Bigfoot Encounters

Reviewing the Intermembral Index Issue
as it relates to the Sasquatch,
it appears to be a fallacy; certainly it's not
prima facie!

By Bobbie Short
Graphic Art & Commentary by Aaron Swepston

Foreword: For readers unfamiliar with the phraseology, "intermembral index or IM, " it is a ratio used to compare limb proportions, expressed as a percentage.¹ª   It is equal to the length of forelimbs (humerus plus radius) divided by the length of the hind limbs (femur plus tibia) multiplied by 100, otherwise written mathematically as:


It is used frequently in primatology since it helps predict primate locomotor patterns. For scores lower than 100, the forelimbs are shorter than the hind limbs, which is common in leaping non-human primates and bipedal hominids (humans). Quadrupedal primates tend to have scores around 100, while brachiating primates have scores significantly higher than 100. The Sasquatch is not believed to be either a quadruped or a brachiating primate in the normal course of its locomotor behavior. This information can also be used to predict locomotor patterns for extinct primates in cases where forelimb and hind limb fossils have been found; it assists in non-human primate identification. ¹ª   

In which of these frames from the Patterson footage do you see hands beneath the knees?

For the intermembral index (IM) discussion
Observe more clearly, the length of arm in relationship to her knee...

Several schools of thought occur when observing the Patterson subject regarding the length of her arms, relative to her body length. Since 2004, the on-going discussion has been about whether or not the Patty subject's arms dangle down to or well below her knee?

The implication is of course, - arms dangling to or beneath the level of the knee is thought to be a check-mark in the plus column for a more ape-like shape …giving the “slouch-forward-knuckle-walker” appearance widely associated with the great apes.

Let's take a hard look and test the reality of Patty's arm-length.

A little background first:

In the November 1967 radio broadcast interviewer Jack Webster aired this exchanged with Roger Patterson and Bob Gimlin:

Webster: Describe it (the creature) to me, Bob

Gimlin: It was a large hairy creature with arms that hang down
beside its, …you know, far down on its sides, below its knees, and it was quite...

Webster: Interrupting, …Do you agree with that, Roger?

Roger: No, I think Bob's a little excited here, I don't believe they were
below the knees; they (the hands) were above the knees.

Webster: But they were well down on the sides, weren't they?

Gimlin: way down, right.

Webster: And I could see that on the film tonight, they were well down on the sides…

What can we gather from the interview dialogue? Not much, other than neither Patterson nor Gimlin could agree on a great deal from memory, even immediately after the event -Gimlin in particular.

Now… if you consider the stills on this page, it appears Patterson had the better judgment; the hands do not extend below Patty's knees. Not bad recall for a man who allegedly had one eye in the camera's aperture and the other on the terrain he was trying to negotiate…

Then from John Green on March 14, 2004 this excerpt from a piece he penned & uploaded on Roger Thomas' site
² where Green is making the argument for Patty not being Bob Heironimus in a suit:  

There is no way to establish for certain if any of the dimensions estimated for the creature in the film are accurate, but what can be established with reasonably accuracy is the length of the creature's legs and arms in relation to one another. From that ratio, which anatomists call the "intermembral index," it is simple to calculate how many inches must be added to the arms of a man of known size in order to make his arms long enough to fit the supposed suit. In my own case the answer turns out to be about 10 inches.  But in order for the arms to bend at the elbow, which they plainly do in the movie, all of that extra length has to be added to the lower arm. The result, in my case, is about 12 inches of arm above the elbow and 29 inches below it — almost as much of a monstrosity as Edward Scissorhands. The creature in the movie has normal-looking arms. It cannot be a man in a suit.”

First of all, the Patterson film is a “film clip,” not a “movie” as John persists in saying. The public version runs less than 50-seconds out of a complete 3 minute/42 second 100-foot reel; that small strip of celluloid does not constitute a "movie." Peter Byrne was quick to tell me his copy of the Patterson film ran only 30 seconds; he obtained it directly from Roger Patterson. Why these discrepancies? Who has the rest of that film? A trivial point you might argue, but no, not if the pubic understands somebody shot a complete roll of film there in Bluff Creek that research has not been allowed to analyzed in its unbroken, unedited state; in fact Gimlin told us two reels of film were shot and nobody questions any of this? People say they have a copy of the Patterson film (and they argue vociferously which generation it is) but what all of them have is just an edited out-take, a spliced excerpt from the original 100 ft roll of film and that reel should run unedited at least 3 minutes 42 seconds or just under 4 minutes if it was shot at 18 fps and some of those edited out-takes are different in time-length from others; still nobody questions it...why? This is really lousy science!

Green was right about one thing when he stated above, "There is no way to establish for certain if any of the dimensions estimated for the creature in the film are accurate..." and certainly this includes the Intermembral Index; - no type specimen, no known size!  

If John's own measurements are correct and the Intermembral Index theorem holds true, then any human with exceptional length of arm should be brachiating in trees. It makes more sense that the IM concept was more probably designed for measuring non-human primates in their fossil remnant state.

