Unit IV: Hominidae Flashcards
Hominidae
(great apes)
- Pan: chimpanzee & bonobo
- Homo: humans
- Gorilla: gorillas
- Pongo: orangutans
Hylobatidae
(lesser apes)
sister to Hominidae
Hylobatidae characteristics
- Extend: 4 genera & 18 species
- Tropical Asia
- Low sexual dimorphism
- Highly arboreal (tree mobility)
- Very long arms and experts at brachiation locomotion
- Omnivorous diet, but >50% fruit
Brachiation Locomotion
using arms to swing from tree to tree, common among hylobatidae
Hominidae general characteristics
- Long arms, short legs, no tail
- Large body size
- Sexual dimorphism (degree varies, typically larger in males)
- Omnivorous, most have preference for fruit
- Large brains for body size
Genus Pongo characteristics
- 2 species in southeast Asia rainforests (endangered)
- Most arboreal and solitary of great apes
- Sexually dimorphic (males are larger)
- Quadruped fist walking (rarely bipedal)
- Omnivorous, preference for fruit
Genus Gorilla
- 2 species in sub-Sahara Africa rainforests (endangered)
- Live in group called troops
- Arboreal and ground dwelling
- Strong sexual dimorphism, males 2x the size
- Quadruped knuckle walking, bipedal for short distances
- Omnivorous, high percentage of diet is foliage (males have prominent sagittal crest)
Sagittal Crest
bone ridges in the skull, provides surface area for jaw muscle attack, common among male gorillas
Genus Pan characteristics
- 2 species in sub-Sahara rainforests (endangered)
- Arboreal and ground dwelling
- Quadruped knuckle walking, bipedal for short distances
- Omnivorous
- (Equally) closest relatives to humans
Chimpanzee specific characteristics
- Larger
- Male-dominated
- More aggressive
Bonobo specific characteristics
- Smaller
- Female dominated
- Less aggressive
- Frequent sexual behavior helps resolve conflicts
- Great preference for fruit
Did humans evolve from chimps?
Humans did not evolve from chimps, but rather from this common ancestor
What are the 3 extinct genera of the intermediate taxa between Humans/Chimps and their common ancestor?
- Ardipithecus (~5-4 mya)
- Australopithecus (~4-2 mya)
- Paranthropus (~3-1 mya)
What is the 1 extant genus from Human’s ancestral line?
- Homo (~3 mya-present)
Genus Ardipithecus characteristics
- 2 extinct species (~4-5 mya)
- Fossils from Ethiopia
- Grasping hallux (adaption for locomotion in trees)
- Hands more similar to modern humans than chimps
- Pelvis shape for walking upright
- Brain slightly smaller than modern chimps
- Reduced canines (less aggression?)
Genus Australopithecus
- 7 to 9 species (~4-2 mya)
- Fossils from eastern Africa
- Thought to be most closely related genus to Homo
- Brain sizes ~35% the size of humans
- High degree of sexual dimorphism (larger males)
- Teeth wear suggest mainly fruit diet, but also veggies and tubers (also meat consumption theory)
Australopithecus Afarensis (“Lucy”)
- oldest member of genus; lived 3-4 mya
- fossils from Ethiopia
- Dentition and jaw traits intermediate between humans and more distantly related apes
- Strong evidence of bipedalism:
(shape of pelvis, angle of femur, attachment of muscles around knee) - Arboreal or terrestrial?
(Curvature of fingers/toes adapted for grasping = arboreal
Loss of grasping hallux = terrestrial)
Grasping Hallux
the adaptation of the big toe for easier locomotion in trees
Genus Paranthropus
- Lived 1.5 to 2 mya
- “Robust” body type:
(strong upper body, large skull with flat face and no forehead, large brow ridges, large grinding teeth for diet) - Most specimens have sagittal crest
- Evolutionary “dead end”
Genus Homo
- 7 or more species (1 extant species = Homo sapiens)
- Genus is about 2.5-3 mya
- Long lower legs (walking, running)
- Smaller teeth
- Larger brains
- Bulge of Broca’s area (essential for speech) becomes visible
- Evidence of tool, fire use, and burial of dead
Broca’s area
part of the brain that controls the ability to produce language; becomes prominent in the Homo genus
What are the defining traits of human lineage?
