Human Evolution Flashcards
Define niche
The term “niche” describes the role an organism plays in a community. A species’ niche encompasses both the physical and environmental conditions it requires (like temperature or terrain) and the interactions it has with other species (like predation or competition).
Name the five groups of
primates
- Strepsirrhines.
They are a suborder of primates that are considered to be among the most primitive, or basal, members of the primate evolutionary lineage. The term Strepsirrhines means “twisted-nosed,” referring to the curved or comma-shaped nostrils they possess. Also known as bush babies, they typically have a more developed sense of smell and a moist nose.
- Characteristics:
- Rhinarium: They have a moist, naked nose (rhinarium) that enhances their sense of smell.
- Compared to other primates, they rely heavily on their sense of smell.
- They have large eyes adapted for nocturnal vision (though some, like certain lemurs, are active during the day).
- They have a more limited ability to perceive colour compared to other primates.
- Their brains are generally smaller relative to their body size compared to haplorhines.
- A “tooth comb” (a group of forward-facing lower teeth) is used for grooming.
- They have a specialised grooming claw on the second toe of each foot.
- They have shorter gestation periods and smaller litters compared to haplorhines.
- Strepsirrhines tend to live in smaller social groups, although some, like ring-tailed lemurs, are more social.
- Tarsiers.
They are small, nocturnal primates found primarily in Southeast Asia. They are known for their large eyes, which help them see in low light, and their unique adaptations for leaping.
- Characteristics:
- Small, with body lengths ranging from 8-16 cm (excluding the tail).
- Large eyes relative to their body size, adapted for nocturnal hunting.
- Long fingers and toes for gripping trees.
- Very strong hind limbs adapted for leaping long distances between trees.
- Tarsiers are nocturnal, being active at night, primarily feeding on insects and small vertebrates (e.g., birds, lizards).
- Tarsiers tend to be solitary or live in small family groups.
- ## Their leaping ability is a key feature—they leap from tree to tree to capture prey.
- Platyrrhines.
They are primates belonging to the infraorder Platyrrhini, also known as New World monkeys. The name Platyrrhines means “flat-nosed,” which refers to the broad and outward-facing nostrils that distinguish them from their Old World counterparts, the Catarrhines.
- Characteristics:
- Found exclusively in the tropical forests of Central and South America.
- They have a flat nose with nostrils that are spaced widely apart and face outward.
- Many species have a prehensile tail (capable of grasping), which they use like a fifth limb for climbing and hanging from trees. This feature is unique to some New World monkeys, such as spider monkeys and howler monkeys.
- Their vision is not as developed as Old World monkeys, but they exhibit trichromatic vision in some species, allowing them to see a range of colours.
- They typically have 36 teeth (dental formula: 2.1.3.3), compared to the 32 teeth of Catarrhines (2.1.2.3).
- Platyrrhines range in size from the small pygmy marmoset (weighing about 100 grams) to larger species like howler monkeys (up to 9 kg).
- They are generally arboreal (tree-living) and diurnal (active during the day), with diverse social structures ranging from small family units to larger troops.
- They often give birth to single offspring at a time, though some, like marmosets and tamarins, commonly have twins.
- Catarrhines.
They are primates belonging to the infraorder Catarrhini, which includes Old World monkeys and apes, including humans. The term Catarrhine means “downward-nosed,” referring to their narrow noses with nostrils that face downward or are closer together compared to the broad, outward-facing nostrils of Platyrrhines (New World monkeys).
- Characteristics:
- Found in Africa and Asia.
Includes a wide range of habitats, from rainforests to savannas and even urban areas. - Narrow noses with downward-facing nostrils (distinct from the flat noses of Platyrrhines).
- They have 32 teeth (dental formula: 2.1.2.3), with two premolars per quadrant, unlike Platyrrhines, which have three.
- Most Old World monkeys have tails, but they are never prehensile. Apes, including humans, do not have tails.
- Well-developed trichromatic color vision, which helps in distinguishing ripe fruits and leaves.
- Generally larger than Platyrrhines, with more robust bodies. Their arms and legs show adaptations depending on locomotion (e.g., quadrupedalism in monkeys versus brachiation in apes).
