Human Evolution: From Cells to Homo Sapiens
History is defined as "the recorded experience of human beings throughout the ages, since the creation of written records." Pre-history, then, is the experience of human beings, and their predecessors, before written records.
Due to the lack of records during this period, it is difficult to attribute exact dates to the majority of the events that occurred in pre-history. However, this article will discuss a rough time line for the evolution from single cell organisms to homo sapiens.
The First Life on Planet Earth
From the creation of the universe to our last common ancestors with the chimpanzees:
- The universe was formed about 12 billion years ago
- The earth was formed about 4.6 billion years ago
- The first living organisms were single cell organisms that lived about 3.5 billion years ago
- Multicellular organisms evolved about 600 million years ago
- The continents took their form less than 100 million years ago
- 25-30 million years ago apes diverged from the old world monkeys.
- Our last common ancestor with the chimpanzees and the bonobos lived about 7 million years ago.
It is important to note that we do not descend from Chimpanzees; they are our cousins. Since our split with the predecessors of the chimpanzees, there have been at least 18 species, known as hominines. (Previously known as hominids.) While all hominines share a common ancestor with Homo sapiens, not all hominines are our ancestors. Some, like the neanderthals, are cousins.
Lucy: The Oldest Human Skeleton
Australopithecus-“the southern ape” lived in eastern and southern Africa from 1-4 million years ago. They were not actually apes, but hominines. Australopithecus were bipedalists that stood about 1 meter (3.5 feet) tall and weighed between 25 and 55 kilograms (55-121 lbs). Their brains were about 500 cc, just slightly more than 1/3 the average size of a brain belonging to a human living today. They were herbivories and travelled distances of 15+ km (9.3 miles) to find the types of stone needed to make their tools. They made choppers and scrappers and other tools involved in food preparation. They also had some ability to communicate verbally, although that portion of their brain was not well developed.
Homo Habilis: Our Prehistoric Ancestor
Homo Habilis lived about 2.3 million years ago. They were the first species belonging to the Genus Homo, the genus humans of today belong too. Their faces were similar to those of apes and had larger brains than the Australopithecus. They are thought to be the first species to make stone tools and made tools for cutting by hitting flakes off stones.
Homo Erectus: Our Predecessor
Homo erectus (also known as Homo ergaster)-“upright-walking human”-displaced the australopithecines. They lived from 2 million to 200,000 years ago and migrated from Southern and Eastern Africa to Northern Africa and Eurasia. Their bodies are similar to humans and their teeth show their growth rates were similar to great apes. Their brains were roughly double those of the Australopithecus.
They made more complex tools, tools that fastened rock to a wood handle, as well. In addition to the choppers and scrapers of the Australopithecus, Homo Erectus made cleavers and hand axes as well. They also learned to start fires as well. This allowed them to cook their food, defend themselves against large animals and provided heat. Their hunting styles showed they were capable of communication, as groups of men worked together to kill larger beasts and bring the meat back to camp for their families.
Homo Sapiens-“consciously thinking human”-followed the Homo erectus, evolving 200,000 years ago. The first Homo sapiens possessed brains near the 1400 ccs of today’s human’s brains. They were able to live in colder climates than their predecessors because of a learned ability to make warmer clothing out of animal skins and warm structures for shelter. They invented knives, spears, bows and arrows, and learned to use spoken language to communicate complex ideas and coordinate their efforts. The basic anatomy and genetics of humans has not changed much over the last 100,000 years. Geographic separation accounts for the emergence of cultures, languages and race. Ice ages permitted travel to New Guinea, Indonesia, Australia about 60,000 years ago and travel to Alaska about 25,000 years ago. Humans have inhabited nearly every inhabitable region in the world for the past 15,000 years.