Prehistoric Ages and Hominins

There is a misconception that history is simply about "the past," but the Greek historian, Herodotus, used the Greek word historiai (inquiry) to describe his work. History is not just about things that happened in the past - history is an inquiry into why things should still matter to us today and how the past continues to impact the present.

The era called "prehistoric" is critical; it includes the majority of the total time on Earth that humankind has spent developing basic human abilities and culture. For roughly 2.5 million years, hominids lived on Earth without leaving a written record of their lives. Although we know a lot about our history, we have no direct knowledge of human life's origins. 

Watch the video: Homo Sapiens Timeline - Our Family Tree

Purpose

This assignment will survey the transformation of our hominid ancestors to the appearance of anatomically modern humans. Students will examine hominid evolution and the emergence of bipedalism and the related physical adaptations and cultural ramifications, and chart patterns of hominid migration.

Learning Outcomes

• Compare and contrast the earliest members of the genus Homo and their variation, and adaptation.
• Describe the skeletal characteristics and the culture of later hominids
• Identify major fossil groups: Australopithecus, Homo habilis, Homo erectus, Homo neanderthalensis, and Homo sapiens

Instructions

• Review each hominid's central points, paying close attention to the evidence presented.
• Read the materials and watch the accompanying videos.
• Record key facts and be ready to present your interpretations of the materials and share during our class discussion.

Human Evolution

Evolution is the process by which living organisms evolve from earlier, more simple organisms. According to the scientist Charles Darwin (1809–1882), evolution depends on natural selection. Natural selection results in the increased reproductive capacities of organisms that are best suited for their living conditions. Darwin's theory was that organisms evolve due to many slight changes over time.

Paleoanthropology is the scientific study of human evolution. Paleoanthropology is a subfield of anthropology, the study of human culture, society, and biology. Most of what is known about humans' origins come from paleoanthropologists' research, scientists who study human fossils. Paleoanthropologists identify the sites where fossils can be found, and determine the age of fossils and describe the features of the bones and teeth discovered. Paleoanthropologists use genetic technology to test their hypotheses.

BC/AD to BCE/CE

BCE stands for "Before Common Era" and is the new way of writing BC, which stands for "Before Christ." Similarly, our current era, referred to as AD, which stands for "Anno Domini" or "in the year of our Lord" (the years dating from Christ's birth), is now denoted as CE, or "Common Era." It is simply not reasonable to ask non-Christians to use the term AD since "our Lord" does not include them.

Primates, like humans, are mammals. Around ten to twelve million years ago, ancestral primate lineage split through speciation—the formation of new and distinct species in the course of evolution. Physical and genetic similarities show that the modern human species, Homo sapiens, has a very close relationship to Africa's great apes (chimpanzees, bonobos, or so-called "pygmy chimpanzees," and gorillas). Ten to twelve million years ago, primates were divided into two branches, one species leading to modern (current) humans. Scientific evidence shows that all people's physical and behavioral traits originated from apelike ancestors and evolved over millions of years.

Watch the video: Prehistory 101

Context

The earliest populations of the Homo lineage emerged from Africa during the Paleolithic Era, or Stone Age, between six to four million years ago. The Paleolithic Age took place simultaneously as the Great Ice Age (also known as the Pleistocene), which ran from about two million years ago until the end of the last glacial (Ice Age) period, about 30,000 BCE. The "Stone Age" name comes from the stone tools and weapons made during that time and is from about two million years ago until the 4th Millennium BCE. The Stone Age ended when the earliest historic civilizations first began using bronze to make ritual vessels, weapons, and tools. The end of the Paleolithic era is the beginning of a new technological era, named the Bronze Age, which began 4500 years ago, to about 2500 BCE.

