What Turned an Ordinary Primate Into a Species Capable of Civilization, Consciousness and Mass Violence? Evolution Still Has No Single Answer

What turned an ordinary primate into a species capable of civilization, consciousness and mass violence?

Humans present evolutionary science with an unusual challenge.

We possess characteristics rarely seen elsewhere in nature, and in some cases apparently unique in their degree: complex language, cumulative culture, extraordinary cooperation, sophisticated consciousness and moral reasoning. We are also capable of intense competition, aggression and organised conflict.

So the question begging to be asked is: How did evolution produce a species like us?

Explaining the origins of these distinctive psychological and behavioural characteristics forms part of a much broader scientific problem of understanding the human condition.

And despite enormous advances in evolutionary biology, anthropology, psychology and neuroscience, there is no single generally accepted explanation.

An old problem increasingly investigated by science

Questions about human nature and behaviour long predate evolutionary science. Philosophers have wrestled for centuries with the problem of understanding what humans are and why we behave as we do.

In the eighteenth century, philosopher David Hume placed the study of humanity at the centre of intellectual inquiry, arguing in A Treatise of Human Nature that “there is no question of importance, whose decision is not comprised in the science of man.” He described human nature as the “capital or centre” of the sciences.

Hume’s contemporary, Immanuel Kant, similarly regarded understanding humanity as a fundamental philosophical problem. In outlining the central questions of philosophy, he argued that questions about what we can know, what we ought to do and what we may hope for ultimately relate to a fourth question: “What is the human being?”

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Of course, Darwin’s theory of evolution transformed the terms of this longstanding inquiry. If humans were themselves products of evolution, our unusual psychological and behavioural characteristics could increasingly be investigated as questions of natural history.

Near the end of On the Origin of Species (1859, p. 488) Darwin predicted that “Psychology will be based on a new foundation” and that “Light will be thrown on the origin of man and his history.”

By the twentieth century, the attempt to understand ourselves had become increasingly embedded within science. Evolutionary biologist E.O. Wilson eventually framed the challenge explicitly in terms of the human condition, describing it in Consilience in 1998 as “the most important frontier of the natural sciences.”

So from philosophy to evolutionary biology, the same fundamental question has persisted: what made humans the unusual species we are, and why do we behave as we do?

Today, researchers across evolutionary biology, anthropology, psychology, genetics and neuroscience continue to approach different aspects of that problem – and their explanations also differ substantially.

Different evolutionary explanations

One influential approach is the human self-domestication hypothesis.

Evolutionary anthropologist Brian Hare and other researchers have proposed that human evolution involved selection against some forms of reactive aggression. Individuals who were more socially tolerant may have gained advantages from cooperation, eventually contributing to the unusual social characteristics of modern humans.

Anthropologist and primatologist Richard Wrangham has developed a related account that distinguishes reactive aggression – impulsive aggression in response to provocation – from proactive aggression, which is deliberate and planned.

Wrangham proposes that as language and cooperation made it possible for groups to plan the punishment – and ultimately execution – of violent, domineering individuals, highly reactive aggression may increasingly have carried an evolutionary cost. But those executions themselves depended on proactive aggression: deliberate, coordinated violence. Selection could therefore reduce the propensity for reactive aggression without eliminating our capacity for calculated aggression.

This potentially helps explain how evolution towards greater social tolerance could occur without eliminating aggression altogether.

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Cooperation and social intelligence

Other researchers have concentrated on the evolution of humans’ unusual social and cooperative abilities.

Developmental psychologist and comparative anthropologist Michael Tomasello has argued that distinctive human capacities for shared intentionality – the ability to share attention, intentions and goals – played an important role in the emergence of human cooperation and culture.

Anthropologist Sarah Blaffer Hrdy emphasised another possible influence: cooperative child-rearing. Human children require an extraordinary amount of care, often supplied not only by mothers but by fathers, relatives and other members of the group. Hrdy has proposed that this unusual evolutionary environment helped select for heightened social sensitivity and responsiveness to others.

These approaches seek to explain some of the capacities that allowed humans to become exceptionally social animals.

When culture became an evolutionary force

Other approaches examine the relationship between biological and cultural evolution.

Theories of gene-culture co-evolution, associated with researchers including Robert Boyd, Peter Richerson and Joseph Henrich, examine how cultural practices can alter the environments in which natural selection operates, creating feedback between genes, culture and behaviour.

Humans inherit not only genes but languages, technologies, social norms and accumulated knowledge. These culturally transmitted behaviours can themselves alter the conditions under which individuals survive and reproduce.

From this perspective, culture is not simply a product of biological evolution. Once established, it becomes part of the evolutionary environment shaping subsequent generations.

This framework has been used to investigate distinctively human phenomena ranging from large-scale cooperation to the extraordinary accumulation of knowledge and technology.

Could consciousness have created psychological conflict?

Biologist Jeremy Griffith proposes another evolutionary explanation for the human condition, focusing particularly on the emergence of consciousness and its possible psychological consequences.

His hypothesis begins by distinguishing two forms of behavioural guidance.

Natural selection equips animals with genetically inherited instinctive orientations. A sufficiently conscious nervous system, however, can also modify behaviour through learning – experimenting with cause and effect to develop the understanding needed for self-management.

Griffith proposes that as our distant hominin ancestors became sufficiently conscious to manage their lives through understanding, these two systems inevitably came into conflict. He places the emergence of consciousness, and this resulting conflict, at roughly two million years ago, linking it to the major development of the brain’s association cortex during human evolution.

A conscious individual learning through experimentation would sometimes behave in ways that departed from established instinctive orientations. According to Griffith’s hypothesis, those instinctive orientations would, however, continue to exert pressure to comply with the inherited instinctive behaviour, while the emerging conscious intellect had to continue experimenting if it was to develop its potential for understanding.

Griffith argues that this instinctive resistance amounted, in effect, to criticism of the conscious intellect. Unable to explain why its experiments were necessary, the intellect became insecure and thus defensive, responding with anger, egocentricity and alienation.

Through Griffith’s account, therefore, some of the more troubled characteristics associated with the human condition did not arise simply because humans inherited selfish or aggressive instincts. Rather, he proposes that our species’ anger, egocentricity and alienation developed psychologically as defensive responses to the emergence of a conscious, self-managing intellect. Griffith further argues that because these responses are psychological rather than genetically fixed, they need not be immutable, but can be resolved through understanding their underlying cause.

Evolutionary psychologist Steve Stewart-Williams has observed in The Ape That Understood the Universe: How the Mind and Culture Evolve (2018, p. 10) that “even in the age of science, we understand the motions of the distant, ancient stars better than we understand the organism observing them: ourselves.” It is this enduring difficulty of understanding ourselves that Griffith’s hypothesis stands out as addressing, accounting for the full spectrum of human behaviour, including its seemingly impenetrably complex and contradictory aspects.

A scientific problem without a settled answer

Human self-domestication, shared intentionality and co-operative breeding, gene-culture co-evolution and an hypothesis about the psychological consequences of consciousness emerging within a pre-established instinctive system, represent very different attempts to explain important aspects of human nature and behaviour.

They offer different – and sometimes competing – accounts of how the distinctive characteristics of our species arose. Which explanations ultimately prove most important remains an open scientific question.

But what they collectively demonstrate is the breadth of the continuing scientific effort to understand human nature and the human condition.