Earliest 'modern' hand nearly two million years old

A tiny, 1.85 million-year-old bone from the little finger of a human ancestor unearthed in East Africa has revealed the oldest "modern" hand ever found, scientists reported Tuesday.

A picture released on August 18, 2015 by Nature Communications shows a OH 86 hominin 
manual proximal phalanx in (from L-R) dorsal, lateral, palmar (distal is top for each) 
and proximal views [Credit: AFP/Rodrigo Dominguez]

The discovery of the pinkie bone pushes back in time a key step in the evolution of our forebear from tree-climbing foragers to tool-wielding hunters, the authors say.

It also hints at the existence of a larger, more human-like creature than others known to have lived at that time in the same region—one of the hotspots of human origin—in modern-day Tanzania.

The hand is one of the critical anatomical features distinguishing humans, and even a 3.6-centimetre (1.5-inch), two-million-year-old fragment can reveal a lot about body type and behaviour.

The shape of our forebears' hands was both a reflection of their stage of evolution, and a driver of that evolution, explained lead author Manuel Dominguez-Rodrigo, a researcher at the Institute of Evolution in Africa in Madrid.

"Our hand evolved to allow us a variety of grips and enough gripping power to allow us the widest range of manipulation observed in any primate," he said by email.

"It is this manipulation capability that interacted with our brains to develop our intelligence, mainly through the invention and use of tools."

A picture released on August 18, 2015 by Nature Communications shows 
an OH 86 hominin phalanx overlaid on a modern human hand
[Credit: AFP/Jason Heaton]

What scientists call "modern human-like" hand anatomy has several defining characteristics.

One is a longer thumb, allowing us to grip more precisely and to open our hands more fully.

Another is the straightening of our phalanges, the general name given to the three bones found in each finger. Curved phalanges were adapted for climbing trees and swinging from branches.

"A modern-like hand in the past would tell us when humans became fully terrestrial and when and how efficiently our ancestors used tools," Dominguez-Rodrigo said.

That transition happened in two main stages.

After the earliest hominins—which includes all members of the Homo genus—began walking on two legs some six million years ago, the hand evolved a longer thumb.

But the fingers remained curved, suggesting that trees remained part of their habitat.

This "double locomotion"—on the ground, through the trees—remained the norm for another four million years.

A picture released on August 18, 2015 by Nature Communications shows people 
excavating the fossiliferous layer at PTK in the Olduvai Gorge, one of the most
 important paleoanthropological sites in the world 
[Credit: AFP/Rodrigo Dominguez]

"I always had trouble understanding how Homo habilis—barely taller than one metre (three feet)—could efficiently hunt animals that big," Dominguez-Rodrigo said.

The existence of a bigger, more modern-looking hominin would help explain this puzzle.

Other experts not involved in the study agreed.

"It brings support to those who challenge the view that Homo habilis was the maker of the stone artifacts becoming abundant in layers of this time period," commented Jean-Jacques Hublin, director of the department of human evolution at the Max Planck Institute for Evolutionary Anthropology.

At the same time, Hublin and others challenged the broad conclusions reached on the basis of such slim evidence.

"One single bone from a pinkie finger does not imply a whole modern human-like skeleton," Hublin said by email.

Another leader in the field, Tracy L. Kivell of the School of Anthropology and Conservation at the University of Kent, was even more sceptical.

"This single bone tells us nothing about what the rest of the hand looked like, let alone what the rest of the skeleton looked like," she told AFP by mail.

"If recent, more complete hominin fossil discoveries have taught us anything, it's that strange combinations of more derived human-like features and more primitive australopith-like features throughout the skeleton are likely the rule, rather than the exception, especially at this time period."

The study has been published by the journal Nature Communications.

Author: Marlowe Hood | Source: AFP [August 18, 2015]

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Apes may be closer to speaking than many scientists think

Koko the gorilla is best known for a lifelong study to teach her a silent form of communication, American Sign Language. But some of the simple sounds she has learned may change the perception that humans are the only primates with the capacity for speech.

Meet Koko, Gorilla Spokesperson [Credit: The Gorilla Foundation]

In 2010, Marcus Perlman started research work at The Gorilla Foundation, where Koko has spent more than 40 years living immersed with humans -- interacting for many hours each day with psychologist Penny Patterson and biologist Ron Cohn.

"I went there with the idea of studying Koko's gestures, but as I got into watching videos of her, I saw her performing all these amazing vocal behaviors," says Perlman, now a postdoctoral researcher in the lab of University of Wisconsin-Madison psychology Professor Gary Lupyan.

The vocal and breathing behaviors Koko had developed were not necessarily supposed to be possible.

"Decades ago, in the 1930s and '40s, a couple of husband-and-wife teams of psychologists tried to raise chimpanzees as much as possible like human children and teach them to speak. Their efforts were deemed a total failure," Perlman says. "Since then, there is an idea that apes are not able to voluntarily control their vocalizations or even their breathing."

Instead, the thinking went, the calls apes make pop out almost reflexively in response to their environment -- the appearance of a dangerous snake, for example.

And the particular vocal repertoire of each ape species was thought to be fixed. They didn't really have the ability to learn new vocal and breathing-related behaviors.

These limits fit a theory on the evolution of language, that the human ability to speak is entirely unique among the nonhuman primate species still around today.

"This idea says there's nothing that apes can do that is remotely similar to speech," Perlman says. "And, therefore, speech essentially evolved -- completely new -- along the human line since our last common ancestor with chimpanzees."

However, in a study published online in July in the journal Animal Cognition, Perlman and collaborator Nathaniel Clark of the University of California, Santa Cruz, sifted 71 hours of video of Koko interacting with Patterson and Cohn and others, and found repeated examples of Koko performing nine different, voluntary behaviors that required control over her vocalization and breathing. These were learned behaviors, not part of the typical gorilla repertoire.

Among other things, Perlman and Clark watched Koko blow a raspberry (or blow into her hand) when she wanted a treat, blow her nose into a tissue, play wind instruments, huff moisture onto a pair of glasses before wiping them with a cloth and mimic phone conversations by chattering wordlessly into a telephone cradled between her ear and the crook of an elbow.

"She doesn't produce a pretty, periodic sound when she performs these behaviors, like we do when we speak," Perlman says. "But she can control her larynx enough to produce a controlled grunting sound."

Koko can also cough on command -- not particularly groundbreaking human behavior, but impressive for a gorilla because it requires her to close off her larynx.

"The motivation for the behaviors varies," Perlman says. "She often looks like she plays her wind instruments for her own amusement, but she tends to do the cough at the request of Penny and Ron."

These behaviors are all learned, Perlman figures, and the result of living with humans since Koko was just six months old.

"Presumably, she is no more gifted than other gorillas," he says. "The difference is just her environmental circumstances. You obviously don't see things like this in wild populations."

This suggests that some of the evolutionary groundwork for the human ability to speak was in place at least by the time of our last common ancestor with gorillas, estimated to be around 10 million years ago.

"Koko bridges a gap," Perlman says. "She shows the potential under the right environmental conditions for apes to develop quite a bit of flexible control over their vocal tract. It's not as fine as human control, but it is certainly control."

Orangutans have also demonstrated some impressive vocal and breathing-related behavior, according to Perlman, indicating the whole great ape family may share the abilities Koko has learned to tap.

Author: Chris Barncard | Source: University of Wisconsin-Madison [August 14, 2015]

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