Big picture: The Anthropocene is a proposed geological epoch recognising that human activities have become the dominant force shaping Earth's geology, ecosystems, and climate systems.
- Anthropocene
- A proposed geological epoch in which human activities have a significant and measurable impact on Earth's geology, ecosystems, and climate.
- Great Acceleration
- The dramatic increase in human activity and its environmental impacts since the mid-20th century, including population growth, resource consumption, and pollution.
Evidence for the Anthropocene in geological records
- Increased greenhouse gas concentrations (CO2 from ~280 to 420+ ppm)
- Widespread plastic pollution in sediments globally
- Radioactive isotopes from nuclear weapons testing (1945 onwards)
- Changes in fossil record — mass extinction of species
- Altered sediment patterns from agriculture and urbanisation
- Novel materials (concrete, aluminium alloys) in geological deposits
Proposed start dates for the Anthropocene
- The Agricultural Revolution (~10,000 years ago)
- The Industrial Revolution (~1750 CE)
- The mid-20th century Great Acceleration (most widely supported — 1950s)
Key concept: Human activities are now a major selective force, driving evolutionary changes in species at unprecedented rates.
Examples of human-driven evolution
- Peppered moth (Biston betularia) — industrial melanism during Industrial Revolution; dark moths had survival advantage on soot-covered trees
- Antibiotic resistance — overuse of antibiotics selects for resistant bacteria
- Pesticide resistance — insects evolve resistance to chemical pesticides within generations
- Pollution-tolerant fish — killifish in polluted US rivers evolved tolerance to PCBs
- Trophy hunting — elephants evolving smaller tusks or tusklessness due to poaching pressure
- Urban evolution — city birds developing different songs, rats becoming poison-resistant
IB exam tip: Use specific named examples when discussing human-driven evolution. The peppered moth and antibiotic resistance are classic IB examples.
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- Artificial selection
- The deliberate breeding of organisms by humans to select for desirable traits, resulting in domesticated plants and animals with reduced genetic diversity.
- Genetic diversity
- The total number of genetic characteristics in the genetic makeup of a species. Higher genetic diversity increases resilience to environmental change.
- Genetic bottleneck
- A sharp reduction in the size of a population, reducing genetic diversity and making the population more vulnerable to disease and environmental change.
Consequences of artificial selection for biodiversity
- Reduced genetic diversity in crop species — modern wheat has far less diversity than wild ancestors
- Monoculture vulnerability — Irish Potato Famine (1845) caused by genetic uniformity
- Livestock breeds losing genetic diversity — a few breeds dominate global production
- Loss of wild relatives as habitats are converted to agriculture
- Dependence on seed banks to preserve genetic diversity
Why genetic diversity matters
- Enables adaptation to changing conditions
- Resistance to diseases and pests
- Resilience to climate change
- Supports ecosystem stability
- Foundation for future crop improvement