New study suggests that last common ancestor of humans and apes was smaller than thought

October 12, 2017, American Museum of Natural History

New research suggests that the last common ancestor of apes—including great apes and humans—was much smaller than previously thought, about the size of a gibbon. The findings, published today in the journal Nature Communications, are fundamental to understanding the evolution of the human family tree.

"Body size directly affects how an animal relates to its environment, and no trait has a wider range of biological implications," said lead author Mark Grabowski, a visiting assistant professor at the Eberhard Karls University of Tübingen in Germany who conducted the work while he was a postdoctoral fellow in the American Museum of Natural History's Division of Anthropology. "However, little is known about the size of the last of humans and all living apes. This omission is startling because numerous paleobiological hypotheses depend on estimates at and prior to the root of our lineage."

Among living primates, humans are most closely related to apes, which include the lesser apes (gibbons) and the great apes (chimpanzees, gorillas, and orangutans). These "hominoids" emerged and diversified during the Miocene, between about 23 million to 5 million years ago. Because fossils are so scarce, researchers do not know what the last common ancestors of living apes and humans looked like or where they originated.

To get a better idea of body mass evolution within this part of the primate , Grabowski and coauthor William Jungers from Stony Brook University compared body size data from modern primates, including humans, to recently published estimates for fossil hominins and a wide sample of fossil primates including Miocene apes from Africa, Europe, and Asia. They found that the common of apes was likely small, probably weighing about 12 pounds, which goes against previous suggestions of a chimpanzee-sized, chimpanzee-like ancestor.

Among other things, the finding has implications for a behavior that's essential for large, tree-dwelling primates: it implies that "suspensory locomotion," overhand hanging and swinging, arose for other reasons than the animal simply getting too big to walk on top of branches. The researchers suggest that the ancestor was already somewhat suspensory, and larger body size evolved later, with both adaptations occurring at separate points. The development of suspensory locomotion could have been part of an "arms race" with a growing number of monkey species, the researchers said. Branch swinging allows an animal to get to a prized and otherwise inaccessible food—fruit on the edges of foliage—and larger body would let them engage in direct confrontation with monkeys when required.

The new research also reveals that australopiths, a group of early relatives, were actually on average smaller than their ancestors, and that this smaller size continued until the arrival of Homo erectus.

"There appears to be a decrease in overall size within our lineage, rather than size simply staying the same or getting bigger with time, which goes against how we generally think about evolution," Grabowski said.

Explore further: Human ancestor was less-chimp-like than thought: study

More information: Mark Grabowski et al, Evidence of a chimpanzee-sized ancestor of humans but a gibbon-sized ancestor of apes, Nature Communications (2017). DOI: 10.1038/s41467-017-00997-4

Related Stories

Out of Eurasia, a great primate evolutionary bottleneck?

October 15, 2013

On the road to our modern human lineage, scientists speculate there were many twist and turns, evolutionary dead ends, and population bottlenecks along the way. But how large were population sizes of common ancestors of the ...

Bigger brains led to bigger bodies in our ancestors

April 18, 2016

New research suggests that humans became the large-brained, large-bodied animals we are today because of natural selection to increase brain size. The work, published in the journal Current Anthropology, contradicts previous ...

Recommended for you

How plants bind their green pigment chlorophyll

October 19, 2018

Chlorophyll is the pigment used by all plants for photosynthesis. There are two versions, chlorophyll a and chlorophyll b. These are structurally very similar to one another but have different colors, blue-green and yellowish ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

thomasct
1 / 5 (1) Oct 12, 2017
Mainstream science will not go outside their time-line/dogma, (fear of losing funding/credibility or just plain ignorant) so they bash on with their outdated theories. .Millions have opened theyfly.com and learned of Billy Meier's 70+ years of et contact. The Pleaidian Mission by Randolph Winters has the condensed story. We've learned from et that humankind in this Dern Universe is approx. 100billion years old; in our Milky Way Galaxy alone there are billions of planets inhabited by intelligent humans; that Earth's inhabitants come from the far corners of this Universe.. not from chimp/gorilla 4M years ago.. that magically gained an extra vertebra to walk upright, sweated instead of panted, lost 50% strength etc.. to then to wander from Tanzania/Ethiopia to become Chinese, Indian, Scandinavian, Syrian, Slavic etc.
TrollBane
not rated yet Oct 16, 2017
thomasct Please take your meds. Ancient Aliens is fiction, not explanation.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.