Primate Fossil 'Mother Lode' Shows Our Ancestors' Rough Past
Newly found primates help to tell the story of primate evolution, shedding light on why our earliest ancestors migrated from Asia to Africa.
A "mother lode" of newly found fossil primates in southern China strengthens evidence that primates first emerged in Asia, with climate change later shifting the evolution of monkeys, apes and even our own species to Africa.
The findings, published in the journal Science, help explain the Asia-Africa story of primate evolution and also demonstrate how sensitive humans and other primates are to climate change.
"Primates like it warm and wet, so they faced hard times around the world - to the extent that they went extinct in North America and Europe," co-author K. Christopher Beard, senior curator at the University of Kansas' Biodiversity Institute, said in a press release.
"Of course," he added, "primates somehow survived in Africa and Southern Asia, because we're still around to talk about it."
Beard and his colleagues discovered six new species of fossil primates dating to 34 million years ago from southern China. All that's left of the primates now are jaw and tooth fragments, which survived so long due to their tough enamel surfaces.
"The fossil record usually gives you a snapshot here or there of what ancient life was like. You typically don't get a movie," Beard said.
He continued: "We have so many primates from the Oligocene (approximately 34–23 million years ago) at this particular site because it was located far enough to the south that it remained warm enough during that cold, dry time that primates could still survive there. They crowded into the limited space that remained available to them."
Some primates had previously migrated to North America, Europe and other parts of Asia. As Beard mentioned, those early populations eventually died out. This was due to a drastic cooling that took place around 34 million years ago. The dramatic change in climate made much of Asia inhospitable to primates, slashed their populations and rendered discoveries of such fossils especially rare, making the new fossil finds all the more important.
Like most of today's primates, the ancient Chinese ones were tropical tree-dwellers, according to the researchers. One of the species, named Oligotarsius rarus, was "incredibly similar" to the modern tarsier found today only in the Philippine and Indonesian islands, they wrote.
"If you look back at the fossil record, we know that tarsiers once lived on mainland Asia, as far north as central China," Beard said. "The fossil teeth described in this paper are nearly identical to those of modern tarsiers. Research shows that modern tarsiers are pretty much living fossils - those things have been doing what they do ever since time immemorial, as far as we can tell."
If the global intense cooling had not occurred 34 million years ago, the main stage of primate evolution may have continued to be in Asia, rather than transitioning to Africa, where it is believed our species eventually emerged.
While humans today have tools to combat cold weather, our species, and certainly all other primates, remains vulnerable to climate change.
"This is the flip side of what people are worried about now," Beard said, explaining that instead of going from a cooler time to a warmer time, "the whole world was already warm, then it cooled off. It's kind of a mirror image."
"The point is that primates then, just like primates today, are more sensitive to a changing climate than other mammals."
The list of the 25 most endangered primates for 2014-2016 has just been released by the International Union for Conservation of Nature (
). The list is updated every two years, and the news is not good. "The world’s primate species are at great risk with more than half of the species threatened with extinction on the IUCN Red List," said Simon Stuart, chair of the IUCN species survival commission, in a statement. Here we look at a sampling of the animals that had the unwelcome distinction of landing on the list. Shown here is the Roloway monkey (
Cercopithecus diana roloway
), from Ghana and central and eastern Côte d’Ivoire. Hunting by bushmeat traders has reduced the forest-dwelling primate's numbers to "small, isolated pockets," according to IUCN. "By any measure, the roloway monkey must be considered one of the most critically endangered monkeys in Africa and appears to be on the verge of extinction," IUCN notes in its report on the 2014-2016 list.
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The Lac Alaotra bamboo lemur (
) lives exclusively in papyrus and reed beds around Madagascar's biggest lake (Lac Alaotra). The most recent population data pegs the remaining animals at 2,500 to 5,000 -- a decrease of about 30 percent in the last 10 years. The lemur's habitat has seen a rapid influx of humans moving into the area to fish and cultivate rice. The conversion of its marshy land into rice habitat in recent decades has shrunk the animal's habitat and put its existence at risk.
The Sumatran orangutan (
) is a sad re-entry on the IUCN top 25 endangered primates list. IUCN notes that the last published surveys counted only about 6,600 of the orangutans left in their native Sumatra, Indonesia, in just nine fragmented areas. It also notes that more recent counts, yet unpublished, indicate the population may exceed 6,600. "But the overall trend in orangutan numbers and habitat area remains decidedly downwards," says the IUCN.
The little Philippine tarsier (
) is a new entry on the list. It faces habitat loss from deforestation and even increased frequency and intensity of typhoons.
The brown spider monkey (
) lives in Colombia and Venezuela and is designated critically endangered thanks to habitat loss and fragmentation, hunting, and the pet trade.
The Preuss’s red colobus (
) inhabits the moist, high-canopy forests of western Cameroon and southeastern Nigeria. Since the start of the 20th century, IUCN says this monkey has disappeared from most of its original range and that the biggest factors in its decline are due to bushmeat hunters and deforestation via logging, agriculture and infrastructure development.
Brazil's northern brown howler monkey (
Alouatta guariba guariba
) faces primary threats from widespread forest loss and fragmentation throughout its range due to logging and agriculture. It may also be impacted by disease outbreaks such as yellow fever, IUCN says.
New to the list is the Perrier’s sifaka (
), which is critically endangered and lives in northeast Madagascar. Population estimates vary between about 1,000 and 2,000 individuals remaining. It's not entirely clear yet how the animal's numbers dwindled to current counts but IUCN says it's likely due to climatic- and human-driven forest size fluctuations.
The majestic Grauer’s Gorilla (
Gorilla beringei graueri
), formerly known as the Eastern lowland gorilla, will be upgraded to Critically Endangered when the 2016
is released by IUCN. The gorillas have in recent decades faced threats ranging from hunting, to habitat destruction, to civil conflict in their native Democratic Republic of Congo.
The Lavasoa Mountains dwarf lemur (
) was only discovered in 2001 in the Lavasoa- Ambatotsirongorongo Mountains in southern Madagascar. Habitat loss and destruction from wood extraction, slash-and-burn cultivation, and accidental fires are among the pressures faced by the bandit-eyed animal.