Dentes de macaco contam a história da antiga migração

• Bethany Augliere 

Nature ( 2016 ) Cite este artigo

Os fósseis encontrados no Canal do Panamá são as evidências mais antigas de macacos na América do Norte.

Os macacos do Novo Mundo, como este prego-prego, chegaram à América do Sul há mais de 30 milhões de anos. Crédito: Bethany Augliere

Dentes fossilizados descobertos no Panamá sugerem que os macacos chegaram à América do Norte milhões de anos antes do que os cientistas pensavam. A descoberta, publicada em 20 de abril na Nature ¹ , revela novas informações sobre a disseminação de primatas pelas Américas.

Uma equipe liderada por Jonathan Bloch, paleontólogo do Museu de História Natural da Flórida em Gainesville, encontrou sete dentes de macaco na Bacia do Canal do Panamá. Os cientistas identificaram os fósseis como pertencentes a uma espécie até então desconhecida, Panamacebus transitus , que viveu há quase 21 milhões de anos, durante o início do Mioceno.

“Nunca teríamos previsto que eles estariam aqui”, diz Bloch. Os dentes são a evidência mais antiga da dispersão de um mamífero da América do Sul para a América do Norte, diz ele. Nenhum outro mamífero é conhecido por ter cruzado o corpo de água que separou os dois continentes no início do Mioceno.

A teoria atual sugere que os primatas cruzaram o oceano Atlântico da África para a América do Sul há cerca de 37–34 milhões de anos fazendo rafting na vegetação. Esses macacos do 'Novo Mundo' - um grupo que inclui saguis e macacos-aranha e bugios - se espalharam e se diversificaram em regiões tropicais da América do Sul.

Os cientistas pensaram que os macacos só chegaram à América Central depois da formação do istmo do Panamá, há 3,5 milhões de anos. A faixa de terra liga as Américas do Sul e do Norte. Mas a descoberta de Bloch sugere que os primatas cruzaram a barreira da água e chegaram à América do Norte quase 18 milhões de anos antes.

“A descoberta é absolutamente espantosa, e afirmações extraordinárias exigem evidências extraordinárias”, diz Richard Kay, um antropólogo biológico da Duke University em Durham, Carolina do Norte.

A rota pela qual os macacos do Novo Mundo se espalharam e se diversificaram é muito debatida. Bloch e seus colegas sugerem que macacos modernos emergiram dos trópicos. Outros contestam isso, argumentando que fósseis semelhantes em idade a P. transitus existem na Patagônia. Mas Bloch observa que P. transitus é pelo menos igual em idade ao fóssil mais antigo em disputa, senão um milhão de anos mais velho.

Este molar superior fossilizado veio da espécie de macaco recentemente identificada P. transitus . Crédito: Aldo Rincon

Dentes nos trópicos

Os trópicos geralmente têm sido um lugar difícil para descobrir fósseis devido à cobertura florestal, diz Bloch, que normalmente trabalha em desertos secos cheios de rocha exposta. Mas a construção para expandir o canal do Panamá , que começou em 2007, expôs rochas contendo fósseis do Mioceno. “Foi uma oportunidade incrível, uma oportunidade única em um século de observar as rochas nos trópicos”, diz ele.

Ele e seus colegas encontraram molares superiores, um canino inferior, dois incisivos e dois pré-molares enquanto cavavam através de terra e rocha em uma pedreira perto das margens do canal. A equipe passou dois anos analisando imagens de alta resolução dos dentes para colocar a espécie na árvore evolutiva. Os molares se assemelham aos dos macacos da família Cebidae, que inclui macacos-prego ( Cebus capucinus ) e macacos-esquilo ( Saimiri sciureus ).

Não existe evidência de que os primeiros macacos a chegar à América Central sobreviveram o suficiente para estabelecer uma população duradoura. Os ancestrais dos macacos encontrados na região hoje chegaram lá muito mais tarde, diz Kay.

Bloch sugere que os macacos do Novo Mundo eram limitados em sua distribuição pela extensão ao norte de seu habitat preferido na floresta tropical. “É por isso que você não encontra macacos no sul da Califórnia, mesmo até hoje”, diz Daniel Gebo, um primatologista biológico da Northern Illinois University em DeKalb.

