{"id":617879,"date":"2026-04-19T21:47:11","date_gmt":"2026-04-19T21:47:11","guid":{"rendered":"https:\/\/www.newsbeep.com\/au\/617879\/"},"modified":"2026-04-19T21:47:11","modified_gmt":"2026-04-19T21:47:11","slug":"ancient-teeth-unlock-million-year-old-secrets-of-where-early-humans-evolved","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/au\/617879\/","title":{"rendered":"Ancient teeth unlock million-year-old secrets of where early humans evolved"},"content":{"rendered":"

Teeth are like tiny\u00a0biological time capsules<\/a>. They tell stories about ancient diets and environments long after their owners have died and landscapes have changed.<\/p>\n

After bones break down, tooth enamel\u00a0stays hard and unchanged<\/a>, even in fossilized teeth that have been buried under sediment and rock for millions of years and are now being uncovered by erosion or excavation.<\/p>\n

Tooth\u00a0enamel forms<\/a>\u00a0when an animal is young, and it remains chemically stable for the rest of that animal\u2019s life. The food an animal eats and the water it drinks during its youth leave chemical signals within the enamel.<\/p>\n

Because of that, hidden within the enamel of fossilized teeth, scientists can find traces of extinct forests, expanding savanna grasslands, shifting climates and evolving animal communities.<\/p>\n

A small group of oryx forage in the open savanna of Awash National Park in Ethiopia, with scattered acacia trees and dry grasses illustrating the park\u2019s semi-arid environment.\u00a0(CREDIT: Zelalem Bedaso) <\/p>\n

These clues from ancient meals are enabling scientists to\u00a0reconstruct pictures of entire ecosystems<\/a>, including forests, wetlands and grasslands that existed at the time. It\u2019s a reminder that in a very real sense, organisms are what they eat.<\/p>\n

Traces of ancient diets in fossil teeth<\/p>\n

To determine which plants ancient animals ate, my colleagues and I collect a small amount of enamel powder from fossilized teeth. We then analyze this powder in the laboratory using specialized instruments that detect chemical signals preserved in the enamel.<\/p>\n

Trees and grasses have\u00a0different ways of using photosynthesis<\/a>\u00a0to convert sunlight into energy. These methods leave distinct chemical patterns in plant tissues, which then become incorporated into the teeth of animals that eat those plants.<\/p>\n

The author conducts fieldwork in the East African Rift, collecting samples from ancient lake and river deposits.\u00a0(CREDIT: Zelalem Bedaso) <\/p>\n

By examining these chemical patterns in tooth enamel, we can determine whether animals primarily fed on trees and shrubs or on grass, providing insight into the vegetation that once covered the ancient landscape.<\/p>\n

We can then figure out how an environment changed over time by collecting fossil teeth from different rock layers. Each layer\u00a0formed at a different time<\/a>\u00a0in the past, so teeth found in deeper layers are typically older than those closer to the surface.<\/p>\n

By analyzing tooth enamel from fossils across these layers, we can compare the chemical signals preserved in the teeth and see how animal diets and the plants growing in the landscape\u00a0changed through time<\/a>.<\/p>\n

Adding that knowledge to data from different types of fossils, we can\u00a0track long-term shifts<\/a>\u00a0in vegetation, climate and ecosystems.<\/p>\n

A changing landscape in the last 4 million years<\/p>\n

Four million years ago, the Afar region looked very different from the\u00a0dry landscape<\/a>\u00a0you will see there today.<\/p>\n

Three tectonic plates are pulling apart at the Afar region, near the Red Sea.\u00a0(CREDIT: Val Rim\/Wikimedia Commons,\u00a0CC BY-SA) <\/p>\n

Fossils, including tooth enamel, reveal that the area supported a diverse range of environments. Rivers flowed through wooded areas, lakes were scattered across the landscape, and grassy plains stretched across the basin.<\/p>\n

Fossilized teeth from animals like antelopes, giraffes, pigs, horses, hippos and elephants show a\u00a0wide range of diets<\/a>. Some animals browsed on leaves and shrubs, while others grazed on grass in open habitats.<\/p>\n

The\u00a0chemical signals in the teeth<\/a>\u00a0indicate that grasslands were expanding at the time, but forests still played an important role. They show that animals moved through this environment and adapted to the food sources around them.<\/p>\n

Around 2 million to 3 million years ago, the environment shifted more drastically toward open grasslands.<\/p>\n

Ethiopia\u2019s Afar Depression and Awash Valley, shaped by rifting and erosion, are among the world\u2019s most important regions for fossil discoveries of human ancestors. Some of those fossils date back 3 million to 4 million years.\u00a0(CREDIT: Zelalem Bedaso) <\/p>\n

Animals that relied on grass flourished, and the populations of those that didn\u2019t adapt declined. Horses and certain antelopes, for example,\u00a0developed teeth<\/a>\u00a0that could grind tough, gritty plants. This adaptation is recorded on their enamel.<\/p>\n

Early humans in a mosaic world<\/p>\n

Early human ancestors, like the famous \u201cLucy<\/a>,\u201d whose skeleton was discovered in the Afar region, lived in this dynamic landscape.<\/p>\n

Fossil teeth from\u00a0Australopithecus afraensis<\/a>, an early human that lived in eastern Africa between about 2.9 million and 3.8 million years ago, indicate that early human relatives did not rely heavily on grass. Instead, the chemical signal in their enamel indicates\u00a0mixed diets and dietary flexibility<\/a>, which included fruits, leaves and roots, depending on what was available.<\/p>\n

In a landscape that combined woodland patches and open savanna, that adaptability may have been key to survival.<\/p>\n

This period of environmental change coincided with several important evolutionary developments and morphological changes in pre-humans. Early human ancestors were\u00a0walking upright<\/a>. Brain size also gradually increased, allowing for more complex behavior and problem-solving.<\/p>\n<\/p>\n

During this time, early humans began making and using\u00a0stone tools<\/a>, marking a major step in technological innovation and helping them adapt to changing environments.<\/p>\n

Diet shapes destiny<\/p>\n

The dietary changes in the East African Rift Valley over the past 4 million years, documented through tooth enamel, are providing important clues for reconstructing the environment in which humans\u2019 ancestors lived and how those environments changed.<\/p>\n

They also show that species that adjusted their diets as landscapes changed were the ones most likely to survive.<\/p>\n

This ongoing research helps explore profound questions of how environmental shifts shaped life on Earth, including human trajectories. And that is helping humanity unlock its collective past.<\/p>\n

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