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 Photo A shows an A. afarensis skull, which is similar in shape but the forehead slopes back and the jaw juts out. Photo A shows a human skull.
The skull of (a) Australopithecus afarensis , an early hominid that lived between two and three million years ago, resembled that of (b) modern humans but was smaller with a sloped forehead and prominent jaw.
Partial skeleton is human-like but child-sized.
This adult female Australopithecus afarensis skeleton, nicknamed Lucy, was discovered in the mid 1970s. (credit: “120”/Wikimedia Commons)

Australopithecus africanus lived between 2 and 3 million years ago. It had a slender build and was bipedal, but had robust arm bones and, like other early hominids, may have spent significant time in trees. Its brain was larger than that of A . afarensis at 500 cubic centimeters, which is slightly less than one-third the size of modern human brains. Two other species, Australopithecus bahrelghazali and Australopithecus garhi , have been added to the roster of australopiths in recent years.

A dead end: genus Paranthropus

The australopiths had a relatively slender build and teeth that were suited for soft food. In the past several years, fossils of hominids of a different body type have been found and dated to approximately 2.5 million years ago. These hominids, of the genus Paranthropus , were relatively large and had large grinding teeth. Their molars showed heavy wear, suggesting that they had a coarse and fibrous vegetarian diet as opposed to the partially carnivorous diet of the australopiths. Paranthropus includes Paranthropus robustus of South Africa, and Paranthropus aethiopicus and Paranthropus boisei of East Africa. The hominids in this genus went extinct more than 1 million years ago and are not thought to be ancestral to modern humans, but rather members of an evolutionary branch on the hominin tree that left no descendants.

Early hominins: genus Homo

The human genus, Homo , first appeared between 2.5 and 3 million years ago. For many years, fossils of a species called H . habilis were the oldest examples in the genus Homo , but in 2010, a new species called Homo gautengensis was discovered and may be older. Compared to A . africanus , H . habilis had a number of features more similar to modern humans. H . habilis had a jaw that was less prognathic than the australopiths and a larger brain, at 600–750 cubic centimeters. However, H . habilis retained some features of older hominin species, such as long arms. The name H . habilis means “handy man,” which is a reference to the stone tools that have been found with its remains.

Visit this site for a video about Smithsonian paleontologist Briana Pobiner explaining the link between hominin eating of meat and evolutionary trends.

H . erectus appeared approximately 1.8 million years ago ( [link] ). It is believed to have originated in East Africa and was the first hominin species to migrate out of Africa. Fossils of H . erectus have been found in India, China, Java, and Europe, and were known in the past as “Java Man” or “Peking Man.” H . erectus had a number of features that were more similar to modern humans than those of H . habilis . H . erectus was larger in size than earlier hominins, reaching heights up to 1.85 meters and weighing up to 65 kilograms, which are sizes similar to those of modern humans. Its degree of sexual dimorphism was less than earlier species, with males being 20 to 30 percent larger than females, which is close to the size difference seen in our species. H . erectus had a larger brain than earlier species at 775–1,100 cubic centimeters, which compares to the 1,130–1,260 cubic centimeters seen in modern human brains. H . erectus also had a nose with downward-facing nostrils similar to modern humans, rather than the forward facing nostrils found in other primates. Longer, downward-facing nostrils allow for the warming of cold air before it enters the lungs and may have been an adaptation to colder climates. Artifacts found with fossils of H . erectus suggest that it was the first hominin to use fire, hunt, and have a home base. H . erectus is generally thought to have lived until about 50,000 years ago.

Questions & Answers

Parkinson's disease is a caused by the degeneration of neurons that release
birabwa Reply
why is it so hard to get to the questions
Eric Reply
why is it so hard to get to questions?
Eric
what types of proteins which are found in hair,hooves and tendons?
Kapalu Reply
what is blood cells
Isaac Reply
It's cells of the blood
Kaique
can biology be also be define has a scientific study that deal with life?
Stanley Reply
do you care asking you a question
Afolayan Reply
name the gas that diffuses into the plants leaves on a bright, sunny day
Tuhemwe Reply
explain why this gas diffuses into the plant's leaves
Tuhemwe
name two gases that diffuses out of the plant's leaves on a bright sunny day
Tuhemwe
Biology olympaid
Khan
what is ecosystem
Rondy Reply
why does a car move yet it is not a living thing?
Sserujja
this is because of the engine and fuel placed on
Gift
I also think it because force has been apply to it.
Stanley
It is aplace where organísms live and associate with each other.
Nasib
what is the reason of swelling due to fracture
Ejaz Reply
Sngy alaka
Khan
how do animals reproduce
Kelvin Reply
be specific because there are so many types of animals and how they reproduce are different
Sheillah
yeah
Chinwendu
just be specific with a particular animal
Stanley
what happens when you sneeze
Asuquo Reply
The sneeze center sends out a signal to tightly close your throat, eyes and mouth. Your chest muscles contract and compress your lungs while your throat muscles relax. All of that means air, saliva and mucus is forced out of your nose and mouth. AAAAAHHHH-CHOOOO.
Hassan
how are you
Ayouba
hy
Ejaz
hii
Ishitha
hello
mahesha
Hello
Madu
Am fine
Abavon
how far
Abavon
hello
Sheillah
with why
Sheillah
with what
Sheillah
I have a question plzz
Sheillah
what is globsl warming
Rondy
Global warming is the overall rise in temperature of the Earth itself which is caused by multiple factors. Such factors include: greenhouse gases, the burning of fossil fuels and other forms of human activity.
Maryam
It's overall effects are known as climate change.
Maryam
thanks
Rondy
good
Haider
No problem.
Maryam
Thank you.
Maryam
what is creatinine?
Haider
Creatinine is a waste product produced in the body during muscle metabolism. This waste product is expelled from the body through urine. Here is it's formula:  C4H7N3O
Maryam
Formula: C4H7N3O
Maryam
ok
Haider
ok
Stephen
Outline the process of cell in the body interms of it's function.
Aliruku Reply
what communication method used mainly by plants
Jerda Reply
what is biology
james Reply
Biology is the study of life
Omoloju
yah
John
Biology is natural science that studies life and living orgasms.
Hilda
any questions from colleague
Sheillah
define nerve impulse
Karlin Reply
A nerve impulse is the way nerve cells (neurons) communicate with one another. Nerve impulsesare mostly electrical signals along the dendrites to produce a nerve impulse or action potential. The action potential is the result of ions moving in and out of the cell.
Sam

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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