When did we become fully human? Fossils and DNA explain the evolution of human intelligence

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When did something like this first appear on the planet? There seems to be a remarkably small agreement on this question. Fossils and DNA suggest that anatomically similar humans, Homo sapiens, evolved about 300,000 years ago. Surprisingly, archeology – tools, artifacts, rock art – suggests that complex technology and cultures, “behavioral modernity,” have evolved more recently: 50,000-65,000 years ago.

Some scientists interpret this as suggesting that the first Homo sapiens were not entirely modern. However, different data follow different things. Skulls and eyelashes tell us about the brain, and artifacts about culture. Our brains probably became modern before our cultures.

For 200,000-300,000 years after the appearance of Homo sapiens, tools and artifacts they remained surprisingly simple, slightly better than Neanderthal technology, and simpler than those of modern hunter-gatherers, such as the so-called Native Americans. Beginning about 65,000 years ago, more advanced technologies began to appear: complex projectile weapons, such as springs and spear throwers, fish hooks, pottery, sewing needles.

People made representative art – cave paintings with horses, ivory goddesses, lion-headed idols, showing artistic flair and imagination. A flute of bird bone suggests music. Meanwhile, the arrival of people in Australia behind with 65,000 years shows that I have mastered navigation.

This sudden flowering of technology is called “The big leap forward”, which is supposed to reflect the evolution of a completely modern human brain. But fossils and DNA suggest that human intelligence became modern much earlier.

When anatomical modernity appeared

Thus, the primitive Homo sapiens bones appear for the first time 300,000 years ago in Africa, with a brain as big or bigger than ours. They are followed by modern anatomical Homo sapiens, at least 200,000 years ago, and the shape of the brain became essentially modern at least 100,000 years ago. At this time, people had brains similar in size and shape to ours. Thus, our African ancestors could theoretically have discovered relativity, built space telescopes, written novels and love songs. Their bones say they were as human as we are.

Because the fossil record is so uneven, the fossils provide only minimal data. Human DNA suggests even older origins for modernity. Comparing the genetic differences between the DNA of modern humans and ancient Africans, it is estimated that our ancestors lived 260,000 to 350,000 years ago. All living people descend from those people, suggesting that we inherited from them the common elements of our species, that is, our humanity.

All their descendants – Bantu, Berber, Aztec, Aboriginal, Tamil, San, Han, Maori, Inuit, Irish – share certain specific behaviors absent from other large monkeys. All human cultures form long-term relationships between men and women to care for children. We sing and dance. We make art. We polish our hair, adorn our bodies with ornaments, tattoos and makeup.

We create shelters. We handle fire and complex tools. We form large, multigenerational social groups with tens to thousands of people. We cooperate to wage war and help each other. We learn, we tell stories, we exchange opinions. We have morals, laws. We contemplate the stars, our place in the cosmos, the meaning of life, what follows death.

How our brains and culture have evolved

The details of our tools, models, families, morals, and mythologies vary from tribe to tribe and from culture to culture, but all living people exhibit these behaviors. This suggests that these behaviors – or at least the capacity for them – are innate. These common behaviors unite all people. They are the human condition, which means being human and results from a common ancestry.

We inherited our humanity from the peoples of southern Africa 300,000 years ago. The alternative – the fact that everyone, everywhere, happened to become fully human in the same way at the same time, starting 65,000 years ago – is not impossible, but a single origin is more likely.

Archeology and biology may seem to disagree, but they actually tell different parts of the human story. Bones and DNA tell us about the evolution of the brain, our hardware. The tools reflect our intellectual power, but also our culture, hardware and software.

Just as you can upgrade your old computer’s operating system, culture can evolve even if intelligence doesn’t. People in ancient times lacked smartphones and spaceflight, but we know from learned philosophers like Buddha and Aristotle that they were just as smart. Our brains haven’t changed, our culture has changed.

Survival required innovation

That creates a puzzle. If the Pleistocene hunter-gatherers were as smart as we are, why has culture remained so primitive for so long? Why did it take me hundreds of millennia to invent bows, sewing needles, boats? And what has changed? Probably more.

First, I left Africa, occupying more than one planet. Then there were simply more people who wanted to make inventions, increasing the chances of a prehistoric Steve Jobs or Leonardo da Vinci. We also faced new environments in the Middle East, Arctic, India, Indonesia, with unique climate, food and dangers, including other human species. Survival required innovation.

Many of these new lands were much more livable than the Kalahari or Congo. The climates were milder, but Homo sapiens also left behind African diseases and parasites. This allowed the tribes to grow, and the larger tribes meant more leaders to innovate and have ideas, more manpower, and better specialization ability. The population has driven innovation.

This triggered feedback cycles. As new technologies emerged and spread – better weapons, clothing, shelter – the number of people could continue to grow, accelerating cultural evolution again.

How human interaction has helped evolution

The numbers have driven culture, culture has grown, accelerating cultural evolution, continuing and ultimately pushing human populations to transcend their ecosystems, devastating wildlife and forcing the evolution of agriculture. Eventually, agriculture caused an explosive population growth, culminating in civilizations of millions of people.

Artifacts reflect culture, and cultural complexity is an emerging property. That is, not only intelligence at the individual level makes cultures sophisticated, but the interactions between individuals in groups and between groups. Like the network of millions of processors to make a supercomputer, we have increased cultural complexity by increasing the number of people and the connections between them.

So our societies and the world have evolved rapidly over the last 300,000 years, while our brains have evolved slowly. We have expanded our number to almost 8 billion, spread all over the globe, we have reshaped the planet. We didn’t do it by adapting our brains, but by changing our cultures. And much of the difference between our old and simple hunter-gatherer societies and modern societies only reflects the fact that there are more complex connections between us.


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