Human Evolution Flashcards
Human Differences
Complex thoughts
Culture
Language
Technology
Human Similarities
We are here because our ancestors reproduced
If reproductive success depends on heritable variation in traits, we are still evolving
Physical changes often provide species with new adaptive challenges and opportunities:
• Global climate change
• Continental drift
• Geological changes
– New environments can arise (e.g., mountain ranges, desert basins)
– Geology may also change connections between two populations without a large
effect on how they live
therapsids
- radiated and dominated many terrestrial environments before dinosaurs did
- largely replaced by dinosaurs in the age of dinosaurs
radiation
gain in species diversity
-gives many chances for adaptation
contraction
loss of species diversity
Reasons for contraction/extinction
– Changing conditions (climate change, continents moving)
– Competition from other clades (therapsids vs. dinosaurs)
– Competition from a successful member (people vs. other hominins)
Advantages of previous radiation
- explored more kinds of environments
- found in more different specific places
- had more chances to adapt
primates -characterized by… (3 points)
– Highly developed stereroscopic vision
∗ Eyes are close together, face forward, and are used together, allows 3-d visualization
– Versatile limbs
∗ Grasping hands and feet
∗ Nails and fingertips (instead of claws)
– Large brains
There are many theories for why primate traits might have been adaptively favored in our ancestor: (5 points)
– Leaping from branch to branch – Climbing and balancing on trees – Exploiting new plant resources – Catching insects – Adaptive foraging
Adaptive foraging
the ability to switch between types of food, and to learn to use new types of food
Ape adaptations
- Apes are more adapted for swinging through trees, whereas monkeys are more adapted for climbing and leaping
- More upright
- Better at hanging, bad at sitting
Why might apes have diversified, and later been replaced by monkeys?
– Changing climactic conditions
– Changes in plants or insects
– Unpredictable adaptive innovations
What if the ape radiation had never happened?
–Less diversity between surviving apes
– Probably no people
frugivory
eating fruit
folivory
eating leaves
insectivory
eating insects
Teeth -Importance?
- important for processing food
- help scientists understand what extinct animals ate (often preserved, highly adapted)
Eye orbits
skeletal cavities where eyes are
Eyes -Importance?
tell us size, shape and position of eyes from fossil animals
What are the advantages and disadvantages of more forward-facing eyes?
- Better for precise tasks, three-dimensional visualization
- Not as good for looking around, being alert
What are the advantages and disadvantages of larger eyes?
- Better for night vision
- More costly? Harder to protect?
In species where there is more variation in male success, we expect:
More sexual dimorphism
More competition between males for females
Gorilla Dimorphism and sexual strategies
live in male-centered groups (one adult male, several adult females)
Chimp Dimorphism and sexual strategies
live in large, well-mixed groups with lots of interactions between males
and females
Which species, gorillas/chimps, should have more sexual dimorphism overall?
Gorillas. Males are huge and strong and compete for females by displaying and fighting. A dominant male has exclusive access to a group of females
Which species, gorillas/chimps, should have larger male genitals?
Chimpanzees have much larger genitals.
Gorillas don’t use genitals as part of sexual competition
Hominins
Characterized by….
refer to people and our upright ancestors
–Walking upright
– Specific changes in chewing design: teeth, jaws and skull
Modern humans
Characterized by…
- small face and teeth
* Less robust skeletal structure
How did upright posture and upright walking evolve?
Theories
–Adaptation to walking on the ground instead of swinging through trees
– Adaptation for keeping cool
– Adaptation for harvesting food
– Adaptation for carrying food
complex foraging
rely on many types of food, including types of food that are difficult to get or process
What adaptations likely favored complex foraging?
Clever hands, upright walking
What further adaptations might complex foraging have favored?
–Big brains
– co-operation, including male-female co-operation
– Social behaviour
Complex foraging may have promoted
co-operation between:
- between females and males, since primate child care is not well suited to a hunting life style
- between people with different skills, since they might have access to food at different times
- among hunters, since hunting success is highly variable
- in teaching and learning
Complex foraging and thinking
Complex foraging favors large brains that can learn a lot
• It also favors a long learning period and communication
Why do human children develop so slowly?
Presumably related to elaborate sociality
-interested in how long it took our ancestors to mature: clues available in dental enamle/molar development
