First hominin muscle reconstruction shows 3.2 million-year-old ‘Lucy’ could stand as erect as we can | University of Cambridge
Australopithecus afarensis (artist's impression)
Illustration by Maurice Wilson
News today that 'Lucy' was more human than we thought should increase the hatred creationists have for her.
Creationists hate the fossil nicknamed by her discoverers, 'Lucy' because 'Lucy in the Sky with Diamonds' by the Beatles was riding high in the pop charts at the time. Her scientific name is
Australopithecus afarensis, so named because she was discovered in the Afar region of Ethiopia in East Africa. Their hatred comes from the fact that her existence refutes just about every creationist superstition, so, rather thn change their minds (something no self-respecting creationist can ever do), creationists try to change the facts or shout abuse at them till they go away.
So concerned are creationist frauds such as Ken Ham and Kent Hovind that they routinely lie about her and how she was discovered, claiming, amongst other things that it is the skeleton of a deformed chimpanzee and that the scientists constructed it out of the fossils of different animals from multiple locations, so it should be regarded as a forgery. Neither of these are true, of course.
Facial reconstructions of what the early hominin (human relative) Australopithecus afarensis may have looked like
Australopithecus afarensis is an extinct hominin species that lived between approximately 3.9 and 2.9 million years ago. The most famous specimen of Australopithecus afarensis is "Lucy," a remarkably complete skeleton discovered in 1974 in the Afar region of Ethiopia. The discovery of Lucy and other A. afarensis fossils has provided significant insights into the story of human evolution.
Lucy's discovery was led by paleoanthropologist Donald Johanson and his team. Her fossilized remains consisted of about 40% of her skeleton, making it an incredibly important find. The age of the fossils and their unique characteristics shed light on a crucial period in human evolution.
Australopithecus afarensis is significant because it is believed to be one of the earliest hominin species to exhibit a combination of ape-like and human-like features. It walked upright on two legs, like modern humans, but also possessed some primitive traits, such as a small brain size and long arms.
The discovery of A. afarensis fossils challenged previous assumptions about the course of human evolution. Prior to this discovery, the prevailing view was that early humans developed large brains before adopting a bipedal, or upright, walking style. However, A. afarensis presented evidence that bipedalism evolved before significant increases in brain size.
The existence of A. afarensis suggests that upright walking was a critical adaptation for our early ancestors. Bipedalism freed the hands for tool use, allowed for greater efficiency in movement across open landscapes, and may have played a role in the development of other characteristics associated with humans, such as increased social cooperation.
Additionally, the discovery of A. afarensis and subsequent research have helped bridge the gap between our common ancestry with other primates and the emergence of the Homo genus, which includes modern humans. It provides valuable evidence of our evolutionary journey and allows scientists to study the changes and adaptations that occurred over millions of years.
In summary, the discovery of Australopithecus afarensis, particularly the famous specimen Lucy, has been instrumental in understanding the early stages of human evolution. It has contributed to our knowledge of bipedalism, the timeline of brain development, and the evolutionary transitions that eventually led to the emergence of modern humans.
The most complete specimen is known to science as AL 288-1 which comprises about 40% of the complete skeleton.
How exactly she fits into the human evolutionary tree is still the subject of debates with some placing her immediately on the
Australopithecus side of what is an artificial line dividing Australopithecines from Hominins and so making her directly ancestral to the
Homo genus, which includes modern humans and some placing her in a side branch, making her a sister species of our immediate Australopithecine ancestor.
The line dividing the Australopiths from the hominins is of course arbitrary because a slowly-evolving species does not cross an imaginary line at a defined time; in reality there is a smooth transition, as in the box on the right, but the reason 'Lucy' is not universally accepted as our direct ancestor is because there are other species competing for that position from South Africa -
Homo naledi and
Australopithecus sediba for example, and, given the tendency of hominid species to interbreed, it is always possible that the ancestor of the stem
Homo could have been two or more Australopiths, and we will probably never know for sure.
But the story was given a little twist yesterday with the publication in
Royal Society Open Science of the results of a new study which shows that 'Lucy' was fully bipedal, that is, she walked upright like we do.
The work was carried out by Dr Ashleigh L. A. Wiseman, of the McDonald Institute for Archaeological Research, University of Cambridge, Cambridge, UK. A Cambridge University news release explains his research:
Digital modelling of legendary fossil’s soft tissue suggests Australopithecus afarensis had powerful leg and pelvic muscles suited to tree dwelling, but knee muscles that allowed fully erect walking.
Lucy’s muscles suggest that she was as proficient at bipedalism as we are
Dr Ashleigh L. A. Wiseman
McDonald Institute for Archaeological Research.
Cambridge University, Cambridge, UK.
Dr Ashleigh Wiseman has 3D-modelled the leg and pelvis muscles of the hominin Australopithecus afarensis using scans of ‘Lucy’: the famous fossil specimen discovered in Ethiopia in the mid-1970s.
Australopithecus afarensis was an early human species that lived in East Africa over three million years ago. Shorter than us, with an ape-like face and smaller brain, but able to walk on two legs, it adapted to both tree and savannah dwelling – helping the species survive for almost a million years.
Named for the Beatles classic ‘Lucy in the Sky with Diamonds’, Lucy is one of the most complete examples to be unearthed of any type of Australopithecus – with 40% of her skeleton recovered.
Lucy’s ability to walk upright can only be known by reconstructing the path and space that a muscle occupies within the body. We are now the only animal that can stand upright with straight knees. Lucy’s muscles suggest that she was as proficient at bipedalism as we are, while possibly also being at home in the trees. Lucy likely walked and moved in a way that we do not see in any living species today.
Australopithecus afarensis would have roamed areas of open wooded grassland as well as more dense forests in East Africa around 3 to 4 million years ago. These reconstructions of Lucy’s muscles suggest that she would have been able to exploit both habitats effectively.
