Human hands may be more primitive than chimp's


Credit: © Eric Isselée / Fotolia
  

Human hands exhibit a long thumb in relation to the fingers.

This is one of the most distinctive traits of humankind compared

to apes and is often cited as one of the reasons for the success of

the species; however there are competing theories on how the
human hand evolved over time.





Human hands may be more primitive than chimp's
Human hands may be more primitive than chimp's. Human hand proportions have changed little from those of the last common ancestor (LCA) of chimpanzees and humans. These findings indicate that the structure of the modern human hand is largely primitive in nature, rather than the result of selective pressures in the context of stone tool-making.

Human hand proportions have changed little from those of the last common ancestor (LCA) of chimpanzees and humans. These findings indicate that the structure of the modern human hand is largely primitive in nature, rather than the result of selective pressures in the context of stone tool-making.
Intrinsic hand proportions of humans and other anthropoid primates.
(a) Drawings of a chimpanzee and human hands are shown to similar scale. (b) Relative length of the thumb=pollical/fourth ray lengths (minus distal fourth phalanx; see inset).  The ranges of humans and modern apes are highlighted (green and red-shaded areas, respectively).

Samples for each boxplot are Homo sapiens (n=40), Pan troglodytes (n=34), Pan paniscus (n=12), Gorilla beringei (n=21), Gorilla gorilla (n=13), Pongo abelii (n=8), Pongo pygmaeus (n=19), Hylobatidae (n=14), Theropithecus (n=5), Papio (n=50), Mandrillus (n=3), Macaca (n=18), Nasalis (n=14), Cebus (n=11) and Alouatta (n=8). The values for Pr. heseloni and Ar. ramidus are projected onto the remaining taxa to facilitate visual comparisons.  See full report for details.
Evolution of the
Human Race from
Apes and of Apes
from Lower Animals
 by Thomas Wharton Jones
Click to order from
Powell's Books

Human hands exhibit a long thumb in relation to the fingers. This is one of the most distinctive traits of humankind compared to apes and is often cited as one of the reasons for the success of the species; however there are competing theories on how the human hand evolved over time.

The researchers measured the hand proportions of humans, living and fossil apes as well as fossils of human ancestors including Ardipithecus ramidus and Australopithecus sediba, to understand the step wise evolution of the hand. Their results show the more recent, convergent evolution of finger elongation in chimpanzees and orangutans and comparatively little change between humans, human ancestors and gorillas.

These results support the hypothesis that the long thumb to fingers ratio of the human hand was acquired convergently with other highly dexterous anthropoids. The findings of the study also challenge the assumption that a chimp-like hand was the starting point of the chimpanzee-human LCA.



Related stories:
Story Source:  Materials provided by Stony Brook University.  Sergio Almécija, Jeroen B. Smaers & William L. Jungers. The evolution of human and ape hand proportions. Nature, 2015

Comments

Post a Comment

Popular posts from this blog

Workout supplements: An emerging eating disorder in men?

Image
therewontbeanydoves.wordpress.com When developing a fictional character, you may not think about the character using large amounts of over-the-counter dietary supplements.  Especially a man who uses large amounts of workout supplements. While there has been widespread publicity on the dangers of the non-prescribed use of anabolic steroids, not much is said about legal, over-the-counter supplements.  Are there risks?  And if so, what are they?  There are several things the writer should consider. Supplement use is becoming an eating disorder with many men who use them to prepare for and recover from a workout. There is growing evidence of a link between muscle-building supplements and testicular cancer. There is evidence that over-the counter medications and supplements are the most common causes of drug-induced liver failure (a rare event, but still a risk.)  There is even evidence that, “certain popular herbal and dietary supplements can also cause liver damage,"
Read more

Using Artificial Intelligence to Predict Violence. . . or to Control It?

Image
Dell EMC InFocus A staple of science fiction is a future where artificial intelligence (AI) is used to control people's behavior, or, in which AI supplants the human element. I have mixed feelings about AI, its uses, and our future.  For one thing, it's questionable that the human brain can increase in size or complexity without causing the system to slow down.  The brain of a "genius" isn't larger than yours or mine, its simply organized differently.  The difference between early versions of humans and modern humans is in large part, size.  Yes, brain organization plays a role, but until the latest iteration of us, brain size was the critical factor. If we as a species have survived based on brain size, and brain size has maxed out, how do we continue to evolve intellectually?  Better organization?  Yes, but can we ever hope to create and control this type of evolutionary activity? One solution to maxed human brain size is creating an interface
Read more

Remember faces but not names? You got it wrong.

Image
Source:   Daily Excelsior So, you think you're good at remembering faces, but terrible with names? New research has revealed we are actually better at remembering names than faces The cringe-worthy experience of not being able to remember an acquaintance's name leads many of us to believe we are terrible with names. However, new research has revealed this intuition is misleading; we are actually better at remembering names than faces. With the Christmas party season fast approaching, there will be plenty of opportunity to re-live the familiar, and excruciatingly-awkward, social situation of not being able to remember an acquaintance's name. This cringe-worthy experience leads many of us to believe we are terrible at remembering names. However, new research has revealed this intuition is misleading; we are actually better at remembering names than faces. The authors of the study, from the University of York, suggest that when we castigate ourselves f
Read more

The Downside of Being 'Class Clown'

Image
Source:  Bart's Blackboard Down side of being dubbed 'class clown' Class clowns' off-task antics amuse and delight their classmates during first and second grades, making them the most sought-after playmates on the playground in early elementary school.  But by the time these mischievous boys are promoted to third grade, they plummet to the bottom of the social circle as classmates' disapproval of their behavior grows, a new study found. Perhaps most worrisome is that by third grade, playful boys may be internalizing others' negative assessments and begin viewing themselves as social failures, possibly setting them on a course for a host of poor academic and developmental outcomes, said researcher Lynn A. Barnett, an educational psychologist and professor of recreation, sport and tourism at the University of Illinois. These sudden reversals in playful boys' social fortunes from first to third grade may be classmates' mirroring of teachers
Read more

M.I.T. Research Explains How Will Rogers Observation Works

Image
Finally it appears that MIT has gotten involved in proving Will's syllogism, "There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves." Read his statement carefully.   ONE learns by reading.   A FEW who learn by observation. Then there's the rest of us. The reason for this, it turns out, is a special circuit in the brain that you or I need to have a functioning version of to actually learn by observing others.  Based on how we all behave, it is a circuit most of us must be missing.   Or perhaps it shorted out the first time we peed on an electric fence and it has yet to grow back.   *  *  *  *  * Brain circuit helps us learn by watching others Scientists pinpoint neural interactions that are necessary for observational learning Researchers have identified a brain circuit required to learn by watching others. This circuit,
Read more