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.

D K P C O F G S

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 facesMore upright and bipedalHowever 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 speciesGiving 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 heidelbergensisOriginated in Africa (600,000 years ago)

then spread to EuropeAppeared 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 humanslarge middle part of the face, angled cheek

bones, and a huge nose for humidifying and warming cold, dry air

bodies were shorterHad 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 toControl firelive in sheltersmade and wore clothingwere skilled hunters of large animals occasionally made symbolic or ornamental

objects

(Cont…)

BehaviorsBuried 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 ancestorAfrican lineages branched off more ancient

positions on human treeThis 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 wavesFirst into Asia then to Europe and Australia

October 2004Peter 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 shapeSuggests 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 processExample: using toolsFound 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 mammalsConcluded 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