird and mammoth bones, were found in Geißenklösterle Cave in the Swabian Jura.
Figure 5Map of Europe during the last Ice Age.
