David Haring/Duke Lemur Center
Researchers have dug up remarkably ancient and well preserved bones in an Indian coal mine. The multi-million-year-old bones, those scientists say, come from rat-sized primates. They appear to have been close relatives of our distant ancestors. And finding them in India comes as something of a surprise.
Primates are mammals that include humans, apes, monkeys and related animals. Early primates were thought to have evolved largely on the continent of Africa. The new find suggests India also may have been a hotbed of early primate evolution.
The researchers share this conclusion in the October Journal of Human Evolution.
Doug Boyer is an evolutionary anthropologist — someone who studies the evolution of humankind. He works at Duke University in Durham, N.C. and wasn’t involved in the new study. In 2010, he and his colleagues reported on a roughly 65-million-year-old fossil found in southern India. They proposed it might be a close relative to the animal that gave rise to current-day primates, tree shrews and flying lemurs. (Flying lemurs glide rather than fly and are not true lemurs.) “It’s possible that India played an important role in primate evolution,” he now concludes.
Discovery in an Indian coal mine
The latest find comes out of a mine in Gujarat, India’s most western state. Evolutionary biologist Rachel Dunn works at Des Moines University in Iowa. She and her colleagues found a set of 25 arm, leg, ankle and foot fossils. All were roughly 54.5 million years old. The tiny tree-dwellers they came from resembled the first primates — animals that lived up to 65 million years ago.
Earlier, researchers digging in the same area — called the Vastan mine — turned up jaws, teeth and limb bones from four ancient primate species. Dunn and her colleagues’ new discovery adds to what scientists have been able to learn from this site.
“The Vastan primates probably approximate a common primate ancestor better than any fossils found previously,” says Kenneth Rose. One of the study’s authors, he’s a paleontologist — a fossil expert. He works at Johns Hopkins University School of Medicine in Baltimore, Md.
The Vastan animals were about the size of living gray mouse lemurs and dwarf lemurs. They likely weighed up to 300 grams (roughly two-thirds of a pound), the scientists estimate. Dunn’s group has posted 3-D scans of the fossils online (at morphosource.org). Doing that allows other researchers to download and study the data.
Most Vastan individuals possessed only a basic climbing ability. That sets them apart from the more specialized body types of the two ancient groups of primates that gave rise to present-day primates, the researchers say. One of those ancient groups is called omomyids. They consisted of relatives of modern tarsiers, monkeys and apes. The other group is called adapoids. These animals included relatives of current-day lemurs, lorises and bushbabies.
The ancient Indian primates also were tree-dwellers, the new report concludes. But unlike lemurs, they couldn’t leap from branch to branch. And they didn’t have the slow-but-sure grips that lorises use to climb trees.
The researchers propose that the Vastan primates probably descended from an animal that also gave rise to omomyids and adapoids. (In other words, it was a common ancestor of all three primate groups.)
When the Vastan primates were alive, India was a drifting landmass. It was headed north (on a tectonic plate) toward a collision with mainland Asia. Rose suspects that being so isolated caused the Indian animals to evolve more slowly than the other primates. Once India joined Asia, its primates then spread around the world.
That’s a controversial idea. An increasing number of scientists suspect primates originated in Asia. Chinese primate fossils date to at least 55 million years ago or or so. That would make them slightly older than the Vastan primates. (The Chinese fossils show signs of having been omomyids.)
In at least one sense, Boyer says, some of the new Vastan fossils may be more specialized than their discoverers claim. Vastan ankle bones, for instance, look similar to those of modern lemurs. That similarity, he says, raises doubts that the Indian primates were direct descendants of primate precursors.
