hominins

• What is a hominin?

  Hominins are primate species that are more closely related to humans than chimps so they are classified on the human branch, they did not evolve in a straight line to homo sapiens, several hominin species co existed at certain points, many lineages died out. They are bipedal, have a large cerebral cortex, reduced canines, nose and chin are prominent, reduced eye ridges, highly sensitive skin, body hair reduced, and complex social behavior.
• When did our Hominin ancestors separate from the Chimpanzee/Gorilla branch?

  Our Hominin ancestors diverged from the Chimpanzee/Gorilla branch around 6 to 7 million years ago.
• What are the 2 major changes that happen on the way to becoming human?

  The two major changes that happened on the way to becoming human is that they became bipedal which means they began to walk upright, and also their brains became a lot larger.
• What caused our ancestors to evolve?

  -wooded savannah's gradually dried out and lost tree coverage due to climate change

  forced to leave trees more often to reach food sources

  -individuals better adapted to land life with variations like narrower stances, lower spinal exits, and big toes angled more similarly to other toes being able to travel in the grasslands easier

  -as the trees disappeared, natural selection would reduce the number of offspring without adaptations helpful for walking and allow for allele frequencies for beneficial adaptations to increase in the gene pool

  -walking upright was crucial for seeing food and predators over tall savanna grass and to efficiently move to and from food sources

  -helped in thermoregulation and the ability to easily carry offspring or food while walking

  *trees were decreasing, (climate was changing) so it was more beneficial to live on the ground

  *being a biped is exposing less of you body to the hot sun and frees your hands to do more

  *moving from place to place exposes more and different food resources
• BE able to describe the bodily changes that occurred because of bipedalism.

  (foot, spine, hip, femur changes)

  -the spinal cord entered the skull lower down so that standing up would be easier

  -big toes were in chimps so they could grasp branches with their feet, but they became aligned with the rest of the toes in order to help propel the body forward

  -thigh bones and hips cooperatively changed so that legs became straight instead of bowed, and they faced forward

  -the lumbar curve in the spine helps with staying upright and also acts as a shock absorber.
• Be able to explain the relationship between bipedalism with enlarged brains and hair loss.

  -all have to do with the hominins evolving

  -an increased brain size was the start of the change between hominins and apes

  -other adaptations like bipedalism and hair loss came along

  -results of hominin intelligence that were changes in their food-gathering methods, parental care, as well as social

  -new adaptations were all linked together due to the changes that had to be made in order for the hominins lifestyle to be easier and beneficial.
• Australopithecus Afarensis species, like Lucy


  -was bipedal

  -had a small brain, about 430 cm3 in volume

  -bodies were about the same size as chimpanzees with

  -arms longer than legs and long, curved digits

  -spent some time in trees

  -opportunistic omnivores, scavenging carcasses and eating a variety of foods

  -jaws were long and narrow

  -had canine teeth
• Homo Erectus, Turkana boy

  -oldest known hominid fossils discovered outside of Africa

  -larger brains of about 1050 cm3.

  -estimated to have lived until about 200,000 years ago

  -probably about the same size as modern humans

  -built and used advanced tools to hunt small game

  -had a large and broad skull

  -had a large face

  -flat noses

  -thick jaw with molar teeth
• Homo Neanderthalensis


  -best-known hominids, also called Neanderthals

  -brains were larger than ours at 1,500 cm3

  -able to construct and use complicated stone and wood tools to hunt big game

  -large rounded eyes

  -large and broad noses

  -thick bones and joints (strong muscles)

  -very large jaw and teeth
• Be able to explain when and how/why H. sapiens migrated out of Africa to populate the world.


  -emerged from Africa in several waves going first to Asia 50-60 thousand years ago and then to Europe 40 thousand years ago and North America 15-35 thousand years ago

  -lived and evolved in Africa and eventually migrated out of Africa between 200,000- 100,000 years ago

  -might have left due to weather patterns that caused northern Africa and the Arabian Peninsula to become a greener environment

  -greener environment provided more food and water elsewhere from competition in Africa

  -new lush environment expanded so did the animals, and as the animals (food) moved the humans followed them
• What is another theory behind the emergence of H. sapiens in the world?

  The Multiregional Evolution Theory

  -theory states that Homo Sapiens evolved in regional populations from Archaic hominids both in and outside of Africa

  -Homo Erectus left Africa around 2 million years ago and dispersed into other areas and over time they evolved into modern humans

  -different populations of Homo Erectus mated

  -gene flow with other populations of Homo Erectus causing gene flow between the populations

  -led into a common species called Homo Sapiens
• How did environmental changes in Africa affect hominin evolution?

  -different weather patterns (more rain) caused the environment to become more green

  -before these weather patterns, most populations would have been trapped by natural barriers

  -environmental changes pressured the hominins to leave the trees and move across the ground to find new food sources

  -learned how to successfully kill these animals and due to a dramatic increase of meat in their diets ( protein and fat= increased amount of calories) the began to grow larger brains
• How/Why did lighter skin color evolve in some groups of Homo sapiens?

  -Melanin= pigment in the skin that absorbs UV rays, darker skin has more active melanin cells

  -ultraviolet radiation from the sun causes mutations and degrades folate (needed for fetal development and spermatogenesis) but it also helps the production of vitamin D (vital nutrient)

  -In these new areas, people are exposed to less sun so they aren't in danger of running low on vitamin D but they are in slight danger of large amounts of UV radiation

  -as hominins migrated out of Africa and into climates further north, there was less sun and with less melanin they had more relative fitness because they got more vitamin D.

  -since there was less sun they weren't exposed to excessive UV radiation
• What do we know about our hominin family tree?

  -we are part of the Homo branch of the our evolution

  -the four main groups are Homo, Australopithecines, Paranthropus, and Ardipithecus

  -we know for sure about the structure of our family tree is that it is very disputed

  -Donald Johanson believes that Homo Heidelbergensis is our most recent direct ancestor but Bernard Wood believes that Homo Heidelbergensis and Homo Neanderthalensis are the same species

  -Wood doesn't believe that H. Heidelbergensis is a species but that H. Neanderthalensis is our most recent ancestor and before that we go back to H. Erectus and H. Ergastor

  -although we can date different species and make theories based on the evidence from dating and fossils, we are still unable to make a widely accepted conclusion about our direct lineage

  -we are the only remaining hominin

  -multiple species were roaming around at various time periods