Bloch irá ao Panamá novamente no próximo mês e procurará na mesma pedreira onde sua equipe encontrou P. transitus . “Eu realmente gostaria de encontrar um crânio ou partes do resto do esqueleto”, diz ele.

Referências

1. 1

   Bloch, JI et al. Nature http://dx.doi.org/10.1038/nature17415 (2016).

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Behavioral evolution

First report of stone tool use by Cebus Monkeys

July 9, 2018 

Coiba National Park, Panama 

White-faced capuchin monkeys in Panama’s Coiba National Park habitually use hammer and anvil stones to break hermit crab shells, snail shells, coconuts and other food items, according to visiting scientists at the Smithsonian Tropical Research Institute (STRI). This is the first report of habitual stone-tool use by Cebus monkeys.

“Despite being studied for more than 25 years at several field sites, no species in the genus Cebus has ever been previously observed habitually using stone tools,” said lead author Brendan Barrett, formerly a short-term fellow at STRI, and now a postdoctoral researcher at the Max Planck Institute for Ornithology and the Max Planck Institute for Evolutionary Anthropology.

To observe white-faced capuchin monkeys (Cebus capucinus), Barrett and colleagues set up motion-sensor-triggered camera traps. Based on a year of data from the cameras, researchers never saw adult females using stone tools, despite their presence at the site. Among males, stone tool use was common. At one site, capuchin monkeys used tools on more than 80 percent of the days they were observed.

Coiba National Park lies about 23 kilometers from Panama’s Pacific Coast and consists of nine larger islands and more than 100 smaller islands. The islands were isolated from the mainland between 12,000 and 18,000 years ago by sea-level rise after the last ice age. Cebus monkeys are found on three of the larger islands, Coiba Island (50,314 hectares), Jicarón Island (2,002 hectares) and Ranchería Island (222 hectares). Stone tool use was only observed on Jicarón Island.

Mono capuchino usa una piedra como martillo en la isla Jicarón, en el Parque Nacional Coiba de Panamá

 

. Crédito: Brendan Barrett 

 

 

 

Este estudio es el primero en informar el uso de herramientas de piedra por monos capuchinos (Cebus capucinus), y es el único informe para una especie del género Cebus. Crédito: Brendan Barrett

Mono capuchino macho usa una piedra para romper las semillas de un almendro indio, Terminalia catappa. Esta especie de árbol es común en las playas de todo el mundo. Crédito: Brendan Barrett

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Capuchins used large stones held in both hands to process tough Terminalia catappa nuts, and smaller stones held in one hand to process smaller items such as hermit crabs and snails. They also transported seeds and stones to processing areas.

Researchers concluded that tool-users spend a large amount of time on the ground, which is possible on this protected island where the monkeys have few predators and resources are likely to be as or more scarce than they are on the mainland. Cebus monkeys on the mainland do not use stone tools, although they commonly pound and rub fruit and small-animal prey such as squirrels and lizards on branches to process them as food.

Species in the genus Sapajus, known as robust capuchin monkeys, native to South America, have long been known to use tools. In fact, tool use is one of the characteristics that distinguishes this group from the smaller monkeys in the genus Cebus, known as gracile capuchins, found in Central and South America.

Chimpanzees (Pan) and macaques (Macaca) also use stone tools. Tool use in macaques is also limited to islands. The use of stone tools by robust capuchins, gracile capuchins in the Americas and macaques in Thailand to process T. catappa nuts will be an interesting opportunity to compare the origins of this behavior. Tool use in other primates likely preceded tool use by the first human relatives roughly 3 million years ago.
“In addition to the excitement of adding a fourth (known) genus of stone-tool using primate to our list, it is exciting to be doing ecological research in Panama’s Coiba National Park, a unique place where there is a lot of potential for discovery for conservation research to be done,” Barrett said. “STRI’s new Coibita field station helps make it possible to do field research on Jicarón and Coiba Islands, remote places where research is logistically challenging.”

