  |
Our Distant Ancestors
Overview
Our understanding of ancient human life results from a small number of fossilized hominid remains that have been discovered. It has been said that the entire worldwide collection of early hominid fossils could fit into the back of a pickup truck. The nature, indeed the existence, of a type of hominid may be suggested by, for instance, a fragment of a jaw bone. This theorizing is not nearly so uncertain as it may seem; nevertheless, there are well-grounded but competing interpretations for most of the significant discoveries.
Still, a consensus of a sort has coalesced around a central story – that humans first appeared in east Africa millions of years ago, and from there spread throughout the world in what could only have been astonishing journeys of heartbreak, adventure, exploration and endurance.
What is less well known is that this journeying forth from Africa seems to have occurred more than once. It was undertaken by different species of humans at different times. In this section we tell their story as far as we know it today. As more evidence is found, the tale expands and will continue to expand. In 2004 scientists discovered a totally different species of human being that until at least 13,000 to 12,000 years ago and possibly into the nineteenth century, shared this planet with us. Named Homo floresiensis, it is a three-foot-tall dwarf hominid with physical features similar to those who lived from 1.5 to 4 million years ago (MYA), and who lived on the isolated Indonesian island of Flores. There is controversy about where it stands in the line of human ancestors, so it is not included in the list below. For more information on floresiensis
click here.
What follows here is a set of articles and links to how our ancestors changed, bodily, into us today. We take up the story of our origins about five million years ago when the human line split from the chimpanzees. Our ancestors left the forests and moved out to the savannah, marking the appearance of the fully walking apes, the australopithecines, several species of which dwelled side by side in Africa from 3.6 million to 2.9 million years ago.
The fossil remains of two australopithecines, named Lucy and Dikka by those who discovered them in Ethiopia, are our distant but direct ancestors. Lucy’s skull was more like that of a chimpanzee than a human, but her leg and pelvic bones were clearly more human in shape. Not long after Lucy and Dikka walked the earth, our ancestors and their cousins began to develop tools.
Standing up, or in the jargon, bipedalism, changed our ancestors, and led to modern humanity, and changed the world, eventually. While some monkeys and apes do, occasionally, stand on their hind legs, it is only in our ancestors that we see upright walking as a “standard feature,” so to speak. What happens when an animal stands up? The front limbs no longer have to bear weight, so they can become finer, and then can achieve more delicate movements, and this dexterity then led to increased toolmaking abilities. The sequencing needed to make increasingly complex tools also led to the brain’s ability to understand increasingly complex sequences, which led to language and mathematics.
Standing up also narrowed the pelvis and led to human babies being born earlier and earlier in their maturation period, so that the human brain develops more after birth in the outside world than did the brain of our ancestors. This spurred an adaptation to environments all over the world. Most other animals live in the habitat they were born to survive in; human beings live all over the world and adapt the world to ourselves. But we are getting a bit ahead of ourselves now.
Between 2.5 and 1.8 million years ago, the first species called Homo appeared. There were at least four branches of the family—Homo habilis, Homo rudolfensis, Paranthropus boisei, and Homo ergaster—all of them considered prehuman and referred to as hominids. Although Homo habilis is considered closer to an australopithecene, many habilis remains have been found with stone tools, a general family trait. Additional technological innovation is not apparent after the stone flake tool appeared some 2.5 million years ago until approximately 1.5 million years ago when the hand axe was fashioned that became the dominant tool for another million years.
Homo ergaster is the first in the line from the chimpanzee-human ancestor to have a modern human body form. H. ergaster was tall and upright and was the first to travel beyond Africa. Its fossilized remains have been found in China and Java where it lived about 1.8 million years ago. H. ergaster then gave rise to H. heidelbergensis who invented the prepared core tool and used a mental template to create many copies of the same tool. Both the Neanderthals and Homo sapiens descended from H. heidelbergensis, although in 1997 a team of geneticists announced that Neanderthals could not be the direct forebears of modern humans because there was too much difference between their genomes
Homo sapiens—modern human beings—emerged as a single small population about 200,000 years ago in Africa, and there is both archaeological and paleoanthropological evidence that suggests H. sapiens remained stable for approximately 100,000 years. Between 80,000 and 60,000 years ago, however, there was a dramatic expansion of certain genetic lineages in the African population at the same time there was a striking change in technology and culture.
Homo sapiens do not appear to have changed physically in this period, but they began to produce many more types of unambiguous symbols and new forms of tools, such as those for scraping skin and shaping bone and wood. After this cultural and technological shift, these modern humans began to leave Africa about 60,000 years ago. As humans spread across the globe, their material and symbolic culture grew richer. By 40,000 years ago, Homo sapiens were sculpting from stone, painting the walls of caves, and creating a greater variety of musical instruments and jewelry, and ritually burying their dead.
It took some 30,000 years more to invent agriculture, and in the 10,000 years that followed (bringing us to the present), agricultural techniques spread around the world. In the last 5,000 years, we have experimented with architecture, raising buildings that range from the ancient pyramids to the Empire State Building, and in the last 300 years industrial technology has replaced human labor in countless areas. At the present time, to acquire a handful of electronic devices is just another day in the life of most Westerners. Culture begets more culture, and the replacement of material artifacts has not just accumulated but continues to accelerate.