Early Hominins PDF

# Early Hominins ## Hominins - Most paleoanthropologists believe a common ancestor to the modern African Apes (Chimps, Gorillas, Bonobos) and the Hominins existed approximately 6-7 million years ago. - Hominins are habitually bipedal primates. - Modern humans are the only extant (living) species...

# Early Hominins ## Hominins - Most paleoanthropologists believe a common ancestor to the modern African Apes (Chimps, Gorillas, Bonobos) and the Hominins existed approximately 6-7 million years ago. - Hominins are habitually bipedal primates. - Modern humans are the only extant (living) species of hominin. ## Bipedalism - The early ancestors of humans and the ancestors of the African apes appear very similar. - The key point of difference between early hominins and early apes were how they walked: early hominins were bipedal, early apes were quadrapedal. - There is a side by side image of two skulls. On the left, it shows the skull of **Sivapithecus** (12.5-8.5 million years ago). This is a possible ancestor of modern Orangutans (quadruped). On the right, it shows the skull of **Paranthropus Boisei** (2.3-1.2 million years ago). This is a Hominin (upright walker). ## Bipedalism: Advantages - We are taller and more intimidating to predators. - Walking on two legs is more efficient in terms of calories used. - We are able to use our front limbs to carry, use tools and to hunt and gather more efficiently. - We expose less of our bodies to direct sunlight, allowing for more efficient cooling. ## Bipedalism - Given the similarities of early apes and early hominins, the primary task is to examine the skeleton to figure out how this organism walked. ## Anatomical marks of bipedalism - Pelvis - Femur - Spine - Foot - Foramen Magnum - There is an image of a human pelvis. - There is an image of a chimp pelvis. - There is an image of a chimp skeleton. - There is an image of a chimp skeleton in a side profile with its spine highlighted. The caption is Spine/Quadruped. - There is an image of a chimp's foot. - There is an image of a human foot. - There is an image of a human spine in a side profile, with the spine highlighted. The caption is Spine/Biped. ## Sahelanthropus tchadensis "Toumai" 7 million years old - There is an image of a skull of **Sahelanthropus tchadensis**. ## Orrorin tugenensis “Millenium Man” ~6 million years ago - There is an image showing fragments of bones of Orrorin tugenensis numbered from 1 to 13. - There is an image depicting an artistic rendition of Orrorin tugenensis . The caption is **Orrorin tugenensis** ## Difficulties in building a family tree - Creating a "family tree" for extinct species is very difficult for two major reasons: - A) The fossil record is incomplete (not all organisms leave behind a record of their existence and - B) Many fossils are too old to derive DNA from, making genetic comparisons impossible. - Family trees of hominin and non-hominin fossils are constantly being redrawn as new discoveries are made. - Additionally, different fossils may be interpreted as the same species by one anthropologist...and different species by another. ## Lucy - 1974: Donald Johanson discovered "Lucy”, a 3 foot 8 inch hominin later classified as Australopithecus afarensis. -There is an image of Lucy’s skeleton. The caption is **Lucy: (AL 288-1) 3.2 mya** ## Comparative anatomy - There is a diagram showing the differences in the leg bones between a chimpanzee, Australopithecus afarensis and Homo sapiens. ## The Laetoli footprints - There are two images: on the left, it shows an area with a series of footprints, on the right, the image shows a single footprint up close. ## A. afarensis cranium (AL-444) - There is an image of an A. afarensis cranium. ## Modern Chimp Skull - There is an image of a modern chimp skull. ## Australopithecus afarensis (left) Chimpanzee (right). -There is an image of an A. afarensis cranium on the left and a modern chimp skull on the right. ## Big Brains and Bipedalism - Bipedalism emerged long before big brains. - What started us on the journey to becoming human was how we moved, rather then the way we thought. Brain changes came later. ## Early Hominins - The term Early Hominins is used to describe the hominins that lived before Genus Homo. They are all found only in Africa. - The fossil record indicates that there were a variety of species of early hominins adapted to various environments in sub-Saharan Africa. ## Robust vs. Gracile - Hominins and other primates are described as robust or gracile. - A robust body is heavy in skeletal structure and muscle. A gracile body is more slender and fine-boned. - There is an image of a **Paranthropus robustus** skull. - There is an image of an **Australopithecus Afarensis** skull. ## Speech - Examinations of australopithecines have determined their vocal tracts were very similar to apes. - As such it is unlikely that they used spoken language. ## Culture - While it is safe to assume that the majority of early hominins (like the majority of primates) were social creatures we know only so much about their culture. - It does seem to be the case that they DID NOT make stone tools: that came later in human evolution.