9-10: Human Evolution

The oldest fossils of hominids and Homo sapiens were found in what continent?

Africa

Large, Complex Brains

As early humans faced new environmental challenges and evolved bigger bodies, they evolved larger and more complex brains. Q: By comparing the three images above, which represents Homo sapiens, our species? A: The skull on the far right represents Homo sapiens. Notice it has the largest brain.

Which human buried their dead, even placing symbols or flowers with the bodies.

Both Neanderthal and Cro-Magnon

Which species was the first to exhibit body proportions similar to ours?

Homo erectus

What is the only hominid alive today?

Homo sapiens, or modern humans are alive today. The other members of the genus, Homo, are extinct.

Adaptive Human Body Shape

Human body shapes vary, but all humans have a sturdier pelvis and longer legs compared to apes, which have longer arms. As early humans spread to different environments, their body shapes changed to help them survive in hot and cold climates. Changing diets also led to changes in body shape. For example short, wide bodies, like the one pictured above, are adapted more to colder climates because they conserve heat better. Q: What do you think the bodies of the early humans in southern Africa were like? A: Considering the climate there is hot and dry, taller and leaner bodies are more adapted to this area.

Walked Upright

The earliest humans climbed trees and walked on the ground. The ability to walk upright on two feet is called bipedalism. Scientists can study the structure of the leg bones and the location of the foramen magnum to determine this characteristic. Q: How do you think this flexibility helped these early humans? A: It helped them get around in diverse habitats and cope with changing climate.

Which human characteristic do you think evolved first, large brain size or the use of symbols?

There is evidence that large brain size preceded the use of symbols. A larger brain allows for more intelligence. Language and the use of symbols requires more intelligence.

Compared to apes, what is a major difference that Lucy and other similar fossils exhibited that made them more human-like?

They appeared to walk upright.

Which hominid did Homo sapiens directly evolve from?

They came from Australopithecus afarensis.

Australopithecus

Various species of this early hominid, including Australopithecus afarensis, lived from 4.2-2 million years ago. Members had both ape-like and human characteristics with smaller brains and projecting lower jaws. They lived in Africa.

When did Homo sapiens first appear?

about 34,000 years ago

Which humans lived in shelters and used fire?

Both Neanderthal and Cro-Magnon

Which humans migrated out of Africa?

Both Neanderthal and Cro-Magnon

Which human had more advanced language capabilities and complex social organizations?

Cro-Magnon

Which human used more sophisticated tools made of horn and bone?

Cro-Magnon

What can dating and the fossil record tell us about the big picture of human evolution?

Dating of human fossils can tell us when certain milestones occurred, such as when we actually became human.

Early hominid fossils exhibited a physical characteristic that made them different from apes. What did they have?

Early hominids exhibited bipedalism.

Used Tools to Get Food

Early humans butchered large animals at least 2.6 million years ago. By at least 500,000 years ago, humans made wooden spears to hunt large animals. Q: What evidence exists to prove this characteristic? A: Cave paintings and tools found with human and animal remains are evidence.

Morphological Evidence

From a few teeth to complete skeletons, scientists have uncovered more than 6,000 individuals hominid fossils. These fossils enable researchers to study changes that occurred in brain and body size, locomotion, diet, and other aspects regarding the way of life for early human species. The image shows a skull of one of our distant relatives, Homo erectus. Other than the structure of the leg bones, scientists can tell if a hominid walked upright. They use the location of the foramen magnum (hole at the base of skull where spinal cord exits) to determine if the hominid walked more upright or more hunched over like an ape. The layers of rock that contain fossils can be dated by many different techniques. Some techniques can even directly estimate the age of the bones and teeth. Advances in dating have made the study of human evolution very exciting.

What continent did hominids originate on?

It is believed that early humans originated in Africa because the oldest hominid remains have been discovered there.

Why do you think our ancestors began to migrate out of Africa?

Many scientists believe that climate change led to food and water shortages. They went in search of "greener pastures."

