Anthropologist finds large differences in gait of early human ancestors

Nov 12, 2012 by Bob Yirka report
'Lucy'
A sculptor's rendering of the hominid Australopithecus afarensis is displayed as part of an exhibition that includes the 3.2 million year old fossilized remains of "Lucy", the most complete example of the species, at the Houston Museum of Natural Science, 28 August 2007 in Houston, Texas.

(Phys.org)—Patricia Ann Kramer, professor of anthropology at the University of Washington, has found that the walking gait between two of our early ancestors was likely so different that it's doubtful they would have done so together, despite being two members of the same species living during roughly the same time period. In her paper published in the American Journal of Physical Anthropology, Kramer outlines how she compared the natural walking speeds of modern humans to those of two members of the Australopithecus afarensis species and found that such large differences existed between two members of our early ancestors that walking together would have been troublesome.

In her study, Kramer compared the bones of Lucy, the famous skeletal remains found in Ethiopia, with those of Kadanuumuu (Big Man in Afar) another member of the A. afarensis species unearthed in 2010, though clearly much larger. Because of their difference in height – Lucy would have been about 3.5 feet tall, Big Man approximately 5 – Kramer wondered if they would have been able to walk around together.

To find out, she enlisted the aid of 36 children and 16 adults who all agreed to have their leg bones measured and then to be tested walking on a treadmill. Scientists know that people have a natural walking gait that is also the optimal speed for . For long legged people, a faster gait is optimal, whereas for those with shorter legs, slower is better. In the case of Lucy and Big Man, the difference in the length of would have been equivalent to the difference in leg bone length between modern children and adults. She used the data from her ' efforts to create a that allowed her to estimate the natural gait of Lucy and Big Man and found them to be 3.4 feet per second, versus 4.4 feet per second. Such a difference would have meant would have had to walk a lot faster than normal to keep up with Big Man, or Big Man would have had to walk a lot slower for the two of them to walk around together; an idea that seems counterintuitive because it would mean one or the other would have had to walk at a pace that consumed more energy.

Kramer notes that her study includes just two specimens of A. afarensis which are of the opposite gender, and who would have lived some distance from one another. Thus, she suggests it's possible that regional differences were at play, or that males of the time were simply much larger than females, which likely would have meant they spent most of their time apart, similar to modern chimpanzees.

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More information: Could Kadanuumuu (KSD-VP-1/1) and Lucy (AL 288-1) have walked together comfortably? American Journal of Physical Anthropology, DOI: 10.1002/ajpa.22169

Abstract
The estimated lower limb length (0.761–0.793 m) of the partial skeleton of Australopithecus afarensis from Woranso-Mille (KSD-VP-1/1) is outside the previously known range for Australopithecus and within the range of modern humans. The lower limb length of KSD-VP-1/1 is particularly intriguing when juxtaposed against the lower limb length estimate of the other partial skeleton of A. afarensis, AL 288-1 (0.525 m). A sample of 36 children (age, >7 years, trochanteric height = 0.56–0.765 m) and 16 adults (trochanteric height = 0.77–1.00 m) walked at their self-selected slow, preferred, and fast walking velocities, while their oxygen consumption was monitored. Lower limb length and velocity were correlated with slow (P < 0.001, r2 = 0.44), preferred (P < 0.001, r2 = 0.55), and fast (P < 0.001, r2 = 0.69) walking velocity. The relationship between optimal velocity and lower limb length was also determined and lower limb length explained 47% of the variability in optimal velocity. The velocity profile for KSD-VP-1/1 (slow = 0.73–0.75 m/s, preferred = 1.08–1.11 m/s, and fast = 1.48–1.54 m/s) is 36–44% higher than that of AL 288-1 (slow = 0.53 m/s, preferred = 0.78 m/s, and fast = 1.07 m/s). The optimal velocity for AL 288-1 is 1.04 m/s, whereas that for KSD-VP-1/1 is 1.29–1.33 m/s. This degree of lower limb length dimorphism suggests that members of a group would have had to compromise their preferences to walk together or to split into subgroups to walk at their optimal velocity.

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Ophelia
5 / 5 (1) Nov 12, 2012
Perhaps someone can explain to me why
Such a difference would have meant Lucy would have had to walk a lot faster than normal to keep up with Big Man, or Big Man would have had to walk a lot slower for the two of them to walk around together; an idea that seems counterintuitive because it would mean one or the other would have had to walk at a pace that consumed more energy.


is "counterintuitive" in view of
Scientists know that people have a natural walking gait that is also the optimal speed for conserving energy. For long legged people, a faster gait is optimal, whereas for those with shorter legs, slower is better.

The latter sentence says that when people with unequal leg lengths walk together they both can't walk at optimal, energy efficient speeds. So why is it counterintuitive that our ancestors also couldn't?

