Sep 12th 2020

When did we become fully human? What fossils and DNA tell us about the evolution of modern intelligence

by Nick Longrich

 

Nick Longrich is Senior Lecturer in Evolutionary Biology and Paleontology at the University of Bath.

 

Mariano/Wikipedia, CC BY-SA

 

When did something like us first appear on the planet? It turns out there’s remarkably little agreement on this question. Fossils and DNA suggest people looking like us, anatomically modern Homo sapiens, evolved around 300,000 years ago. Surprisingly, archaeology – tools, artefacts, cave art – suggest that complex technology and cultures, “behavioural modernity”, evolved more recently: 50,000-65,000 years ago.

 

Some scientists interprAdd Editor Letteret this as suggesting the earliest Homo sapiens weren’t entirely modern. Yet the different data tracks different things. Skulls and genes tell us about brains, artefacts about culture. Our brains probably became modern before our cultures.

Tree diagram showing human evolution.
Key physical and cultural milestones in modern human evolution, including genetic divergence of ethnic groups. Nick Longrich, Author provided

The “great leap”

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 and spear-throwers, fishhooks, ceramics, 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, arrival of humans in Australia 65,000 years ago shows we’d mastered seafaring.

The Venus of Brassempouy, 25,000 years old. Wikipedia

This sudden flourishing of technology is called the “great leap forward”, supposedly reflecting the evolution of a fully modern human brain. But fossils and DNA suggest that human intelligence became modern far earlier.

Anatomical modernity

Bones of primitive Homo sapiens first appear 300,000 years ago in Africa, with brains as large or larger than ours. They’re followed by anatomically modern Homo sapiens at least 200,000 years ago, and brain shape became essentially modern by at least 100,000 years ago. At this point, humans had braincases 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 relativity, built space telescopes, written novels and love songs. Their bones say they were just as human as we are.

300,000 ya skull, Morocco. NHM

Because the fossil record is so patchy, fossils provide only minimum dates. Human DNA suggests even earlier origins for modernity. Comparing genetic differences between DNA in modern people and ancient Africans, it’s 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, Aboriginal, Tamil, San, Han, Maori, Inuit, Irish – share certain peculiar behaviours absent in other great apes. All human cultures form long-term pair 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 tools. 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 the 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 behaviours. That suggests these behaviours – or at least, the capacity for them – are innate. These shared behaviours unite all people. They’re the human condition, what it means to be human, and they result from shared ancestry.

We inherited our humanity from peoples in southern Africa 300,000 years ago. The alternative – that everyone, everywhere coincidentally became fully human in the same way at the same time, starting 65,000 years ago – isn’t impossible, but a single origin is more likely.

The network effect

Archaeology and biology may seem to disagree, but they actually tell different parts of the human story. Bones and DNA tell us about brain evolution, our hardware. Tools reflect brainpower, but also culture, our hardware and software.

Just as you can upgrade your old computer’s operating system, culture can evolve even if intelligence doesn’t. 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 brains didn’t change, our culture did.

Middle Stone Age technology.

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 Arctic, India, Indonesia, with unique climates, foods and dangers, including other human species. Survival demanded innovation.

Many of these new lands were far more habitable than the Kalahari or the 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 specialise. Population drove innovation.

Beijing from space. NASA

This triggered feedback cycles. As new technologies appeared and spread – better weapons, clothing, 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 ecosystems, devastating the megafauna and forcing the evolution of farming. Finally, agriculture caused an explosive population increase, culminating in civilisations of millions of people. Now, cultural evolution kicked into hyperdrive.

Artefacts reflect culture, and cultural complexity is an emergent property. That is, it’s 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, 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 connections between us.

