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The first animal in the world was probably a carnivore . This is one of the surprising conclusions of a study without a comparison that elaborates on the dietary preferences throughout the animal kingdom since its emergence 800 million years ago. The research, published in the journal “Evolution Letters”, also reveals that there are many more fans to the meat of what the scientists believed and that human choice -eat everything – it is the most strange.
The researchers from the Department of Ecology and Evolutionary Biology at the University of Arizona (USA) sought data on the dietary habits of more than a million species of animals, from sponges to insects or domestic cats. A species is classified as a carnivore if it eats other animals, fungi or protists (organisms, unicellular eukaryotes, many of whom live bacteria). As a vegetarian, if you depend on terrestrial plants, algae or cyanobacteria; and an omnivore, eating a mix of diets, carnivorous and herbivorous.
Then, the scientists mapped the vast data set of animal species and their dietary preferences in an evolutionary tree constructed from DNA sequence data to unravel the relationships between them. “Ours is the largest study done to date that examines the evolution of the diet in all the tree of animal life”, says Cristian Román-Palacios, lead author of the article.
The research suggests that, among the animals, the carnivores are the most common: 63% of the species. Another 32% are herbivores, while humans belong to a small minority, only 3% of omnivores.
butterflies and moths are almost all herbívorasProtistas in the plate
The researchers were surprised to find that pulling the thread of many of the carnivorous species, current up to the base of the evolutionary tree an animal, makes more than 800 million years ago, earlier than the oldest fossils known that paleontologists have been able to assign to the origins of animals with certainty. However, the same does not occur with the herbivores, whose diet seems to be much more recent.
But if the first animal was a carnivore, what the hell is fed? According to the authors, of protists, including choanoflagellates : small organisms and single-celled considered the closest living relatives of animals. Living as plankton in sea water and sweet, the choanoflagellates vaguely resemble a shuttlecock of badminton. It is possible that the common ancestor of animals today outside a creature very similar.
“The ancient creature that is more closely related to all animals living today, could have eaten bacteria and other protists instead of plants”, says John Wiens, co-author of the study.
flies killer (family Asilidae) are aggressive predators that feed on insects – Daniel Stolte/UAComer green
In the plant based diet , the authors believe that it is not the engine of evolution, the emergence of new species as was believed. An example often cited are the insects, with 1.5 million species. Many new species of flowering plants appeared during the Cretaceous period, about 130 million years ago, and it is believed that this botanical diversity unprecedented coincided with an increase in insect species. However, what happened with insects does not necessarily apply to other groups within the animal kingdom.
The study also revealed that the diet omnivorous (“eat all”) are quite rare, which suggests the possible explanation of that the evolution prefers the specialists about the generalists. “You can be better at what you do if that is all you do,” notes Wiens. “In terrestrial vertebrates, for example, eating a diet of leaves often requires teeth and a gut very modified. The same thing happens when it is carnivorous. Nature in general seems to avoid the dilemma of being a ‘jack of all, master of nothing’, at least for diets”.
The black vultures and andean condors are birds carnivores who specialize in eating carrion – Roman-Palaces /UASomos rare
This need for specialization could explain why omnivores, like humans, are rare , according to the authors. It could also make sense of the fact that the diets have not changed much for so long. “There is a big difference between eating leaves all the time and eat fruits once in a while,” says Wiens. “The specializations required to be a herbivore or carnivore efficient could explain why the two diets have been conserved during hundreds of millions of years,” he says.
