Understanding the Late Miocene: A Pivotal Era in Earth's History
The history of our planet is divided into distinct chapters known as geological time scales. One of the most transformative periods in this timeline is the Late Miocene (also referred to as the Upper Miocene). This era represents a critical juncture in both the geological evolution of the Earth and the biological lineage that eventually led to modern humans.
Spanning from approximately 11.63 million years ago (Ma) to 5.333 million years ago, the Late Miocene is a sub-epoch of the Miocene epoch. It is characterized by significant shifts in climate, landscape, and the evolutionary trajectories of various species.
ไม่มีภาพประกอบGeological Classification and Timeline
According to the International Commission on Stratigraphy (ICS), the Late Miocene is divided into two distinct stages: the Tortonian and the Messinian. These stages mark specific intervals of time that help geologists and paleontologists organize the Earth's history.
To understand where the Late Miocene fits within the broader geological framework, it is helpful to look at its relationship to the Neogene and Paleogene periods. The Late Miocene sits within the Neogene, following the Middle Miocene and preceding the Pliocene epoch.
Chronological Breakdown
The following table provides a detailed view of the geological subdivisions surrounding the Late Miocene, illustrating the progression of epochs and stages.
| System / Period | Series / Epoch | Stage / Age | Age (Ma) |
|---|---|---|---|
| Quaternary | Pleistocene | Gelasian (younger) | 2.58 |
| Neogene | Pliocene | Piacenzian | 3.600 |
| Zanclean | 3.600 – 5.333 | ||
| Neogene | Miocene | Messinian | 5.333 – 7.246 |
| Tortonian | 7.246 – 11.63 | ||
| Serravallian | 11.63 – 13.82 | ||
| Langhian | 13.82 – 15.97 | ||
| Burdigalian | 15.97 – 20.44 | ||
| Aquitanian | 20.44 – 23.03 | ||
| Paleogene | Oligocene | Chattian (older) | > 23.03 |
Biological Evolution and Hominin Origins
The Late Miocene was a period of profound biological change, particularly regarding the evolution of primates. The evolutionary tree of the Hominidae family (great apes) underwent several critical splits during this time.
The sequence of divergence began with the gibbons (family Hylobatidae), followed by the orangutans (genus Pongo). Subsequently, the lineage split toward the gorillas (genus Gorilla) and finally toward the chimpanzees (genus Pan). Most significantly, the split between the hominin lineage (the ancestors of humans) and the chimpanzee lineage is estimated by some researchers to have occurred between 4 and 8 million years ago—placing this monumental event squarely within the Late Miocene.
Regional Biodiversity: The Iberian Peninsula
Environmental changes during this epoch also dictated the survival and diversity of animal species in specific regions. In the Iberian Peninsula, a trend toward increasing aridity (dryness) was observed. This shift in climate led to a notable change in herbivore populations:
- Grazers: Animals that feed on grasses increased in diversity as open environments expanded.
- Browsers: Animals that feed on leaves and shrubs saw a decline in diversity as their habitats changed.
- Predators: Both felids (cats) and canids (dogs) experienced an increase in diversity during this period.
Key Facts
- Timeframe: The Late Miocene lasted from 11.63 Ma to 5.333 Ma.
- Subdivisions: It consists of two stages: the Tortonian and the Messinian.
- Human Evolution: The divergence between the human (hominin) and chimpanzee lineages likely occurred during this epoch.
- Climate Impact: Increasing aridity in regions like the Iberian Peninsula shifted animal populations from browsers to grazers.
- Predator Trends: Felid and canid diversity increased during this era.
Frequently Asked Questions
What are the two stages of the Late Miocene?
The Late Miocene is divided into the Tortonian stage and the Messinian stage.
When did the human lineage split from chimpanzees?
Scientific estimates place the splitting of the hominin and chimpanzee lineages between 4 and 8 million years ago, which falls within the Late Miocene.
How did climate change affect animals in the Iberian Peninsula?
As the region became more arid, the diversity of grazers increased, while the diversity of browsers declined.
What is the difference between a grazer and a browser?
In biological terms, grazers are animals that primarily eat grasses, while browsers are animals that feed on leaves, twigs, and other high-growing vegetation.
Which epoch follows the Miocene?
The Miocene epoch is followed by the Pliocene epoch.