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Big Era One

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Humans in the Universe
13 Billion - 200,000 Years ago

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The Creation of Adam
The Creation of Adam

A Pictorial Archive from Nineteenth-Century Sources. Mineola, NY: Dover Publications, Inc.

This Big Era and the Three Essential Questions

Humans are part of a universe that is older and larger than we can begin to imagine. How was this universe created? How was the earth created? How and when were our ancestors created? What is our place in the universe? Are we important, or are we insignificant?

This Big Era sets the stage for human history. It is about the creation of our environment, of the world we live in, its landscapes, its plants and animals. It is also about the evolutionary steps that led to the creation of our species, Homosapiens. Understanding this era is vital if we are to grasp how human history fits into the larger history of our earth and the universe as a whole. This is because our ideas about the universe, the earth, and our own existence as a species affect how we think about ourselves and our history. They help us understand our place in the larger universe of which we are a part. So "creation myths," stories that help us understand how everything around us came to be, seem to exist in all human societies.

Humans and the Environment
Humans and the Environment arrow item

In the story of creation in the Bible’s Book of Genesis, God made human beings. But he did so only after he had created everything else that was to be part of his universe. The creation took seven days. This is how it began in the biblical account: "And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness. And God called the light Day, and the darkness he called Night."1 After making day and night, God created the seas, dry land, grass, fruit trees, the sun, the moon, fish, birds, cattle, every kind of "creeping thing," and, finally, man and woman. Then he rested.

This infrared image from NASA’s Spitzer Space Telescope shows hundreds of thousands of stars crowded into the swirling core of our spiral milky way galaxy.

NASA Jet Propulsion Laboratory
California Institute of Technology
Milky Way IR Spitzer

In thinking about this story, notice that God first made the entire physical and natural environment, everything from the stars to green grass, then fashioned human beings and put them into this setting. In the creation story that modern science tells, the environment was also created before humans, but the time scales are very different. According to modern science, humans evolved on a planet that had already existed for over four-and-a-half billion years. The terrestrial environment shaped the creation of our species. Moreover, the environment of the earth was itself the product of the earlier history of the cosmos as a whole. Consequently, in introducing Big Era One we must begin at the beginning, setting the debut of Homo sapiens within the largest possible scene in both time and space.


The Universe

Modern science suggests that the universe was created about 13.7 billion years BP. What existed before that moment? At present, we have no way of answering that question. Many astronomers would say that the query is meaningless because neither time nor space existed before the creation of the universe. There was nothing. Even so, there must have been at least the possibility of something, because in this "nothingness" a sort of explosion occurred. Within a split second of that explosion, something did exist. The early universe was tiny and fantastically hot, a searing cloud of energy and matter, much hotter than the interior of the sun. For a trillionth of a second the universe expanded faster than the speed of light, until it was bigger than an entire galaxy. Then the rate of expansion slowed, though expansion continues to the present day.

Pioneer plaque
The solar system is depicted at the bottom of this famous NASA plaque mounted on 1972’s Pioneer spacecraft, carrying a message to potential extraterrestrials. The arrow at the bottom indicates the spacecraft’s trajectory through the planets. Other symbols include naked, friendly humans, neutral hydrogen, and the relative position of the sun to the center of the galaxy.

NASA. Wikimedia Commons

As the universe expanded, it cooled down. After about 300,000 years, it was cool enough that protons and electrons could combine to form atoms of hydrogen and helium. These are the simplest atoms of all. After about one billion years, huge clouds of hydrogen and helium began to collapse in on themselves. As they did so, their centers got hotter and hotter. When they were hot enough, hydrogen atoms began to fuse together violently like vast hydrogen bombs. In this way, the first stars lit up. Hundreds of billions of stars appeared, gathered in hundreds of billions of clusters that we call "galaxies." In the stars, new chemical elements were created, so that as stars lived and died, they generated the energy and raw materials needed to make new and more complex types of matter. So it is no accident that complex objects such as planets and human beings appear near stars.

Our Galaxy

Our attention now turns to one tiny part of the universe. Our sun and the planets that circle around it were created about 4.5 billion years BP, so they are about one third of the age of the universe. They were created about two thirds of the way from the center of a galaxy we call the "Milky Way." Look up at the heavens on a clear night, and the Milky Way looks like a pale creamy pathway through the stars.