- Highly social animals, often living in large and complex groups with hierarchical structures.
- Larger brains relative to body size compared to Platyrrhines, allowing for more advanced cognitive abilities.
- Apes.
They are a group of primates that belong to the superfamily Hominoidea, which includes humans, chimpanzees, gorillas, orangutans, gibbons, and bonobos. Apes are part of the order Primates and are closely related to monkeys, although they have distinct features that set them apart.
- Characteristics:
- Unlike most monkeys, apes do not have tails.
- Apes generally have larger brains relative to their body size compared to monkeys, enabling advanced cognitive abilities.
- Many apes live in complex social groups and display behaviours such as cooperation, empathy, and communication.
- Apes are adapted for a variety of movements, including climbing, brachiation (swinging between branches, especially in gibbons), and walking upright for short distances.
- Most apes are omnivorous but primarily consume fruits, leaves, and other plant matter. Some species also eat insects or small animals.
Describe the types of
species within each group
- Strepsirrhines Species Examples:
- Lemurs: Found only in Madagascar (e.g., ring-tailed lemur, mouse lemur).
- Lorises: Found in Southeast Asia (e.g., slow loris).
- Galagos (Bush babies): Found in Africa. - Tarsier Species Examples:
- Only tarsiers: Philippine tarsier and Bornean tarsier. - Platyrrhines Species Examples:
- Capuchins (e.g., tufted capuchin).
- Howler monkeys.
- Spider monkeys.
- Tamarins and marmosets. - Catarrhines Species Examples:
- Old World monkeys: Baboons, macaques, colobus monkeys.
- Apes - Apes Species Examples:
- Lesser apes: Gibbons (e.g., siamangs).
- Great apes: Gorillas, chimpanzees, bonobos, orangutans, and humans.
Describe what types of
species are in the hominin
group
The hominin group includes species that are part of the tribe Hominini, which comprises humans and our closest extinct relatives. These species are more closely related to modern humans (Homo sapiens) than to chimpanzees and bonobos. They are characterized by traits such as bipedalism (walking on two legs), smaller canine teeth, and increased brain size.
- Main groups of hominins:
- Early Hominins
These are some of the earliest members of the hominin lineage, showing both ape-like and human-like features.
Examples:
- Sahelanthropus tchadensis (7–6 million years ago): One of the oldest known species, possibly bipedal.
- Orrorin tugenensis (6 million years ago): Showed signs of upright walking.
- Ardipithecus (e.g., A. ramidus, A. kadabba): Lived in forested environments; partially bipedal.
- Australopithecines
These hominins were fully bipedal and lived in Africa. They had small brains and large teeth.
Examples:
- Australopithecus afarensis (e.g., “Lucy,” 3.9–3 million years ago): Famous for being bipedal with a mix of ape-like and human-like features.
- Australopithecus africanus (2–3 million years ago): Similar to A. afarensis but slightly more advanced.
- Paranthropus species (e.g., P. boisei, P. robustus): Known for their large jaws and teeth adapted for chewing tough foods.
- Early Genus Homo
These species were characterized by larger brains and the use of tools.
Examples:
- Homo habilis (“Handy man,” ~2.4–1.4 million years ago): First species to be associated with stone tools.
- Homo rudolfensis (~1.9 million years ago): Similar to Homo habilis but with a larger brain.
- Later Genus Homo
These species are more closely related to modern humans and show significant advances in brain size, tool use, and culture.
Examples:
- Homo erectus (1.9 million–110,000 years ago): Spread from Africa to Asia; used fire and tools.
- Homo heidelbergensis (700,000–300,000 years ago): Likely the ancestor of both Neanderthals and modern humans.
- Homo neanderthalensis (Neanderthals, 400,000–40,000 years ago): Lived in Europe and Asia; adapted to cold climates; used tools and had complex social structures.
- Homo floresiensis (“Hobbits,” ~100,000–50,000 years ago): Small-bodied species found on the island of Flores, Indonesia.
- Homo sapiens (Modern humans, ~300,000 years ago to present): The only surviving hominin species, characterized by complex culture, language, and technology.
explain the difference
between hominins and
hominids
Hominids = humans + great apes.
