Evolving Upright Posture Is No Walk in the Park
The transition from
quadruped to biped
is much more complex
than once thought
by Jerry Bergman, PhD
A new study completed at Harvard University attempting to help solve the problem of the evolution of upright posture required for walking on two feet found it to be far more complex than once believed. This conclusion supports the trend that, as scientific research progresses, evolution is made not more probable, but less probable.
In their paper in Science Advances on October 25th, Bishop and Pierce admit that
The evolutionary transition from early synapsids to therian mammals involved profound reorganization in locomotor anatomy and function, centered around a shift from “sprawled” to “erect” limb postures. When and how this functional shift was accomplished has remained difficult to decipher from the fossil record alone.[1]
Figure 1. The illustration shows a tegu lizard (sprawled), an alligator (semi-upright), and a greyhound (upright). The diagram shows the sprawled to erect posture, which does not appear as a major transition. The research reviewed in this paper has determined that this seemingly simple change involved “profound reorganization” which was far more complex than once believed before the detailed examination by Professor Pierce was completed. Illustration from Bishop and Pierce (Harvard University), 2024.
Since the fossil record does not show evidence of how the evolution from sprawled to erect posture (as shown in Figure 1) could have occurred, researchers have attempted to biomechanically model hindlimb forces. The authors presented the challenges to model hindlimb forces as follows:
The reorganization of the synapsid locomotor system … formed a cornerstone to the ecological radiation of mammals in the Cenozoic. Central to this was a shift from reptile-like “sprawled” postures, with the limbs held to the side of the body, to the “erect” postures of therians (marsupials and placentals), with the limbs held close to the body midline. In addition to kinematic differences, sprawling and erect locomotion involve marked differences in stability, musculoskeletal mechanics, neural control, and bone loading.[2]
Fossils Missing
Despite what the authors claim is an “exceptional fossil record spanning 100+ million years,” they admit that “interpreting this [fossil] record has proved challenging… disparate lines of evidence and reasoning, prior studies frequently conflict…. consequently little consensus [exists] on when the erect locomotor behavior of extant therians first evolved.”
Upright posture among therians (placental mammals) supposedly evolved long before humans began to walk upright on two limbs. Iconic images of linear evolutionary progress from ape to man have long been rejected by modern anthropologists (see my article from 10 April 2018).
Fig 2 The linear model of evolution from ape to modern human which is now rejected by evolutionists. From Wikimedia commons.
Fig 3 Another example of the linear model as shown in Time-Life books popular in the 1960s. From Wikimedia commons.
Because the evidence has failed to support the linear model, as shown in Figures 2 and 3, newer charts show a wide variety of fossils in a scattered plot that do not depict linear evolution (Fig 4).
Fig 4 An example of the modern non-linear evolution showing a large variety of primates and humans fossils exist but do not show ladder evolution. From Wikimedia commons
Field Noise, Not Ladders
The linear model was rejected by Bishop and Pierce for similar reasons:
Arguing against a simple, gradualistic (linear) narrative of locomotor evolution, Kemp proposed that advanced therapsids and early cynodonts were facultatively capable of a broad range of limb postures, akin to extant crocodylians before a committed shift to exclusively erect postures in advanced cynodonts. This hypothesis implies that a transient phase of increased locomotor versatility was a key facilitator of the evolution of novel locomotor behaviors on the line to mammals.[3]
In other words, as the lack of evidence for horse evolution is explained away by postulating horses existed in great variety, as do dogs today. The reason for the shift in explanation comes from the difficulty in plotting a linear progression against a background of wide equine variety.[4] This produces what is called, in the sound and electromagnetic spectrum, field noise.
