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Report on the Film of a Supposed Sasquatch

D.W. Grieve

The following report is based on a copy of a 16mm. film taken by Roger Patterson on October 20th, 1967, at Bluff Creek, Northern California, which was made available to me by René Dahinden in December 1971. In addition to Patterson's footage, the film includes a sequence showing a human being (height 6 ft. 5½ in.) walking over the same terrain.

The main purpose in analysing the Patterson film was to establish the extent to which the creature's gait resembled or differed from human gait. The bases for comparison were measurements of stride length, time of leg swing, speed of walking and the angular movements of the lower limb, parameters that are known for man at particular speeds of walking. Published data refer to humans, with light footwear or none, walking on hard level ground. In part of the film the creature is seen walking at a steady speed through a clearing of level ground, and is it data from this sequence that has been used for purposes of comparison with the human, pattern. Later parts of the film show an almost full posterior view, which permits some comparisons to be made between its body breadth and that of humans.

My subjective impressions have oscillated between total acceptance of the Sasquatch on the grounds that the film would be difficult to fake, to one of irrational rejection based on an emotional response to the possibility that the Sasquatch actually exists.

The film has several drawbacks for purposes of quantitative analysis. The unstable hand-held camera gave rise to intermittent frame blurring. Lighting conditions and the foliage in the background make it difficult to establish accurate outlines of the trunk and limbs even in un-blurred frames. The subject is walking obliquely across the field of view in that part of the film in which it is most clearly visible. The feet are not sufficiently visible to make useful statements about the ankle movements. Most importantly of all, no information is available as to framing speed used.

Body shape and size

Careful matching and superposition of images of the so-called Sasquatch and human film sequences yield an estimated standing height for the subject of not more than 6 ft. 5 in. (196 cm.). This specimen lies therefore within the human range, although at its upper limits. Accurate measurements are impossible regarding features that fall within the body outline. Examination of several frames leads to the conclusion that the height of the hip joint, the gluteal fold and the finger tips are in similar proportions to the standing height as those found in humans. The shoulder height at the acromion appears slightly greater relative to the standing height (0.87:1) than in humans (0.82:1). Both the shoulder width and the hip width appear proportionately greater in the subject creature than in man (0.34:1 instead of 0.26:1; and 0.23:1 instead of 0.19:1, respectively).

If we argue that the subject has similar vertical proportions to man (ignoring the higher shoulders) and has breadths and circumferences about 25 per cent greater proportionally, then the weight is likely to be 50-60 per cent greater in the subject than in a man of the same height. The additional shoulder height and the unknown correction that should be allowed for the presence of hair will have opposite effects upon an estimate of weight. Earlier comments that this specimen was "just under 7 ft. in height and extremely heavy" seem rather extravagant. The present analysis suggests that Sasquatch was 6 ft. 5 in. in height, with a weight of about 280 lb (127 kg.) and a foot length (mean of 4 observations) of about 13.3 in. (34 cm.).

Timing of the gait

Because the framing speed is unknown, the timing of the various phases of the gait was done in terms of the numbers of frames. Five independent estimates of the complete cycle time were made, from 'R. toe-off', 'L. toe-off, 'R. foot passing L.', 'L. foot passing R.' and 'L. heel strike' respectively giving:

Complete cycle time = 22.5 frames (range 21.5 - 23.5). Four independent estimates of the swing phase, or single support phase for the contra-lateral limb, from toe-off to heel strike, gave:

Saving phase, or single support = 8.5 frames (same in each case). The above therefore indicates a total period of support of 14 frames and periods of double support (both feet on the ground) of 2.75 fames. A minimum uncertainty of ± 0.5 frames may be assumed.

Stride length

The film provides an oblique view and no clues exist that can lead to an accurate measurement of the obliquity of the direction of walk which was judged to be not less than 20 degrees and not more than 35 degrees to the image plane of the camera. The obliquity gives rise to an apparent grouping of left and right foot placements which could in reality have been symmetrical with respect to distance in the line of progression. The distance on the film between successive placements of the left toot was 1.20 X the standing height. It an obliquity of 27 degrees is assumed, a stride length of 1.34 X the standing height is obtained. The corresponding values in modern man for 20 degrees and 35 degrees obliquity are 1.27 and 1.46 respectively.

A complete set of tracings of the subject were made, and in every case when the limb outlines were sufficiently clear a construction of the axes of the thigh and shank were made. The angles of the segments to the vertical were measured as they appeared on the film. Because of the obliquity of the walk to the image plane of the camera (assumed to be 27 degrees), the actual angles of the limb segments to the vertical in the sagittal plane were computed by dividing the tangent of the apparent angles by the cosine of 27 degrees. This gave the tangent of the desired angle in each case, from which the actual thigh and shank angles were obtained. The knee-angle was obtained as the difference between the thigh and shank angles. A summary of the observations is given in the following table.

The pattern of movement, notably the 30 degrees of knee flexion following heel strike, the hip extension during support that produces a thigh angle of 30 dregrees behind the vertical, the large total thigh excursion of 61 degrees, and the considerable (46 degrees) knee flexion following toe-off, are features very similar to those for humans walking at high speed. Under these cinditions, humans woul,d have a stride length of 1.2 X stature or more, a time of swing of about 0.35 sec, and a speed of swing of about 1.5 X stature per second.

Conclusions

The unknown framing speed is crucial to the interpretation of the data. It is likely that the filming was done at either 16, 18, or 24 frames per second and each possibility is considered below.

If 16 fps is assumed, the cycle time and the time of swing are in a typical human combination but much longer in duration than one would expect for the stride and the pattern of limb movement. It is as if a human were executing a high speed pattern in slow motion. It is very unlikely that more massive limbs would account for such a combination of variables. If the framing speed was indeed 16 fps it would be reasonable to conclude that the metabolic cost of locomotion was unnecessarily high per unit distance or that the neuromuscular system was very different to that in humans. With these considerations in mind it seems unlikely that the film was taken at 16 frames per second.

Similar conclusions apply to the combination of variables if we assume 18 fps. In both cases, a human would exhibit very little knee flexion following heel strike and little further knee flexion following toe-off at these times of cycle and swing. It is pertinent that subject has similar linear proportions to man and therefore would be unlikely to exhibit a totally different pattern of gait unless the intrinsic properties of the limb muscles or the nervous system were greatly different to that in man.

If the film was taken at 24 fps, Sasquatch walked with a gait pattern very similar in most respects to a man walking at high speed. The cycle time is slightly greater than expected and the hip joint appears to be more flexible in extension than one would expect in man. If the framing speed were higher than 24 fps the similarity to man's gait is even more striking.

My subjective impressions have oscillated between total acceptance of the Sasquatch on the grounds that the film would be difficult to fake, to one of irrational rejection based on an emotional response to the possibility that the Sasquatch actually exists. This seems worth stating because others have reacted similarly to the film. The possibility of a very clever take cannot be ruled out on the evidence of the film. A man could have sufficient height and suitable proportions to mimic the longitudinal dimensions of the Sasquatch. The shoulder breadth however would be difficult to achieve without giving an unnatural appearance to the arm swing and shoulder contours. The possibility of fakery is ruled out if the speed of the film was 16 or 18 fps. In these conditions a normal human being could not duplicate the observed pattern, which would suggest that the Sasquatch must possess a very different locomotor system to that of man.

D. W. GRIEVE, M.SC. PH.D.
Reader in Biomechanics
Royal Free Hospital School of Medicine
London