Hominids are a broad group that includes all modern and extinct great apes, such as humans, chimpanzees, gorillas, orangutans, and their ancestors. This group is characterized by traits like larger bodies, complex brains, and diverse locomotion styles, including knuckle-walking in gorillas and bipedalism in humans.
Hominins = humans + species directly in the human lineage (closer to us than to chimpanzees).
In contrast, hominins are a narrower group within the hominids, including only humans and our closest extinct relatives, such as Australopithecus and Homo erectus. Hominins are distinguished by traits like consistent bipedal locomotion, smaller teeth, larger brains, and advanced tool use. While hominids encompass all great apes, hominins specifically focus on species directly related to the human lineage, excluding modern apes like chimpanzees and gorillas.
explain the niche of Homo
habilis
Time period: Lived approximately 2.4 to 1.4 million years ago during the early Pleistocene.
Habitat: Inhabited open savannahs, woodlands, and areas near water sources in East and Southern Africa.
Diet: Omnivorous, primarily consuming plant material, fruits, seeds, and occasionally scavenged meat (evidence of tool use suggests meat processing).
Tool use: Known as the “handy man” for creating simple stone tools (Oldowan tools) used for cutting, scraping, and breaking bones for marrow.
Behaviour: Likely scavengers rather than hunters, using tools to exploit new food sources.
Social structure: Likely lived in small groups, which may have provided protection and facilitated food-sharing.
Cognitive abilities: Showed evidence of increased brain size (600-750 cm³) compared to earlier hominins, indicating more advanced problem-solving and tool-making skills.
Ecological role: Occupied a transitional niche as both gatherers and opportunistic scavengers, aiding survival in changing environments.
explain the niche of Homo
erectus
Habitat: Lived in diverse environments, including savannahs, grasslands, and wooded areas across Africa, Asia, and Europe.
Diet: Omnivorous, consuming meat, plants, and possibly cooked food, showing adaptability to resources.
Tool Use: Crafted and used Acheulean tools (e.g., hand axes) for hunting, food preparation, and survival.
Social Structure: Likely lived in cooperative groups, engaging in hunting, food sharing, and possibly caring for others.
Fire Use: Among the first hominins to use fire for cooking, warmth, protection, and social interaction.
Cognitive Abilities: Larger brain (~600–1,100 cc) enabled problem-solving, rudimentary communication, and planning.
Locomotion: Fully bipedal with long legs and a narrow pelvis, adapted for endurance walking and persistence hunting over long distances.
Shelter: Used natural shelters and possibly built simple structures for protection from the elements.
explain the niche of Homo
neanderthalensis
Habitat: Lived in cold, glacial environments in Europe and parts of Western Asia during the Pleistocene Epoch.
Diet: Primarily carnivorous, hunting large mammals like mammoths, bison, and deer, though they may have also gathered plants.
Adaptations:
Stocky build with a large chest and shorter limbs to conserve heat (adapted to cold climates).
Strong, muscular physique suited to close-range hunting and heavy physical tasks.
Larger brain size than modern humans, possibly for processing complex environmental information.
Social Structure: Likely lived in small, family-based groups, with evidence suggesting care for the elderly and sick.
Tools and Technology: Used sophisticated tools, including flint tools, and were likely capable of fire-making and possibly clothing production.
Communication: Evidence of symbolic behaviour, such as burial practices, may indicate basic language or symbolic communication.
Competition and Interaction: Coexisted with Homo sapiens at times and may have interbred with them, contributing to modern human genetics.
define what genus and
species humans belong to
Genus: Homo
Species: Homo sapiens
So, humans are scientifically known as Homo sapiens.
Explain what species Lucy
was and the niche of this
species
Lucy refers to the fossil of Australopithecus afarensis, an early hominin species that lived in Africa about 3.2 million years ago.
