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Human Evolution

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Primate Evolution

What is a "cave man"?

What if you were to wake up with a group of Neanderthals? They were close relatives to modern humans. Still you might find them to be a bit different from your usual friends.

Human Evolution

Humans evolved during the later Cenozoic. New fossil discoveries continue to alter the details of what we know about human evolution. The major evolutionary events are well understood though.

Primate Ancestors

Primates are monkeys, apes, and humans.  Common characteristics of these are that they have opposable thumbs, binocular vision, and flexible shoulders.  Primates are broken into two major groups: nocturnal and higher primates.  Nocturnal primates have large eyes, and excellent hearing.  Examples are prosimians, lemurs, and tarsiers.  Higher primates include monkeys, apes, and humans. 

Primate classification starts with the hominids.  Hominids are human like that ate both meat and vegetables and walked upright on two feet.  They lived about 4-6 million years ago.  They have common characteristics with gorillas, orangutans, and chimpanzees, but with a larger brain cavity.  Humans evolved from primates . Humans are part of the apes, but we did not evolve from apes , which also include chimpanzees and gorillas. Apes and humans have a primate common ancestor.

Hominids

Animals of the genus, Ardipithecus lived roughly 4 to 6 million years ago. These animals had brains roughly the size of a female chimp. Although they lived in trees, they were bipedal. That is, they could stand on two feet. What are the advantages to being bipedal? An organism that can stand up can see farther. This is important if you live in a grassland. A bipedal organism uses its hands and arms for hunting.

One type of hominid is the Australopithecus.  This ape like creature had a small brain cavity, but humanlike jaw and teeth.  It was one of the earliest hominids.  Australopithecus means “Southern Ape.”  In the 1920s, Raymond Dart first discovered a fossil skull of the Australopithecus in South Africa.  Later in 1974 Donald Johansen discovered Lucy, an Australopithecus that was between 2.9 to 3.4 million years old.  She had a small brain, and walked upright.  Australopithecus afarensis lived between 3.9 and 2.9 million years ago ( Figure below ). These animals were completely bipedal. Their brains grew rapidly across the generations.

Model of Australopithecus afarensis

Australopithecus afarensis is a human ancestor that lived about 3 million years ago.

The Homo erectus is the third type of hominid found.  It has a larger brain than the Homo habilis , and is also similar to humans.  The Homo erectus lived 1.6 million years ago.  This species migrated out of Africa 1 million years ago.


Homo

The genus Homo , which has modern humans as its only living species, appeared about 2.5 million years ago. These human-like primates developed the first stone tools. The Homo habilis was named “the handy man” because it was found with simple stone tools.  Louis, Mary, and Richard Leakey found this fossil in East Africa.  It was more similar to present day humans, and lived 1.5 to 2 million years ago. Homo erectus evolved in Africa about 1.8 million years ago.   II has a larger brain than the Homo habilis , and is also similar to humans.  The Homo erectus migrated out of Africa 1 million years ago. Fossils of these animals show a much more human-like body structure. This allowed them to travel long distances to hunt. Cultures began and evolved.

Homo sapiens

Homo sapiens is our species. We originated about 200,000 years ago in Africa. Evidence of a spiritual life appears about 32,000 years ago. The evidence includes stone figurines that probably have religious significance ( Figure below ).

Stone figurines created by early Homo sapiens

Stone figurines likely indicate a spiritual life.

Homo sapien means “wise humans.”  They evolved about 300 000 years ago and probably lived during the same time as Neanderthals and Cro-Magnon man. 

The Neanderthal had short heavy bodies with thick massive bones, small chins, and heavy brow ridges.  They lived in family groups in caves and hunted mammoths, deer, and other large animals.  The Neanderthal evolved about 125 000 years ago and disappeared about 35 000 years ago. 

Cro-Magnon men lived in caves, were spear carriers, made stone carvings, and almost identical to modern humans.  They cared for their elderly, and buried their dead.  This species was about 1.6-1.7 meters tall.  The Cro-Magnon evolved about 40 000 to 10 000 years ago and were found in Europe, Asia, and Australia. 

Homo sapien-sapien is what species we are. The other subspecies within this grouping is Homo sapien Neandertales (the Neandertals). Many people classify Neandertals as their own specie.

 

Vocabulary

  • ape : The group of primates that includes gibbons, orangutans, gorillas, chimpanzees and humans.
  • Homo : The genus of great apes that includes Homo sapiens (modern humans) and extinct human ancestors, such as Homo neanderthalensis .
  • primate : The group of mammals that includes lemurs, monkeys and apes.

Summary

  • Australopithecus afarensis was completely bipedal and had a growing brain.
  • Homo erectus evolved 1.8 million years ago. These organisms left behind signs of an early culture.
  • Our species is Homo sapiens . We evolved 200,000 years ago in Africa, and spread.

Practice

Use the resource below to answer the questions that follow.

  1. What was Darwin's little heresy?
  2. What was "the missing link" thought to be?
  3. Why weren't the Neanderthal and Homo erectus fossils that were found thought to be the missing link?
  4. What was the problem with the fossil evidence from Africa? What was found to be incorrect and why?
  5. Why is it difficult to identify whether an apelike fossil is a direct human ancestor or not?
  6. List the traits that separate humans from apes.
  7. Why did the DNA of humans and apes seem as if they did not share a common evolutionary ancestor? How was that resolved?
  8. When was the last common ancestor between chimps and humans? When was the last between Neanderthal and humans?
  9. What is the scientific evidence for the creation of humans by a deity?

Review

  1. Why is being bipedal a good thing?
  2. What is the evidence that humans evolved from apes?
  3. Why are the ice ages important for the spread of modern humans?

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