Walking (video)
One Step at a Time. The earliest humans climbed trees and walked on the ground. This flexibility helped them get around in diverse habitats and cope with changing climates.
Silhouette of Sahelanthropustchandensis. Image courtesy of Karen Carr Studios From at least 6 to 3 million years ago, early humans combined apelike and humanlike ways of moving around. Fossil bones like the ones you see here record a gradual transition from climbing trees to walking upright on a regular basis.
7–6 million years ago
Sahelanthropusmayhavewalked on two legs.
Becoming bipedal By 6 million years ago
The oldest evidence for walking on two legs comes from one of the earliesthumansknown, Sahelanthropus. Walking upright may have helped this species survive in the diverse habitats near where it lived—including forests and grasslands.
Leg support 6 million years ago
Silhouette of Orrorintugenensisforfemur. Image courtesy of Karen Carr Studio. The upper part of this thigh bone is similar in size to those of other large apes. But the angled part more closely resembles that of modern humans. It formed a strong bridge with the hip to support the body’sweight, suggestingOrrorintugenensiswalkedupright.
Strong knee 4.1 million years ago
Every time you take a step, you briefly stand on one leg—putting stress on your leg bones. The wide area of bone just below this the knee joint in Australopithecusanamensisis a result of that stress. It provides strong evidence that this individual walked upright.
Mostly bipedal By 4 million years ago
Silhouette of AustralopithicusafarensiswithvertebraeFossils from around this time period come from early human species that lived near open areas and dense woods. Their bodies had evolved in ways that enabled them to walk upright most of the time, but still climb trees. As a result, they could take advantage of both habitats.
Curved spine 2.5 million years ago
The curve of your lower back absorbs shock when you walk. It is uniquely human. You can see a similar curve in the spine of this earlyhuman, Australopithecusafricanus, whowalkedupright in a way very similar to modern humans.
Hip support 1.95 million years ago
The size and broad shape of the hip bones of Homo erectus are similar to a modern human’s, showing that this early human species had given up climbing for walking.
Fully bipedal By 1.9 million years ago
Silhouette of Homo erectus pelvis. Image courtesy of Karen Carr Studios The pelvis and thigh bones (outline to right) of Homo erectus are similar to modern humans, and show that this early human was able to walk long distances. That ability was a big advantage during this time period. East Africa’s environments were fluctuating widely between moist and dry, and open grasslands were beginning to spread.
Long leg 1.89 million years ago
The long thigh bones of Homo erectus enabled its owner to take long strides and therefore to walk farther and faster than earlier humans.
Compare a Chimp with an Early and Modern Human
Modern chimpanzees occasionally walk upright, but their skeletons are not adapted for regular walking on two legs. Early humans evolved skeletons that supported their bodies in an upright position. Modern humans have bodies adapted for walking and running long distances on two legs.
Skull
Drawings of skulls of a chimpanzee (left), early human (middle), and modern human (right). Image courtesy of Karen Carr Studios The spine of a chimpanzee connects with the skull at the back, holding the head at an angle.
The spine of early humans connected with the skull underneath, stabilizing the head when walking upright.
Your spine connects with your skull underneath and near the center, holding your head firmly upright.
Upper Leg Bone
Drawings of upper leg bones of a chimpanzee (left), early human (middle), and modern human (right). Image courtesy of Karen Carr Studios Because the connection between the upper thigh and hip bones is short in chimpanzees, the hip muscles cannot contract effectively to provide support for upright walking.
The connection between the upper thigh and hip bones was longer in early humans than in chimpanzees, and its base thicker. The hip muscles could provide support for walking.
The connection between your upper leg and hip bones is long. Its base is strong and able to withstand the stresses of walking and running.
Lower Knee
Drawings of lower knee bones of a chimpanzee (right), early human (middle), and modern human (left). Image courtesy of Karen Carr Studios The chimpanzee knee joint is lightly built, so chimpanzees cannot rest their weight on one leg at a time to walk for long periods.
The early human knee joint was strong, enabling this early human to regularly support its weight on one leg at a time during walking.
Strong knee joints help support your body’s weight on one leg at a time while walking long distances.
Benefits and Costs of Walking
Scene illustrating a few of the benefits of upright walking. Image courtesy of Karen Carr Studios
Benefits
As environments changed, walking on two legs helped early humans survive by:
- making it easier to pick fruits and other food from low-lying branches;
- freeing hands for carrying food, tools, or babies;
- enabling early humans to appear larger and more intimidating;
- helping early humans cover wide, open landscapes quickly and efficiently.
Silhouette of a modern human with back pain Costs
Does your back ever hurt?
Back pain and other skeletal problems are relatively common in modern humans, an unfortunate side effect of walking upright. Distributing all our weight on just two limbs can have painful consequences, like lower back pain, slipped disks, arthritis in hips and knees, and collapsed foot arches.
Try it!
