Australopithecus, a genus of extinct hominins, has been a subject of intense research to understand their way of life, including their dietary habits. Scientists employ various methods to reconstruct the diets of these early human relatives, including analyzing dental morphology, microwear patterns on teeth, plant microfossils in dental calculus, and stable isotope ratios in teeth and bones. This article synthesizes current knowledge about Australopithecus diets, focusing on key species and the factors that influenced their food choices.
Dietary Analysis Methods
Dental Morphology
The size, shape, and structure of teeth and jaws provide clues about the types of food a species is adapted to eat. For example, robust skulls, large mandibles, and thick enamel suggest an ability to consume hard and brittle foods.
Dental Microwear Texture Analysis
Different foods interact differently with teeth, leaving distinct microscopic textures and abrasions on the enamel surface. Hard, abrasive foods create complex patterns, tough foods leave long, narrow scratches, and fruits may leave pits. Analyzing these patterns helps determine the types of food consumed.
Plant Microfossil Analysis
Dental calculus, the hardened plaque on teeth, can trap microscopic plant fossils called phytoliths. These phytoliths can be extracted and identified to determine the types of plants consumed.
Stable Isotope Analysis
This method involves analyzing the ratios of different carbon isotopes (carbon-13 to carbon-12) in tooth enamel. Different photosynthetic pathways in plants (C3 vs. C4/CAM) result in distinct carbon isotope ratios. Analyzing these ratios in hominin teeth can reveal the proportions of C3 and C4/CAM plants in their diet. Nitrogen isotopes (nitrogen-15) can also be measured to estimate an animal's trophic level, or how much meat they consumed.
Read also: The Hoxsey Diet
Dietary Adaptations and Preferences of Australopithecus Species
Australopithecus afarensis
Au. afarensis, known from sites like Hadar and Dikika in Ethiopia, lived between 3.9 and 2.9 million years ago. Their diet has been investigated using microwear texture analysis and stable isotope analysis.
Microwear Texture Analysis: Studies suggest that Au. afarensis primarily consumed softer foods.
Stable Isotope Analysis: Results indicate a diet including a significant proportion of C4/CAM plants, such as grasses, sedges, and succulents. The median δ13C value for Au. afarensis is −7.4‰, with a range of −13.0‰ to −2.9‰. This is statistically distinct from C3-browsing giraffes and C4-grazing alcelaphini found in the same sediments. The nominal percentage of C4 intake for Au. afarensis individuals has a median value of 22% and a range of 0-69%.
Au. afarensis consumed more C4/CAM foods than modern Pan (chimpanzees) and Gorilla. There was no statistically significant temporal trend in δ13C values through the Hadar Formation, suggesting that their diet did not change significantly over time in response to environmental changes.
Australopithecus africanus
Au. africanus, found in South Africa, is younger than Au. afarensis. Stable isotope analysis of Au. africanus shows δ13C values that do not differ significantly from Au. afarensis. The ranges of variation in δ13C values for these two taxa broadly overlap (Au. afarensis: −13.0‰ to −2.9‰; Au. africanus: −11.3‰ to −1.8‰). A recent study measuring nitrogen-15 levels in Au. africanus teeth suggests that this species did not consume a large amount of meat.
Read also: Walnut Keto Guide
Australopithecus sediba
Au. sediba, discovered at Malapa, South Africa, dates back approximately 2 million years. This species exhibits a mix of primitive and derived traits, aligning it with other Australopithecus species and early Homo.
Phytolith Analysis: The first extraction of plant phytoliths from dental calculus of Au. sediba revealed the consumption of both dicotyledons (tree leaves, fruits, wood, and bark) and monocotyledons (grasses and sedges).
Stable Carbon Isotope and Dental Microwear Texture Data: The two individuals examined consumed an almost exclusive C3 diet, likely including harder foods. Like Ardipithecus ramidus and modern savanna chimpanzees, Au. sediba preferred C3 foods over widely available C4 resources.
Other Australopiths
Au. anamensis: Earlier than Au. afarensis, Au. anamensis focused on C3 plant foods.Au. bahrelghazali: This species consumed substantial amounts of C4/CAM foods.Paranthropus robustus: This robust australopith retained a range of C4/CAM intake similar to Au. afarensis and Au. africanus.Paranthropus boisei: This species specialized on a narrow range of C4/CAM foods.
Environmental Influences and Dietary Adaptability
The diets of Australopithecus species were influenced by environmental changes and the availability of different food resources. The expansion of hominin diets to include C4/CAM foods signals a major ecological and adaptive divergence from the last common ancestor shared with African great apes.
Read also: Weight Loss with Low-FODMAP
Au. afarensis expanded its diet to exploit a range of viable resources, despite habitat variation. Fluctuating environmental conditions did not perceptibly influence the C4/CAM consumption patterns of Au. afarensis in the Hadar Formation.
Unanswered Questions and Future Research Directions
Several questions remain regarding the diets of Australopithecus species. For example, why did Au. afarensis eat softer foods despite having morphological features suggesting they could consume tougher foods? Why did they expand their diets to include more grasses and sedges?
One theory proposes that Au. afarensis used hard foods as a “fallback” in seasons when softer foods weren’t available. Others suggest that their expanding diets were a result of fluctuations in the environment, and that their ability to eat hard and soft foods allowed them to survive short and long-term climate fluctuations and corresponding changes in available resources.
Future research should focus on:
- Larger sample sizes for stable isotope analysis to better understand the range of dietary variation within and between species.
- Combining isotopic data with proteomic and genetic data to deepen the biological context of dietary adaptations.
- Investigating the social dimensions of diet, such as differences in food consumption between males and females.
- Analyzing additional material from Laetoli, Woranso-Mille, and other localities to fill the gap in knowledge about C4/CAM consumption patterns of hominins between Au. anamensis and later C4/CAM-consuming australopiths.
tags: #diet #of #australopithecus