- Adaptations for bipedalism
- Evolution of big brains
List of adaptation for bipedalism:
- Foramen magnum more anterior (where the spine connects to skull)
- Trunk
- S-curve of spine
- Larger surfaces for muscles supporting upright posture
- Expanded lumbar area - Shortened forearms
- Pelvis and legs
- Narrow pelvis
- Femur angles towards midline
- Long legs - Feet
- All toes point forward
- Enlarged heal and arch (to take impact of walking)
Advantages of Bipedalism
- frees hands for caring items, tool use
- may be particularly beneficial in open habitats (travel greater distances for food)
What is the reason for an increase in brain size/evolution of big brains?
- Increase in brain size is due to increase in body size, or may be linked to increased meat intake (energy)
- Positive feedback between cultural/linguistic complexity, technology advances, and diet
What are the 4 benefits of evolution of BIG BRAIN?
– Store information
– Quickly process information
– Problem solving
– Abstract ideas
What are the 2 costs of evolution of BIG BRAIN?
– Lots of energy
* Your brain is ~2% of your body size but uses ~20% of your energy
– More difficult childbirth (we have narrow hips, but babies have a big brain)
What is the history of Homo?
- oldest Homo species were in Africa
- Some species migrated out of Africa before the first H. sapiens (eg. H. erectus, H. neanderthalensis, and Denisovans in Eurasia)
- Before Homo sapiens, there were Homo species in Africa, Europe, and Asia
Where did Homo sapiens originate?
- Oldest H. sapiens fossils are all from Africa
- First H. sapiens fossils in other continents are 30-60,00 years old
Why do populations outside of Africa have less diversity?
Consistent with:
- Younger populations
- Bottleneck during founder event
What are the Pros & Cons of UVB:
Pros:
- causes synthesis of vitamin D, which is needed for absorption of calcium
Cons:
- damages skin surface, causes sunburns and some skin cancer
What are the 2 Ultraviolet Lights besides visible light?
UVA & UVB
What are the Pros & Cons of UVA?
Pros:
- Less intense than UVB (but still causes skin damage)
Cons:
- Breaks down folate
- Deficiency of folate can lead to birth defects and decreased sperm production
How is UV radiation distribution?
- Near equator: high levels of UV radiation (both types, due to more direct sunlight)
- Near poles: less UV light
What are determinate of Skin Pigmentation?
- Human ancestors in Africa (moved from forest to Savanna)
- with less shade, more exposure to UV light - Selection for cooling mechanisms
- more sweat glands and less hair from chimps - More skin exposure = selection for more melanin pigmentation
- melanin protects from UVA, preventing too much breakdown of folate
- since UVB levels are so high, vitamin D synthesis persists despite melanin - Migration to Europe = lower UV radiation (as move up latitude)
- this movement protected from loss of folate, but loss of vitamin D
- alleles that results in less pigmentation have high fitness due to increased ability to make essential vitamin D
What is the hypothesis of skin pigmentation?
Hypothesis that skin pigmentation is a balance between the pros (vitamin D production) and cons (folate breakdown) of UV radiation
- natural selection favors less/more melanin depending where you live
What are recent evolution in Homo sapiens?
- Selection at high altitude
- Lactose Intolerance
What occurs in Homo sapiens at high altitudes?
Lower concentration of oxygen in the air, leads to Hypoxia:
- deficiency of oxygen
- lots of complications (including fatigue, dizziness, headaches, insomnia, nausea, vomiting, and dilated veins)
What is Homo sapiens’ Plastic response to high altitude?
increased red blood cell production (uptake of oxygen) when you move to high altitudes
Phenotype plasticity
same genotype can produce different phenotypes
(change depending on environment, but not over generations)
What are examples of some populations experiencing evolution across generations?
Selection for allele that increase fitness at high elevations:
- Andes Mountains:
- variants of hemoglobin that carry more oxygen
- allows greater uptake/delivery of oxygen - Tibetan Plateau:
- naturally higher production of red blood cells, rates of breathing, and lung capacity
- expanded blood vessels = increased blood flow and delivery of oxygen
EPAS1
gene linked to red blood cell production
LCT
lactase gene
MCH
major histocompatibility complex (immune system)
Explain why some people may be Lactose Intolerance.
- Most mammals only drink milk early in develop while nursing, which means lactase expression is reduced after wearing
- It is costly to produce when not needed (not drinking milk)
- In most mammals, lactase is not produced after drinking milk (in nursing)
What is the Enzyme lactase for?
to break down lactose (sugar) in milk
Human Niche construction
the ability to change the environment and resources we receive
Explain the Evolution of lactase persistence.
Alleles that keep lactase gene turned on past weaning were “selected for” because they provided higher fitness