- Press your fingers beneath the top bones of both of your hips.
- Now stand on one leg at a time.
- Can you feel the muscles contract?
These are the muscles that support your body during walking. They attach to the areas that curve inward above the hip socket
New Tools, New Foods(video)
Stone core and flakefromLokalalei, Kenya, about 2.3 million years old
Dawn of technology By 2.6 million years ago
Early humans in East Africausedhammerstonesto strike stone cores and produce sharp flakes. For more than 2 million years, early humans used these tools to cut, pound, crush, and access new foods—including meat from large animals.
How Do We Know This Zebra Was Food?
Scanning electron micrograph image of cut marks on fossil bone Stone tool marks on this zebra bone look like those made during butchery experiments. Scientists have made experimental stone tools and used them to butcher modern animals. There is a strong similarity between the marks their tools made and the marks on fossil animal bones, indicating that early humans used stone tools to butcher animals by at least 2.6 million years ago.
Handaxescame in handyBeginning 1.7 million years ago
Around this time, toolmakers began to strike huge flakes off stone cores. They shaped the largeflakesintohandaxesbystrikingsmaller flakes all around the edges. These multipurpose tools dominated early human technology for more than a million years. Ancienthandaxeshavebeenfound in Africa, Asia, and Europe. Learn more about them and other Early Stone Age tools.
HandaxeMakers Cope with Catastrophe
Handaxefrom Bose, China, about 803,000 years old. Smithsonian scientists and their Chinese colleaguesfoundthesehandaxes in thesame sediment layer with tektites, small rocks that formed during a meteor impact 803,000 years ago.
Sincethehandaxes and tektiteswere in the same layer, both are the same age. Early humans must have moved into the area right after the impact. They may havemadethehandaxesfromrocksthat were exposed when forests burned.
A huge meteor impact occurred in the atmosphere near China 803,000 years ago and the shock caused earth rocks to melt and explode, forming tektites. Widespread forest fires followed. Shortly after, humans moved into the barren landscape and scavenged for resources.
What’s cooking?By 790,000 years ago
Control of fire provided a new tool with several uses—including cooking, which led to a fundamental change in the early human diet. Cooking released nutrients in foods and made them easier to digest. It also rid some plants of poisons.
The earliest hearths are at least 790,000 years old. Some researchers think cooking may reach back more than 1.5 million years.
Woodenthrustingspear, Schöningen, Germany, about 400,000 years old. Hunting Large Animals
By at least 500,000 years ago, early humans were making wooden spears and using them to kill large animals.
Early humans butchered large animals as long as 2.6 million years ago. But they may have scavenged the kills from lions and other predators. The early humans who made this spear were hunting large animals, probably on a regular basis.
Reducing the risk
Hunting large animals was a risky business. Long spears like this one were thrust into an animal, enabling our ancestors to hunt from a somewhat safer distance than was possible with earlier weapons. Three wooden spears like the 400,000-year-old one illustrated here werefound at Schöningen, Germany, alongwith stone tools and the butchered remains of more than 10 horses.
Oldest evidence of hunting
Horse shoulder blade orscapulafromBoxgrove, England, about 500,000 years old The semicircular wound on this fragment of a horse shoulder blade was made by a weapon such as a spear, indicating it was killed by early humans. Other horse bones from the same site have butchery marks from stone tools.
Explosion of technologyBy 100,000 years ago
Eventually new kinds of toolsreplacedstonehandaxes. Some were small or made of several parts. Some were made of bone, ivory, or antler. Over the past 100,000 years, as modern humans spread around the world, the pace of technological change accelerated—leading to today’s extraordinary diversity of specialized tools.
BoneneedlesfromXiaogushan, Liaoning Province, China, about 30,000–23,000 years old Making clothing
Awls and perforators were probably invented in Africa and carried to colder climates, where they were used to pierce holes in clothing. Later, humans used bone and ivory needles to sew warm, closely fitted garments.
Carving and shaping
Burins are specializedstone flakes with sharp, chisel-like tips. Humans used them to work bone, antler, ivory, and wood and to carve designs and images on the surfaces of these materials.
Fishing
More than 70,000 years ago, humans in Central Africa used some of the earliest barbed points to spear huge prehistoric catfish weighing as much as 68 kg (150 lbs.), enough to feed 80 people for two days. Later, humans used harpoons to hunt large, fast marine mammals.
Hunting fast and dangerous prey
Spear-throwers provided leverage for hurling spears and darts greater distances with more speed and accuracy and with less chance of injury from prey. Stone or bone points, attached to spears or darts, enabled humans to exploit fast-moving prey like birds and large, dangerous prey like mammoths.
Humans began making pottery for storage purposes Storing things
Early humans may have made bags from skin long ago. By around 26,000 years ago, they were weaving plant fibers to make cords and perhaps baskets. About 20,000 years ago, in China, they began making pottery.
