Chapter 34: Humans
Section 2: Hominid Evolution: Human Ancestors and Relatives
Hominid Evolution: Human Ancestors and Relatives
Between 4 and 9 million years ago, the hominoid line in Africa gave rise to a small group of species that we now recognize as our ______
o______
oNot yet human but showed several evolutionary trends that distinguish them from other hominoids
What Are Hominids?
Hominids were ______that ate both meat and vegetable foods, as modern humans do
As time progressed, the ______, ______, and ______of these animals changed shape in ways that made it easier for them to walk upright on two legs
o______
Because our ancestors could walk erect, their hands were free to use tools more often
At the same time, the thumb of the hominid hand became more and more independent from the other fingers
The evolution of an ______enabled ancient hominids to grasp objects and use them as tools more effectively than other primates
Hominids also displayed a remarkable increase in ______
o______, our closest relatives among the apes, have a brain size of about 280 – 450 cubic centimeters
oThe brain of Homo sapiens, on the other hand, ranges in size from 1200 – 1600 cubic centimeters
Enormously expanded human ______
______
How Did Hominids Evolve?
Much of our most recent evidence for hominid evolution comes from a small area in eastern Africa between ______
There, several researchers have found fossils of several species of hominids dating from about 4 million to about 1.5 million years ago
Australopithecus: The First Hominids
The first hominid fossil to be found, a nearly complete skull of a young child, was discovered in South Africa in 1924
o______
______
Because the skull belonged to a child, it could not be used to determine how adults of the species looked
But 12 years later, investigators in Africa found fossils of adult australopithecines
oOne of the fossils was part of a hip bone, indicating that Australopithecus ______
An essential step in the evolution of our species from an apelike ancestor
Since those discoveries, researchers have found many more complete hominid fossils
In 1974, a team led by Donald Johanson and Tim White found a nearly complete Australopithecus skeleton
From the shape of the pelvic bone, it was clear that this skeleton had been that of a ______
o______
In 1977, anthropologist Mary Leakey made another discovery: a set of fossil ______
From the size of the prints, they were probably a parent and an offspring
oClear evidence that the animals that made the footprints ______, as humans do
No stone tools have been found among Australopithecus fossils, but they may have used ______as tools in a way similar to that of chimpanzees today
Most current studies suggest that there were at least four species of Australopithecus
o______
o______
o______
o______
These species all lived between 4 and 1.5 million years ago, walked upright, and had much smaller brains than present-day humans
Homo habilis
For a while, australopithecines were the only known links in the chain of human evolution
Then anthropologist Richard Leakey found another hominid fossil with a smaller ______and significantly larger ______than the australopithecines
Leakey felt this species was similar enough to humans to be placed in our own genus, Homo
Fossils of this hominid were found along with tools made of ______
o______
______
Near one of these fossil finds is the oldest human settlement yet discovered (Kenya)
The settlement was found at a level in the rock dated at 1.9 million years ago
The main site is a circular stone structure about 4 meters in diameter
Inside, the floor is littered with animal bones and stone tools
Homo erectus
Within a few hundred thousand years Homo habilis disappeared and was replaced by a larger brained species called ______
By 1 million years ago, this species had spread over most of the Old World, from Africa to Europe to Asia
Homo erectus was an excellent ______
oCarefully chipped and balanced hand axes have been found with Homo erectus fossils throughout the world
In caves in China that are at least half a million years old, charred animal bones have been found around fire sites
oMust have used ______
Homo sapiens
About 500,000 years ago, the first hominids assigned to our own species appeared
These hominids, often called ______, would not be easily recognizable as modern humans
Little is known about this species
Around 150,000 years ago, a new hominid walked on Earth
First discovered in the Neander valley in Germany, this species was called ______, or Homo neanderthalensis
Now, based on more complete fossil evidence, Neanderthals have been placed in our own species and are called Homo sapiens neanderthalensis
Neanderthal man could probably walk down a busy street today and not be noticed
These early members of our species were successful for a time and became common throughout ______by 70,000 years ago
The first hominids truly identical to modern humans appeared in locations scattered throughout the Old World roughly 100,000 years ago
These large-brained people, called ______, were more slender than the Neanderthals and had a more complex culture
They made a wide variety of stone and bone tools, including spear points, knives, chisels, and needles
Fossils of Cro-magnon are now classified as modern humans, ______
Most paleontologists interpret the dates of Cro-Magnon fossils found throughout the world as indicating that modern humans originated in ______and from there spread out over the rest of the world
However and wherever Cro-Magnons originated, there is ample fossil evidence that they lived side by side with Neanderthals in several locations for some time
Then, around 30,000 years ago, the Neanderthals ______
Some scientists believe that Cro-Magnons interbred with Neanderthals, ______
Others believe that the more intelligent newcomers killed off their older relatives
In either case, only Homo sapiens sapiens remained to populate the rest of the world