Ancient deer teeth offer fascinating insights into how early humans lived

Understanding what the environment looked like millions of years ago is how our earliest ancestors lived and survived. Habitat shaped everything, from what food was available, where water could be found, how predators and prey interacted.

For decades, South African anthropogenic scientists have attempted to reconstruct the landscape in which the species is favored. Australopithecus sedibafor , for , for , . Paranthropus robustus And Homo nelidii Once lived. These were hominins who inhabited the region between 2.5 million and 0.25 million years ago. Cradle of Humankind is a UNESCO World Heritage Site that has been the single richest source of early human fossils for over 90 years.

A long-held view has been that this domestication experienced a dramatic environmental change about 1.7 million years ago: the shift from forest plains to open grasslands. This change likely occurred when the global climate became cooler and drier, with stronger weather patterns. These broader changes, linked to the expansion of polar ice sheets and shifts in atmospheric circulation, reduced the availability of year-round rainfall in southern Africa.

Trees and shrubs, which depend on constant moisture, give way to hardy grasses that are adapted to long dry seasons and intense sunlight. In forested areas, thick trees and shrubs once provided leafy vegetation for animals to browse on. As the landscape evolved, short grasses became dominant, supporting grazing animals.

The sudden change is thought to have reshaped the setting in which early humans evolved, possibly affecting their diet, movement and survival strategies.

But was the switch really so sudden?

I am a paleoecologist who is part of a team that specializes in reconstructing ancient environments by studying fossil animals. We set out to test the “sudden switch” idea, using a large dataset of fossil deer teeth. Anteaters (bovids) are particularly useful for reconstructing past environments in Africa: they are abundant in the fossil record, they occupy many habitats today as well as in the past, and their teeth preserve clear signs of their diet.

We examined more than 600 fossil teeth from seven well-dated sites in Palana, covering a broad time period from 3.2 million to 1.3 million years ago.

The results of our study, published in Paleogeography, Paleoclimatology, Paleoecologywere amazing. Across all seven sites spanning nearly two million years, the anthills consistently show strong grazing indicators. Herbivory dominated throughout, challenging the old model of a sudden forest-to-grassland shift 1.7 million years ago. Instead, the evidence points to a more stable but diverse landscape: a mosaic environment. Some fossil species even exhibited different feeding strategies from their modern relatives, highlighting that ancient anteaters adapted to past conditions in distinct ways.

It tells us more about the world early humans evolved in – but it also reminds us to be careful. Fossil animals didn’t always behave like their modern relatives, so overexplaining the past threatens direct parallels.

Visiting sites

To interpret the fossils in context, we needed to be sure when each site was formed. Previous work often relies on broad age estimates based on the types of animals found in each sediment layer. This is a method called biochronology – which can only give a precise idea of ​​when different species lived. This made it difficult to line up fossils from the many cave sites in the cradle on a reliable timeline. Thanks to recent improvements in radiometric dating, a method that measures how radioactive elements change into other elements over time, the exact age of rocks can be found.

Layers of calcite deposited in caves (known as flowstones) were recently formed by geologists in multiple sites at the same time, providing a regional framework for the entire area. This means researchers can now compare fossils from different caves knowing they represent the same window of time. This is a huge step in testing whether the climate shifts were truly regional events.

Reading food with teeth

The method used in this study is called Mesoir analysis of teeth. It records the long-term effect of diet on herbivore tooth surfaces throughout life. Simply put, different foods wear teeth in different ways:

• Browsers (such as turtles or giraffes), which eat leaves and twigs, are generally faster, because their food wears less on the teeth.
• Grazers (such as wildebeest or zebra), which feed mostly on silica-rich grasses and are often covered in tusks, produce blunter cusps by grinding their heavy teeth.
• Mixed feeders show intermediate clothing, reflecting general behavior and a diet that changes with the seasons or local flora.

By scoring the shape and relief of the CUSP on each fossil tooth, we assessed whether past populations were more inclined to browsing or grazing.

The results show that the environment currently has a mix of different habitats: open grassy areas interspersed with patches of trees and shrubs. This would have created a patchwork of ecological niches, offering early humans a diverse range of resources.

Some sites – including the famous Sterkfontein Caves, one of the most complete early hominin skulls ever discovered, “Mrs. Plus” – showed a bimodal pattern in tooth wear, implying that even within the same community, some antelopes were grazing while others were browsing. This suggests that plant structure shifted spatially or seasonally, and that animals adapted their diets accordingly. They switched between food sources as conditions changed.

Lessons from deer diet

One of the most important discoveries is that some fossil antlers fed very differently from their modern relatives. For example, some groups that are almost exclusively browsers today were highly grass-focused in the domestication fossil record. Others showed unexpected flexibility, with members of the same tribe adopting different strategies within the same site.

This has two important implications.

We cannot always rely on modern analogies. Assume that extinct animals behaved like their living relatives, because the fossil record shows surprising changes in diet. This means that reconstructions based solely on the presence of species may misrepresent or exaggerate reality.

Flexibility was essential. The fact that herbivores could switch between grazing and browsing suggests that the rearing environment was dynamic, and that survival often depended on adaptation. What do we know about early humans, who thrived by exploiting many resources?

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