 

Nick Longrich, Senior Lecturer in Evolutionary Biology and Paleontology, University of Bath

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Browse articles by author

More Essays

May 1st 2021
EXTRACT: " The sad reality is that the Mizrahim (Jews of Middle Eastern and North African descent) were discriminated against from the day of Israel’s inception, whose Ashkenazi (European Jewish) leaders viewed them as intellectually inferior, “backward,” and “too Arab,” and treated them as such, largely because the Ashkenazim agenda was to maintain their upper-class status while controlling the levers of power, which remain prevalent to this day." ..... " The greatest heartbreaking outcome is that for yet another generation of Israelis, growing up in these debilitating conditions has a direct effect on their cognitive development. A 2015 study published in Nature Neuroscience found that “family income is significantly correlated with children’s brain size…increases in income were associated with the greatest increases in brain surface area among the poorest children.” "
Apr 25th 2021
EXTRACT: "We all owe Farah Nabulsi an enormous debt of gratitude. In a short 24-minute film, The Present, she has exposed the oppressive indecency of the Israeli occupation while telling the deeply moving story of a Palestinian family. What is especially exciting is that after winning awards at a number of international film festivals​, Ms. Nabulsi has been nominated for an Academy Award for this remarkable work of art. " 
Apr 25th 2021
EXTRACT: "When I crashed to the floor of my home in Bordeaux recently after two months of Covid-19 dizziness, I was annoyed. The next day I collapsed again. Now I was worried. What I didn’t know was that my brain was sloshing around inside my skull, causing a mild concussion. Nor did I know that I was in for a whole new world of weird and wonderful hallucinations."
Apr 13th 2021
EXTRACT: "Overall, our review has found that there isn’t evidence to back up the claims that veganism is good for your heart. But that is partly because there are few studies ....... But veganism may have other health benefits. Vegans have been found to have a healthier weight and lower blood glucose levels than those who consume meat and dairy. They are also less likely to develop cancer, high blood pressure and diabetes. "
Apr 8th 2021
EXTRACT: "Pollock’s universe, the universe of Mural, cannot be said to be a rational universe. Nor is it simply devoid of all sense. It is not a purely imaginary world, although in it everything is in a constant state of flux. Mural invokes one of the oldest questions of philosophy, a question going back to the Pre-Socratic philosophers Parmenides and Heraclitus – namely, whether the nature of Reality constitutes unchanging permanence or constant movement and flux. For Pollock, the only thing that is truly unchanging is change itself. The only certainty is that all is uncertain."
Apr 8th 2021
EXTRACT: "Many present day politicians appear to have psychopathic and narcissistic traits too. It’s easy to spot such leaders, because they are always authoritarian, following hardline policies. They try to subvert democracy, to reduce the freedom of the press and clamp down on dissent. They are obsessed with national prestige, and often persecute minority groups. And they are always corrupt and lacking in moral principles."
Apr 6th 2021
EXTRACT: "This has led some to claim that not just half, but perhaps nearly all advertising money is wasted, at least online. There are similar results outside of commerce. One review of field experiments in political campaigning argued “the best estimate of the effects of campaign contact and advertising on Americans’ candidates choices in general elections is zero”. Zero!"
Mar 30th 2021
EXTRACT: "The Father is an extraordinary film, from Florian Zeller’s 2012 play entitled Le Père and directed by Zeller. I’m here to tell you why it is a ‘must see’." EDITOR'S NOTE: The official trailer is attached to the review.
Mar 28th 2021
EXTRACT: "Picasso was 26 in 1907, when he completed the Demoiselles; de Kooning was 48 in 1952, when he finished Woman I.  The difference in their ages was not an accident, for studies of hundreds of painters have revealed a striking regularity - the conceptual painters who preconceive their paintings, from Raphael to Warhol, consistently make their greatest contributions earlier in their careers than experimental painters, from Rembrandt to Pollock, who paint directly, without preparatory studies."
Mar 26th 2021
EXTRACT: "Mental toughness levels are influenced by many different factors. While genetics are partly responsible, a person’s environment is also relevant. For example, both positive experiences while you’re young and mental toughness training programmes have been found to make people mentally tougher."
Mar 20th 2021

