What did Earth look like in the Neogene? (23.04–2.58 Ma)

Key events of this period

• Early Hominins

  6 Ma

  African fossils around 7–6 million years old, including Sahelanthropus, lie near the early history of the human lineage. Evidence for upright walking coexists with traits suited to climbing, and interpretations of the earliest fossils remain debated. Human evolution was a branching process, not a single moment when a modern-style walker appeared.

  References: Sahelanthropus tchadensis (Smithsonian Human Origins) · Walking Upright (Smithsonian Human Origins) · Earliest evidence of hominin bipedalism in Sahelanthropus tchadensis (2026)

• Messinian crisis & Mediterranean refilling

  5.33 Ma

  Restricted Atlantic exchange left enormous salt deposits in the Mediterranean between 5.97 and 5.33 million years ago. Marine conditions returned around 5.33 million years ago; Sicilian erosion features support a rapid refilling flood. How far water levels fell, and exactly how refilling unfolded, remain debated.

  References: Micallef et al.: Land-to-sea indicators of the Zanclean megaflood

• Panama Isthmus

  3 Ma

  Panama emerged gradually as islands grew and seaways narrowed over millions of years. Multiple lines of evidence place the final continuous land bridge near 2.8 million years ago, restricting exchange between the Caribbean and Pacific. Animal migrations between the Americas had already begun, then accelerated as the connection became established.

  References: Formation of the Isthmus of Panama (O’Dea et al., 2016) · Formation of the Isthmus of Panama — full paper (2016)

• Northern Hemisphere Ice Sheets Expand

  2.6 Ma

  Northern Hemisphere glaciation intensified around 2.7–2.6 million years ago, within a longer cooling trend. Changes in Earth’s orbit and tilt paced repeated cold and warm intervals, with feedbacks from ice, oceans and greenhouse gases. The cycles later grew longer, shifting from roughly 41,000 to 100,000 years.

  References: Role of land-ocean interactions in stepwise Northern Hemisphere Glaciation (2024) · Milankovitch (Orbital) Cycles and Their Role in Earth’s Climate (NASA, 2020)