Transcript Humans and early hominids

By Edward Zhu, David Flores, and Hammad Ahmed
Major features that make us
human
Upright posture and bipedal movement
 Reduced jawbone and shortened
digestive tract
 Larger brain
 Tool use
 Symbolic thought and use of language

Hominoids and Hominids

Hominoids are a clade
including gibbons,
orangutans, gorillas,
chimpanzees,
bonobos, and
humans, along with
extinct species that
descended from the
same ancestor.


Hominids are a clade
including humans and
all species more
closely related to
humans than other
living hominoids.
A species on the
human branch of the
evolutionary tree; a
member of the family
Hominidae, including
Homo sapiens and
our ancestors.
DKPCOFGS
Paleoanthropology
The study of human origins and
evolution.
 Paleoanthropologists have found 20
extinct that are more closely related to
humans than to chimpanzees.

 Those of which are called hominids
Earliest Hominid
The oldest hominid is Sahelanthropus
tchandensis, which lived 7 million years
ago.
 Sahelanthropus and other early
hominids shared some characteristics of
humans.

 Flat canine teeth and flat faces
 More upright and bipedal
 However had smaller brain
Misconceptions

Our hominid ancestors were not
chimpanzees or any modern apes.
 Chimpanzees and humans are two
divergent branches from a common
ancestor that wasn’t a chimpanzee or a
human.
Misconceptions

Human evolution is not a progressive
ladder with steps of ancestral
hominoids.
 If human evolution is a parade, then many
splinter groups traveled down dead ends,
and several different human species
coexisted.
Misconceptions

Various human characteristics such as
upright position, enlarged brain, did not
evolve together at once.
 Differing rates of evolution in different
features is known as mosaic evolution.
Australopiths

The various pre-Homo hominids are
classified in the genus Australopithecus
(“southern ape”) and are known as
australopiths.
 They are a paraphyletic assemblage of
hominids that lived between 4million to
2million years ago.
Australopiths
Australopithecus africanus walked fully
erect and had human-like hands and
teeth.
 However had one-third the brain size of
a present-day human.

Lucy


In 1974, in Ethiopia, paleoanthropologists
discovered a 3.24million-year-old Australopithecus
afarensis skeleton that was 40% complete. “Lucy”
was only about 1m tall.
Softball sized head, afarenis skulls have a longer
jaw.
Artist’s rendition of what A. afarenis may have looked like.
Bipedalism
Hominids most likely became bipedal
due to the increase of a savanna
environment with fewer trees.
 Hominids began to walk long distances
on two legs around 1.9million years ago.

Tool Use

Other hominoids can use tools.
 Orangutans use sticks to retrieve insects
from nests. Chimps use rocks to smash
open food.

The oldest evidence of tool use are cut
marks found on bones, 2.5million years
ago.
Early Homo
The earliest fossils that
paleoanthropologists place in our genus
Homo are those of the species Homo
habilis, ranging in age from about 2.4 to
1.6 million years
 Stone tools have been found with this
species

 Giving this species its name “handy man”

Compared to australopiths, H. habilis
have a shorter jaw and a larger brain.
Homo Ergaster
Existed between 1.9 and 1.6million
years ago, they were the first fully
bipedal and large brained hominids.
 They had longer slender legs for long
distance walking, and had more
sophisticated tool use.
 Their teeth may suggest that they
cooked/mashed their food before eating.

Homo Erectus
Homo erectus was the first hominid
species to migrate out of Africa where
they originated 1.8million years ago.
 They colonized Asia and Europe and
their fossils are sometimes called
“Beijing man” and “Java man”

Neanderthals
Also Known as Homo Neanderthalensis
 Discovered in 1856 in the Neander Valley in
Germany

(Cont...)
At first thought to be considered a stage
in evolution of Homo erectus into Homo
sapiens
 Discovered actually descended from
Homo heidelbergensis

 Originated in Africa (600,000 years ago)
then spread to Europe
 Appeared in Europe and the Near East
(200,000 years ago)
Homo heidelbergensis to
Neanderthals
(Cont…)

Similarity to humans
 Brain same size as present day humans

Went extinct 30,000 years ago
 Did not contribute to gene pool of present day
humans
 Proof is found in their DNA
○ Compared their DNA to the DNA of Europe, Africa,
and Asia
○ Analysis shows that the Neanderthals form a clad
○ The Europeans are more closely related to
Africans, and Asians
(Cont…)

Differences to humans
 large middle part of the face, angled cheek
bones, and a huge nose for humidifying and
warming cold, dry air
 bodies were shorter
 Had thick bones and prominent brow
Some reasons for this
 Lived in cold areas

(Cont…)
Earlier humans lacked heavy brow
ridges that H. erectus and Neanderthals
had
 More slender

(Cont…)

Ability to
 Control fire
 live in shelters
 made and wore clothing
 were skilled hunters of large animals
 occasionally made symbolic or ornamental
objects
(Cont…)

Behaviors
 Buried their dead and marked grave with
offerings (flowers)
 No other early human species practiced this
Homo sapiens
Now clear that the ancestors of humans
originated in Africa
 In 2003, researchers in Ethiopia
discovered 160,000 year old fossil of
Homo sapiens (oldest known fossil of
our own species)

(Cont…)

Based on research
 DNA analysis shows that all living humans are
closely related besides Neanderthals
 Europeans and Asians have a common
ancestor
 African lineages branched off more ancient
positions on human tree
 This suggests that all humans have ancestors
that originated from Africa
○ Supported by analysis of mitochondrial DNA and Y
chromosomes from members of various
populations
(Cont…)

Study of the y chromosome show that
humans spread beyond Africa in 1 or more
waves
 First into Asia then to Europe and Australia

October 2004
 Peter Brown, and Thomas Sutikna discovered
skeleton of adult hominid that dated 18,000
years ago (Homo florensiensis)
○ Had smaller brain and was shorter (similar to
Australopith)
○ similar to Homo sapiens
 Skull thickness, proportions and teeth shape
 Suggests that it descended from H. erectus
(Cont…)
“Shrinkage” occurred which isolation on
the island resulted in selection for
greatly reduced size.
 Rapid expansion of Homo sapiens may
have occurred by our mental process

 Example: using tools
 Found more evidence of sophistication
○ Geometric markings on pieces of ochre
(77,000 years old in South Africa)
○ 36,000 year old painting found in caves
(Cont…)
Gene FOXP2 was identified in 2001
being essential for language
 If mutated, suffer a range of
impediments and reduced activity
 Compared to homologous gene of other
mammals

 Concluded that it experienced intense
natural selection
Features that are lost/emphasized as
humans evolved.
Spinal cord placement is right under the
skull to accommodate the bipedalism.
 Larger brain with capabilities of tool use
and cognitive thought.
 Flatter face, less protruded jaw.

Sources

http://humanorigins.si.edu/research