True, the lower forearm might possibly be an a half-inch or so longer in these frames than what is perceived as the norm, but the visible arm-length in this Patty illustration does not exceed levels of accepted extension. Her length of arm is clearly in proportion to the rest of her body.

is another visual greatly enlarged and in motion, fyi...

Certainly there are no frames in the spliced ‘look-back' sequence where Patty's arms dangle to or beneath her knees in what might superficially be regarded as an ‘ape-like' characteristic and again we cannot base sasquatch-traits on one sasquatch. Of course general research has not had access to the whole 100-foot roll of
unedited film, John has; we may never know why research was not allowed to study the rest of that film footage for analysis in it's unedited state and that anyone would withhold it for 43 years, is highly suspect in my opinion.

Next, we have a quote by anatomist Jeff Meldrum at the Idaho State University: “It has been obvious to even the casual viewer that the film subject possesses arms that are disproportionately long for its stature.”
³ - That sounds impressive but it appears to be more in the manner of an ideological barrier: spoon-fed baloney …verbal trickery. I would say the baloney pile is stacked fairly high and the spread of misinformation in epidemic proportions. All of us are casual observers as Meldrum put it, but looking at the visuals posted on this page, there appears to be no unreasonable length of arm; no instances in these stills from the highly edited "Patterson film clip" where Patty's arms hang “below the knees” as Gimlin recalled incorrectly and Patty's arms do not appear “disproportionately long for her stature,” …baloney!

Certainly in this skillful demonstration generously provided by Aaron Swepston, her arms seem to be ‘in proportion to the rest of her body.' When did bigfoot length of forearm take on prima facie credibly? It doesn't, it is my opinion this is more smoke & mirror deception perpetrated to make a case for an unknown species of ape when all indications are more reasonably checked in a column listing the human element… of course the genetic issue of the hair notwithstanding.

Referring again to John Green, Meldrum continues his slant: “His recognition of the significance of the unhumanly long arms of the film subject is a point that has not previously been articulated in such a straightforward manner. It is such a fundamental observation that it is considered a break through in assessing the validity of this extraordinary film.”

"Unhumanly long arms?" "Break-through?" Not so fast. Film does not lie; it does not show typical ape like characteristics in the arms and leg lengths; I see nothing to indicate disproportionately long arms; a "break-through," no, I would call it propaganda; verbal trickery to form a mindset.

“Anthropologists typically express limb proportions as an intermembral index (IM), which is the ratio of combined arm and forearm skeletal length (humerus + radius) to combined thigh and leg skeletal length (femur + tibia) x 100. The human IM averages 72. The intermembral index is a significant measure of a primate's locomotor adaptation. The forelimb-dominated movements of the chimp and gorilla are reflected in their high IM indices of 106 and 117 respectively. Identifying the positions of the joints on the film subject can only be approximate and the limbs are frequently oriented obliquely to the plane of the film, rendering them foreshortened to varying degrees. However, in some frames the limbs are nearly vertical, hence parallel to the filmplane, and indicate an IM index somewhere between 80 and 90, intermediate between humans and African apes. In spite of the imprecision of this preliminary estimate, it is well beyond the mean for humans and effectively rules out a man-in-a-suit explanation for the Patterson-Gimlin film without invoking an elaborate, if not inconceivable, prosthetic contrivance to account for the appropriate positions and actions of wrist and elbow and finger flexion visible on the film. This point deserves further examination and may well rule out the probability of hoaxing.”

Meldrum is correct about the “imprecision [or vagueness] of his preliminary estimate” because, one could easily argue, that it is NOT beyond the "mean for humans," ... especially if the Sasquatch ends up a new branch or sub-branch of what's possible in the genus Homo. And why do we debate apes verses humans when no ape ever evolved to walk upright? The great apes are quadupeds, they are not upright walking bipeds like the Sasquatch and too, North America has no fossil record of apes; why this push to make an ape out of something that walks upright? It's not good science - apes are in fact a contemporary relative of ours, not our ancestors ... school yourselves, read Pavelka.

There was this interesting if not applicable remark attributed to the late Dr. Carl Sagan in his body of works titled, "The Fine Art of Baloney Detection,” he was quick to point out that "science is a way of thinking much more than it is a body of facts,” well glory halleluiah, Sagan called it!

In fact, there is so much baloney being sliced here that Dr. Meldrum seemingy went out on a very thin limb redesigning the skeletal structure of the Sasquatch foot with an unseemly center-hinge and he did this never having x-rayed or dissected a Sasquatch foot, which I find… <deep breath> absolutely stunning. Bolstered by the brilliance of his decision to redesign the skeletal structure of the Sasquatch foot to fit his bias, he then announces he has named it ”Antropoidipes ameriborealis” (The North American ape foot) without ever providing any proof that his vision of the Sasquatch foot is authentic beyond theory.

In reality, neither side of the discussion comes out the absolute winner because research doesn't have a holotype from which to draw any conclusion; but then general research isn't making the claim, Dr. Meldrum did and apparently with John Green's heirarchical blessing.

