Earliest baboon found at Malapa

A team from Wits University's Evolutionary Studies Institute has discovered a fossil monkey specimen representing the earliest baboon ever found.

Male P. angusticeps in lateral (top left), oblique (top right), dorsal (middle) 
and inferior (bottom) views [Credit: Wits University]

Dating back more than 2 million years ago (between 2.026-2.36 million years ago), the partial skull was found at Malapa, in the Cradle of Humankind World Heritage Site, the same site where the partial skeletons of the new early hominin species, Australopithecus sediba, were discovered in 2010.

"Baboons are known to have co-existed with hominins at several fossil localities in East Africa and South Africa and they are sometimes even used as comparative models in human evolution," says Dr Christopher Gilbert (Hunter College, CUNY), lead author of the study published in the journal PLOS ONE.

The skull, found during excavations for A. sediba, confirms earlier suggestions that the fossil baboon species to which it belongs, Papio angusticeps, was in fact closely related to modern baboons, and quite possibly the earliest known members of the modern baboon species Papio hamadryas.

CT scans show UW 88-866 in oblique (left) and lateral (right) views 
[Credit: Wits University]

Modern baboons (genus Papio) are typically divided into a number of populations recognised as either species or subspecies spread all throughout sub-Saharan Africa and into the Arabian Peninsula. Despite their evolutionary success, modern baboon origins in the fossil record have not well-understood or agreed upon.

"According to molecular clock studies, baboons are estimated to have diverged from their closest relatives by ~1.8 to 2.2 million years ago; however, until now, most fossil specimens known within this time range have been either too fragmentary to be definitive or too primitive to be confirmed as members of the living species Papio hamadryas," says Gilbert.

"The specimen from Malapa and our current analyses help to confirm the suggestion of previous researchers that P. angusticeps may, in fact, be an early population of P. hamadryas."

A comparison of morphology in UW 88-886 (left), P. angusticepts males (CO 100, center),
 and P. izodi males (TP 89-11-1, right) [Credit: Wits University]

Analyses of the specimen at Malapa, and the group of fossil specimens traditionally placed in the fossil species P. angusticeps, suggest that P. angusticeps displays anatomy that is consistent with modern baboon populations.

"If you placed a number of P. angusticeps specimens into a modern osteology collection, I don't think you'd be able pick them out as any different from those of modern baboons from East and South Africa," says Gilbert.

Furthermore, the estimated age of the specimen from Malapa, ~2.026-2.36 Ma, is in almost perfect agreement with molecular clock analyses for the initial appearance of modern baboons. Thus, the specimen at Malapa may help to solve the evolutionary origins of these highly successful animals and confirm the estimates of molecular studies.

In addition, because monkeys are widely recognised as key time-sensitive elements in the fossil record, the fact that the Malapa P. angusticeps specimen is well-dated allows future studies to better estimate the age of fossil sites where the species is found. South African early hominin sites, in particular, may be able to achieve more accurate age estimates on the basis of these new findings.

Source: University of the Witwatersrand [August 19, 2015]

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Fossil study reveals dogs evolved with climate change

Old dogs can teach humans new things about evolution. In Nature Communications a new study of North American dog fossils as old as 40 million years suggests that the evolutionary path of whole groups of predators can be a direct consequence of climate change.

Two early dogs, Hesperocyon, left and the later Sunkahetanka, were both 
ambush-style predators. As climate changes transformed their habitat, 
dogs evolved pursuit hunting styles and forelimb anatomy to match 
[Credit: Mauricio Anton]

"It's reinforcing the idea that predators may be as directly sensitive to climate and habitat as herbivores," said Christine Janis, professor of ecology and evolutionary biology at Brown University, who worked with lead author Borja Figueirido, a former Brown Fulbright postdoctoral researcher who is now a professor at the Universidad de Malaga in Spain. "Although this seems logical, it hadn't been demonstrated before."