Charles Darwin discovered that slight variations begin to creep into its respective gene pools whenever a species is physically separated, creating diversity. Biological and genetic similarities show that the modern human species, Homo sapiens, has a very close relationship to the great apes of Africa (chimpanzees, bonobos, or so-called "pygmy chimpanzees," and gorillas). Most scientists currently recognize some 15 to 20 different species of early humans. Scientists do not all agree about how these species are related. Scientists also debate how to identify and classify particular species of early humans and what factors influenced each species' evolution and extinction. Humans first evolved in Africa, and much of their evolution occurred entirely on that continent.

Over time, some creatures developed the physical ability for two-footed locomotion and moved out of the forest edges to survive on the grasslands. Scientists surmise that during the million-year periods of colder weather on Earth about 10 million years ago. Climate changes probably sparked the development of hominid species' physical characteristics. Plant patterns changed, forests expanded or retreated, animals adapted to changing physical environments in Africa. The ice age caused sea levels to drop, making it easy for groups to obtain food as they moved along the coasts. Shellfish and other aquatic food sources rich in omega-3, iron, and other nutrients beneficial to brain development would have been plentiful.

Hominid/Hominin

Hominid is the term given to all modern and extinct great apes, including chimpanzees, gorillas, orangutans, humans, and all their immediate ancestors. Hominids begin making better use of a characteristic that apes, chimpanzees, gorillas, and orangutans had: free use of the forelimbs, opposable thumbs, allowing them to grasp, manipulate, and carry things. The crucial hominid physical elements are:

• bipedalism (walks on two legs) and opposable thumbs: all hominids
• increasing brain size (associated with increasing conceptual abilities): all Homo species
• complex human larynx (associated with more excellent speech): Homo sapiens 

Hominin is a term given to humans and all extinct bipedal ancestors who walked upright on two feet. The word 'hominid' comes from 'Hominidae' and refers to the extinct members of the zoological "tribe" Hominin, of which only one species exists today - Homo sapiens or human beings. The linkage of this zoological tribe is known from various species fossil remains of Australopithecus, Homo habilis, Homo erectus, Homo neanderthalensis (the Neanderthals), and Homo sapiens.

Hominids predate and sometimes overlap the first Homo species known as the Australopithecines. Anthropologists use Australopiths as a catchall term for hominins (species on the human branch after it split from chimpanzees) living between 1.2 and 4.4 million years ago. Australopiths were the first hominins that seem fully committed to bipedal life on the ground, out of the trees. These first hominids had not yet developed the large brain, teeth structure, and skeletal features identified as Homo (from Latin homō 'man'). According to the fossils recovered to date, Australopithecus species (Australopithecus afarensis in eastern Africa, Australopithecus africanus in southern Africa) survived for at least 700,000 years, more than twice as long as our species, Homo sapiens.

Watch the video: Australopithecus Afarensis

Homo habilis is considered the earliest human species. Homo habilis inhabited parts of sub-Saharan Africa from roughly 2.4 to 1.5 million years ago. In 1959 and 1960, archaeologists Louis and Mary Leakey discovered a hominid fossil at Olduvai Gorge in northern Tanzania. Leakey named the fossil Homo habilis (Latin: "man of skill," "able man" or "handyman"). Louis and Mary Leakey and other researchers found tools made of lava rock that made the task of survival for Homo habilis easier. In 1967, Richard Leakey's team found two hominid skulls and some bones near the Omo River in Ethiopia. And 38 years later, dating techniques established that they were 195,000 years old. More recent dating of fossils found at Jebel Irhoud in Morocco suggests that Homo sapiens, or anatomically modern man, evolved in Africa's networks beginning 300,000 years ago.

Watch the video: Becoming Human

The 1974 discovery "Lucy" in Ethiopia mystifies the scientific community and has pushed the hominid era back to as long ago as 6,000,000 BCE. Like the australopithecines, Homo habilis is bipedal. Homo habilis had a 50% larger brain than australopithecines and other pre-Homo hominids. This greater cranial capacity, plus opposable thumbs, enabled Homo habilis to become the first toolmaker. Most scientists believe Homo habilis did not have the conceptual abilities to figure out how to hunt fast animals and gather plant foods and scavenge meat from animals' corpses or the remnants of other animals' kills.

