Hominin/Human Evolution Midterm 1.4

Here are your flashcards in question-and-answer format:

### Hominin Evolution & Adaptive Radiation

1. What is adaptive radiation, and how does it apply to hominins?

Adaptive radiation refers to the rapid diversification of a species into multiple forms to exploit different ecological niches. In hominins, this began in the late Miocene and continued through the Pliocene and early Pleistocene, leading to the emergence of bipedal species adapted to various environments.

2. What were some major trends in hominin evolution during the late Miocene, Pliocene, and early Pleistocene?

- Shift from arboreal to terrestrial habitats

- Increasing reliance on bipedal locomotion

- Changes in dentition reflecting dietary shifts

- Gradual increase in brain size

- Tool use and cultural developments

3. What characteristics distinguish hominins from apes?

- Habitual bipedal locomotion

- Smaller canine teeth and reduced sexual dimorphism in dentition

- Increased brain size relative to body size

- More advanced tool use and cultural behaviors

4. Why is bipedal posture and locomotion crucially important in hominin evolution?

Bipedalism freed the hands for tool use, increased energy efficiency in locomotion, allowed for better thermoregulation, and enhanced visual surveillance of the environment.

### Hunting vs. Scavenging Debate

5. What is the hunting vs. scavenging debate in early hominin diets?

The debate concerns whether early hominins primarily hunted their prey or scavenged carcasses left by other predators.

6. What evidence would you look for in fossil animal bones at a paleoarchaeological site to determine hominin involvement?

- Cut marks from stone tools (indicating butchery)

- Evidence of percussion marks (suggesting marrow extraction)

- Association with stone tools in a stratified context

7. How could you determine whether hominins hunted or scavenged animals?

- Presence of tooth marks from carnivores before or after tool marks (if tool marks come first, hunting is more likely)

- The anatomical location of cut marks (on meaty bones vs. scavenged remains)

- The presence of complete vs. fragmented skeletons (hunters likely bring back more complete carcasses)

8. Why does the hunting vs. scavenging debate exist?

It exists because early hominins likely engaged in both behaviors, and the fossil record is often incomplete or ambiguous.

9. Why do researchers believe early Homo increased their reliance on vertebrate prey?

- Reduction in tooth size and jaw robustness, suggesting a shift to softer, higher-energy foods

- Increase in brain size, which requires high-energy diets

- Archaeological evidence of stone tool use for butchering animals

### Diet & Habitat Evidence

10. How can teeth and jaws provide information about hominin diets?

- Large, thick enamel molars suggest a diet of tough, fibrous foods (e.g., Australopithecus).

- Smaller teeth with thinner enamel suggest reliance on softer, higher-energy foods (e.g., Homo).

11. How can body size estimates help reconstruct hominin diets and ecology?

- Larger body sizes often indicate a shift toward more energy-rich diets.

- Smaller body sizes may correlate with more arboreal lifestyles and lower-calorie diets.

12. How does thorax (ribcage) shape relate to dietary differences between Homo ergaster and Ardipithecus?

- Homo ergaster has a more barrel-shaped ribcage, indicating a more efficient digestive system for a high-quality diet.

- Ardipithecus has a more conical ribcage, suggesting a larger gut for digesting fibrous plant materials.

### Tooth Evolution & Sexual Dimorphism

13. What were the two general evolutionary trends in hominin teeth?

- Reduction in canine size and loss of honing complex

- Enlargement of molars in early hominins, followed by a reduction in later Homo species

14. What was unusual about sexual dimorphism in Australopithecus and Paranthropus?

- While males were larger than females, their canine size did not show the extreme dimorphism seen in apes, suggesting changes in social structure.

### Brain Size & Energy Demands

15. When did brain size increase significantly in the genus Homo?

Around 2 million years ago, beginning with Homo erectus.

16. Why is maintaining a large brain energetically costly?

The brain consumes a disproportionately high amount of energy relative to body mass.

17. What might have allowed early Homo to meet the energetic costs of a larger brain?

- Increased consumption of meat and animal fat

- More efficient food processing with tools and fire

- Reduced gut size due to a higher-quality diet

18. How can we determine whether hominins were responsible for accumulating mammal bones at a site?

- Presence of cut marks and tool-associated modifications

- Patterns of bone breakage consistent with human tool use

- Spatial association between bones and hominin artifacts

19. How can we decide whether hominins hunted or scavenged animals?

- Position of cut marks relative to carnivore tooth marks

- Butchery patterns and access to high-value meat parts

- Presence of complete vs. partial skeletons

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