24. Human evolution
Contents of the chapter
24.1 Features special to humans
24.2 Africa as the birthplace of humankind
Human evolution is one of the mysteries of scientific world. It is being solved piece by piece with the help of fossil findings and genetic studies.
The development of the first primates dates back 70 million years. Monkey fossils found in Africa date back 20 million years.
The earlierst human ancestors lived in the savannas of Africa about five million years ago.
The spread of our ancestors from Africa to other continents began at a time when they had developed adaptations to cooler climates and seasonal variations.
There have been three main stages in human evolution:
- The southern ape of Africa (genus Australopithecus)
- Homo habilis and Homo erectus
- Homo sapiens and Homo neanderthalensis, as well as many other extinct Homo species.
Stages of human evolution. Australopithecus is known as the southern ape of Africa. Neanderthal humans lived at the same time as modern humans, before becoming extinct.
24.3 The southern apes of Africa - the first two-legged walkers
Based on fossil footprints, it has been concluded that the southern ape living in the African savannas moved in an upright position. Their bone structure, as determined by the fossil finds, also supports this. The southern apes lived 6 to 1,6 million years ago. Their brains, about 500 cubic centimeters in size, were no larger than those of chimpanzees.
The southern apes used sticks and stones as tools for gathering and defending their food. The upright posture of the apes freed their hands to search for food over a wider area and to transport food over longer distances.
Their upright posture also gave the advantage of being able to detect predators more easily in a grassland environment. During dry periods, the southern apes had to extend their search for food to greater distances. The upright posture used less energy when compared to the four-legged posture of previous organims.
The best-known primate fossil discovery was made in Ethiopia during the early 1970s. The discovery concerned a southern ape fossil, which was determined to be 3.2 million years old. The fossil was named Lucy, as it has been inferred from the bones that the individual was a female who died at a young age. It has also been observed from the bones that in search of shelter and food, this southern ape was able to climb a tree with its muscular, elongated arms. Based on the dental analysis, Lucy's diet consisted mainly of fruit.
The genus Homo, a group of organisms including modern humans, is considered to have descended from Lucy’s species, Australopithecus. Apparently these two species did not compete with each other. Instead, the development of different diets in these two species allowed them to coexist.
Food was sought by searching, not by systematic hunting or cultivation. This is referred to as gathering. Hunting skills were only developed at a later stage in human evolution. Based on dental analysis, meat was also part of the southern ape diet, but it may have only been consumed when carcasses were left over by other predators.
Australopithecus africanus, or the southern ape of Africa.
24.4 Ancestors as craftsmen and hunters
Homo habilis developed in the African savanna 2–1.5 million years ago. These ancestors were named the ‘handy humans’ because of their craftsmanship skills. Access to food became easier when tools made of stones and bones made hunting more efficeint. Homo habilis likely used tools for butchering meat, which they scavenged from more fearsome carnivores.
Based on fossil findings, Homo habilis were a taller species when compared to the southern apes. Their brain size also grew in a chain of generations, as meat was high in protein.
Based on their height and brain size, Homo habilis is considered one of the earliest members of the genus Homo. Game hunting supported developing communication between individuals.
The Homo habilis already knew how to use tools.
Homo erectus, or the upright human, lived about 1.7 million years ago. The brain size (900–1100 cm3) was twice that of that of the southern ape. The structure of the brain became more human: among other things, the frontal lobe became larger and the occipital lobe smaller. Based on the structure of the brain, it has been concluded that Homo erectus was already able to speak.
Proficiency in the manufacture of tools and weapons brought the element of planning to hunting. This increased the amount of game humans could catch and kill, therefore improving the chances of survival.
The invention of fire made it possible to cook food. Fire also helped humans to protect themselves from predators. The development of bones, brains and skills also made it possible for humans to adapt to a cooler climate. As a result, Homo erectus began to spread towards Asia and Europe.
Search the internet for images with the keywords "Homo erectus" and "Homo habilis". You will notice various different perspectives regarding the number of species, classifications, and species characteristics presented.
Homo erectus at the Vienna Museum of Natural History.
24.5 The study of human evolution
The study of human evolution is challenging. Our ancestors have naturally lived in areas where nature has produced a lot of food. In these kinds of areas, the bones of dead individuals are also disintegrated rapidly. For this reason, not many fossils of our human ancestors have been found.
