The Journey of Human Development and Natural Selection
Evolution
Evolution is the change in the characteristics of a species over several generations, relying on the process of natural selection.
- The theory of evolution is based on the idea that all species are related and gradually change over time.
- Evolution relies on genetic variation, which affects the physical characteristics of an organism.
Human Evolution
Human evolution is the process by which human beings developed on Earth from now-extinct primates.
According to the scientist Charles Darwin (1809–1882), evolution depends on a process called natural selection. Natural selection results in the increased reproductive capacities of organisms that are best suited for the conditions in which they are living.
Key Hominin Species
Here are some of the significant hominin species in the evolutionary timeline:
Australopithecus
Appeared around 4.2 million years ago in East Africa. They measured 1.2-1.4m tall, weighed 33-67kg, and had a brain volume of 400-500 cm³. They were bipedal (though similar to chimpanzees in gait) and used simple wood tools.
Homo Habilis
Appeared around 2.4 million years ago (Lower Paleolithic) in Africa. They were 1.2-1.4m tall, weighed 40-50kg, and had a brain volume of 650 cm³. Known as the “skillful human,” they could communicate and made rudimentary tools.
Homo Ergaster
Appeared around 1.8 million years ago in Ethiopia, Kenya, Tanzania, and Eritrea. They were 1.6-1.8m tall, weighed 52-68kg, and had a brain volume of 950 cm³. They migrated on foot and were capable of building rafts to cross seas.
Homo Erectus
Appeared around 1.8 million years ago (Lower Paleolithic) in Africa, Asia, and Europe. They were approximately 1.8m tall, weighed 70kg, and had a brain volume of 800-1250 cm³. They invented fire and learned how to maintain it. They were the first hominins to migrate out of Africa and reach Europe.
Homo Antecessor
Appeared around 300,000 years ago in Europe (Atapuerca, Burgos). They were 1.7-1.8m tall, weighed 60-90kg, and had a brain volume of 1125 cm³. They communicated through sounds or gestures, engaged in hunting, fruit gathering, and cannibalism.
Homo Neanderthalensis
Lived from 200,000 to 35,000 years ago (Middle Paleolithic) in Europe and Asia. They were about 1.65m tall, weighed 70kg, and had a brain volume of 1500 cm³. They were the first to bury their dead and were skilled hunters and gatherers.
Homo Sapiens (Cro-Magnon)
Appeared around 195,000 years ago (Upper Paleolithic) and spread globally. They were 1.5-1.8m tall, weighed 61-75kg, and had a brain volume of 1600 cm³. This is our species, modern humans. Around 35,000 years ago, they created extraordinary artistic works in caves, including paintings and sculptures.
Primate Lineage Divergence
Around 10-12 million years ago, the ancestral primate lineage split through speciation from one common ancestor into two major groups:
Great Apes
They remained in forests with an arboreal lifestyle, living in trees. Great apes are also quadrupeds, meaning they move around on four legs on the ground.
Hominins
They became terrestrial, living on land. From being quadrupeds, they evolved to bipeds (moving around on their two back legs), and the size of their brain increased. This is the group that, through evolution, gave rise to modern humans.
The Process of Hominization
Hominins developed a number of features that distinguished them from apes; this process is called Hominization. Climate changes might have been the starting point of this process: when the climate became drier, forests were replaced by grasslands with fewer trees, prompting apes to come down from the trees to look for food.
Key Features of Hominization
The features that distinguish hominins from the rest of the apes are:
Bipedalism
Upright walking changed the position of the spinal cord. Hands were no longer used for walking, freeing them to make and use tools, carry, and throw.
Cranial Change
This involved a smaller jawbone and teeth, the appearance of a chin, and a vertical forehead. The brain also significantly increased in size.
Changes in the Hand
The development of the opposable thumb made holding objects easier and allowed for greater dexterity.