Human evolution

Homo sapiens is a special kind of primate, part of the hominid family that also includes the great apes. Over millions of years, humans developed important traits such as walking on two legs, using their hands skillfully, and speaking complex languages. Modern humans interbred with older human types, showing that human evolution did not happen in a straight line but more like a web.

Primates began to diverge from other mammals about million years ago, during a time called the Late Cretaceous period. Over time, different groups of primates evolved, leading to apes and eventually to hominids, which include humans. The lineage that led to humans split from chimpanzees and bonobos several million years ago. The genus Homo, to which modern humans belong, first appeared over two million years ago, with anatomically modern humans showing up in Africa around 300,000 years ago.

Before Homo

Main article: Australopithecus

For evolutionary history before primates, see Evolution of mammals, History of life, and Timeline of human evolution.

The story of primates began long ago, about 65 million years back. Early primates lived in places like North America, China, and Africa. Over many years, these primates changed and evolved into many different kinds. Some moved to Africa and later became the apes and humans we know today.

One early primate was Plesiadapis, found in North America, and another was Archicebus from China. Primates eventually spread around the world. Scientists think the ancestors of humans and African apes may have lived in Europe or Western Asia before moving to Africa.

In Africa, primates evolved into many groups, such as lemurs, lorises, and anthropoids, which include monkeys and apes. The earliest known catarrhine, a kind of early ape, is Kamoyapithecus, found in Kenya and living about 24 million years ago.

About 4 million years ago, a group of primates called Australopithecus appeared in Africa. These early human relatives walked on two legs and lived across the continent until around 2 million years ago. There were different kinds of australopiths, such as A. anamensis, A. afarensis, and A. africanus. Some scientists think other species, like P. robustus and P. boisei, might be part of a different group called Paranthropus.

Evolution of genus Homo

Main article: Homo

The earliest known member of the genus Homo is the Ledi jaw. It lived between 2.75 and 2.8 million years ago. This discovery shows early humans may have used stone tools. Around this time, the human SRGAP2 gene changed, which may have helped the brain develop faster.

Over the next million years, brain size increased quickly. Homo erectus and Homo ergaster were among the first to use fire and complex tools. They were also the first to leave Africa, spreading across Africa, Asia, and Europe.

Modern humans, Homo sapiens, likely evolved in Africa from earlier human species like H. heidelbergensis. Around 50,000 to 100,000 years ago, they migrated out of Africa. They met and mixed with other human species like Neanderthals and Denisovans. This left a small amount of their DNA in modern humans outside of Africa.

Homo sapiens is the only surviving species in the genus Homo. Some extinct Homo species may have been ancestors of modern humans, while others were likely distant cousins. Scientists are still learning about how these early human species are related.

Anatomical changes

Since Homo sapiens separated from its last common ancestor shared with chimpanzees, human evolution has included many important changes. These changes are in how the body looks, grows, works, behaves, and lives.

Walking on two legs, or bipedalism, was a major change. Early humans who could walk on two legs first appeared about 6 to 7 million years ago. Bipedalism freed the hands to carry things and allowed better balance and vision. It also changed the shape of the skeleton, including the legs, pelvis, and spine.

Another big change was the increase in brain size. Modern humans have a brain about three times larger than that of a chimpanzee. This growth allowed for better problem-solving, learning, and language. The brain kept growing after birth, which meant human children needed more care and time to develop. This led to longer periods of dependency on parents and changes in how families and societies worked.

Use of tools

Using tools shows intelligence and may have helped shape human evolution. Tools let early humans get more energy from food. Using tools may have pushed early humans to grow bigger brains, which need a lot of energy.

The oldest known tools are simple stone pieces found in Kenya. They are about 3.3 million years old. More advanced stone tools appeared in Ethiopia around 2.6 million years ago. These are called Oldowan tools. Early humans likely made and used these tools. A special feature in the human hand helps us grip and use tools better than other apes.

See also: Hunting hypothesis

Transition to behavioral modernity

Further information: Behavioral modernity

About 50,000 years ago, human culture started to change fast. People began using new tools, making jewelry, and creating art such as cave drawings. They learned clever ways to hunt animals and traveled to new places far from home. These changes show that early humans were becoming smarter and more creative.

Some scientists think these changes happened suddenly, like a big leap. Others believe they happened slowly over many thousands of years. Either way, this time was very important for how humans live and think today.

Recent and ongoing human evolution

Main article: Recent human evolution

Human populations are still changing over time. This happens because of natural selection and genetic changes. Today, humans are still adapting to new places and ways of living. For example, people who live high up in places like Tibet have genetic changes that help them breathe better in thin air.

Evolution also happens because of diseases and changes in food. Some people have genetic changes that protect them from malaria. Others can drink milk as adults because of changes in their genes. Cultural changes, like better healthcare and education, also affect how humans change. These changes influence things like when people have children and how our brains grow.

History of study

The study of human evolution started with early scientists like Carl Linnaeus. He grouped humans with other animals. Later, Charles Darwin wrote On the Origin of Species in 1859. This book helped people accept that humans came from earlier ape-like ancestors.

In the 1900s, scientists found important fossils. One was the Taung Child. It showed features that connect apes and humans. Another find was "Lucy," an early human ancestor from Ethiopia. These discoveries helped prove that Africa is where humans first evolved. Later, genetic research showed that modern humans began in Africa and then moved around the world. They also mixed with other ancient human groups.

Evidence

The evidence for human evolution comes from many areas of science. Fossils have been an important source, and since the 1970s, studying DNA has become very helpful too. By watching how living things grow and change, scientists learn about how all life, including humans, evolved.

Humans share close family ties with bonobos, chimpanzees, and gorillas. By comparing DNA, scientists found that human DNA is very similar to chimpanzee DNA. Genetic tools help estimate when different species separated from each other.

Fossils show the early steps of human evolution. Early human-like species lived millions of years ago. Later, more advanced species appeared and began making simple tools. Over time, the brain grew larger.

Modern humans, Homo sapiens, appeared in Africa around 300,000 years ago. As they moved around the world, they sometimes met other human species. Today, many people carry a small amount of DNA from these ancient meetings.

Species list

See also:

This list shows different kinds of humans in chronological order. Some names you may have heard of, while others are still being studied, especially within the genus Homo. For more details, you can read the individual articles.