Without open access science, this research would not have been possible.
Muscle reconstructions have already been used to gauge running speeds of a T-Rex, for example. By applying similar techniques to ancestral humans, we want to reveal the spectrum of physical movement that propelled our evolution – including those capabilities we have lost.
Dr Ashleigh L. A. Wiseman.
The research recreated 36 muscles in each leg, most of which were much larger in Lucy and occupied greater space in the legs compared to modern humans.
For example, major muscles in Lucy’s calves and thighs were over twice the size of those in modern humans, as we have a much higher fat to muscle ratio. Muscles made up 74% of the total mass in Lucy’s thigh, compared to just 50% in humans.
Paleoanthropologists agree that Lucy was bipedal, but disagree on how she walked. Some have argued that she moved in a crouching waddle, similar to chimpanzees – our common ancestor – when they walk on two legs. Others believe that her movement was closer to our own upright bipedalism.
Research in the last 20 years have seen a consensus begin to emerge for fully erect walking, and Wiseman’s work adds further weight to this. Lucy’s knee extensor muscles, and the leverage they would allow, confirm an ability to straighten the knee joints as much as a healthy person can today.
Lucy was a young adult, who stood at just over one metre tall and probably weighed around 28kg. Lucy’s brain would have been roughly a third of the size of ours.
To recreate the muscles of this hominin, Wiseman started with some living humans. Using MRI and CT scans of the muscle and bone structures of a modern woman and man, she was able to map the “muscle paths” and build a digital musculoskeletal model.
Wiseman then used existing virtual models of Lucy’s skeleton to 'rearticulate' the joints – that is, put the skeleton back together. This work defined the axis from which each joint was able to move and rotate, replicating how they moved during life.
Finally, muscles were layered on top, based on pathways from modern human muscle maps, as well as what little “muscle scarring” was discernible (the traces of muscle connection detectable on the fossilised bones).
These reconstructions can now help scientists understand how this human ancestor walked.
Dr Wiseman's paper is published open access:
Abstract
To understand how an extinct species may have moved, we first need to reconstruct the missing soft tissues of the skeleton, which rarely preserve, with an understanding of segmental volume and muscular composition within the body. The Australopithecus afarensis specimen AL 288-1 is one of the most complete hominin skeletons. Despite 40+ years of research, the frequency and efficiency of bipedal movement in this specimen is still debated. Here, 36 muscles of the pelvis and lower limb were reconstructed using three-dimensional polygonal modelling, guided by imaging scan data and muscle scarring. Reconstructed muscle masses and configurations guided musculoskeletal modelling of the lower limb in comparison with a modern human. Results show that the moment arms of both species were comparable, hinting towards similar limb functionality. Moving forward, the polygonal muscle modelling approach has demonstrated promise for reconstructing the soft tissues of hominins and providing information on muscle configuration and space filling. This method demonstrates that volumetric reconstructions are required to know where space must be occupied by muscles and thus where lines of action might not be feasible due to interference with another muscle. This approach is effective for reconstructing muscle volumes in extinct hominins for which musculature is unknown.
Figure 1.
Workflow diagram outlining the process for the current study. Comparative data were collected from a male human, in which MRI data from [
22] were used to guide muscle LoAs, segmental and inertial properties. The bone geometries were poor quality, necessitating these parameters to be scaled to high-quality CT data (data from [
11,
47]). For both the human and AL 288-1, joint centres and axes were created. A convex hull was created of each body segment of AL 288-1, of which the centre of mass and inertial properties was corrected following Coatham et al. [
48]. A polygonal muscle approach was implemented [
18], producing muscle LoAs which were implemented into the biomechanical model of AL 288-1. Note: while [
22] included the
M. psoas major (visualized here), it was excluded from the current study due to uncertainty over thorax reconstructions. LAR, long-axis rotation; FE, flexion/extension; ABAD, abduction/adduction. *[
22]; **[
11,
48].
Figure 2.
Here, Brassey et al. [
27] reconstructed pelvis (shown in purple) was modified (shown in grey), in which the sacroiliac and pubic joints were rearticulated. Specifically, the distance between the ischiopubic ramus was reduced and both Os coxae were internally rotated, thus improving sacroiliac articulation.
Figure 3.
Completed views (ventral, dorsal, lateral and medial) of the polygonal muscle modelling approach in AL 288-1, in which 36 muscles were created per lower limb—this total does not differentiate between muscles composed of multiple heads (i.e. the M. extensor digitorum longus). The polygonal muscles of AL 288-1 are shown in comparison to three-dimensional muscles of the human which were segmented from MRI scan data. Intrinsic muscles of the foot were not modelled; rather, only ‘foot' muscles which crossed the ankle joint were included due to the sparsity of preserved foot material. See electronic supplementary material, S2 for a diagram illustrating muscle origin and insertions in which the colours correspond to the muscle colours used here. Full muscle configurations shown here, refer to electronic supplementary material, S3 to visualize deep musculature.
The significance of this, and something creationists will need to dismiss for whatever reason they can settle on, is that it shows full bipedalism had evolved in an Australopithecine before the
Homo genus was on the scene. This means one of two things: either it had evolved in a common ancestor from which
A. afarensis and the
Homo genus evolved, or
A. afarensis is the ancestor of
Homo.
Of course, this doesn't settle the question of exactly where
A. afarensis fits in the ancestry of
Homo sapiens but is does help understand how and when what is now a uniquely human trait evolved.
And of course, Dr Wiseman shows no doubt at all that his findings have an explanation in the Theory of Evolution or that it requires a supernatural magician to explain it. And all this evolution took place millions of years before creationists believe Earth existed.
Thank you for sharing!