Genetics is a branch of biology concerned with the study of genes, genetic variation and heredity. It plays an important role in piecing together the story of human evolution.
Scientists looking for the remains of Neanderthal fossils and dwellings in Spain.
24.6 Modern humans
The descendants of modern humans, who lived in Africa about 200,000 years ago, initially spread to Europe and Asia. At a later stage, the species also spread to Australia and the Americas. In the wake of various unfavourable periods, only a small percentage of modern humans survived to produce offspring. The cooling of the climate into the ice age and volcanic eruptions significantly taxed human populations in some places.
About 100,000 years ago, several human species inhabited the Earth together with the modern human. These include the Floresin human (fossil findings from Indonesia), the Denisovan human (from Siberia), the Luzon human (from the Philippines) and the Neanderthal human.
Of the early humans, Neanderthals (Homo neanderthalensis) lived in Europe 200,000 to 30,000 years ago. The Neanderthals had a robust build and they were shorter than modern humans. The brain was big: 1,500cm3.
A strong build was useful when hunting for large animals. Neanderthals knew how to make clothes from animal skins. Keeping a campfire was a new skill in handling fire. However, these skilled hunters disappeared 30,000 years ago. The species Homo sapiens may have contributed to the destruction of Neanderthals as they competed for habitat and food.
Modern humans, who spread from the northern parts of Africa, also interbred with their Neanderthal neigbours. The proportion of Neanderthal-inherited genetic material is about two percent and is found in all non-African populations. As an example, a gene form that causes redness in the cheeks has been found in the genome of both Neanderthals and Europeans.
Journey of Mankind Becoming Human
The Neanderthal human had a robust build, and lived in Europe with modern human 200,000 to 30,000 years ago.
At the time of the disappearance of Neanderthals, the Homo sapiens living in Africa and Eurasia were already in many respects skilled and advanced members of the human race. Big game hunting became more efficient thanks to inventions such as bows and spears. Cave paintings from this time show the development of artistic talents and human culture. The Homo sapiens also began to bury their dead with various weapons and jewellery, which the deceased were believed to need in life after death.
Discovered in 1868, Cro-Magnon 1 was among the first fossils to be recognized as belonging to our own species—Homo sapiens, who had arrived in Europe 40000 years ago. This famous fossil skull is from one of several modern human skeletons found at the famous rock shelter site of Cro-Magnon in France.
Modern human (Homo sapiens sapiens) gradually adapted to different climatic conditions and inhabited new areas. Population growth brought new challenges, and skills developed toward starting agriculture.
24.7 The evolution of human characteristics
Many human traits serve as signs for various stages of human evolution. The DNA's of humans and chimpanzees are 99% identical. While there are many similarities in the structures of these two species, there are also many differences. Modern humans are the only primate species that walks upright. In humans, this is made possible by the structures of the spine, pelvis and legs.
Skeletons of great apes. From left to right: gibbon, gorilla, chimpanzee, orangutan and human.The flexible and sturdy spine keeps the upper body upright. The forward-turned big toe of the legs and the curved arch of the foot allow for vertical walking.
There are similarities in the instinctive functions of humans and chimpanzees. Instinctive functions are inherited. The instinctive functions of newborn offspring are essential for survival. How would a newborn survive if instinctive functions did not guide him to fumble with his mother’s breasts and thus get milk for food?
The intensity of the gripping reflex is explained as a remnant of a time when a small offspring had to grip firmly on his mother’s fur and stay with the moving mother.
The human thumb and forefinger can touch one another, unlike those of a chimpanzee.
Humans are capable of fine motor skills that allow us to complete extremely meticulous tasks. Surgical procedures, drawing and various other kinds of work require the cooperation of different parts of the brain in addition to the senses of sight and touch. Three-dimensional vision and color vision are the most important characteristics in the development of human sight.
The structure of the human cerebrum makes it possible for us to produce speech. A small baby is capable of recognizing a familiar face and communicating with the people, animals, and objects around them with facial expressions and sounds. On average, a child learns to speak during their second year of life. When a child lives with other people, they learn to talk and communicate with the others in different ways. Along with social development, the skills and knowledge learned by individuals are passed on to the next generation through communication and learning.
Different character traits can be seen in the games played by young children. Belonging to a group is important for every person. Whether a group is a kindergarten circle of friends, a school class, a hobby circle, a group of co-workers, or whatever, it can be observed that sociality is one of the most important species-specific features of Homo sapiens.