What did macaque monkeys eat 2.5 million years ago?

The fossil dental remains of a 2.5-million-year-old macaque obtained at the Guefaït site (Morocco) have made it possible to reconstruct for the first time the diet and habitat of this type of primate at that time in Africa.

The work is the work of a team that includes experts from the Catalan Institute of Human Paleoecology and Social Evolution (IPHES), at the Rovira i Virgili University (URV) of Tarragona and which is one of the CERCA institutions of the Generalitat of Catalonia.

Through multiple analyzes carried out on the internal and external structure of these fossils, the research team has been able to verify that these animals exploited different habitats in order to obtain the necessary resources for their survival. So much so, that they obtained food both from wooded areas and from more open spaces. This information on the feeding ecology of the genus Macaca is also very important to understand the paleoecology of hominins, since both lineages occupied similar ecological niches and may represent a good analogous model to explain the evolution of hominins in the Plio-Pleistocene of Africa. In this way, studying the ecology of these fossil primates can help to understand their adaptive capacities in the changing and increasingly open environments that occurred in this period in Africa.

This is the main conclusion of the study, led by Iván Ramírez-Pedraza, a researcher at IPHES, and by Laura Martínez, a researcher at the University of Barcelona (UB). Researchers from the Rovira i Virgili University, the University of Barcelona (UB), the Autonomous University of Barcelona (UAB), the Institute of Evolution in Africa in Madrid, the Museum of Natural Sciences of Madrid (MCNM) have also participated in the work. ) and the Milan and Fontanals Institute of the Higher Council for Scientific Research (CSIC), in Spain; as well as the Mohammed Primero University (UMP) and the National Institute of Archeology and Heritage Sciences (INSAP), in Morocco.

The macaque remains now analyzed are part of the set of fossils recovered in various excavation campaigns carried out during 2018 and 2019, within the framework of a transdisciplinary project of Spanish-Moroccan collaboration, which have made it possible to obtain more than 3,200 vertebrate fragments ( amphibians, reptiles, and small and large mammals, including elephants, rhinos, and hippopotamuses, among others) from the early Lower Pleistocene, dating back around 2.5 million years.

The studied sample corresponds to four cercopitécido teeth from 2.5 million years ago with a morphology that allows assigning them to the genus Macaca. Based on the size of the teeth, it has been estimated that these macaques weighed around 12 kilos. In a previous study published in the Journal of Human Evolution by the same research team, both the size and morphology of the teeth were considered to be compatible with those of the extant North African species (the Barbarian macaque, Macaca sylvanus).

A small sample from the collection of macaque teeth found in Guefaït. (Photo: IPHES / URV / CERCA)

The diet of a lifetime

The relevance of this work lies in the fact that, for the first time, a combined multi-proxy analysis has been carried out on fossil dental remains of the genus Macaca from 2.5 million years in Africa. The application of these techniques has made it possible to extract information both on the diet and on the paleoecological conditions of this primate from the first years of its life to the last months before its death.

These data have been obtained by applying three techniques that have proven to be complementary: stable isotope analysis and dental microwear, since each of them explains different things to us. In this sense, Iván Ramírez-Pedraza has declared: “The novelty of our work is that, thanks to the richness and good conservation of the Macaca remains, we have been able to use the three techniques on the same individual, something never applied to this type until now.” of primates and we have developed a very exhaustive study”.

On the one hand, an isotopic study of the teeth has been carried out, analyzing the isotopic signal of the bioapatite of dental enamel. This type of analysis provides information related to the protein origin of the food ingested, especially in the first years of the animal’s life. On the other hand, an analysis of dental microwear has been carried out, which consists of quantifying a series of marks, such as grooves and holes, formed on the surface of the tooth during the masticatory cycle by particles that are harder than the enamel surface. dental.

In the case of the Macaca de Guefaït, two types of dental microwear analyzes have been carried out that provide information on the animal’s diet in the medium and short term. This is the case of oral microwear, specifically the microtexture of the tooth, which provides information on a relatively long stage of its life, and microwear on occlusal surfaces, which provides information on diet in the shorter term, that is, weeks or days before the death of the individual.

This work also presents a new reference collection of microwear in extant guenons. The combination of these studies has allowed the research team to extract data on both the diet and the paleoecological environment in which the Macaca cf. sylvanus during the Plio-Pleistocene.

In this sense, the microwear analysis shows that the Macaca cf. sylvanus de Guefaït fed mainly on fruit, seeds and leaves, but would also have incorporated other abrasive foods such as grasses and grasses. “This dietary diversity shows us the ability and flexibility of fossil macaques when it comes to consuming different foods,” says Iván Ramírez-Pedraza. “It also gives us information on the richness of resources and probably microhabitats in the Guefaït area during the Plio-Pleistocene”, he concludes.

Implications for human evolution

The data extracted from the paleodiet of the Macaca cf. sylvanus are “very important to be able to infer the ecological conditions in which the Plio-Pleistocene hominins lived in North Africa”, explains Laura Martínez, a UB researcher.

Evidence of the earliest hominins in North Africa is dated to around the Plio-Pleistocene boundary (about 2.4 million years ago) at the Ain Boucherit site in Algeria. The ecological context of this first population of our lineage is a key issue to understand the dispersals of our ancestors and other mammals in these territories. “If we take into account the proximity of Guefaït to Ain Boucherit, the knowledge of the feeding ecology of Macaca cf. sylvanus can provide clues about some of the ecological resources these first hominins might have had”, explains Dr. M. Gema Chacón, researcher at IPHES-CERCA and co-director of the project together with Dr. Robert Sala Ramos, professor at the URV.

Presence of Macaca sylvanus in Africa

Molecular data indicates that Macaca sylvanus diverged before all other living macaques (which we find in Asia). Guefaït’s teeth are more similar to those of the present-day African subspecies than to fossil forms from Europe. The species may have been present continuously for the last 5 million years in Africa, but interestingly there is a gap in the fossil record between 2.5 and 0.2 million years ago, which contrasts with the more continuous record. that is observed in Europe. Future studies will have to clarify if this absence is due to a local extinction of this species in Africa or if it is simply a sampling problem. The investigation also confirms the absence of frosts, the species Theropithecus gelada, in Guefaït, a primate genus that has been described in Ahl in Oughlam, another Moroccan site that is almost the same age. Given that guemons are good ecological indicators, the presence of Macaca in Guefaït and of Theropithecus in Ahl on the Oughlam could give us clues about the type of landscape. In this case, the Macaca would be linked to a greater vegetation cover and the Theropithecus to more open spaces.

The new study is titled “Multiproxy Approach to Reconstruct Fossil Primate Feeding Behavior: Case study for Macaque from the Plio-Pleistocene Site Guefaït-4.2. (Eastern Morocco). And it has been published in the academic journal Frontiers in Ecology and Evolution. (Source: URV)