Giant Ground Sloths developed three different times for the same reason

When cooling, drying the climate turned the litter to giants – before humans potentially drove huge animals for extinction.

Today’s sloths are small, famous sluggish herbivors moving through the tropical canopies of rainforests. But for tens of thousands of millions of years, South America was a staggering diversity of sloths. Many were groundbreaking giants, with some Behemoth approaching 5 tons of weight.

The staggering size area is of particular interest to Alberto Boscaini at the University of Buenos Aires in Argentina and his colleagues.

“Body size correlates with everything in an animal’s biological features,” says Boscaini. “This was a promising way of studying [sloth] development.”

Boscaini and his colleagues prepared data on the physical features, DNA and proteins of 67 off and vibrant sloths – groups of closely related species – to develop a genealogy that shows their evolutionary conditions.

The researchers then took this evolutionary story that covered a period of 35 million years, adding information about each sloth’s habitat, diet and lifestyle. They also studied trends in the development of body size, making estimates of body mass of 49 of the old and modern sloth groups.

The results suggest that the development of body size in body size was heavily affected by climatic and habitat changes. For example, some slot nuisance began to live in trees – similar to today’s sloth – and shrunk in body size Asy did.

Meanwhile, three different lineage of sloths developed independently elephantine proportions – and it seems that they did this within the last millions of years as the planet cooled and growth in the Andes made South America drier.

“Givantism is closer to cold and dry climate,” says team member Daniel Casali at the University of São Paulo, Brazil.

Many of these different slots disappeared in two stages: one surround 12,000 years ago, and the other spawn 6000 years ago, says Boscaini.

“This is in line with the extension of Homo sapiensFirst all over the American supercontinent and later in the Caribbean, ”he says – who are whore some giant sloths lived. Notary, the only surviving sloth that lives in trees, is much harder for humans to hunt than massive earth women.

The idea that humans were the death of ancient Megafauna is well supported, says Thaís Rabito Pansani at the University of New Mexico involved in the study.

“In science, however, we need more evidence lines to strengthen our hypotheses, especially in unresolved and much discussed from, such as the extinction of megafauna,” she says. The new evidence coasts this story.

“Releases thrived in most of their history,” says Casali. “” “[The findings] Teach us how a very successful [group] Can become so vulnerable very quickly. “

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