If you had to guess which tool-inventing ancestor Kubrick was going for in 2001, the safest bet would be Homo habilis, an Eve from roughly two million years ago. The face looks right. The behaviour fits early hominins, too. But tools aren’t unique to human ancestors. Our first tool users probably weren’t male. And our most important early invention probably wasn’t a weapon.

Far from some great symbol of human uniqueness, tool use is a convergent trait. Lots of intelligent problem solvers do it. They don’t even have to be mammals. The octopus uses tools with its tentacles, and it’s more closely related to a clam. Crows are avid tool users. They don’t even have hands.

The early hominins Kubrick portrays mostly ate grasses and bugs and fruits and tubers. Like other primates’ today, our ancestors’ first “tools” were probably rocks to break open nuts and sharp sticks to dig up some kind of ancient turnip. But Tool Triumphalists, like Kubrick, want the “Dawn of Man” to be the moment we started using tools as weapons to hunt animals and beat the crap out of each other. Fine, except for one more catch:

The first such weapons might well have been invented by a female. Right now, somewhere in Senegal, a chimp is hunting. She’s carrying a spear in one hand, made from a branch she snapped off a young tree, then took some time to prepare, pulling away all the leaves and offshoots, then chewing the end to a point with her powerful teeth. Her offspring clings to her back as she moves through the grass, hanging on to her long black fur. The kid’s been suckling for months now. The mother is lean and hungry. She’s looking for meat.

She’s learned that during the day bush babies – tiny, small-brained, big-eyed primates – tend to sleep in the hollows of trees. When she finds one, she stabs it with her stick. It wakes up, snarling and scratching. It’s too small and weak to be a mortal danger, but it could definitely wound her, and it might kill her offspring. Better to use a spear, which keeps it at a safe distance. She stabs the bush baby again and pulls it out of the tree only when she is sure that it’s dead.

When male chimps go hunting, they sometimes use spears, but their own bodies, bigger and stronger than the females’, are often weapon enough. Even if they’re injured as a result, no offspring will starve. From an evolutionary point of view, their injuries aren’t as costly, because males aren’t caretakers in chimp society. Generally speaking, innovation is something that weaker individuals do in order to overcome their relative disadvantage. As a primatologist in Kenya told me years ago, “Women do clever things because we have to.” She was talking about the female primates she’d observed being clever, but of course, she meant human women, too. From a scientific perspective, we female primates have more to gain – and more to lose. Most of us are smaller and weaker than the males. Given that our bodies are the ones that have to build, birth, and nurse babies, females also have more urgent food and safety needs than males. Simple tools were the easiest way to meet those needs. If the females in question were also good problem solvers – as all higher primates are – then it makes sense for females to be inventors, though that’s not the picture we usually paint of our ancestors.

Habilis – “handy man,” or in this case “handy woman” – lived in the grassy highlands of Tanzania between 2.8 and 1.5 million years ago. This Eve of tool making was a pinch over four feet tall, with long arms and strong legs and a brain around half the size of ours. We have no idea how furry she was, nor how fatty her breasts. But she was brainier than australopithecines like Lucy, and overall more like modern humans. She was an opportunistic eater, as we are, happily snacking on all sorts of food. Her jaws were strong, and her tooth enamel was thick, but she wasn’t in the habit of cracking hard nuts or tubers with them. Why would she when she had handy stone tools to break open (and break down) tougher fare?

In the places where we’ve found her fossils, we’ve also found hundreds of stone tools. In the Olduvai Gorge in Tanzania, archaeologists unearthed so many fossils and tools that the Oldowan tool technology was named after it. The Oldowan tools are one good reason we should think of Habilis as an Eve of tools. Though chimps use tools today, and Lucy also used primitive stone tools, the Oldowan style – adopted by later australopithecines and finally by Habilis and Homo erectus after her – was our first advanced tool technology. Our Eves deliberately shaped these large pebbles, carefully chipping off bits of a stone at just the right angle to make axes or scrapers or awls. In the beginning, she used stones that were already pretty close to the shape she wanted, mostly river cobbles, already smoothed by water. Eventually, she used rocks from miles away that, if hit just the right way, would flake into the specific shapes she was after. She could use one sort of tool to dig up tubers, another to pound their fibres into something edible, and yet another to chop up grasses and nuts.

Habilis used the flaked-off bits, too. Longer, thinner, sometimes delicate looking, but tough as nails, such flakes let her do more delicate tasks: carving meat away from sinew, peeling fat from the skin, delicately removing bitter parts of a plant to get at the good stuff. She used certain kinds of stones to cut off the juiciest steaks and others to break open bones to get at the marrow, which she sucked still warm from the animal.

If she could get to an animal that was still warm, that is. While Habilis loved a hot cut of meat, she probably didn’t do much big-game hunting. Most of the animal bones scientists have found near her fossils and tools are from the beasts’ extremities. She was likely a scavenger: a thief like a baboon or a hyena, but much less dangerous. If some big predator had made a kill, she’d probably stay hidden until it had finished feeding, then run in to steal part of the carcass. Maybe she’d use her stone axe to hack off the lower part of a leg and then pick it up and run like hell. Habilis was by no means the top of the food chain. Like many hominins, she was often prey.

So her stone tools weren’t exactly triumphant. No alien light shone in her eyes. Like the mother chimp hunting with a spear in Senegal, Habilis was simply a very smart primate using everything she could to survive. She walked through the tall grass in fear, clutching a rock axe and whatever bit of stolen meat she could find, baby in tow or even in arms.

Tool use is the first trait in this book that’s purely a set of behaviours – not an organ, not neurological hard wiring, but something our Eves used their cognitive and physical abilities to do in order to change their relationship with the world around them. Put it this way: paleo-archaeologists don’t really care about rocks; they care about what rocks can tell us about the lives of the creatures who used and shaped them. Without a hungry person nearby, a fork is just a stick with some pointy bits – tool use, in other words, is about the relationship between the object, its intelligent user, and the world in which both are situated. The study of ancient tools is always the study of ancient behaviour. And for an evolutionary biologist, thinking about hominin tool use is a way of tracing changes in the habits and capabilities of all those pro-social, problem-solving hominin brains along humanity’s ancestral line. Brains don’t become fossils. But the artefacts of tool-using behaviour can and do – particularly when they’re made of rock and usefully situated near the fossilised bones of their makers, and even more so if they’re near some obviously butchered bones. The reason any of us should care about Oldowan tools, in other words, is that they might be able to tell us something about the minds and social lives of our ancestors: how they made stuff, how they collaborated, how they overcame adversity.

That last one is particularly important. For every species that does it, tool use is fundamentally about solving problems. At the dawn of humanity, deep in the dry savanna, Habilis had a ton of problems. She had hunger. She had predators. Every morning she wrestled with the angels of death and disease and despair. She used her stone tools to help solve many of these problems.

But her biggest problem wasn’t something she could throw a rock at. It was part and parcel of her own body. Evolution had dealt her a lousy hand.

Excerpted with permission from Eve: How The Female Body Drove 200 Million Years of Human Evolution, Cat Bohannon, Hutchinson Heinemann.