The successor to Homo habilis was Homo erectus. Homo erectus (Latin: "upright man") originated in Africa starting about 1.9 million years ago during the Pleistocene Epoch. Homo erectus was an adaptable species. Homo erectus developed all the abilities and technologies of its predecessor Homo habilis. The brain capacity of Homo erectus was twice that of australopithecines. Homo erectus made more advanced tools for digging, scraping, and cutting to meet their needs using the more remarkable conceptual ability. Homo erectus probably was the first species to use fire to help make tools and for cooking. Cooked food expands diet by making digestible a more comprehensive range of foods and preserving foods to make them last over a more extended period. Homo habilis used fire to provide warmth, allowing humankind to live in colder climates and ward off predators. Homo habilis developed the beginnings of spoken language, which boosted chances for survival. Homo erectus eventually became the first hominids to migrate out of Africa and settle in India, China, Southeast Asia, and Europe.

Watch the video: Stone Tool Technology 

Approximately two million years elapsed between the time Homo erectus left Africa and Homo sapiens followed. During this span, Homo heidelbergensis, named for the Germany location where the remains were discovered. Neanderthals (the 'th' pronounced as 't') are our closest extinct human relatives. Their bodies were shorter and stockier than ours, another adaptation to living in cold environments. Neanderthals' brains were just as large as Homo sapiens and often larger. Neanderthals inhabited Eurasia from the Atlantic regions of Europe eastward to Central and southwest Asia and as far as the Mediterranean. 

Watch the video: Homo Neanderthalensis

Neandertal became the archetypal "cavemen;" they lived in shelters, made and wore clothing; were skilled hunters of large animals, ate plant foods, and made symbolic or ornamental objects. There is evidence that Neanderthals buried their dead with offerings. Neanderthals lived between 200,000 and 30,000 years ago.

Watch the video: Neanderthals and Us Natural History Museum

The successor to Homo erectus is Homo sapiens (Latin: "wise man"), the species to which all modern human beings belong. Human beings physically resemble the primates more closely than any other known living organisms. Homo sapiens evolved in Africa. Homo sapiens emerged circa 400,000 BCE and evolved over the next 350,000 years. Homo sapiens inherited all the abilities and characteristics of Homo erectus, plus developed a brain eventually 33% larger than H. erectus. This increased brain size made possible significantly greater conceptual thought.

Gradually, homo sapiens evolved into fully behaviorally and anatomically modern humans. Humanlike remains of hominins provide clues about the origin of homo sapiens (modern human). There are three (3) main Homo species: Australopithecus, Homo habilis, and Homo erectus. Several extinct species are classified as either ancestral to or closely related to modern humans, most notably Homo neanderthalensis.

Homo sapiens developed a kind of larynx (voice box) allowing much more complex speech, which let it communicate much more complex knowledge rather than rely on instincts or just what they could learn in one lifetime. Homo sapiens used its more remarkable conceptual ability to make more complex tools than did Homo erectus. With these tools, it was able to hunt (rather than scavenge) large animals. By circa 40,000 BCE, Homo sapiens evolved with all the physical characteristics of today's humans. It has upright posture, fine motor abilities, complex conceptual thought, and developing extraordinary human speech.

Watch the video: How Neanderthal are You?

According to paleo archaeologists, approximately 100,000 to 60,000 years ago, homo sapiens migrated out of Africa separately and populated the world. Some scientist posits that homo sapiens succeeded in such different environments and survived instead of going extinct because humans underwent a dramatic cognitive change that involved a greater capacity for complex language, and symbolic use of material culture. This change in cognition means most major behavioral advances had already occurred with our common ancestor and other species such as Homo heidelbergensis – Neanderthals.