== Early Humans ==
This section will contain a brief history of early humans. This will not be elaborated on for two reasons- the first being much of this era is pre-speech so everything that we know is learned from archeological remains. The second being that this topic doesn't have a large role in the AP World History Exam.
All early ancestors of humans originated from Africa. Some species like the Australopithecus Afarensis went extinct there too. The migration of early humans towards other continents started with Homo Erectus about 2 million years ago. Homo Sapien, the modern human, migrated out about 100,000 years ago, spread across Asia about 60,000 years ago, with Australia and the Philippines following and last the Americas using the theorized Bering Strait land bridge.
=== Australopithecus Afarensis ===
Australopithecus afarensis is one of the most widely known early human species. Au. afarensis lived from about 4 million years ago and went extinct about 2 million years ago. Lucy, an Au. afarensis fossil, is one of the most famous early human skeletons. Discovered in 1971 in Ethiopia, Africa, it consists of several hundred fragments of bones that make up 40% of a female Au. afarensis body.
=== Homo Habilis ===
Homo Habilis, meaning handy man, marked the start of the Paleolithic Era and lived from about 2 million years to 1.5 million years ago. Homo Habilis is least like the modern Homo Sapien of the Homo genus. The first Homo Habilis fossils were found in East Africa. This species was one of the earliest users of stone tools which consisted of very simple tools such as a sharpened stone.
=== Homo Erectus ===
About 1.9 million years ago Homo Erectus, meaning upright human, emerged in Africa as a new species of early human. Homo Erectus better hunting skills and ability to create fire allowed them to migrate to colder regions such as Europe or Asia. Homo Erectus were contemporaries with Homo Habilis for several hundred years until their superior skills allowed them to replace Homo Habilis.
=== Neanderthal ===
Homo Neanderthalensis was an early human species that lived in Eurasia from about 200,000 to 30,000 years ago. Homo Neanderthalensis is similar to modern humans anatomy-wise. Although sometimes depicted as crude, archeologists have found that they used tools, controlled fire and even buried their dead. This would suggest the ability of complicated thinking and some idea of the afterlife.
== Modern Humans ==
=== Homo Sapiens ===
Homo Sapien is the modern human being. Some of the oldest fossils found date back to 160,000 years ago which proves that they did not come after the Neanderthals but were their contemporaries. Homo Sapiens originated in Africa.
Between 150,000 and 40,000 years ago, homo sapiens started to exhibit behavioral modernity. Archaeologists observe that after this change, there is evidence of more complex behavior, especially because their tools become more varied and more intricately made. There is much debate over whether this change was gradual or whether it occurred in a period as short as 10,000 years. Until 11,500 years ago, they lived as hunter-gatherers, as with earlier human species.
=== Spread ===
Compared to other species of human, homo sapiens were more adaptable to different climates. About 70,000–50,000 years ago, they spread out of Africa to a greater number of regions. Humans that exhibited behavioral modernity were able to spread to more climates than previous human species.
The spread of modern humans was also marked by the extinction of earlier human species like the Neanderthals and Denisovans. Though some of the latter may have died due to competition and diseases brought by modern humans, there is also evidence that they interbred with them.
Wherever modern humans spread, they developed minor genetic differences. The first modern humans had dark skin, due to a high content of melanin to shield them from the high levels of sunlight ultraviolet radiation (UVR) near the Equator. Those who moved further away from the Equator developed lighter skin, reducing melanin content improve the body's vitamin D production. It took up to 20,000 years, but sometimes considerably less, for humans to adopt the optimal skin color for a region. Another example is the emergence of epicanthic folds among humans living in cold, windswept climates, such as the Central Asian steppes during the Last Glacial Period. Although they live in warmer climates, East Asian populations have substantial ancestry from populations who developed this trait.
By 65,000 years ago, modern humans had spread as far as Australia, but had not yet spread to colder regions like Europe. As sea levels were lower during the Last Glacial Period, many areas that are now separated by seas were joined by land. They may have also used simple boats to reach places like Australia. By 30,000 years ago, modern humans had populated all but the coldest regions of Europe and Asia. By 14,000 years ago, they had reached the northeast corner of Asia and crossed to the Americas ago via a land bridge that is now the Bering Strait. The Last Glacial Period ended around 11,700 years ago. Other more isolated islands were not reached until later, particularly the voyages of the Austronesian peoples between 3000 BC and 1200 AD.