Anthropology answers the question “what does it mean to be human?” by studying the full arc of our species, from the earliest fossil ancestors to living cultures today. Rather than offering a single definition, the field identifies a constellation of traits that, taken together, distinguish us from every other species on Earth: walking upright, building unusually large brains, creating symbols, teaching each other, making tools, and developing language. No single trait is the answer. It’s the combination, and the way each trait fed the others over millions of years, that made us human.
Walking Upright Came First
If you expected the story to start with big brains, anthropology says otherwise. The earliest hominin fossils, dating to between seven and four million years ago in Africa, already show signs of bipedalism. These ancestors walked on two legs while their brains were still roughly the size of a chimpanzee’s. Freeing the hands from locomotion opened the door to carrying food, using tools, and eventually gesturing to communicate. Bipedalism wasn’t a response to intelligence. It was a precondition for it.
Brains That Tripled in Size
The human brain is the most energy-hungry organ relative to body size in the animal kingdom, and its growth over the last two million years is one of the defining stories of our lineage. Early members of the genus Homo, sometimes called Homo habilis, had brain volumes averaging around 609 milliliters. Homo erectus, appearing roughly 1.8 million years ago, jumped to an average of about 959 milliliters. By the time anatomically modern humans appeared at least 300,000 years ago (the oldest fossils come from Jebel Irhoud cave in Morocco), brain volume had reached around 1,500 milliliters in late Pleistocene populations.
What drove this expansion? One compelling line of evidence points to environmental stress. Research comparing brain size across thousands of years of climate data found that colder, more arid periods correspond to larger brains, not the warm, food-rich periods you might expect. Pleistocene humans averaged brain masses about 11% larger than Holocene (post-ice-age) humans. The pattern suggests that unpredictable environments rewarded the kind of flexible problem-solving a bigger brain provides: planning ahead, innovating new tools, cooperating in groups to survive harsh conditions.
Symbolic Thought and Art
Many animals are clever. Crows use tools, dolphins recognize themselves in mirrors, and chimpanzees plan for future events. But no other species creates symbols, abstract marks or objects that stand for something beyond themselves. This capacity is what anthropologists consider a threshold for modern human cognition.
The earliest solid evidence comes from southern Africa. At Blombos Cave, engraved pieces of ochre date back roughly 100,000 years, with the tradition of mark-making at that single site spanning more than 30,000 years. At Diepkloof Rock Shelter, geometric patterns scratched into ostrich eggshell fragments extend from about 109,000 to 52,000 years ago. These weren’t random scratches. Analysis of the patterns shows they were deliberately structured and repeated, hallmarks of symbolic communication.
Rock art pushed the timeline even further. Hand stencils discovered on the island of Sulawesi in Indonesia have been dated to at least 67,800 years ago, making them the oldest known examples of cave art attributed to our species. That these stencils appear not in Africa or Europe but in Southeast Asia tells us that symbolic behavior was not a local invention. It traveled with humans, or arose independently in widely separated populations, suggesting it is deeply embedded in what our brains do.
Language: Biology Meets Culture
Language is often cited as the single most distinctive human attribute. Other species communicate, and some, like songbirds, even learn their vocalizations by imitation. But no animal communication system combines a limited set of sounds and rules to generate an essentially unlimited range of meanings. That combinatorial power, what linguists call syntax and semantics together, is unique to humans.
The biological roots run deep. A gene called FOXP2 was the first identified link between genetics and speech ability. When it’s disrupted, people struggle severely with the coordinated mouth and tongue movements needed for fluent speech. Compared to chimpanzees, the human version of FOXP2 carries two specific amino acid changes that arose after our lineage split from our common ancestor. When researchers introduced these human-specific changes into mice, the animals showed measurable differences in learning, behavior, and the physical structure of brain cells involved in motor circuits. A regulatory change in the same gene is found in nearly all modern humans but is absent in Neanderthals and Denisovans, suggesting that fine-tuning of this gene contributed to the particular form of language we use today.