“The capuchins of Coiba National Park provide us with an amazing opportunity for studying how and why stone tool use emerges, as well as what record it leaves behind,” said Meg Crofoot, research associate at STRI and professor of anthropology at the University of California, Davis. “White-faced capuchins are a very well-studied species, so stumbling upon a tool-using population—the only one known for the entire genus—was really unexpected and serves as an important reminder of the behavioral diversity waiting to be discovered. It highlights the importance of remote and little known areas like Coiba National Park, and serves as a vivid call to action to conserve behavioral, cultural and genetic diversity.”

Members of the research team are affiliated with STRI, the Max Planck Institute for Ornithology in Radolfzell, Germany, the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, the Animal Behavior Graduate Group at UC Davis, the Department of Anthropology at the University of Pennsylvania and Estación Científica Coiba, AIP, Panama. Research was funded by a Coss Award for International Field Research, a STRI short-term fellowship and a L.S.B. Leakey Foundation grant, funds from the Max Planck Institute, a Packard Foundation Fellowship and a grant from the U.S. National Science Foundation.

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Barrett, B.J., Monteza-Moreno, C.M., Dogandižić, T., Zwyns, N., Ibañez, A. and Crofoot, M.C. 2018. Habitual stone-tool aided extractive foraging in white-faced capuchins, Cebus capucinus. bioRxiv. http://dx.doi.org/10.1101/351619

First North American Monkey Fossils Found in Panama Canal Excavation

In Animals, Research News, Science & Nature, Spotlight / 22 April 2016 / 0 comments

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By Beth King

“Cebus capucinus,” the species of Cebus common in Panama today. (Photo by Andres Hernandez, Smithsonian Tropical Research Institute)

Seven fossil teeth exposed by the Panama Canal expansion project are the first evidence of a monkey on the North American continent before the Isthmus of Panama connected it to South America 3.5 million years ago. A team including Carlos Jaramillo, staff scientist at the Smithsonian Tropical Research Institute (STRI), published this discovery online in the journal Nature. They named the new monkey species Panamacebus transitus in honor of Panama and the monkey’s movement across the ancient seaway that divided North and South America.

The 21 million-year-old teeth were found in the Las Cascadas Formation during a five-year intensive fossil salvage project by field crews from STRI, the University of Florida and the New Mexico Museum of Natural History and Science. Most of the mammal groups represented in the Las Cascadas formation have North American origins, despite the fact that South America is much closer, supporting the idea that Central America and western Panama represented a long peninsula extending south from North America.

“Cebus capucinus,” the species of Cebus common in Panama today. (Photo by Sean Mattson, Smithsonian Tropical Research Institute)

During the salvage project, researchers rushed in behind engineers as they dynamited the steep canal banks. The researchers collected exposed fossils and described each location before heavy rains and fast-growing vegetation obscured evidence of the dramatic tectonic events that lifted the land bridge out of the sea to connect North and South America.

“I asked my boss for a million dollars to dig a hole in the ground,” Jaramillo said. “Then the Panamanian people voted for the Panama Canal Authority to spend $5.6 billion dollars to expand the Canal and unlocked a treasure trove for us, containing this new monkey species and many other fossils.”

“We suggest that Panamacebus was related to the capuchin (also known as “organ-grinder” monkeys) and squirrel monkeys that are found in Central and South America today,” said Jonathan Bloch, curator of vertebrate paleontology at the Florida Museum of Natural History on the University of Florida campus and lead author on the study. “Prior to this discovery, New World monkeys were thought to have evolved in isolation on South America, cut off from North America by a wide seaway.”

Before the monkey teeth were discovered, the oldest evidence of movement of a mammal from South to North America are 8.5–9 million-year-old fossil remains of giant sloths. The authors of this report suggest two explanations: 1) that mammals from South America were more adapted to life in the South American-derived forests still found in Panama and Costa Rica than to other forest types characteristic of Northern Central America or 2) that the lack of exposed fossil deposits throughout Central America means that evidence of these dispersals has yet to be revealed.

The U.S. National Science Foundation contributed $3.8 million as part of the Panama Partnership for International Research and Education led by researchers from the Florida Museum of Natural History. As the expansion nears its completion, the tally of fossils identified so far includes bats, horses, squirrels, small camelids, crocodiles, turtles and ferocious bear dogs. The new, wider third lane of the Panama Canal will open for business June 26.