16. The Emergence of Humans (~2.5 Ma – 70 ka)
Summary After their ancestors had evolved from chimpanzees and other hominids, the first humans emerged in east Africa about 2.5 million years ago when they started to create stone tools. They spread from Africa to Eurasia about 2 million years ago, and over time they started to wear clothes, to hunt large game, to control the fire and to cook. 100,000 years ago there were at least six human living species roaming Africa and Eurasia, among them Homo neanderthalensis, Homo denisovan and our species Homo sapiens.
Keywords Evolution of Life; Ice Age; Mammals; Technology
While mammals thrived worldwide as the dominant terrestrial vertebrates, a particular brainy type of mammal evolved in an ecological niche in east Africa about 2.5 million years ago: These were the humans – us.
The ancestors of humans, belonging to the family of great apes which are also called hominids, had parted from the ancestors of the orangutans about 14 million years ago; from the ancestors of the gorillas about 8-9 million years ago; and ultimately from the ancestors of the chimpanzees and bonobos, which are the most closely related living species to us today, about 6 million years ago. In the following millions of years they started to walk upright on two legs instead of on four legs, which made their hands free for new delicate tasks. Their brains became larger, which required a higher calorie input but also enabled them to comprehend their environments better. Other evolutionary trends were that their babies were born prematurely, which required them to be brought up for longer times and probably contributed to the development of a stronger pair bond between mother and father, and that the fertile period of females became hidden, in contrast to other closely related species.
A major evolutionary turning point was then reached around 2.5 million years ago when they started to create and to use stone tools, with hand axes being famous examples. This time roughly coincides with the beginning of the current ice age, also called the Quaternary glaciation, which started 2.58 million years ago and which is characterized by periodically recurring cold glacial periods. During these glacial periods, which are separated by warm interglacials like the current Holocene which started 11,700 years ago, much of northern Eurasia and north America are covered by ice sheets.
The starting time of the creation of stone tools marks the beginning of the Stone Age, which lasted until the beginning of the creation of bronze tools around 3300 BCE. The first creators of stone tools led paleoanthropologists to ascribe them to the genus Homo. In biological taxonomy a genus comprises several closely related species, with a species denoting organisms which can produce fertile offspring. Following historian Yuval Noah Harari, here all organisms belonging to the genus Homo are called humans. This means that over time several human species evolved, with our species Homo sapiens (“wise man”) being only one example amongst many.
Homo neanderthalensis in a cold northern region of Eurasia. (© Painted by Charles R. Knight in 1911 / Wikimedia Commons / Public Domain)
One of the earliest human species was Homo erectus (“upright man”) which evolved about 2 million years ago. This was also about the time when it spread from Africa to Eurasia as the first human species. Around 500,000 years ago Homo neanderthalensis (“man from the Neander valley” which is a fossil site in Germany) inhabited Europe and western Asia, while Homo erectus also lived in the eastern parts of Asia such as China. As humans advanced into colder regions, they started to wear clothes made of skins and fur. Homo neanderthalensis was more muscular and had larger brains than Homo sapiens.
Around 400,000 years ago humans regularly hunted large game. While they occasionally used fire since about 800,000 years, they used it on a regular basis since about 300,000 years ago. The control of fire led to the advent of cooking which allowed humans to eat more kinds of food and which even led to anatomical changes in their teeth and intestines.
Our species Homo sapiens evolved around 200,000 years ago in east Africa. It still lived in that area around 100,000 years ago, while at least five other human species – among them Homo neanderthalensis and Homo denisovan – roamed through other parts of Africa and the vast spaces of Eurasia. This human diversity, however, would soon be gone in the wake of the Cognitive Revolution which started about 70,000 years ago.