Biodiversity and Hominin Evolution Notes

Learning Objectives

• Examine the evolution of early hominins

• Define unique traits of Homo sapiens

• Explore the value of biodiversity

• Define ecosystem services and their economic implications

• Identify and discuss threats to biodiversity

Hominin Evolution

• Hominins: Most derived group among hominids, sharing a recent common ancestor with chimpanzees but did not evolve from them.

Derived Traits of Hominins

• Bipedalism: Walk upright on two legs

• Cranial Capacity: Larger brain supporting complex thought

• Tool Use: Development of tools significantly aids survival

• Physical Changes: Reduced jawbones and teeth; shorter digestive tract

Timeline of Hominin Evolution

• Sahelanthropus tchadensis: First hominins, appearing 6.5 million years ago

  • More upright than other apes

  • Reduced canine teeth

• Australopiths: Flourished from 4 to 2 million years ago, demonstrating human-like adaptations (e.g., Lucy)

  • Walked fully erect

  • Human-like hands and feet

• Homo Erectus: Existed from 1.8 to 0.2 million years ago, migrated out of Africa, and utilized fire

  • Taller: 5-6 Feet

  • Used fire to cook food

  • Migrated from Africa

• Neanderthals: Lived from 400,000 to 40,000 years ago, adapted to cold environments

  • Lived in Europe and Asia

  • Short, stocky bodies

  • Common Ancestor with humans

  • Reduced melanization

• Homo sapiens: Emerged around 200,000 years ago in Africa; migrated worldwide and developed advanced tools and social structures

  • Lighter skeletons, skull is thin-walled

  • Smaller teeth, hunting and fishing with tools

  • Developed sophisticated societies and cultural practices

Significance of Hominins

• Interbreeding Evidence: Neanderthals and Homo sapiens interbred; modern humans' DNA contains up to 4% Neanderthal genes, particularly in Europeans and Asians.

• Cognitive Advancements: Enhanced survival through sophisticated tools and social practices led to the dominance of Homo sapiens and eventual replacement of other hominins

  • Homo sapiens started to outcompete other species

Biodiversity

• Intrinsic Value:

  • Inspires art and spirituality, underlying many human experiences.

• Ecological Value:

  • Essential for ecosystem function; higher biodiversity supports complex food webs.

• Economic Value:

  • Ecosystem services: Benefits provided by ecosystems including products, processes maintaining healthy environments, and cultural value.

  • Challenges in quantifying economic value; tangible benefits like lumber are easier to measure than aesthetic contributions which are often realized only after loss.

Threats to Biodiversity

• Habitat Loss/Degradation:

  • Human activities modify up to 75% of Earth’s land; leads to significant habitat loss across biomes.

• Invasive Species:

  • Introduced species can dominate environments, harming local biodiversity and altering ecosystem services.

• Overexploitation:

  • Unsustainable harvesting practices decrease populations, affecting all biodiversity levels and leading to ecological imbalances (e.g., trophic cascades).

• Global Change:

  • Increased CO2 levels contribute to rising temperatures and biodiversity loss; species face challenges such as altered habitats and reduced resources.

Monitoring and Measuring Threats

• Importance of continuous monitoring of biodiversity to implement conservation strategies.

• Use of indicator species as simpler measures of environmental health and biodiversity.

Key Takeaways

• Understanding evolution and traits of hominins gives insight into human development.

• Biodiversity is not merely a resource but a vital component of ecological and economic systems.

• Addressing biodiversity threats requires recognition of human impact and commitment to sustainable practices.