On Humans How Climate Crafted Humanity (Or Did It?) ~ Jessica Thompson
Last Common Ancestor's Intelligence
- The last common ancestor of humans and chimpanzees likely had a large brain relative to body size, signifying early intelligence.
- This ancestor probably lived in diverse environments, not only dense tropical rainforests as traditionally thought.
Miocene Ape Diversity and Habitat
- Fossils show diverse ape populations across Eurasia in the Miocene, indicating apes lived in more varied habitats than today.
- This complicates pinpointing the exact environment of the last common ancestor beyond just tropical rainforests.
How Climate Shaped Human Evolution and the Explosive Growth of Our Brains
Jessica Thompson unpacks the complex relationship between ancient climate changes and human evolution, challenging the simplistic 'savannah hypothesis' that humans emerged solely as forest dwellers moved to open grasslands.
She explains that early human ancestors, such as Australopithecines, already showed adaptability by living in diverse habitats beyond dense rainforests, which hints at a gradual build-up of flexibility and tool use before the genus Homo emerged around 2.8 million years ago.
Crucially, the rise in brain size did not occur as a neat step tied to a single climate event or dietary shift but rather over a longer, nuanced timeline with critical gaps in fossil evidence, notably for brain size between 2.8 and 2 million years ago.
Jessica highlights that access to calorie-rich resources like bone marrow and later innovations like fire helped sustain growing brains by lowering the energy costs of nutrition.
Ultimately, she argues that human evolution is a story of increasing adaptability, technological innovation, and cooperative behavior, which culminated in Homo sapiens' remarkable ability to thrive in all environments and continuously engineer their own evolution.