Chimps Make Tools, Too
Chimpanzees in Guinea used this stoneanvil and hammerstoneto crack open oil palm nuts, an energy-rich food. Nut cracking is one of the most sophisticated examples of chimpanzee tool use.(Specimen courtesy of ProfessorTetsuroMatsuzawa, KyotoUniversity Primate Research Institute, Kyoto, Japan)
Chimpanzeestoneanvil, hammerstonewithpalmnuts, ant-dipping tool, and spear Researchers in Senegal observed a chimpanzee sharpen this stick and use it to spear bush babies sleeping inside tree hollows—the first time chimpanzees were observed using tools to hunt. (Specimen courtesy of Dr. JillPruetz, Iowa StateUniversity, Iowa)
Chimpanzees in Guinea use specially prepared sticks like this to “fish” for ants, a high-protein food. They make holes in the side of a nest, insert the stick, and pull it out—covered with ants. (Specimen courtesy of Dr. KathelijneKoops and Dr. William McGrew, Cambridge University, England)
Benefits and Costs of Eating Meat
Illustrations of the benefits and costs of eating meat. Benefits
- Meat is a concentrated source of calories, protein, fat, and nutrients.
- Unlike many plants, most meat does not naturally contain toxic chemicals; so it was a relatively safe food for early humans.
- Meat is more quickly digested than plants and does not require large guts, saving energy for the brain and other organs.
Costs
- Hunting and scavenging large animals is risky and less predictable than gathering plants.
- Dangerous animals competed with early humans to obtain meat.
- Meat spoils quickly and can contain tapeworms and other parasites.
Changing Body Shapes and Sizes
Short bodies, long guts By 6 million years ago
Australopithecusafarensis, "Lucy", reconstructedskeletonThe earliest human species were small in size and usually had long arms and short legs. Their plant-based diet required a large digestive tract. A wide rib cage made room for the stomach, intestines, and other organs that break down food.
Tall bodies, short guts By 1.9 million years ago
As some early humans adapted to hot climates, they evolved narrow bodies that helped them stay cool. Long legs enabled them to travel longer distances. Eating meat and other foods that could be digested quickly led to a smaller digestive tract, making more energy available for tall bodies and large brains.
Compact bodies, short guts By 400,000 years ago
When early humans spread to colder climates, their body shapes evolved in ways that helped them stay warm. Short, wide bodies conservedheat. Early humans continued to depend on bothraw meat and cooked food, both of which couldbe efficiently processed in a short digestive tract.
Adapted to Hot Climates
This is the skeleton of an eight- to nine-year-oldHomo erectusboy who lived in East Africa about 1.6 million years ago. The pelvis shows he was male. His teeth tell his age. The boy was 1.6 m (5 ft 3 in) tall and weighed 48 kg (106 lb). If he had reached adulthood, he might have grown to nearly 1.85 m (6 ft). His tall, lean body was well adapted to hot, dry environments.
Narrow body
Notice the narrow pelvis of this species. The slender body shape helped keep the body cool, a big advantage in hot climates.
Long legs
The lower legs ofHomo erectuswere long, a feature that helped dissipate heat.
ThisHomo erectusboy lived in a hot, dry part of East Africa near an ancient marsh. His species was one of the first to spread beyond Africa, where it encountered a variety of environments.
Adapted to Cold Climates
Homo neanderthalensis; SkeletonAnaverage adult male Neanderthal stood only about 1.63 m (5 ft 4 in) tall. That’s not much taller than the skeleton of the eight- to nine-year-oldHomo erectusboy at right. Neanderthals of Europe, who had evolved by about 200,000 years ago, had to endure winter cold and even ice ages. Their short, broad bodies were well adapted to these challenging climates.
Broad body
A short, broad body shape helps to retain heat, which is useful in cold environments like those inhabited by Neanderthals.
Short legs
The lower leg bones in this Neanderthal skeleton are short compared to the upper leg bones, a feature that reduced heat loss. Compare them with those of theHomo erectusskeleton at left.
This reconstructed skeleton includes parts of two Neanderthal individuals from different times and places. One individual lived in western Europe 70,000 years ago. The other inhabited a cave inwhat is now Israel 60,000 years ago. Both sites were cold and dry, like most of the places where Neanderthals lived.
Bodies Adapted to Diverse Climates and Diets
As early humans spread to different environments, they evolved body shapes that helped them survive in hot and cold climates. Changing diets also led to changes in body shape.
The bodies of early humans were adapted to very active lifestyles. Their bones were thicker and stronger than ours. Starting about 50,000 years ago, as a result of less physically demanding lifestyles, humans evolved bones that were sleeker and weaker.
The Shrinking Human Gut
Early humans ate mainly plants, which take a longer time to digest than meat does. Long digestive tracts helped process this food.
Modern humans eat a diet that includes meat and cooked foods. We can process these foods efficiently with a shorter digestive tract.
Bigger Brains: Complex Brains for a Complex World