But genes only build the hardware. Language itself is cultural. Children don’t inherit English or Swahili through DNA. They absorb whatever language surrounds them, and they do so with a speed and ease no other primate can match. This intersection of biological capacity and cultural transmission is a recurring theme in anthropology’s answer to what makes us human.
Tools and Cumulative Technology
Stone tools are the most durable record of human ingenuity, and their progression tells a story of accelerating complexity. The Oldowan tradition, simple cobbles with a few flakes knocked off to create a cutting edge, dates to about 1.8 million years ago and is associated with early Homo species. Around 1.76 million years ago, the Acheulean tradition appeared, producing carefully shaped handaxes that required planning the final form before striking the first blow. This technology lasted for over 1.5 million years and spread across Africa, Europe, and Asia, making it the longest-lasting tool tradition in all of prehistory.
What changed with modern humans was not just the tools themselves but the rate of change. Anthropologists use the term “cumulative culture” to describe how human societies build on previous innovations rather than reinventing them each generation. A chimpanzee that learns to use a stick to fish for termites doesn’t improve on the technique and pass the improved version to its offspring. Humans do this constantly. Each generation inherits the knowledge of the last, tweaks it, and hands down something better. This ratchet effect is why technology that barely changed for a million years eventually gave way to bone needles, boats, and, eventually, computers.
Shared Intentionality and Cooperation
The engine behind cumulative culture is not raw intelligence alone. It’s a social capacity that anthropologists call shared intentionality: the ability to form a common goal with another person, understand each other’s roles, and coordinate action toward that goal. You experience this every time you cook a meal with someone, play a team sport, or even have a conversation. Each participant holds a mental model of what the other knows and intends.
Other great apes cooperate, but their cooperation is largely parallel. Two chimpanzees may chase the same prey, but research suggests they are each pursuing their own goal rather than executing a shared plan with defined roles. Humans, by contrast, develop collaborative skills early. Toddlers point at things to share attention, not just to request objects. This seemingly simple act, directing someone else’s gaze to create a shared experience, is something no other primate does spontaneously.
Over the last several hundred thousand years, increasingly sophisticated forms of shared intentionality gave rise to teaching through cooperative communication, collaborative innovation, and eventually social norms that stabilize knowledge across generations. Coordinating around shared reasons for doing things powered the rapid innovation especially characteristic of the last tens of thousands of years of human history.
Genetics: Similar Yet Profoundly Different
The human genome and the chimpanzee genome are frequently described as roughly 98 to 99% identical in their protein-coding regions. That number is real but can be misleading. It measures only the parts of the two genomes that align neatly, the stretches where you can lay one sequence next to the other and compare letter by letter. When you account for inserted, deleted, or duplicated segments that don’t align at all, overall similarity drops to somewhere between 85 and 90%, depending on the method.
The differences that matter most for “being human” are often not in the genes themselves but in the switches that control when and where genes are active. Small regulatory changes can alter brain development, facial structure, or the timing of growth in ways that have outsized effects. The FOXP2 example illustrates this perfectly: the protein-coding changes matter, but a regulatory change found only in modern humans may have been equally important for shaping language ability. Humanness, at the genetic level, is less about having unique genes and more about running a very similar genetic program with subtle but consequential differences in timing and intensity.
Four Fields, One Question
Anthropology approaches the question of humanness from four interconnected directions. Biological anthropology studies fossils, genetics, and anatomy to trace how our bodies and brains evolved. Archaeology examines the material record, tools, art, and structures, to understand how behavior changed over time. Linguistic anthropology investigates how language shapes thought and social life. Cultural anthropology studies living human societies to understand the enormous range of ways people organize families, economies, beliefs, and identities.
No single field can answer the question alone. The fossil record shows when brains expanded, but only archaeology reveals what those brains were doing. Genetics explains the biological capacity for language, but only linguistic and cultural anthropology can show how that capacity plays out in thousands of distinct languages and meaning systems. Being human, from an anthropological perspective, is not a checklist of traits. It is an ongoing process in which biology, environment, and culture continuously shape each other, producing a species that is, so far, the only one capable of asking what it means to exist.