The climate in North America's heartland back around 40 million years ago was warm and wooded. Dogs are native to North America. The species of the time, fossils show, were small animals that would have looked more like mongooses than any dogs alive today and were well-adapted to that habitat. Their forelimbs were not specialized for running, retaining the flexibility to grapple with whatever meal unwittingly walked by.

But beginning just a few million years later, the global climate began cooling considerably and in North America the Rocky Mountains had reached a threshold of growth that made the continental interior much drier. The forests slowly gave way to open grasslands.

Pups of the plains

Did this transition affect the evolution of carnivores? To find out, Figueirido and the research team, including Jack Tseng of the American Museum of Natural History in New York, examined the elbows and teeth of 32 species of dogs spanning the period from ca. 40 million years ago to 2 million years ago. They saw clear patterns in those bones at the museum: At the same time that climate change was opening up the vegetation, dogs were evolving from ambushers to pursuit-pounce predators like modern coyotes or foxes -- and ultimately to those dogged, follow-a-caribou-for-a-whole-day pursuers like wolves in the high latitudes.

"The elbow is a really good proxy for what carnivores are doing with their forelimbs, which tells their entire locomotion repertoire," Janis said.

This is a skeleton of a 30-million-year-old fossil dog, Archaeocyon, in the 
American Museum of Natural History canid collection. The earliest dogs, 
going back 40 million years in North America, were animals no larger 
than a Chihuahua or a common house cat today 
[Credit: © AMNH/D. Finnin]

The telltale change in those elbows has to do with the structure of the base where the humerus articulates with the forearm, changing from one where the front paws could swivel (palms can be inward or down) for grabbing and wrestling prey to one with an always downward-facing structure specialized for endurance running. Modern cats still rely on ambush rather than the chase (cheetahs are the exception) and have the forelimbs to match, Janis said, but canines signed up for lengthier pursuits.

In addition, the dogs' teeth trended toward greater durability, Figueirido's team found, consistent perhaps with the need to chow down on prey that had been rolled around in the grit of the savannah, rather than a damp, leafy forest floor.

Not an 'arms race' of limbs

The study, with some of Janis' prior research, suggests that predators do not merely evolve as an "arms race" response to their prey. They don't develop forelimbs for speedy running just because the deer and the antelope run faster. While the herbivores of this time were evolving longer legs, the predator evolution evident in this study tracked in time directly with the climate-related changes to habitat rather than to the anatomy of their prey species.

After all, it wasn't advantageous to operate as a pursuit-and-pounce predator until there was room to run.

"There's no point in doing a dash and a pounce in a forest," Janis quipped. "They'll smack into a tree."

If predators evolved with climate change over the last 40 million years, the authors argue, then they likely will have to continue in response to the human-created climate change underway now. The new results could help predict the effects we are setting in motion.

"Now we're looking into the future at anthropogenic changes," Janis said.

Source: Brown University [August 18, 2015]

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Remains of ancient primate found in Oregon

Scientists have unearthed fossil teeth and a jaw fragment in Oregon. And these have helped flesh out the features of an ancient animal that once lived in North America. A new species of primate, it had features similar to a modern lemur’s.

Artist’s conception of what North America’s last nonhuman primates might have
 looked like. The animals are shown on a hackberry tree. It’s the most common 
plant known from the sediment layer in which the fossils were found 
[Credit: Christopher Herndon]

Primates are a group of mammals that includes monkeys, lemurs, gorillas and humans. The Sioux are a tribe of Native Americans. The newfound primate’s genus name comes from a Sioux term for monkey: Ekgmowechashala. These last nonhuman primates to live in North America vanished around 26 million years ago. No other primates lived in North America until humans arrived well over 25 million years later. This timeline comes from the new study. It was published June 29 in the American Journal of Physical Anthropology.

Joshua Samuels works for the National Park Service in Kimberly, Ore. As a paleontologist, he studies ancient fossils. He and his colleagues dug up the ancient primate bones between 2011 and early 2015. They found two complete teeth, two partial teeth and a jaw fragment.

