The theory of evolution can be described as a masterpiece taking into consideration the amount of research and evidence supporting the theory. However there are always some disjointed dots within the theory which in most cases are filled with assumptions or at times just left hanging for future researchers to complete the puzzle. One such case is the adapoids and omomyoids which are two distinct groups of early primates which have attracted a lot of attention from researchers. Research so far has indicated the existence of over 180 species of the two groups (Hartwig, 2002) which is evidenced by fossils from North America, Europe, Asia and North Africa. However between the two groups is there an indication that one of the two groups gave rise to primates.
The adapidae is said to have existed in the Eocene Epoch around 54 million years ago and had various distinct characteristics which I tend to believe should be an indication that they gave rise to primates. The adapids weighed around 100g to 6 kg but most were more than 500g which is relatively larger than the omomyoids and the fact that primates average more weight of the two, the adapids are closer. The second distinctive characteristic was that they had small eyes which means that they were diurnal another similarity with modern primates. The early primates also displayed dentition characteristics of frugivorous and folivorous diets which indicated that they ate both fruits and leaves. This consumption pattern is similar to monkeys and apes which appeared later in the evolution path.
The adapids have been said to have had lemur-like adaptations which is a very useful characteristics in making the distinction between the two early primates. The lemurs are mostly terrestrial animals, they had fingers on their feet and went on torpor as a means of adaptation during the dry season. These characteristics can be traced in primates such as fingers and nails on feet instead of claws. There was also evidence of leaping in some groups and the possession of grooming claw is an interesting characteristic since primates love grooming.
The omomyoids also did exist within the same time of between 55 – 34 million years ago in the northern continents. They also had various characteristics which I believe disqualify them from being the most probable ancestor of primates. As noted earlier the omomyoids were smaller in weight ranging from 30g to 2.5 kg and averaging below 500g. The early primates are also said to have been nocturnal which is evidenced by large eyes which is contrary to primates which are more of diurnal creatures. The omomyoids were also primarily insectivorous which is another characteristic which is not common among modern primates. The group also lacked a very important feature which was crucial to the evolution of primates which is synapomorphy; the trait that is shared by two or more taxa and inferred to have been present in the most recent ancestor, whose own ancestor in turn is inferred to not possess the trait. The comparison with the tarsier is another limitation since they have their eyes fixed to the skull which is not a characteristic of modern primates. Finally John G. Fleagle notes that the most primitive omomyoid, Teilhardina is very similar to early adapids (2013).
Fleagle, J. G. (2013). Primate adaptation and evolution (3rd ed.). Amsterdam: Elsevier/Academic Press.
Hartwig, W. C. (2002). The primate fossil record. Cambridge: Cambridge University Press.
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