The city of Homs has been ravaged by war, leaving millions of people homeless an

Mar 20th 2021
EXTRACT: "There are two main rival models of ethics: one is based on rights, the other on duties. The rights-based model, which traces its philosophical origins to the work of John Locke in the 17th century, starts from the assumption that individuals have rights ....... According to this approach, duties are related to rights, but only in a subordinate role. My right to health implies a duty on my country to provide some healthcare services, to the best of its abilities. This is arguably the dominant interpretation when philosophers talk about rights, including human rights." ........ "Your right to get sick, or to risk getting sick, could imply a duty on others to look after you during your illness." ..... "The pre-eminence of rights in our moral compass has vindicated unacceptable levels of selfishness. It is imperative to undertake a fundamental duty not to get sick, and to do everything in our means to avoid causing others to get sick. Morally speaking, duties should come first and should not be subordinated to rights." ..... "Putting duties before rights is not a new, revolutionary idea. In fact it is one of the oldest rules in the book of ethics. Primum non nocere, or first do no harm, is the core principle in the Hippocratic Oath historically taken by doctors, widely attributed to the ancient Greek philosopher and physician Hippocrates. It is also a fundamental principle in the moral philosophy of the Roman statesman Marcus Tullius Cicero, who in De Officiis (On Duties) argues that the first task of justice is to prevent men and women from causing harm to others."
Mar 18th 2021
EXTRACT: "Several studies have recently compared the difference between antibodies produced straight after a coronavirus infection and those that can be detected six months later. The findings have been both impressive and reassuring. Although there are fewer coronavirus-specific antibodies detectable in the blood six months after infection, the antibodies that remain have undergone significant changes. …….. the “mature” antibodies were better at recognising the variants."
Mar 15th 2021
EXTRACT: "Like Shakespeare, Goya sees evil as something existing in itself – indeed, the horror of evil arises precisely from its excess. It overflows and refuses to be contained by or integrated into our categories of reason or comprehension. By its very nature, evil refuses to remain within prescribed bounds – to remain fixed, say, within an economy where evil is counterbalanced by good. Evil is always excess of evil." ....... "Nowhere is this more evident than in war. Goya offers us a profound and sustained meditation on the nature of war ........ The image of a Napoleonic soldier gazing indifferently on a man who has been summarily hanged, probably by his own belt, expresses the tragedy of war – its dehumanization of both war’s victims and victors."
Mar 14th 2021
EXTRACT: "A blockchain company has bought a piece of Banksy artwork and burnt it. But instead of destroying the value of the art, they claim to have made it more valuable, because it was sold as a piece of blockchain art. The company behind the stunt, called Injective Protocol, bought the screen print from a New York gallery. They then live-streamed its burning on the Twitter account BurntBanksy. But why would anyone buy a piece of art just to burn it? Understanding the answer requires us to delve into the tricky world of blockchain or “NFT” art."
Mar 14th 2021
EXTRACT: "Exercise is good for your health at every age – and you can reap the benefits no matter how late in life you start. But our latest research has shown another benefit of being physically active throughout life. We found that in the US, people who were more physically active as teenagers and throughout adulthood had lower healthcare costs."
Mar 10th 2021
EXTRACT: "Although around one in 14 people over 65 have Alzheimer’s disease, there’s still no cure, and no way to prevent the disease from progressing. But a recent study may bring us one step closer to preventing Alzheimer’s. The trial, which was conducted on animals, has found a specific molecule can prevent the buildup of a toxic protein known to cause Alzheimer’s in the brain."
Feb 24th 2021
EXTRACT: "The art historian George Kubler observed that scholars in the humanities “pretend to despise measurement because of its ‘scientific’ nature.” As if to illustrate his point Robert Storr, former dean of Yale’s School of Art, declared that artistic success is “completely unquantifiable.” In fact, however, artistic success can be quantified, in several ways. One of these is based on the analysis of texts produced by art scholars, and this measure can give us a systematic understanding of how changes in recent art have produced changes in the canon of art history."
Feb 24th 2021
EXTRACT: "The most politically sensitive option we looked at was the virus escaping from a laboratory. We concluded this was extremely unlikely."
Feb 16th 2021
EXTRACT: ".... these men were completely unaware that they had put their lives in the hands of doctors who not only had no intention of healing them but were committed to observing them until the final autopsy – since it was believed that an autopsy alone could scientifically confirm the study’s findings. As one researcher wrote in a 1933 letter to a colleague, “As I see, we have no further interest in these patients until they die.” ...... The unquestionable ethical failure of Tuskegee is one with which we must grapple, and of which we must never lose sight, lest we allow such moral disasters to repeat themselves. "