Any suggestion that nature redesigned the bone structure in Patty's foot based on plaster casts or that Patty is more human or less human than an ape has no merit worth discussing; without a holotype it's all speculation and conjecture... yet observers stand idly by, doing nothing, saying nothing, in essence allowing this theory to take root as if it were fact; it's baloney.

In John Green's own words, “There is no way to establish for certain if any of the dimensions estimated for the creature in the film are accurate," yet the ape theorists continue to wildly speculate without earning advantage in the discussion. I was reminded too that the provisional concept that the subject in the Patterson clip had "disproportionately long arms" contains not one comparative study to fall back on... this isn't good science!

We h
umans have a poor innate grasp of probability. We believe that all effects must have deliberate causes like the case of the midtarsal break and we easily succumb to selective validation.

The case for sasquatch being an unknown ape by reason of the IM or Intermembral Index – without a holotype - is unscientific.

The purpose of this writing is to counter and correct what I believe is bad science. The scientific world operates on theories and hypotheses. Yet to be valid these must have their foundation in some plausible evidence which appears to recur and correlate over time.

The longer arms claim simply does not appear to be supported by the filmed evidence. The midtarsal break theory is just that – a theory, which seems to have a less than valid case for its proposal.

There is in this research, a HUGE failure to legitimatize and generate REAL science and the result is a growing frustration among the serious participants who are unable to show me where I'm wrong in this effort.

Hopefully, as sasquatch research becomes more scientific, we must all learn something of the nature of scientific inquiry. We absolutely must learn to question the validity of the various theories and hypotheses we encounter and in the process not be dazzled by scientific verbiage or an individual's credentials. We must also understand that a theory remains a theory until proven by science to be fact.

The point here is not to argue issues or besmirch another person's work; there is no malicious intent in this; moreover, this piece is simple deductive reasoning. This effort is more about provoking independent thought in research. It is my hope that what I've said here will stir a renewal in critical thinking and fact finding in bigfoot research.

Following a concept blindly without due process is like the myopic rat to the pied piper. Study deeply a concept and weigh its scientific value before you argue pro or con.

Bobbie Short Sept 2010
Graphic artwork of the Patterson creature by Aaron Swepston. 2010
Sources & Citations below...
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Commentary by Aaron Swepston:
“I wonder why so many people perceive Patty as having unusually long arms. Again, referring back to the film, I have a few ideas. First, she swings her arms widely, creating a rather large arc as she walks.

This is a bit unusual for normal human walking, but not if one is walking briskly in an effort to get somewhere reasonably fast without breaking into a run. Another thing is the relatively high set to the butt, or rather the top of the butt where the low back and waist begin. That gives the appearance that the arms hang well below the hips, but if you measure where the wrists and hands swing relative to the lower edge of the buttocks and the thighs, the point at which the hand and wrist cross the leg and buttocks is exactly where it would swing in a normal human.

By no means does her hand reach anywhere near her knees, as many seem to suggest. It's not an opinion; it's clearly measurable from the film. The arms do not hang lower on the body than do a man's. The shortness claimed of the legs is likewise not supported by examination of the film. If you consider the legs ending where they disappear behind the logs and brush, then certainly they would be short, but just because they are obscured by foreground debris does not mean that legs do not go on to the ground where we cannot see them. Examining frames where the full leg length is visible, and making measurements of those, then we see how truly long the legs are. They are quite long compared to what people generally tend to illustrate or describe.

Again, people can say whatever they wish, but clear measurements of the clearest frames in the film do not lie, do not distort, and portray a figure which demonstrates exact human proportions in terms of arm and leg lengths relative to one another. Patty, in spite of what so many people have maintained for decades, has human proportions, not ape-like proportions.

That somebody, even somebody of great repute, made the claim that Patty has disproportionately long arms, and that people ever since have adopted that claim as fact, does not change a thing.

If more people would examine and question what they have been told, if they would not just assume what they hear is accurate, if they would do their own homework, many of these fallacies would be overturned. Maintaining myths does nothing to get us closer to the truth. There is a truth to be found, and exposing long held myths should be foremost for anyone honestly seeking to discover that truth.”

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It is appropriate here to thank and acknowledge Aaron Swepston in Washington State for his insight and his contribution to the discussion. The artistic graphic overlay on the Patterson film subject was Aaron's work; we are grateful for his oeuvre on this time consuming project...

Below is a video series featuring Aaron; among many things, i
n his off-time he is a veteran celebrity hang-glider enthusiast as seen on the David Letterman Show.

More overlay graphics follow...

Graphic work by Aaron Swepston 2010

¹ Sagan, Carl Dr: The Fine Art of Baloney Detection. Parade Magazine, p 12­13,
February 1, 1987.

¹ª Ankel-Simons, F. (2007) Primate Anatomy (3rd ed.). Academic Press pp. 49–53.

Conroy, G.C. (1990) Primate Evolution (1st ed.). New York: W.W. Norton and Co.


² Source: “Thoughts on the Patterson-Gimlin Footage” By John Green, 14 March 2004 :

³ Source: “Thoughts on the Patterson-Gimlin Footage” By John Green, 14 March 2004 :

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