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ape A group of rather large “Old World” primates that lack a tail. They include the gorilla, chimpanzees, bonobos, orangutans and gibbons.
bushbabies Also known as galagos, these are small, large-eyed, nocturnal, tree-dwelling primates. They get their name for their baby-like cries. Known as vertical clingers and leapers, they can spring off the trunk of one tree and turn around in mid-air to face the next tree it will latch onto.
colleague Someone who works with another; a co-worker or team member.
continent (in geology) The huge land masses that sit upon tectonic plates. In modern times, there are six geologic continents: North America, South America, Eurasia, Africa, Australia and Antarctica.
data Facts and/or statistics collected together for analysis but not necessarily organized in a way that give them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.
descendant A blood relative of a person who lived during a previous time.
evolution (v. to evolve) A process by which species undergo changes over time, usually through genetic variation and natural selection. These changes usually result in a new type of organism better suited for its environment than the earlier type. The newer type is not necessarily more “advanced,” just better adapted to the conditions in which it developed.
evolutionary An adjective that refers to changes that occur within a species over time as it adapts to its environment. Such evolutionary changes usually reflect genetic variation and natural selection, which leave a new type of organism better suited for its environment than its ancestors. The newer type is not necessarily more “advanced,” just better adapted to the conditions in which it developed.
evolutionary biologist Someone who studies the adaptive processes that have led to the diversity of life on Earth. These scientists can study many different subjects, including the microbiology and genetics of living organisms, how species change to adapt, and the fossil record (to assess how various ancient species are related to each other and to modern-day relatives).
evolve (adj. evolving) To change gradually over generations, or a long period of time. In living organisms, the evolution usually involves random changes to genes that will then be passed along to an individual’s offspring. These can lead to new traits, such as altered coloration, new susceptibility to disease or protection from it, or different shaped features (such as legs, antennae, toes or internal organs). Nonliving things may also be described as evolving if they change over time. For instance, the miniaturization of computers is sometimes described as these devices evolving to smaller, more complex devices.
fossil Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.
journal (in science) A publication in which scientists share their research findings with the public. Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject. The best journals are peer-reviewed: They send out all submitted articles to outside experts to be read and critiqued. The goal, here, is to prevent the publication of mistakes, fraud or sloppy work.
landmass A continent, large island or other continuous body of land.
lemur Any of many primate species that tends to have a cat-shaped body and usually a long tail. They evolved in Africa long ago, then migrated to what is now Madagascar, before this island became separated from the east coast of Africa. Today, all wild lemurs (some 33 species of them) live only on the island of Madagascar.
limb (in physiology) An arm or leg. (in botany) A large structural part of a tree that branches out from the trunk.
loris Any of several species of small, nocturnal, tree-dwelling furry primates with round heads and small ears. All have strong fingers and toes. Most can move swiftly when spooked, but tend, in fact, to mke slow, very deliberate movements.
mammal A warm-blooded animal distinguished by the possession of hair or fur, the secretion of milk by females for feeding the young, and (typically) the bearing of live young.
online A term that refers to things that can be found or done on the Internet.
paleontologist A scientist who specializes in studying fossils, the remains of ancient organisms.
precursor A substance from which some later thing is made. It may be a compound that will change into something else as a result of some chemical or biological reaction.
primate The order of mammals that includes humans, apes, monkeys and related animals (such as tarsiers, the Daubentonia and other lemurs).
species A group of similar organisms capable of producing offspring that can survive and reproduce.
tarsier A bushy furred, small greyish chipmunk- to squirrel-sized primate that lives in the treetops and becomes active at night. From their heads to the end of their bodies, these small animals tend to run about 13 centimeters (5 inches). Their tails can run twice that length.
tectonic Surface activity on a large rocky body (such as a planet or moon) as liquid rock flows up to the surface where it solidifies, then slowly drifts atop molten rock, carrying surface features with it.
Journal: R.H. Dunn et al. New euprimate postcrania from the early Eocene of Gujarat, India, and the strepsirrhine-haplorhine divergence. Journal of Human Evolution. Vol. 99, October 2016, p. 25. doi: 10.1016/j.jhevol.2016.06.006.