Overview

Extinction events are periods in Earth’s history when large numbers of species vanish in a relatively short geological timeframe. These events have reshaped ecosystems, driven evolutionary change, and influenced the trajectory of life on Earth.

Definition

Extinction Event:
A rapid and widespread decrease in the biodiversity on Earth, marked by the loss of a significant proportion of species across multiple taxa.

Types of Extinction Events

  • Background Extinction: Ongoing, low-level extinction due to environmental changes, competition, and other natural factors.
  • Mass Extinction: Catastrophic, global events causing the loss of a substantial percentage of species in a short period.

Major Mass Extinction Events (Timeline)

Event Name Approximate Date (Million Years Ago) Estimated Species Lost Major Causes
Ordovician-Silurian 443 ~85% Glaciation, sea level drop
Late Devonian 372 ~75% Anoxia, climate change
Permian-Triassic 252 ~96% Volcanism, methane release
Triassic-Jurassic 201 ~80% Volcanism, climate change
Cretaceous-Paleogene 66 ~76% Asteroid impact, volcanism

Diagram: Five Major Mass Extinctions

Extinction Events Timeline

Source: Wikimedia Commons

Causes of Extinction Events

  1. Asteroid Impacts:
    Example: Chicxulub impact at the end of the Cretaceous period.
  2. Volcanic Activity:
    Massive eruptions release gases, causing climate change.
  3. Climate Change:
    Rapid shifts in temperature, sea level, and ocean chemistry.
  4. Anoxia (Oxygen Depletion):
    Oceanic anoxic events reduce available oxygen for marine life.
  5. Methane Release:
    Sudden release from oceanic methane clathrates can warm the climate.
  6. Human Activity (Current Era):
    Habitat destruction, pollution, and overexploitation.

Recent Breakthroughs

Genomic Insights

  • CRISPR Technology:
    Allows precise gene editing, enabling scientists to study extinct species’ genomes and potentially “de-extinct” certain organisms.
  • Ancient DNA Sequencing:
    Advances in sequencing have reconstructed genomes from extinct species, such as the woolly mammoth and Neanderthals.

Monitoring Extinction Risk

  • AI and Big Data:
    Machine learning models predict species at risk by analyzing environmental, genetic, and population data.
  • Environmental DNA (eDNA):
    Detects rare or elusive species from trace genetic material in water, soil, or air.

Recent Study

  • Reference:
    Leclère, D., Obersteiner, M., Barrett, M., et al. (2020). “Bending the curve of biodiversity loss.” Nature, 585, 551–556.
    This study models scenarios to halt or reverse biodiversity loss, emphasizing the urgency of conservation efforts to prevent a sixth mass extinction.

Surprising Facts

  1. Permian-Triassic Extinction (“The Great Dying”) wiped out over 90% of marine species and 70% of terrestrial vertebrate species—making it the most severe extinction event known.
  2. Some species, known as “Lazarus taxa,” reappear in the fossil record after supposedly going extinct, suggesting survival in isolated refuges.
  3. Current extinction rates are estimated to be 100–1,000 times higher than natural background rates, primarily due to human activities.

Impacts on Health

  • Loss of Biodiversity:
    Reduces genetic resources for medicines, food, and disease resilience.
  • Emerging Diseases:
    Habitat disruption can force species into new areas, increasing zoonotic disease risk (e.g., COVID-19).
  • Ecosystem Services:
    Extinctions disrupt pollination, water purification, and climate regulation, affecting human health and food security.
  • CRISPR and Conservation Medicine:
    Gene editing may help restore lost traits in endangered species or improve disease resistance, but ethical and ecological risks remain.

Timeline of Extinction Events and Human Influence

  • Prehistoric Mass Extinctions:
    Driven by natural phenomena.
  • Holocene Extinction (Current):
    Accelerated by human impact—sometimes called the “Sixth Mass Extinction.”
  • 2020s:
    Global initiatives (e.g., UN Biodiversity Targets) and technological breakthroughs (CRISPR, AI) aim to monitor and mitigate extinction risk.

Extinction Events and CRISPR Technology

  • De-extinction:
    CRISPR enables attempts to revive extinct species by editing the genomes of closely related living organisms.
  • Conservation:
    Potential to enhance genetic diversity and disease resistance in endangered populations.
  • Ethical Considerations:
    Risks of unintended ecological consequences and genetic contamination.

Conclusion

Extinction events have profoundly shaped life on Earth. Recent technological breakthroughs, such as CRISPR and AI, offer new tools for understanding and potentially mitigating biodiversity loss. The relationship between extinction and human health is increasingly evident, as ecosystem disruptions can affect disease emergence, food security, and access to vital resources. Ongoing research and conservation efforts are critical to preventing further loss and sustaining planetary health.

References

  • Leclère, D., Obersteiner, M., Barrett, M., et al. (2020). “Bending the curve of biodiversity loss.” Nature, 585, 551–556. Link
  • IPBES Global Assessment Report on Biodiversity and Ecosystem Services (2019).
  • National Geographic, “The Sixth Mass Extinction,” 2022.