hominids - Lisana

What is a hominid?

A hominid is a member of a species on the human branch of evolutionary tree; they are a species more closely related to humans than to chimpanzees. A primate of their family that includes humans and their fossil ancestors

Australopithecus afarensis (Lucy)

Australopithecus afarensis had both ape and human like features. They had apelike face proportions and a braincase about 1/3 the size of a human's. What made their face apelike was a flat nose and a lower jaw that stuck out farther. Australopithecus afarensis had long, strong arms with curved fingers that helped them grasp things. Lucy's species had small canine teeth like all other early humans, and were bipedal. Their adaptations made for living on the ground and in trees was important to their successful species life span of approximately 1 million years while climates changed.

Homo erectus (Turkana boy)

Homo erectus had human-like body proportions with longer legs and shorter arms compared to their torso. These adaptations show that they lived on the ground proving they lost the ability to climb trees. Homo erectus has an expanded brain case closer to modern humans. Homo erectus made the earliest hand axes and the first major stepping stones for stone tool technology.

Changes in the: knee

Human knee joints are enlarged to better support an increased body weight. Humans walk with their knees straight and the femur angled.

Homo neanderthalenis

Neanderthals are modern humans closest extinct human relative. Their skull features are a large middle part of the face, large brow ridges, highly angled cheek bones, and a huge nose for humidifying and warming cold, dry air. Their bodies were short and big compared to ours which was an adaptation for colder climates. Their brains were as large as ours and often larger which was proportional to their larger bodies. They lived in Europe 50,000 years ago and eventually spread to the Near East.

When did hominids seperate from the chimp/gorilla branch?

Our hominid ancestors separated from the Chimpanzee/Gorilla branch around 5-7 million years ago.

Out of Africa theory

The "Out Of Africa" theory says that all modern humans branch from a group of Homo sapiens who emmigrated from Africa and spread throughout Eurasia over thousands of years. They replaced other early humans (like Neanderthals), rather than interbreeding with them. Once the hominis became bipedal meat eaters (carnivores) they had to walk farther to find food and that is when they began to leave Africa spreading into the world.

Changes in the: foot

The human foot evolved to act more like a platform to support the weight of the body rather than acting as a grasping structure like in early hominids. Human feet have an arch and this is important because they help with absorbing the energy every time a step is taken. The big toe helps with balance while walking.

Changes in the: spine

The modern humans spine is straight to help with posture while walking on two feet and is no longer bent over/hunched from walking on all four limbs.

Changes in the: pelvis

The pelvis becomes stronger to hold all of the organs while standing straight and upward. Before it was the rib cage that used to hold the organs while the hominids were bent over on all fours.

What are the two major changes that occurred on the way to becoming human

The two major changes are brain size (brain case size/shape) and bipedalism (legs, feet, back, and pelvis)

How did environmental changes affect hominin evolution?

What they ate and where they could find food changed. This was depending on the climate and environment they were in. An environment with few plants would mean they were probably carnivorous. Their skin color also changed depending on the environment. UV rays darken skin tone because of active melanin.

Relationship between bipedalism: enlarged brains

When hominids became bipedal they learned they could now hold things with their hands which lead to the tools. After tools were made, it directly led to hunting and they then became meat eaters.

Relationship between bipedalism: hair loss

When hominids became bipedal, they lost all of their hair. When they began to walk upright, they were able to walk and run further distances much faster. They needed a way to keep their body heat down since the way they moved changed. Hair loss happened in places where the sun hit the hominids the most (back). Hair on the head has been retained to help reflect and radiate heat before it reached the skin.