Human Ancestors Evolved As Forests Gave Way To Grasslands

Ancient humans evolved as grasslands in East Africa expanded.

Ancient humans evolved as grasslands in East Africa expanded. Sergey Novikov/Shutterstock


Our ancestors were able to flourish in East Africa after a change in climate pushed the environment to form open grasslands. This shift in the ecosystem saw archaic humans go extinct as members of the newly evolved Homo genus began to dominate. The study is published in Nature Ecology & Evolution.

Researchers recreated the environment in which the Homo genus evolved by using direct evidence from fossils in order to get a clearer picture of our origins. They found that as the climate changed, the animal species associated with the woodlands were replaced by those found in grasslands. But of even more interest were the diets of these species.


Analyzing the teeth of the earliest known member of Homo, they found that as this environment shifted, and the new genus replaced more archaic species of ape, its diet remained similar. They found that while most other species at the time altered their diets to feature more grasses as the grasslands expanded, the early Homo species did not and instead stayed consistent with the diet of more ancient ape species that evolved in a more forested environment.  

“We weren't necessarily surprised that the diet of early Homo was similar to Australopithecus,” explains Chris Campisano, from the Institute of Human Origins, in a statement. “But we were surprised that its diet didn't change when those of all the other animals on the landscape did.” This seemingly rules out the notion that the Homo genus evolved as a result of a change in their diet in response to the spread of grasslands.

Modern humans are thought to have evolved around 200,000 years ago, but our history goes much further back. In 2013, researchers discovered the oldest remains of a species belonging to our own genus, which dated to 2.8 million years ago, pushing back the known date of Homo by an impressive 400,000 years.

One of the most famous archaic human fossils ever discovered is that of Lucy, a 3.2-million-year-old fossil of a more ancient species known as Australopithecus afarensis. The revelation that the Homo genus came into existence much closer in time to these more primitive apes changed what we thought we knew about where our ancestors came from.


By looking at the species of other animals living during the period, it becomes possible to build up an idea of what the environment was like at the time. If, for example, there were species such as giraffes and monkeys knocking about, then it’s a fairly good sign that the region was covered in woodland, while if antelope and wildebeest dominated, then it's likely it was a grassland.


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