In other words, in the case of evolution of the sprawled to erect posture, evolutionists are unable to produce evidence of linear evolution. The evidence shows that a large range of limb designs exist, allowing a large range of locomotor versatility. As with horse evolution, this variety does not explain the transitions from the “sprawled” posture design where the limbs are located on the side of the body, to bi-segmented, and lastly to the “erect” parasagittal, tri-segmented limb postures of therians where the limbs are directly under the body.[5]
Discussion
Professor Stephanie Pierce, who directed the study, has been studying the evolution of the mammalian body plan for almost a decade. She has observed that the problems uncovered in her new study also exist in other parts of the synapsid body, such as the vertebral column.
The picture is emerging that the full complement of quintessentially therian traits was assembled over a complex and prolonged period, with the full suite attained relatively late in synapsid history…. how these animals evolved, … wasn’t just this simple, linear evolutionary story.[6]
She added that the transition “was really complicated and these animals were probably living and moving in their environments in ways that we hadn’t appreciated before. There was a lot happening and mammals today are really quite special.”[7] Furthermore,
Beyond mammals, the study suggests that some major evolutionary transitions, like the shift to an upright posture, were often complex and potentially influenced by chance events…The researchers speculate that due to this “ecological marginalization,” the evolutionary trajectory of synapsids may have changed so much that it altered the way they moved. Whether this hypothesis turns out to be supported or not, understanding the evolution of mammal posture has long been a complex puzzle. .. advances in computing power and digital modeling have provided scientists new perspectives to address these ancient mysteries.[8]
Summary
These findings from Harvard University’s Department of Organismic and Evolutionary Biology are not very kind to evolutionism. They echo what is true of evolutionary research in general: the more detail, the more complicated an evolutionary explanation becomes.
As Fischer and Blickhan, two of the leading researchers in the evolution of tetrapod locomotion, wrote 18 years ago:
The evolution of therian mammals is to a large degree marked by changes in their motion systems. One of the decisive transitions has been from the sprawled, bi-segmented to the parasagittal, tri-segmented limb.[9]
By comparing Blickhan and Fisher’s statement from 2006 with Harvard’s new conclusion below, it is clear that no progress has been made in solving the problem of upright posture in the last 18 years. Their anatomical analyses evaded an evolutionary explanation. The key trait that allegedly fueled the spectacular evolutionary success of mammals, including humans, is
their distinctively upright posture. Yet, the earliest known ancestors of modern mammals resembled reptiles, with limbs stuck out to their sides in a sprawled posture. The shift from a sprawled stance, like that of lizards, to the upright posture of modern mammals, as in humans, dogs, and horses, marked a pivotal moment in evolution. It involved a major reorganization of limb anatomy and function in synapsids — the group that includes both mammals and their non-mammalian ancestors — eventually leading to the therian mammals (marsupials and placentals) we know today. Despite over a century of study, the exact “how,” “why,” and “when” behind this evolutionary leap has remained elusive.[10]
Eighteen years is a long time in science, especially for research as observational as anatomy. Darwinians always hope that further research will clarify the picture of evolution, but over time, problems generally increase. Often, research that was intended to demonstrate evolution has achieved the opposite goal.
References
[1] Bishop, Peter, and Stephanie E. Pierce. 2024. Late acquisition of erect hindlimb posture and function in the forerunners of therian mammals. Science Advances 10(43)DOI:10.1126/sciadv.adr2722.
[2] Bishop and Pierce, 2024.
[3] Bishop, and Pierce, 2024.
[4] Bergman, J. 2024. The Horse Evolution Icon Exposed. Creation Research Society Quarterly. Fall 61:133-145.
[5] Fischer, M., and R. Blickhan. 2006. The tri-segmented limbs of therian mammals: Kinematics, dynamics, and self-stabilization—A review. Journal of Experimental Zoology 305(11):935-52; doi: 10.1002/jez.a.333.
[6] Harvard University, Department of Organismic and Evolutionary Biology. 2024. How mammals got their stride. ScienceDaily, www.sciencedaily.com/releases/2024/10/241025141605.htm.
[7] Harvard University, 2024.
[8] Harvard University, 2024.
[9] Fischer and Blickhan, 2006.
[10] Harvard University, 2024; emphasis added.
Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,900 publications in 14 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.