These constraints introduce particular challenges for inferring the ecomorphology of primate origins, as morphology and environmental context must first be inferred before the relationship between the two can be considered. Fossils can be integrated in comparative analyses and observations of extant model species and laboratory experiments of form—function relationships are critical for the functional interpretation of the morphology of extinct species.
Recent developments have led to important advancements, including phylogenetic comparative methods based on more realistic models of evolution, and improved methods for the inference of clade divergence times, as well as an improved fossil record. Introduction Extant primates are characterised by a number of anatomical features that are, in their majority, not unique to the order, but in combination serve to distinguish them from other mammals Martin, , , Broadly, the most prominent hypotheses of primate origins can be grouped into those that emphasise the importance of locomotor behaviour in shaping the ancestral primate adaptive profile and those emphasising the importance of diet.
However, a consensus regarding the ecological significance of inferred ancestral primate traits has proved hard to reach. It is perfectly conceivable that early primates had similarly flexible diets, in which case hypotheses seeking to understand the adaptive profile of ancestral primates in the context of derived dietary adaptations may have overestimated the relevance of specific foods, unless it can be argued that they relate to the exploitation of a critical resource.
The case against a singular dietary specialisation being the key determinant of optical convergence, for example, is supported by data from the lorises, which have the most convergent eyes of any strepsirrhines, yet feed on a range of foods including vertebrates, invertebrates, exudates, and nectar; binocular vision appearing to benefit in particular faunivory and nectarivory Nekaris, Ideally, therefore, hypotheses of form—function relationships in ancestral primates, and of their ecological role, should be verified using a multidisciplinary approach including functional anatomy, palaeoecology, and a broad phylogenetic comparative approach.
Here, we present a broad ecomorphological framework for the study of primate origins and provide a brief review of current knowledge, with examples pertinent to an ecomorphological contextualisation of primate origins. We discuss some of the reasons why a consensus on the adaptive origins of the order has remained elusive, highlighting specific challenges faced by attempts to apply an ecomorphological framework to the past, and suggest some promising avenues for future research.
An ecomorphological framework for primate origins In a palaeontological context, it is important to distinguish between the use of the term ecomorphology as a broad concept aimed at characterising the adaptive relationship between an organism's morphology and its ecological role, from its use to describe methods to infer aspects of palaeoenvironments. These approaches are based on the assumption that the functional significance of the morphology they consider is known, that that function translated into corresponding behaviour in the fossil organisms, and that that behaviour was indicative of the environment those fossils occupied.
This includes the question of how organism form reflects adaptation to a specific environmental context i. At the first level of analysis, and in the absence of directly ancestral fossils, ancestral morphologies have to be inferred. Uncertainties associated with such inferences vary between characters. For example, all living primates, except for the clearly derived modern humans, have a grasping foot.
It seems therefore unproblematic to infer that the last common ancestor LCA of living primates also had a grasping foot. This raises the legitimate, and functionally important, question of what structures were present in ancestral primates.
Similarly, metric variables measured on a continuous scale, such as body mass, typically take on a range of values across a clade of interest, rendering an intuitive, informal estimate of ancestral values unreliable.
In these cases, phylogenetically informed average values can be derived and serve in lieu of ancestral values, based on assumptions of evolutionary processes e. Platyrrhines evolved from an African anthropoid and migrated across the Atlantic to South America; supported by evidence. Platyrrhines evolved from an anthropoid in Africa that migrated south on land to Antarctica and then to Patagonia, at the southern tip of South America; supported by evidence.
Old World and New World anthropoids evolved independently from different promisian lineages in Africa and South America, respectively; no evidence.
Click Card to flip What was the first South American primate? It is not valid; no evidence supports this hypothesis because there were no anthropoids in North America during the Eocene or Oligocene. Yes, this hypothesis is supported by evidence because the continents were much closer together back then and similar fossils that date from the same time on both sides of the Atlantic were discovered. Yes, evidence of similar fossils support this hypothesis.
In the end, however, grasping hands and feet are an obvious benefit when transporting larger bodies through tree branches. Visual Predation Hypothesis: All of the adaptations of the primates would appear to be obviously useful to a species or group of species foraging for fruits and insects on trees near the forest floor.
This is exactly what the Visual Predation Hypothesis predicts. Stereoscopic vision is very important in gauging the distances of such food sources, and reduced olfaction can be explained as a side effect of orbital convergence of the eyes. Reduced claws and grasping limbs make foraging for such small game much easier.
All of these make the Visual Predation Hypothesis the most supported hypothesis concerning the origins of the primates.
As omnivores, early primates were able to eat the fruits, gums, and other products of the flowering plants, as well as the insects that fed upon them. In: Tuttle R ed The functional and evolutionary biology of primates. Primates in North America: S. Primates, Plesiadapiformes : the evidence for gliding behavior reconsidered. Primates , with a description of a new genus and species.Journal of Human Evolution, 15 6 , — This raises the legitimate, and functionally important, question of what structures were present in ancestral primates. An ecomorphological framework for primate origins In a palaeontological context, it is important to distinguish between the use of the term ecomorphology as a broad concept aimed at characterising the adaptive relationship between an organism's morphology and its ecological role, from its use to describe methods to infer aspects of palaeoenvironments. New York: Academic Press. Tuttle, H.
Both, though, may hold critical information for clarifying the context of primate origins, and below we review recent data that may prove pertinent to their interpretation. According to the competitive exclusion principle, no two species can occupy the same niche in the same environment for long because of competition. Hildebrand, D. Google Scholar Stern, J.
Stereoscopic vision helped in discerning plants at low levels of light and in improving the hand-eye-coordination required to forage such foods. We see the arrival of Apidium and Aegyptopithecus. Journal of Human Evolution, 15 6 , — Vertical Clinging and Leaping — a newly recognized category of locomotor behavior of Primates. Their teeth reflect a diversity of food and habitat. Clades and lineages to be included in taxon are in black; those to be excluded are in grey.
Behavioral Ecology and Sociobiology, 8, — Folia Primatologica, 53, — Google Scholar Walker, A. Oxford: Blackwell. Galago locomotion.
Galago locomotion. Google Scholar Napier, J. Primates, 27 3 , —
Google Scholar Preuschoft, H. All the other scenarios are less consistent with the pattern of trait acquisition through time observed in the fossil record. In: Tuttle R ed The functional and evolutionary biology of primates. In the absence of direct evidence of ancestral primate behaviour, the most likely source of information on behavioural flexibility will come from comparative analyses of brain anatomy and the phylogenetic mapping of neural characteristics see section below on Brain size and anatomy. American Journal of Primatology, 22, — Temperature regulation and oxygen consumption in the Phillippine Tarsier, Tarsius syrichta.