Our sun is a star, and like all other stars, it was formed from the collapse of a huge cloud of gas and dust particles. More than 99 percent of this material went to make up the sun, but wisps of matter orbited around it at various distances. Over time, the matter in each orbit was drawn together by gravity or by violent collisions into lumps of matter that eventually formed the planets. This is how our earth was formed. At first, it was extremely hot. The heavy metals within it melted and sank to the center of the earth to form its core. Lighter materials rose to the surface, and gases bubbled up to form the earliest atmosphere.

The Earth

The early earth was a violent place, bombarded by asteroids, and bubbling with heat from its interior. If you visited its surface, you would have seen landscapes full of volcanoes. But you would not have been able to breathe because its atmosphere contained no oxygen. Slowly, the number of asteroid impacts diminished, the surface cooled, and, about 4 billion years BP, water vapor in the atmosphere condensed to form the first oceans.

This 2002 scanning electron micrograph (SEM) shows an amoeba in its trophozite phase, a vegetative period spent feeding, moving about, and reproducing.

Wikimedia Commons
Hartmannella vermiformis

Eventually, the earth’s surface hardened and congealed, forming a number of thin plates that floated on the hot, molten material beneath. These plates slowly moved around the surface, and where they collided, they formed huge mountain chains. Where they moved apart, they created huge tears in the earth’s surface. You can see one of these tears in Africa’s Rift Valley. Some of these huge valleys eventually filled up to form new oceans. This process, known to geologists as "plate tectonics," means that the surface of the earth has changed continuously. As it changed so did the landscapes and weather patterns at the surface of the earth.


Early Life Forms

Life evolved in this ever-changing environment. The first living organisms probably evolved deep within the seas. Around volcanic vents at the bottom of oceans, complex chemicals engaged in ever-changing reactions powered by the heat from these volcanoes. Those reactions led to the formation of complex chemicals that eventually created the first living organisms. Did life evolve only on our earth? At present, we do not know for sure. It seems likely, however, that life has evolved many times, wherever planets appeared that are similar to our earth.

The earliest living organisms consisted of single cells, as most living organisms do even today. The earliest organisms probably fed off the chemicals leaking from deep-sea volcanoes. Their fossil remains can be identified today, and the oldest of these remains can be dated to about 3.5 billion years BP. Like all living organisms, those early single-celled creatures were subject to the laws of evolution. Minor changes in organisms were passed on from generation to generation. Those organisms that flourished best in particular environments multiplied most successfully and left the most descendants. In this way, generation by generation, the average features of species gradually changed and diversified, eventually forming entirely new species. And the number and variety of different species increased.

Homo erectus skull

Naturmuseum Freiburg
Wikimedia Commons
Homo erectus skull—Naturmuseum Freiburg

By as early as 3.5 billion years BP, some single-celled organisms began to derive energy directly from sunlight by using the chemical reaction known as photosynthesis. Since then, the sun’s energy has been the main "battery" driving life on earth. Photosynthesizing organisms breathed in carbon dioxide and breathed out oxygen. So, as they multiplied, the amount of oxygen in the atmosphere increased. Living organisms were already shaping the earth’s atmosphere. Eventually, more complicated cells appeared that could "breathe" oxygen. These are known as "eukaryotic" cells. From about 600 million years BP, organisms appeared that were made up of many individual eukaryotic cells. These were the first "multi-celled" organisms. Large, multi-celled organisms eventually colonized the land, in the form of plants, fungi, and animals.


One hundred million years BP, the most flourishing land-based animals were the reptiles we call dinosaurs. About 65 million years BP, however, most of them died off in what was probably a catastrophic meteor impact. Now other types of large animals could flourish in their place. Most successful of all in the last 65 million years has been the large class of animals called mammals. These are warm-blooded, fur-bearing animals that nourish their young in their mothers’ wombs and feed their infants with mother’s milk. After the dinosaur calamity, mammals began to spread, multiply, and diversify, occupying many of the niches once inhabited by dinosaurs. There appeared grass-eaters, meat-eaters, swimming mammals such as whales, and even flying mammals such as bats.

Our hominin ancestors used tools known as Acheulean hand axes from about 1.4 million years BP. This specimen was found in France. What useful tasks might an individual have been able to perform with this axe?

