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 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 Went extinct 30,000 years ago 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 Some reasons for this 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