Niche of Australopithecus afarensis
Australopithecus afarensis was a bipedal species that primarily lived in savanna and woodland environments. It had a mixed diet that included fruits, leaves, seeds, and possibly small animals, showcasing its ability to gather a variety of resources. Lucy’s adaptations for bipedalism allowed her to walk upright on two legs, which helped in traveling across open landscapes and spotting predators. However, she likely retained some climbing abilities, enabling her to climb trees for food or safety. Living in small groups, A. afarensis likely relied on cooperation for protection, foraging, and survival. Lucy’s species played a crucial role in the evolution of bipedalism and social structures among early human ancestors.
explain the difference
between a biped and a
quadruped
The difference between a biped and a quadruped lies in their mode of locomotion—how they move around.
Biped: An organism that walks on two legs. Humans and birds are examples of bipeds. Bipedalism allows for upright walking, which helps with carrying objects, using tools, and scanning for predators in open environments.
Quadruped: An organism that walks on four legs. Most modern mammals, like dogs, cats, and deer, are quadrupeds. This body structure is typically associated with faster movement, balance, and stability in various habitats like forests, grasslands, and savannas.
discuss the femur
differences between biped and
a quadruped
The femur (thigh bone) differences…
- In Bipedal Organisms (e.g., Humans)
-The femur is angled inward toward the knee.
- This inward angle creates a more stable, weight-bearing structure, which supports upright walking.
- The shape and orientation of the femur allow the upper body’s weight to be efficiently transferred down the legs to the knees and feet.
- The longer, thicker femur in bipeds helps support the forces generated during walking, running, and balancing on two legs. - In Quadrupedal Organisms (e.g., Dogs, Cats)
- The femur is more vertical and less angled inward.
- This structure supports a body posture where the animal walks on all four legs.
- The orientation of the femur allows for stability and support across the back limbs, distributing the weight evenly across the four legs.
- In quadrupeds, the femur is adapted to provide speed, balance, and traction, rather than supporting upright locomotion.
explain the selection
pressures against being
arboreal (living in trees)
Predation risk: Predators can easily access tree-dwelling animals, making arboreal life dangerous.
Resource availability: Trees provide limited access to food compared to ground-based ecosystems with more diverse food sources.
Energy expenditure: Climbing and living in trees can be energetically costly, especially when compared to more efficient terrestrial movement.
Limited mobility: Arboreal living may restrict movement and adaptability to new environments, reducing chances of migration or accessing broader habitats.
Vulnerabilities to environmental changes: Climatic or habitat changes that affect forests may reduce the suitability of arboreal life, encouraging evolution toward ground-based survival strategies.
discuss the foot
differences between a arboreal
biped and a quadruped
- Arboreal Biped (e.g., early humans or tree-dwelling bipeds)
Opposable toes: Toes are more flexible and able to grasp, aiding in climbing trees.
Curved toes: Helps with gripping tree branches.
Arched foot: Often present, but not as developed as in fully terrestrial bipeds.
Longer toes: Adapted for grasping or wrapping around tree branches.
Flexible ankle: Allows more movement for gripping or holding onto surfaces.
- Quadruped (e.g., most non-human primates or four-legged mammals)
Flat, straight toes: Toes align to support walking on all fours.
Non-opposable toes: Lack of flexibility for grasping, focus on stability.
More uniform toe length: Toes are generally similar in length, contributing to even weight distribution.
No pronounced arch: Feet are adapted for stable, flat contact with the ground.
Stiffer ankle: Less flexible than in bipeds, suited for walking on all fours.
discuss the skull
differences between a biped
and a quadruped
- Foramen Magnum Position:
Biped: Positioned more centrally at the base of the skull (underneath), aligning the head with the spine for upright posture.
Quadruped: Positioned towards the back of the skull, allowing the head to be held in a horizontal position.
- Facial Angle:
Biped: More vertical face with a flatter profile (reduced prognathism), as the face is not extended forward.
Quadruped: More pronounced face with a forward-projecting snout (greater prognathism) for a horizontal body posture.
- Jaw Structure:
Biped: Smaller, less robust jaw with a more vertical alignment of teeth.
Quadruped: Larger, stronger jaw with teeth adapted for grinding and shearing food.
- Teeth and Chewing:
Biped: Teeth adapted for omnivorous diets, with molars suited for grinding and premolars for shearing.