Kathleen Cohen
World Images
Biface hand axes

One family of mammals, the primates, were specialist tree-dwellers. To survive in trees they needed good 3-D vision and a brain large enough to process a lot of visual information. They also needed hands that could grip things with precision. Our own ancestors, the hominins, belonged to a branch of the "great apes," a group of primates that had learned to live at least part of the time on the ground. The first hominins (a term replacing the older word "hominid") appeared about six million years BP, in Africa. What distinguished the first hominins from other great apes was that they could stand upright. Their brains, however, were about the size of those of modern chimpanzees. In Africa, hominins flourished, alongside many other species, and in time a great variety of different hominin species appeared.


Humans and Other Humans
Humans and Other Humans arrow item

Early hominins probably lived much like modern chimpanzees or gorillas, that is, in small, family-sized groups that gathered most of their food from plants but also ate insects and small animals. They also occasionally scavenged the meat of larger animals. From about two million years BP, some hominins, from the species known as Homo erectus, migrated out of Africa along the warmer southern fringe of the Eurasian landmass from Europe to China. During the next two million years, new species of hominins appeared in this huge region, some with larger brains. One of those species, known as Neanderthals, flourished in the last 500,000 years.

How did our hominin ancestors live? Like chimpanzees and gorillas, our closest relatives, they were highly social animals that lived in family groups probably ranging from five or six to thirty or forty individuals. We can be pretty sure that they were smart, because chimpanzees are smart. We know they could use and make stone tools because we have found remains of those tools dating from about three million years BP. Modern attempts to make stone tools show how hard the work is, but they also show that using them could make quite a difference to the diets of early hominins. With sharp stone flakes, you could butcher the remains of a large animal very efficiently—as long as the other scavengers, such as hyenas, left you in peace. Using sharpened sticks, maybe hardened in a fire, you could also get at roots of plants. Some early hominins may have used fire. We have strong evidence for the use of fire by hominins living in China in 500,000 BP. Some evidence from Africa suggests that hominins were using fire even earlier than that.

We can also be reasonably sure that early hominin societies were quite complex. Studies of chimpanzee groups today show that they compete for status, making complex alliances with one another to achieve higher standing. Politics of this kind require a lot of "political" intelligence. We also know that chimps care for each other. Mothers have much care for their offspring, and they appear genuinely distraught if their babies come to harm. Hominins almost certainly engaged in behaviors that were equally complex.

Humans and Ideas
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The Spread of Human Ancestors up to 200,000 Years Before Present

A varied stone tool kit, elemental social organization, and the control of fire all enabled Homo erectus to become a well-traveled species, one successfully adapted to a large part of the world. Even so, there is still something alien about this creature. Despite its likely successes at social cooperation and competition on a small scale, it did not, as far as we know, evolve complex rules for sharing food, resolving conflicts, or strategizing long-term survival. Homo erectus fossil and tool sites have so far turned up no evidence that they knew anything of symbolic expression, religion, art, or even how to build a simple fireplace. As far as we know, this species produced no wall paintings, no stone carvings, no intentional burial of the dead. In fact, their lifeways changed remarkably little in the two million or more years that they survived, certainly compared to the changes human society has undergone in the past several millennia. The evolutionary processes that produced Homo sapiens, the "wise human" (a name we have given ourselves!), involved not only anatomical changes and greater tool-making skills but also the emergence of social communities that consciously shared a life of symbols, ceremonies, and aesthetic expression.

We may ask, then, why was it that the history of early hominins, like that of chimpanzees, was so different from that of our own species of hominin? Why did these earlier hominins remain confined to Africa and the southern part of Eurasia, never adapting to colder, northerly regions and never reaching Australia or the Americas? Why did they never build villages or cities? Why are chimps still living in roughly the same parts of Africa where their ancestors lived two or three million years BP, and why have their numbers probably remained roughly the same throughout that entire period? Why, by contrast, did Homo sapiens occupy all the great landmasses excepting Antarctica and grow to number more than 6 billion today, living in the vast communities we call cities? In short, what is so different about our own species of hominins? We will take up that question in Big Era 2.

Teaching Units for Big Era One

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How Did We Get Here, Anyway?
The Foundations of Human History
13,000,000,000-200,000 Years Ago

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The horizon of human history
13,000,000,000 - 4,000,000 years ago

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Human ancestors in Africa and beyond
7,000,000 - 200,000 Years Ago

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1 King James Version, Gen 1: 3-5

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