The lazy are small herbivores of slow movements that live suspended from the branches of the trees in the jungles of South America, but it was not always like that. About 15 million years ago there were a variety of different species, some giants and others of only ten kilos.
A team of scientists led by the universities of São Paulo (Brazil) and Buenos Aires (Argentina), and in which the National Museum of Natural Sciences (MNCN) of Madrid has collaborated, has rebuilt the expansion and decline of these mammals that had an incredible ability to adapt, at least until Homo Sapiens arrived, which practically ended them.
Through the combination of the study of fossils, genomic data and advanced evolutionary models, the authors have rebuilt the evolutionary history of the lazy and the size modifications they developed to adapt to the changes of the climate and survive both in the meadows (terrestrial environment) and in the trees.
The study, whose details have been published this Thursday in the journal Science, recalls that lazy appeared 35 million years ago in South America, a region that for several million years evolved isolated from the rest of the world giving rise to numerous native and unique mammals.
The first lazy were corpulent animals that lived on the ground and weighed between 80 and 350 kilos.
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These animals were adapting their size to different lifestyles, diets and habitats until about 15 million years ago there could be up to a hundred genres distributed throughout the American continent, some of more than four tons (the terrestrial) and others of less than ten kilos (tree).
“15 million years ago there was a great variety of lazy sizes, the first ones were the size of a anthill and then evolved towards much larger sizes, around a ton and, at the same time, towards much smaller sizes of fifty kilos or less,” said Juan Cantalapiedra, researcher at the MNCN and co -author of the study.
Specifically, the study divides these mammals into “three great ecologies: ‘terrestrial’, which were the largest, ‘semi -overd’, with more intermediate carvings that did not allow a fully tree life, and ‘fully arboreal’, which needed to be very small, like the current ones,” says the Paleobiologist of the MNCN.
But about 14 or 15 million years ago, the climate began to change and the earth began to cool and those environmental changes replaced forests with more open landscapes and wooded meadows that favored the expansion of large mammals, especially the great herbivores such as lazy, mastodons, or antelopes and buffalo.
As a result of this climate change, giant species, such as Megatherium Americanum, reigned in the landscapes of the Pleistocene, between 2.5 million years and approximately 12 thousand years ago.
Catastrophic for laziness of large size
But, the arrival of Homo Sapiens to the American subcontient about 15 thousand years ago was catastrophic for large laziness. The study details that the transition between the Pleistocene and the Holocene, the giant lazy people succumbed quickly – first in the continent and then in the islands – unable to face human expansion. Only the smallest species that lived in the trees remained.
His extinction chronology goes hand in hand with human expansion. “No previous climate crisis affected them so radically, which points to anthropogenic pressure how the new variable and as the final blow,” explains Alberto Boscaini, of the University of Buenos Aires (Argentina).
Unlike the giants, the smallest lineages, who led a fully tree life – they struck between ten and twenty kilos like the current ones – and that were relatively recent (they emerged about three million years ago), they managed to survive humans and extend their lineage until today.
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For the authors, the long evolutionary history of the lazy shows that they were able to adapt to geological, climatic and ecological changes and reinvent themselves to survive in trees and on earth. “This group turned versatility into the opportunity,” says Daniel Casali of the University of San Pablo (Brazil) and co -author of the study.
However, his abrupt final shows a harsh reality: “The arrival of something unexpected, in this case humans, is enough to end a success story. Lizzas are the example that there is never anything insured or constant,” Cantalapiedra concludes.
With EFE information
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