Quadruped: Teeth often specialized for herbivory or carnivory, with large molars for grinding in herbivores or sharp canines in carnivores.
- Skull Shape:
Biped: Rounder skull with a larger braincase, reflecting a larger brain size.
Quadruped: More elongated skull, with less emphasis on brain size and more on jaw strength.
- Muscle Attachments:
Biped: Reduced attachment for neck muscles, as the head is more balanced.
Quadruped: Stronger muscle attachment sites for neck muscles to support the head in a horizontal position.
discuss the advantages
and disadvantages of
bipedalism
- Advantages of Bipedalism:
Efficient Locomotion: Allows for long-distance walking and running, conserving energy compared to quadrupedalism.
Freeing of Hands: Hands are free for tool use, carrying objects, and other tasks, which was important for early human survival.
Height Advantage: Provides an elevated vantage point for spotting predators or prey over long grass and terrain.
Thermoregulation: Reduces the surface area exposed to the sun, which helps in maintaining body temperature in hot climates.
Improved Mobility in Open Landscapes: Bipedalism is well-suited for traversing open savanna environments, which were becoming more common during human evolution.
- Disadvantages of Bipedalism:
Stress on the Spine: Bipedalism places more stress on the lower back and spine, which can lead to joint issues or pain.
Slow Movement: Although efficient for long distances, bipedalism is less agile and slower than quadrupedalism, making it harder to escape predators.
Vulnerability to Injury: Bipedalism creates more opportunities for falls and injuries due to the reliance on only two limbs for balance.
Complicated Birth Process: Bipedalism and the evolution of a larger brain have resulted in more complex childbirth compared to quadrupedal species.
discuss the spine
differences between a biped
and a quadruped
- Biped (Human) Spine:
S-shaped curve: The spine has a distinct S-curve, with a lumbar curve (lower back) and cervical curve (neck) to help balance the body upright.
Vertical alignment: The spine is positioned vertically to support the weight of the body while standing and walking.
Compact vertebrae: The vertebrae in the lumbar region are larger and more robust to support the upright posture.
Shorter thoracic region: The thoracic part of the spine is shorter in comparison to quadrupeds.
Pelvic tilt: The pelvis is tilted forward to align with the vertebral column, aiding in bipedal locomotion.
- Quadruped Spine:
Horizontal alignment: The spine is horizontal, aligned with the body to support walking on all fours.
C-shaped curve: The spine typically has a gentle C-shape, with little or no lumbar curve.
Flexible spine: The vertebral column is more flexible to allow for greater movement in different directions while running or walking.
Longer thoracic region: The thoracic spine is longer, contributing to the longer body and helping with stability during movement.
Level pelvis: The pelvis is more horizontal and does not tilt forward as in bipeds.
discuss the teeth and jaw
differences between a biped
and a quadruped
- Teeth
- Biped:
Smaller, more generalized teeth, with less pronounced canine teeth.
Larger molars and premolars adapted for grinding and crushing a varied diet, particularly plant material.
Smaller incisors suited for cutting.
- Quadruped:
Larger canine teeth, particularly in carnivores, for tearing meat.
More pronounced molars for grinding, but not as specialized for plant material as in bipeds.
Teeth size and shape may vary more depending on diet, but typically more uniform and specialized for specific food sources.
- Jaw
- Biped:
Smaller, more vertically aligned jaw with a more pronounced chin.
Stronger and more efficient chewing muscles for a varied diet, adapted for vertical chewing (up and down).
- Quadruped:
Larger, more robust jaw with a horizontal alignment.
Stronger jaw muscles for chewing and tearing, adapted for a side-to-side motion in chewing, which is more effective for grinding plant material or tearing meat.
discuss the pelvis
differences between a biped
and a quadruped
- Pelvis in Biped:
Broad and bowl-shaped: Supports internal organs in an upright position.
Shorter and wider: Allows for the alignment of the legs under the body, providing balance for walking on two legs.
Pelvic inlet (opening): Circular and larger, which accommodates the human birth process.
Iliac bones: Positioned more laterally (to the sides), contributing to stability and support during bipedal movement.
