Human evolution is the evolutionary process that led to the emergence of anatomically modern humans beginning with the evolutionary history of primates-in particular genus Homo-and leading to the emergence of Homo sapiens as a distinct species of the homid family which includes the great apes. This process involved the gradual development of traits such as human bipedalism and language as well as interbreeding with other hominins which indicate that human evolution was not linear but a web. Then when did something like us first appear on the planet? It turns out there is remarkably little agreement on this question. Fossil and DNA suggest people looking like us, anatomically modern Homo sapiens evolved around 3000,000 years ago. Surprisingly, archaeology –tools artefacts and cave art- suggest that complex technology and cultures, “behavioral modernity, evolved more recently around 50,000 -65,000 years ago. Some scientists interpret this as suggesting the earliest Homo sapiens were not entirely modern. Yet the different data tracks different things. Skulls and genes tells us about brains, artefacts about culture. Our brains probably became modern before our culture.
For 200,000-300,000 years after Homo sapiens first appeared, tools and artefacts remained surprisingly simple, little better than Neanderthal technology and simpler than those of modern hunter-gatherers such as certain indigenous Americans. Starting about 65,000 to 50,000 years ago, more advanced technology started appearing: complex projectile weapons such as bows, spear-throwers, fishhooks, ceramic and sewing needles. People made representational art-cave paintings of horses, ivory goddesses, lion headed idols, showing artistic flair and imagination. A bird bone flute hints at music. Meanwhile, the arrival of humans in Australia 65,000 years ago shows we had mastered seafaring. Sudden flourishing of technology is called “great leap forward”, supposedly reflecting the evolution of a fully modern brain. But fossils and DNA suggest that human intelligence became modern far earlier. Bones of primitive Homo sapiens first appear 300,000 years ago in Africa with brain as larger as or larger than ours. They are followed by anatomically modern Homo sapiens at least 200,000 years ago and brain shape become essentially modern by at least 100,000 years ago. At this point humans had braincase similar in size and shape to ours.
Assuming the brain was as modern as the box that held it, our African ancestors theoretically could have discovered relatively built space telescope, written novels and love songs. Their bones say they were just as human as we are. Because the fossil record is so much patchy, fossil provides only minimum dates. Human DNA suggests even earlier origins for modernity. Comparing genetic differences between DNA in modern people and ancient Africans, it is estimated that our ancestors lived 260,000 to 350,000 years ago. All living humans descend from those people, suggesting that we inherited the fundamental commonalities of our species, our humanity, from them. All their descendants –Bantu, Berber, Aztec, Aborigines, Tamil, San, Han, Maori, Inuit and Irish – share certain peculiar behaviors absent in other great apes. All human cultures form long term power bonds between men and women to care for children. We sing and dance. We make art, we preen our hair, adorn our bodies with ornaments, tattoos and makeup. We craft shelters, we wield fire and complex tool. We form large multigenerational social groups with dozens to thousands of people. We cooperate to wage war and help each other. We teach, tell stories, trade. We have morals, laws. We contemplate the stars, our place in cosmos, life’s meaning, what follows death.
The details of our tools, fashions, families, morals and mythologies vary from tribe to tribe and culture to culture but all living humans show these behaviors-or at least the capacity for them- are innate. These shared behaviors unite all people. They are the human condition. What it means to be human and they result from shared ancestry. We inherited our human from peoples in southern Africa 300,000 years ago. The alternative- that every one, everywhere coincidentally became fully human in the same way at the same time starting 65,000 years ago- is not impossible but single origin is more likely. Archaeology and biology may seem to disagree, but they actually tell different parts of the human story. Bones and DNA tells us about brain evolution, our-hardware. Tools reflect brain power, but also culture, our hardware and software. Just as you can upgrade your old computer operating system, culture can evolve even if intelligence does not. Humans in ancient times lacked smartphones and spaceflight but we know from studying philosophers such as Buddha and Aristotle that they were just as clever. Our brain did not change, our culture did. That creates a puzzle. If Pleistocene hunter-gatherers were as smart as us, why did culture remain so primitive for so long? Why did we need hundreds of millennia to invent bows, sewing needles boats? And what changed? Probably several things. First we journeyed out of Africa, occupying more of the planet. There were then simply more humans to invent increasing the odds of a prehistoric Steve Jobs or Leonardo da Vinci. We also faced new environments in the Middle East, the Artic, India, and Indonesia with unique climates, foods and dangers including other human species. Survival demanded innovation.
Many of these new lands were far more habitable than Kalahari or Congo climates were milder, but Homo sapiens also left behind African diseases and parasites. That let tribes grow larger and larger tribes meant more heads to innovate and remember ideas, more manpower and better ability to specialize. Population drove innovation. This triggered feedback cycles. As new technologies appeared and spread- better weapons, clothing and shelters-human numbers could increase further accelerating cultural evolution again. Numbers drove culture, culture increased numbers, accelerating cultural evolution, on and on ultimately pushing human populations to outstrip their ecosystem, devastating the megafauna and forcing the evolution of farming. Finally, agriculture caused an explosive population increase, culminating in civilization of millions of people. Now cultural evolution kicked into hyper drive. Artefacts reflect the culture and cultural complexity is an emergent property. That is, it not just individual-level intelligence that makes cultures sophisticated but interactions between individuals in groups and between groups. Like networking millions of processors to make a supercomputer, we increased cultural complexity by increasing the number of people and the links between them. So our societies and world evolved rapidly in the past 300,000 years, while our brains evolved slowly. We expanded our numbers to almost 8 billion, spread across the globe, and reshaped the planet. We did it not by adapting our brains but by changing our cultures. And much of the difference between our ancient, simple hunter-gatherer societies and modern societies just reflects the fact that there are lots more of us and more connection between us.
