Millions of years of evolution can change the structure of a species considerably. Fossils indicate that over millions of years the process of natural selection gave rise to modern humans. Charles Darwin proposed that humans, gorillas, and chimpanzees all evolved from a common ancestor. Although the fossil record of human origin is incomplete, many fossil finds suggest that Darwin's hypothesis is correct.
Fossil evidence indicates that a small insect-eating mammal resembling a shrew lived about 80 million years ago. This ancient mammal was the ancestor of the first primates, the mammalian group that includes prosimians, monkeys, apes, and humans. Evidence reveals that these first primates evolved about 50 to 60 million years ago.
According to fossil record, the group of modern primates that most closely resembles early primates is the prosimians. A prosimian is a member of a group that is mostly night-active primates that live in trees. These prosimians were common about 38 million years ago in North America, Europe, Asia, and Africa.
About 36 million years ago a revolution occurred in the way primates lived. Primates became diurnal. Unlike the prosimians, diurnal primates became active during the day and slept at night. This allowed them more opportunities to feed and better detect predators. These day-active primates are called monkeys.
Feeding mainly on fruits and leaves rather than insects, monkeys were among the first primates to have an opposable thumb that stands out at an angle from the other fingers and can be bent in at an angle in order to grip things. This greatly increased the level of skill in the hand.
Fossil evidence indicates that humans evolved from the same evolutionary group that gave rise to apes. Apes, which share a common ancestor with monkeys, first appeared about 30 million years ago. Apes have larger, more developed brains than monkeys and have no tails.
The members of the group that led to the evolution of humans are called hominids. Hominids are primates that can walk upright on two legs. They were fully bipedal, meaning they could walk fully upright on two legs. The second hominid characteristic was they had a much larger brain volume than that of the apes.
Scientists have found many fossil evidence of the species homo erectus. The first fossil of homo erectus was called Java man whose bones are thought to be 500,000 years old. Homo erectus was the direct ancestor of modern day human species, homo sapiens. The name homo sapiens is from the Latin homo, meaning 'man,' and sapiens, meaning 'wise.' These early humans are thought to have evolved first in Africa, and then migrated to Europe and Asia.
Early modern humans lived by hunting and had complex patterns of social organization and the use of sophisticated language. Humans have what no other animal is thought to have ever had-cultural evolution. Through culture we have found ways to change our environment to suit our needs, rather than changing ourselves in response to the environment. This allows humans to stand far above all other life forms and reign superior in the evolution process. It also brings exciting potential and enormous responsibility.
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