Grasslands, apes and the first hominins
Neogene
Cenozoic Era · 23.03 – 2.58 million years ago
The Neogene Period ran from 23.03 to 2.58 million years ago, a span of about 20 million years in which the world took on a recognisably modern shape. Continents settled close to their present positions, great mountain ranges rose, and grasslands spread across much of the land.
It is also our own origin story. Apes diversified across Africa and Eurasia, and late in the period the first hominins — members of the human lineage — began walking upright on the African savannah as the planet slid towards the ice ages.
Key facts
- Began
- 23.03 MaMillion years ago
- Ended
- 2.58 MaMillion years ago
- Duration
- 20.5 million years
- Era
- Cenozoic“Recent life”
- Global temperature
- ~17°CRoughly 14–18°C · today 14.5°C
- Plants on land
- Flowering plants
- Atmospheric CO₂
- ~300–600 ppm; ~400 ppm in the mid-Pliocene warm period
- Oxygen
- ~21%, essentially modern
- Sea level
- Mostly above today; ~10–25 m higher in the mid-Pliocene
- Continents
- Near-modern; Panama closes, Himalaya and Alps rise
- Signature life
- Grazing horses, apes, early hominins, megalodon
- Began with
- A brief Antarctic glaciation at ~23 Ma
- Ended with
- Onset of the Northern Hemisphere ice ages
Ages follow the International Chronostratigraphic Chart (ICS). Global temperatures are rough reconstructions after Scotese et al. (2021); ancient CO₂, oxygen and sea-level values carry large uncertainties.
Epochs of the Neogene
- Miocene23.03 Ma – 5.333 Ma
- Pliocene5.333 Ma – 2.58 Ma
Continents and oceans
By the Neogene the continents were within a few hundred kilometres of where they are today. India's continuing push into Asia raised the Himalaya and Tibetan Plateau, Africa's collision with Europe built the Alps, and Arabia joined Asia, closing the last eastern link between the Mediterranean and the Indian Ocean.
Around 6 million years ago the Mediterranean was cut off from the Atlantic. During the Messinian Salinity Crisis, about 5.97 to 5.33 million years ago, it partly evaporated and left salt deposits more than a kilometre thick in places, before the Atlantic broke through at Gibraltar in a giant flood.
In the Americas, the Isthmus of Panama gradually emerged, and by roughly 3 million years ago it formed a continuous land bridge. It separated the Atlantic from the Pacific, reshaped ocean currents and allowed animals to walk between North and South America.
Climate and atmosphere
The early Neogene was warm. During the Miocene Climatic Optimum, about 17 to 15 million years ago, temperatures were well above today's and the Antarctic ice sheet probably shrank. A sharp cooling around 14 million years ago re-established a large, permanent East Antarctic ice sheet.
Cooling and drying continued, and in the Late Miocene, between about 8 and 6 million years ago, grasses using C4 photosynthesis — a pathway that copes well with heat, drought and lower carbon dioxide — spread across the tropics and subtropics. The mid-Pliocene, around 3 million years ago, was the last time carbon dioxide stood near today's levels, with sea levels perhaps 10–25 metres higher than now. Soon after, ice sheets began to grow across North America and Europe.
Life in the Neogene
Neogene ecosystems would look broadly familiar to a modern visitor, with recognisable families of mammals, birds and plants. The spread of open grasslands drove the evolution of fast-running grazers with high-crowned teeth, and of the predators that hunted them.
Grasslands and grazers
Horses, antelopes, camels and rhinoceroses flourished on the new grasslands. Many horse lineages evolved tall, hard-wearing teeth to grind tough, gritty grass, and longer legs for speed in open country.
Apes and hominins
The Miocene was a heyday for apes, with many species in Africa, Europe and Asia. Around 7 million years ago Sahelanthropus lived in what is now Chad, and by about 3.2 million years ago Australopithecus afarensis — the species of the famous 'Lucy' skeleton — was walking upright in East Africa.
Ocean giants
The giant shark Otodus megalodon, which may have exceeded 15 metres, hunted whales from roughly 20 to 3.6 million years ago. Baleen whales grew larger, and kelp forests and seals spread along cooling coastlines.
The Great American Biotic Interchange
Once Panama connected the continents, animals crossed in both directions. Armadillos, porcupines and giant ground sloths moved north, while cats, dogs, bears, camels and horses moved south, transforming South America's fauna.
Timeline of key events
- 17 Ma
Miocene Climatic Optimum
Global temperatures climb well above today's for about two million years before a sharp cooling.
- 8 Ma
C4 grasslands spread
Heat- and drought-tolerant grasses expand across tropical and subtropical regions over the next few million years.
- 7 Ma
Sahelanthropus lives in Chad
One of the oldest possible members of the human lineage lives near an ancient lake in central Africa.
- 5.97 Ma
Mediterranean begins drying out
Cut off from the Atlantic, the Mediterranean partly evaporates in the Messinian Salinity Crisis.
- 5.33 Ma
Zanclean flood refills Mediterranean
Atlantic water breaks through at Gibraltar and rapidly refills the basin, marking the start of the Pliocene.
- 3.66 Ma
Laetoli footprints made
Upright-walking hominins, probably Australopithecus afarensis, leave tracks in volcanic ash in Tanzania.
- 3 Ma
Isthmus of Panama completes
A land bridge joins the Americas, enabling the Great American Biotic Interchange.
- 2.7 Ma
Northern ice sheets grow
Large ice sheets begin to wax and wane across North America and Europe, heralding the ice ages.
How the Neogene ended
The Neogene ended without a mass extinction, as the Earth cooled into a new pattern of repeated ice ages. Its end, 2.58 million years ago, is fixed near a reversal of Earth's magnetic field and the intensification of Northern Hemisphere glaciation. The boundary was moved to this age in 2009; before that, the Quaternary was usually said to begin about 1.8 million years ago.
Where to see Neogene fossils
At Ashfall Fossil Beds in Nebraska, complete skeletons of rhinos, horses and camels lie where they died after a volcanic eruption about 12 million years ago, and nearby Agate Fossil Beds preserves earlier Miocene mammals. Riversleigh in Queensland documents the evolution of Australia's marsupials, and Sharktooth Hill in California is packed with Miocene marine fossils.
For the human story, Laetoli in Tanzania preserves hominin footprints about 3.66 million years old, and Hadar in Ethiopia yielded Lucy. Rusinga Island in Kenya is famous for the early ape Proconsul.
Surprising facts about the Neogene
- When the Mediterranean dried out, its floor lay well over a kilometre below sea level in places, and rivers such as the Nile carved deep canyons to reach it.
- The Atlantic flood that refilled the Mediterranean may have happened remarkably fast — some models suggest most of the basin filled in a matter of months to a couple of years.
- The animals at Ashfall Fossil Beds died from breathing volcanic ash blown from an eruption roughly 1,600 kilometres away, in what is now Idaho, on the hotspot that now lies beneath Yellowstone.
- Fossils show that giant camels lived on Ellesmere Island in the Canadian High Arctic about 3.4 million years ago, when the region was forested.
- The Miocene had far more kinds of apes than today, ranging across Africa, Europe and Asia, compared with just a handful of living ape groups.
- Carbon dioxide levels in the mid-Pliocene, about 3 million years ago, were similar to today's — which is why scientists study that interval to understand where our climate may be heading.
Where it sits in deep time
The globe beside this article shows Earth 15 million years ago, reconstructed from the PALEOMAP paleo-elevation models. Step to another period and watch the continents drift into place.