Other Evidence

Millions of stone tools (like the ones pictured above), figurines, cave paintings, footprints, and other traces of humans in the prehistoric record tell about where and how early humans lived. This evidence also gives us clues as to when certain technological innovations were invented. Q: Aspects of the environment that early humans lived in can be determined by studying footprints. What types of human behaviors may be assumed by studying various footprints? A: If a group of footprints from different individuals are found, it is assumed this group lived in a social situation.

Homo sapiens

Modern humans replaced the European Neanderthals about 34,000 year ago. These first Homo sapiens are referred to as Cro-Magnons. Most scientists believe these modern, more sophisticated humans out-competed the Neanderthals for resources and drove them to extinction. However, some believe the Cro-Magnon and Neanderthals actually interbred, resulting in humans containing some Neanderthal DNA. Even though they are now extinct, Cro-Magnons had complex social organizations, modern language capabilities, and lived by hunting. These humans spread across Siberia to North America. By about 12,500 years ago, humans had reached all the way down to South America.

Which hominid species is our closest extinct relative?

Neanderthal

Which human is shorter, stockier, and more muscular?

Neanderthal

Both Neanderthal and Cro-Magnon

Neanderthals were stronger and stockier than Cro-Magnons with slightly smaller brains and a prominent brow ridge. They both used tools, language, fires, and buried their dead. Cro-Magnons were more sophisticated and are the same as modern humans.

Molecular Evidence

Recall that scientists are able to compare evidence of evolution at the molecular level. Our genetics provide evidence of how closely we are related to one another and to all other species. This evidence can indicate the prehistoric migrations of our species all over the world. By using molecular clocks, it can be determined that we are very closely related to apes and diverged into separate species from a common ancestor. Q: What do scientists compare at the molecular level to determine evolutionary relationships? A: The base sequences in DNA and amino acid sequences in proteins are used for comparisons.

Which species is designated as the first "human"?

Remember that humans belong in the genus Homo, so the first human to appear is Homo habilis.

Social Life

Sharing food, caring for infants, and building social networks helped our ancestors meet the daily challenges of their environments.

Use of Symbols

Symbols (shown in this ancient cave) changed the way humans lived and provided new ways to cope with an unpredictable world.

After comparing the two skulls, which skull do you think belongs to a Cro-Magnon?

The skull on the left is a Cro-Magnon, and the one on the right is a Neanderthal. The Cro-Magnon skull on the left is identical to a modern human skull. The Neanderthal skull is flatter on top, giving them a slightly smaller brain than ours.

Why did the Neanderthals evolve to have shorter and stockier bodies than other humans did?

They lived in Europe which had a colder climate.

Homo neanderthalensis

This early human is referred to as Neanderthal man. He lived in Europe 200,000 to 40,000 years ago. Neanderthals are our closest extinct human relative. They were stockier and shorter than us, but their brains were almost as large. They made and used sophisticated tools, used fire, lived in shelters, and buried the dead.

Homo erectus

This early human lived between 1.89 million and 143,000 years ago. Early African Homo erectus fossils (sometimes called Homo ergaster) possessed modern human-like body proportions with relatively elongated legs and shorter arms compared to the size of the torso. These features are considered adaptations to a life lived on the ground and the ability to run long distances. This species was the first to migrate out of Africa into Europe and Asia.

Homo habilis

This species, one of the earliest members of the genus Homo, lived 2.4-1.4 million years ago. It has a slightly larger brain case and smaller face and teeth than in Australopithecus or older hominid species. But it still retains some ape-like features, including long arms and a moderately protruding face. The name means "handy man," referring to its use of stone tools.

Neanderthals had a wide, stocky body. Why did they evolve to have this characteristic?

because they migrated to Europe with a colder climate

Clues about early human behavior can be determined by looking at what piece of evidence?

footprints

As early humans faced environmental changes and evolved larger bodies, what other human characteristic evolved?

larger, more complex brains