Author: Kevin B. Rosenbloom, C.Ped, Sports Biomechanist
All patients have something in common – they are coming to the clinicians, the expert, for an answer. Having knowledge of our biomechanical history, evolutionary past and what paleoanthropologists are learning more about humans gives context of why many problems exist in the foot, ankle, knees, hips and lower back. Sharing evolutionary history with patients is fun, uplifting, interesting and directly applicable to the evolutionary mismatch of shoes and modern flat ground.
Consider this a major evolutionary mismatch: asphalt, concrete, wood floors and the perfectly even walking surfaces that are only a few hundred years old. It is interesting to consider how our body has been designed through millions of years of evolution. The Kevin Orthopedic research team will begin with a series of dives into the world of paleoanthropology, beginning with an introduction of the footprints at Laetoli.
What is Laetoli?
In 1976, Mary Leakey and her team discovered fossilized footprints at Laetoli in northern Tanzania. Along with Paul Abell two years later, the team uncovered the entire 27 meter site. Site G, as it is now known, contained approximately 70 human-like footprints from three early hominin individuals who clearly demonstrated bipedalism (Laetoli Footprint Trails). The footprints showed no occurrence of knuckle-walking and emphasized a leisurely human-like gait around 1 meter/second (Raichlen et al. 2010). In 2015, another site, site S, was discovered approximately 150 meters away from site G and contained additional human-like tracks by 2 hominin individuals that traversed the same paleo surface and direction as the previous site (Masao et. al 2016).
Figure 1. Test-pit L8 at Laetoli Site S.
Photo credit: Masao et al., eLife 2016. Licensed under CC BY-SA 4.0
Identifying the origin of the prints
When observing the sites, researchers deduced that these prints were made in a mixture of volcanic ash and later cemented with soft rain water and additional ash sediments. The researchers dated the sediments in the environment at approximately 3.6-3.8 million years old by using stratigraphy and potassium-argon dating (Leakey 1981). According to the time period and other discoveries found not far from Laetoli, Australopithecus afarensis appeared to be the most likely candidate to have left the prints at Laetoli (Johanson et al. 1978, White 1980, Hay & Leakey 1982, Stern et al. 1983, White & Suwa 1987).
Who were Australopithecus afarensis?
The species known as Australopithecus afarensis might sound familiar to some, but a specific individual AL 288-1 (Johanson et al. 1978), commonly referred to as Lucy, has recently become more well known. Although Lucy was a partial skeleton, she was one of the most complete found of her species and it delighted researchers. The collected data over the past decades regarding A. afarensis displayed important findings in hominin evolution, such as: spinal attachment beneath the skull, a robust and broad-shaped pelvis (ilium), femoral heads and shafts indicating the thigh bones were angled inward, strong knees indicating strong joints, hallux not abducted in the foot, compact and arched feet (Walking with Lucy). However, A. afarensis did display traits in common with pan troglodytes (chimpanzees), such as: height, elongated skull with small brain case, face and jaw that is robust and juts outward from the brain case, shoulder blades suited for arboreal travel, and long arms with curved fingers (Walking with Lucy). The traits listed above are important because they show almost a hybridization of modern human and modern chimpanzee characteristics.
Figure 2. Australopithecus afarensis adult male
Photo Credit: Tim Evanson, flickr 2012. Licensed under CC BY-SA 2.0
Studying the Laetoli footprints
After some general research, one article seems to provide valuable insight. According to the collaborative efforts of the team members from Arizona and New York, experimental prints were compared to the footprints left at Laetoli and modern humans. In general, their experiment was to analyze a few features, including but not limited to, the center of pressures and depths of the foot impressions left from each group. The control group consisted of subjects walking through sand at a normal and modern gait. The experimental group performed the same procedure, but changed the posture in which they were walking, which the researchers called “bent-knee, bent-hip” or BKBH. This was to simulate an ape walking bipedally. The results stated that the prints at Laetoli prints and of the normal, modern control group were more similar to one another. The BKBH prints displayed significant depressions in toe depth compared to the others (Raichlen et al. 2010).
Figure 3. Three dimensional scans of experimental footprints and a Laetoli footprint.
Photo Credit: Raichlen et al., PLOS One 2010. Licensed under CC BY-SA 4.0
Although the hominin species that made the footprints at Laetoli is not 100% confirmed, there is substantial evidence to support Australopithecus afarensis’ contribution. In conjunction with the Raichlen et al. study, it is demonstrated that this species had adaptations that demonstrated human-like bipedal kinematics approximately 3.6 million years ago. Further research has shown that bipedalism evolved even earlier (approx. 4.4 mya) but walked very differently to modern humans (Lovejoy et al. 2009).
Why is bipedalism so important?
Bipedalism is rare in nature, with only a few species ever showing morphology and adaptation to upright walking. It is an adaptation most commonly associated with modern day humans and yet a general audience has not contributed it to humanity’s success. Previously, people have stated that the significant difference that separates man from animal is the comparison of brain sizes and that this innovative organ is more advanced than any other. It has the ability to create remarkable things, the inference being that the large brain evolved first, followed by tool usage and finally bipedalism. According to the previously listed research in this article, that does not seem to be the case. Many sources have stated that bipedalism is more energy efficient when compared to walking on all four limbs (Louis 2007), it’s advantageous in seeing predators, useful in carrying food and infants, and allowed the hands to explore their dexterity, eventually creating tools (When We First Walked). This information, along with the info generalized in this article would show any reader that bipedalism was an early key to human innovation, creativity and complexity.
Kevin Orthopedic specialists enjoy taking time to look into the past when approaching biomechanics today. When considering hominin bipedalism, a few considerations need attention: the morphological differences between species, the specific behaviors we can infer, the environments in which species live(d) and the sediments species walked upon. This lab believes that the differences that originate from the distant past could well be having an effect on human walking habits in modern, urban environments. Kevin Orthopedic specialists are working on developing these ideas practical ways to bring enhance anatomical foot structure and life performance.
References & Works Cited
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“Walking With Lucy,” California Academy of Sciences. Accessed 20 Feb. 2019. https://www.youtube.com/watch?v=xT8Np0gI1dI.
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Kevin B. Rosenbloom, C.Ped, Sports Biomechanist
Kevin B. Rosenbloom, founder and president of KevinRoot Medical, is a renowned certified pedorthist and sports biomechanist practicing in Santa Monica, CA. With his continuing research on the historical development of foot and ankle pathologies, comparative evolution of lower extremities and the modern environmental impacts on ambulation, he provides advanced biomechanical solutions for his patients and clients.