Sacrum: More curved, helps support the upper body and maintain an upright posture.
- Pelvis in Quadruped:
Narrow and elongated: Designed to support the horizontal body structure.
Longer and less wide: Facilitates four-legged movement, where the legs extend outward rather than directly under the body.
Pelvic inlet: More oval in shape, reflecting the different demands of locomotion and support.
Iliac bones: Positioned more horizontally, helping with leg placement during walking or running.
Sacrum: Less curved, supports a more horizontal posture.
explain the difference in
brow ridge between a human
and an ape
- Human Brow Ridge:
Relatively small or absent.
The forehead is smooth and vertical.
The brow ridge is less pronounced due to a smaller, less prominent facial structure.
- Ape Brow Ridge:
More prominent and pronounced.
The brow ridge forms a noticeable horizontal protrusion above the eyes.
Reflects the larger, more robust facial bones of apes.
define cultural evolution
The transmission of knowledge, beliefs, practices, and technologies from one generation to another.
It occurs through social learning rather than genetic inheritance.
Involves the development and passing on of language, art, tools, and social norms.
Can lead to changes in human behavior and society over time.
Influences human survival and adaptation through innovation and shared practices.
discuss the cultural
evolution of tools
- Early Stone Tools:
Oldowan tools (around 2.6 million years ago) are the earliest known tools, made by early Homo species like Homo habilis. Simple tools such as flakes and choppers were used for cutting, scraping, and processing food.
- Acheulean Tools:
Developed by Homo erectus around 1.7 million years ago. More advanced, including hand axes and cleavers, designed for more specific tasks like butchering animals.
- Mousterian Tools:
Used by Neanderthals (around 300,000 to 30,000 years ago). Characterized by flint tools with more refined shapes, such as scrapers, points, and blades, indicating a more complex approach to toolmaking.
- Upper Paleolithic Tools:
Associated with anatomically modern humans (Homo sapiens) around 40,000 years ago. Tools became even more specialized and sophisticated, including blades, bone tools, and the creation of art (e.g., cave paintings). Tools were made for a wide variety of tasks, including fishing, sewing, and artistic expression.
- Tool Use and Cultural Development:
Tools reflect advancements in cognitive abilities, communication, and social structures. The development of tools also indicates increased planning, foresight, and the ability to adapt to diverse environments.
- Transition to Modern Tools:
Over time, tools evolved with the introduction of materials like metals, which led to the rise of agricultural and industrial tools.The cultural evolution of tools played a key role in shaping human society, economy, and technology.
discuss how fire allowed
for Homo erectus to leave Africa
Improved survival in colder climates: Fire provided warmth, enabling Homo erectus to survive in cooler regions outside of Africa.
Protection from predators: Fire acted as a deterrent to predators, helping Homo erectus stay safe as they ventured into new territories.
Extended activity time: Fire allowed for extended daylight hours by providing light at night, giving Homo erectus more time to hunt, gather, and socialize.
Cooked food: The ability to cook food using fire made it easier to digest, unlocking more nutrients and supporting the development of larger brains, which would have been crucial for adapting to new environments.
Social development: The control of fire likely contributed to the development of social structures, as groups could gather around the fire for warmth, communication, and collaboration. This increased their ability to cooperate and adapt when moving across regions.
discuss how the use of fire
for light caused cultural
evolution
Extended Activity Hours: Fire provided light during nighttime, allowing humans to engage in activities such as socializing, tool-making, and cooking after dark.
Socialization and Communication: Fire allowed for gathering around a central source of light, fostering more complex social interactions, which contributed to the development of language, culture, and social structures.
Cultural Practices: The ability to control fire facilitated the development of rituals, storytelling, and other cultural practices that were shared within groups.
Improved Diet: Cooking with fire improved the nutritional value of food, which may have contributed to better health, brain development, and the evolution of early human societies.
Tool and Shelter Development: Fire was also used for making tools (such as hardening wooden spears) and providing warmth, which influenced the development of early shelters and protection from predators.
Technological Innovation: The mastery of fire may have spurred technological innovations and the development of other tools, further advancing human cultural evolution.