All came from rocky sediment at Oregon’s John Day Formation. This rock layer, or stratum, contains fossils from between 30 million and 18 million years ago. A tooth and jaw fragment from the same species had been found there previously. All the fossils belong to a new species of Ekgmowechashala, the researchers say. Partial jaws and teeth of a related species had turned up at sites in South Dakota and Nebraska.

The scientists figured out the age of the fossils based on their position between layers of volcanic ash. The ages of those layers was already known. That let the scientists determine that the new fossils must be between 28.7 million and 27.9 million years old.

Where did the primates come from?

Millions of years ago, land connected what is now Alaska and Russia. The ancient primates probably crossed that “land bridge” around 29 million years ago, the researchers now say. That journey would have taken place some 6 million years after other North American primates had died out.

Samuels says the new fossils appear to resemble those from a 34-million-year-old primate from Thailand, in Southeast Asia. The new fossils also are similar to a 32-million-year-old primate from Pakistan, which lies between the Middle East and India.

Erik Seiffert is a paleontologist at Stony Brook University in New York. He suggested an Asian–North American primate connection back in 2007. But Samuels and his team “have laid out the evidence in more detail,” Seiffert now says.

Some researchers suspect Ekgmowechashala’s closest present-day relatives would have been tarsiers. These small primates live on islands in Southeast Asia. Other scientists think the now extinct North American primates were more closely related to lemurs. They exist only in Madagascar. It’s an island off of the East Coast of southern Africa.

K. Christopher Beard agrees with Samuels’ team that Ekgmowechashala is likely more related to the lemurs. A paleontologist, Beard works at the University of Kansas in Lawrence. But he argues that to confirm this, scientists need to find ankle bones. They should point out whether the ancient primate species had a greater kinship to lemurs or to tarsiers.

Author: Bruce Bower | Source: Student Science [August 13, 2015]

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Humans responsible for demise of gigantic ancient mammals

Early humans were the dominant cause of the extinction of a variety of species of giant beasts, new research has revealed.

A glyptodon, a giant relation of the armadillo 
[Credit: WikiCommons]

Scientists at the universities of Exeter and Cambridge claim their research settles a prolonged debate over whether mankind or climate change was the dominant cause of the demise of massive creatures in the time of the sabretooth tiger, the woolly mammoth, the woolly rhino and the giant armadillo.

Known collectively as megafauna, most of the largest mammals ever to roam the earth were wiped out over the last 80,000 years, and were all extinct by 10,000 years ago.

Lewis Bartlett, of the University of Exeter, led the research, which also involved the universities of Reading and Bristol and is published in the journal Ecography. He said cutting-edge statistical analysis had helped solve the mystery almost beyond dispute, concluding that man was the dominant force in wiping out the creatures, although climate change could also have played a lesser role.

The researchers ran thousands of scenarios which mapped the windows of time in which each species is known to have become extinct, and humans are known to have arrived on different continents or islands. This was compared against climate reconstructions for the last 90,000 years.

Examining different regions of the world across these scenarios, they found coincidences of human spread and species extinction which illustrate that man was the main agent causing the demise, with climate change exacerbating the number of extinctions. However, in certain regions of the world – mainly in Asia – they found patterns which patterns were broadly unaccounted for by either of these two drivers, and called for renewed focus on these neglected areas for further study.

Lewis Bartlett, a researcher from the University of Exeter’s Centre for Ecology and Conservation, said: “As far as we are concerned, this research is the nail in the coffin of this 50-year debate - humans were the dominant cause of the extinction of megafauna. What we don’t know is what it was about these early settlers that caused this demise. Were they killing them for food, was it early use of fire or were they driven out of their habitats? Our analysis doesn’t differentiate, but we can say that it was caused by human activity more than by climate change. It debunks the myth of early humans living in harmony with nature.”

Dr Andrea Manica, of Cambridge University, was lead supervisor on the paper. He said: “Whilst our models explain very well the timing and extent of extinctions for most of the world, mainland Asia remains a mystery. According to the fossil record, that region suffered very low rates of extinctions. Understanding why megafauna in mainland Asia is so resilient is the next big question."

Source: University of Exeter [August 13, 2015]

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