Exam 3 Flashcards
(18 cards)
What are hominins?:
all the species that are more closely related to humans than to chimpanzees.
What trait is most important in hominin evolution?
Bipedalism.
What is morphology?:
the study of the form and structure of organisms and their specific structural features. This includes aspects of the outward appearance (shape, structure, color, pattern) as well as the form and structure of the internal parts like bones and organs.
What is a derived trait?:
present in an organism, but was not present in the last common ancestor of a group of organisms.
Aridity Hypothesis
suggests that the expansion of drier, savannah-like environments in Africa played a significant role in the evolution of hominins.
The Savannah Hypothesis
broader idea that suggests hominin evolution was driven by the transition from forest to savanna environments.
Environmental Pressure: As forests shrank and grasslands expanded, early hominins were forced to adapt to new conditions.
Adaptive Traits: This led to the evolution of traits such as:
Bipedalism: For efficient travel across open areas.
Tool Use: To access new food sources and defend against predators.
Larger Brains: To navigate complex social interactions and solve problems in a changing environment.
The Variability Selection Hypothesis
proposes that the unpredictability of environmental changes, rather than a specific environment, drove hominin evolution.
Key Points:
Fluctuating Environments: Instead of a one-time shift to savanna, this hypothesis emphasizes that environments were constantly changing and unpredictable.
Adaptability: Hominins who could adapt to a variety of conditions (wet, dry, hot, cold, etc.) were more likely to survive and reproduce.
Behavioral Flexibility: This favored the evolution of traits such as:
Larger Brains: To process information and make decisions in novel situations.
Tool Use: To exploit a variety of resources.
Social Learning: To learn new behaviors from others.
Evidence: This hypothesis is supported by evidence that hominins occupied a range of different environments and exhibited diverse behaviors.
The Social Brain Hypothesis
suggests that the increasing complexity of hominin social life was a major driver of brain evolution. It posits that the demands of navigating complex social relationships led to larger and more sophisticated brains.
Key Points:
Social Complexity: As hominins began living in larger groups, they faced new challenges, such as:
Cooperation: Working together to hunt, gather food, and defend against predators.
Competition: Competing for resources and mates.
Communication: Communicating effectively with others.
Brain Evolution: These challenges favored the evolution of larger brains with enhanced cognitive abilities, such as:
Social Intelligence: Understanding the behavior of others.
Empathy: Recognizing and responding to the emotions of others.
Language: Communicating complex ideas and coordinating group activities.
Evidence: Studies of primate brain size and social behavior support the idea that there is a link between social complexity and brain size.
The Aquatic Ape Hypothesis
suggests that a period of semi-aquatic adaptation influenced the evolution of certain human traits.
Key Points:
Aquatic Adaptation: Proponents of the AAH argue that early hominins spent a significant amount of time in or near water.
Traits: This led to the evolution of traits such as:
Hairless Skin: To reduce drag in water.
Subcutaneous Fat: For buoyancy and insulation.
Bipedalism: For wading in shallow water.
Voluntary Breath Control: For diving.
Criticism: The AAH is controversial and lacks strong support from the fossil record. Many of the traits cited as evidence can be explained by other factors.
What is important about the foramen magnum?:
large opening at the base of the skull through which the spinal cord passes to connect with the brain.
Know the Dental formulas differences between Apes and us, like 2:1:2:3:
2 Incisors
1 Canine
2 Premolars
3 Molars …on each side of both the upper and lower jaws. So, to calculate the total number of teeth:
(2+1+2+3)×2×2=32
Dental Formula in Apes
2 Incisors
1 Canine
2 Premolars
3 Molars …on each side of both the upper and lower jaws. They also have a total of 32 teeth.
What tooth is particularly good for determining sexual dimorphism in primates?:
The canines
Canine Teeth:
often the most sexually dimorphic teeth in primates. This means that the size and shape of canine teeth tend to differ more between males and females than other teeth do.
Ardi
discovered in the Afar region of Ethiopia.
The most complete Ardipithecus ramidus skeleton dates to about 4.4 million years ago, making it one of the oldest hominin fossils discovered.
The significance of Ardi is that it predates Australopithecus afarensis (like Lucy) by about a million years, giving us a glimpse into an earlier stage of hominin evolution.
High level knowledge of Au. Afarensis (timeframe for example).:
lived from approximately 3.9 to 2.9 million years ago.
Key fossil discoveries include “Lucy” and the Laetoli footprints.
They were bipedal but retained some ape-like features.
They are considered an important species in the evolution of humans.
Why was Taung child important?:
discovered in 1924 by miners working in a limestone quarry at Taung, South Africa. The fossil was identified by Raymond Dart, an Australian anatomist and anthropologist, who recognized its significance. Dart named it Australopithecus africanus, meaning “southern ape of Africa.” This was the very first early hominin fossil found in Africa, which was a game-changer because, at the time, many scientists believed that human origins were in Europe or Asia.
Who was known as being robust and why?:
refers to the Paranthropus genus (formerly classified as Australopithecus).
They had distinctive craniodental features adapted for chewing tough, fibrous foods.
Key features include large chewing muscles, a sagittal crest, large molars, and thick enamel.
They represent an evolutionary side branch and are not direct ancestors of Homo.