Or is this just more crappy science writing?
LariAnn
1 / 5 (3) Nov 12, 2012
Study of the leg lengths of modern humans as related to walking speed and stride length is science, but speculation about gaits of species for which we have only partial skeletons and no actual observation of a live specimen is just that, speculation. It may make for a nice animated graphic or science fiction movie, but IMHO it is not science.

Besides, observe groups of modern humans walking together and see how many or how frequently very tall individuals are seen walking with very short individuals. My bet is that those of similar height tend to walk together more frequently than those of significantly differing heights.
Torbjorn_Larsson_OM
5 / 5 (1) Nov 12, 2012
On the other hand we have the Laetoli footprints, that shows different individuals of australopithecines comfortably walking with the same stride. In fact, one of the individuals walking in the footprints of another! [ http://en.wikiped.../Laetoli ]

As I remember it, similar prints have now been found with Erectus, who would also have some sexual dimorphism.

@ Ophelia: I think the prediction was that these individuals would prefer not to walk together, i.e. walking together would be counterintuitive.
Torbjorn_Larsson_OM
3.7 / 5 (3) Nov 12, 2012
@ LariAnn: Your claims is rejected by having precisely scientists studying this.

There is no difference and of course there _can't_ be any difference in observing the mechanics. The opposite claim is usually predicted on the individual being creationist, not caring for how observations are done because the results rejects his or her religion.

In the case of partial skeletons the uncertainty may be slightly increased in case they have to estimate leg lengths (say). Skeletal and muscular arrangements are known from fossils. (You can see muscle attachments and estimate size from the different constraints on the bones I think; I'm no paleontologist.)

And the found prints are a good test for the predictions of gait models. I believe they have done gait models since the 70's from what I can see on the Laetoli print papers, and certainly dinosaur gaits et cetera must have been early (prints, bones, et cetera). Annoyingly the history here isn't much on the web yet.
TheGhostofOtto1923
4 / 5 (12) Nov 12, 2012
the walking gait between two of our early ancestors was likely so different that it's doubtful they would have done so together, despite being two members of the same species living during roughly the same time period.
The smaller ones could have been pets. Seriously, what is the point here? Members of different tribes with identical physiologies would have had trouble not killing and eating one another, let alone walking around together.
Torbjorn_Larsson_OM
5 / 5 (2) Nov 13, 2012
TGO, the point is that early hominins had large sexual dimorphism.

As for cannibalism, it isn't warranted by observation. We are more peaceful than chimps, yet observation of chimp cannibalism is rare. [ http://en.wikiped...impanzee ]

Late hominids _did_ practice cannibalism frequently. [ http://www.scribd...annibals ] But there is no observation of earlier such, despite having evidence of eating other animals. [ http://news.disco...213.html ] So it looks to be a cultural thing.

Who knows when it kicked in, but betting today would give you that the late H. erectus did it so predicting the antecessor/neanderthal practice.
TheGhostofOtto1923
4.3 / 5 (12) Nov 13, 2012
As for cannibalism, it isn't warranted by observation. We are more peaceful than chimps, yet observation of chimp cannibalism is rare
Chimps don't suffer under the chronic overpopulation and resulting conflict that humans have throughout their existence.

Goodall observed cannibalism of a baby by 2 dominant females, as well as warfare among groups over resources and reproductive rights. As soon as hominids developed weapons which enabled them to hunt the predators which had kept their numbers in check, their pops exploded. The next tribe became their greatest enemy.

Tribal dynamics became the dominant driver of human evolution, as those tribes which combined internal cohesion coupled with external animosity would prevail in conflict and repro rights. Humans were quickly selected for communication, planning, memory, culture.

Collectively we are more violent than chimps against enemy tribes. We have been selected for it. Internal altruism supports tribal warfare.
TheGhostofOtto1923
4.3 / 5 (12) Nov 13, 2012
The only reason that this has not gained more acceptance is because of all the unfortunate implications of tribalism. It tells us that gangs and wars are natural. It tells is that religions evolved to assist us in conducting war.
http://rechten.el...RID2.pdf

-But it explains so much.
TheGhostofOtto1923
4.3 / 5 (12) Nov 13, 2012
It tells us for instance that it is every bit as immoral to murder members of ones own tribe, as it is NOT to murder members of other tribes. This explains how gangs operate, by victimizing and their neighbors to benefit their membership.

It informs us of ongoing Efforts to breed these tendencies out of the human race, by conducting Preengineered wars to attract people with these tendencies and leave them on the battlefield. 'The meek shall inherit the earth' - this is a Promise and a Goal. The establishment of the perception that the entire race is of ONE TRIBE, is essential to ending conflict on this planet.

We can appreciate ongoing Efforts to do this by the establishment of one culture, one language, one consistent diet, one economy, etc to rehomogenize the human race and to counteract it's universal tendency to diverge like any other species; to undo the conditions imposed by the fall of the tower of babel so to speak.
tkjtkj
5 / 5 (1) Nov 18, 2012
I remember taking my children, ages 5 or so .. on very nice walks .. I dont recall ever making calculations of relative energy expenditures ..
Go figure ...