In late November 2023, I travelled with colleagues from the the UK and France to Johannesburg, South Africa. We visited the hominin fossil collections at Wits University, toured the Cradle of Humankind and, more specifically, Sterkfontein cave system, attended a two day long workshop called BrAIn (evolution of the brain in our own lineage and the future application of AI technology to this field), and also managed a day off to head on safari! Wow, what a week! It was an utter dream come true to hold some of the palaeoanthropology’s most famous fossils AND to visit Sterkfontein to see where some of these fossils were found!!

Many many thanks to my funders: Leverhulme Trust and the Isaac Newton Trust.

In the photos below (from left to right), we can see the top of the excavations at Sterkfontein, followed by a necessary selfie (had to prove I was there, right?!). Then we have the team heading down into one of the caves. Next, we can see what that same view looks like, but facing the other direction from inside the cave! Finally, we have Dr Amelie Beaudet and Professor Dominic Stratford walking in the Cradle of Humankind towards Sterkfontein. If we look over towards the left of the photo (imagine you can see what the camera is cutting off), we have Kromdraii, Rising Star, Drimolen…. To the right, we have Swartkrans. I have spent over a decade learning and then researching these caves and I never realised just how close all these systems are – you can stand on top of the hill, spin in a circle and see them all!! For me, that was eye-opening and changed my perception a little about the hominin material from South Africa. I once thought this region was extremely vast, but knowing now that the area is much smaller than I thought, I’m now excited to think what else is out there in SA if most of what we have found to date comes from such a small geographic region!

Below, I share some photos from inside the vault at Wits itself! From left to right: happy me receiving my pass to work with the collections and standing at the entrance to the vault! I was very happy to finally see the famous Little Foot skeleton in person – that was a dream come true!! Next, we have Dr Julia Aramendi Picado scanning some specimens whilst Amelie and I stand by smiling (we were working, I promise!). Finally, we have the famous sediba skull. The preparation on this skull was phenomenal! Hats of to the preparators who evidently worked very tirelessly to expose this specimen.

So, what’s next? Well, I have a few months of data preparation and analysis to come… Watch this space!

Hot off the press – the soft tissue reconstructions of Lucy were published today in Royal Society Open Science – and the best part? ALL DATA IS FULLY OPEN ACCESS.

Read the press release here

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.

A Cambridge University researcher has digitally reconstructed the missing soft tissue of an early human ancestor – or hominin – for the first time, revealing a capability to stand as erect as we do today.

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.

Wiseman was able to use recently published open source data on the Lucy fossil to create a digital model of the 3.2 million-year-old hominin’s lower body muscle structure. The study is published in the journal Royal Society Open Science.  

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’s ability to walk upright can only be known by reconstructing the path and space that a muscle occupies within the body,” said Wiseman, from Cambridge University’s McDonald Institute for Archaeological Research.

“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,” Wiseman said.

“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.”

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). “Without open access science, this research would not have been possible,” said Wiseman.  

These reconstructions can now help scientists understand how this human ancestor walked. “Muscle reconstructions have already been used to gauge running speeds of a T-Rex, for example,” said Wiseman. “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.”

Written by Fred Lewsey and Ashleigh Wiseman

There was a busy start to 2023 with two new papers published!

Paper 1: We started off the year with our publication on quantitative biomechanics of the Euparkeria capensis pelvis and hindlimb – this is a Middle Triassic critter which may or may not have walked bipedally. We tested the pitch of this critter to establish if it could have maintained an erect posture, or if the pitch (i.e., downwards momentum) would have been too much and thus it could only have walked on all four legs (quadrupedalism).

We used musculoskeletal models and static simulations (i.e., a singular pose, no movement was modelled) to test the influence of body posture on locomotor potential. We show that the resulting negative pitching moments around the centre of mass were prohibitive for sustainable bipedality and thus conclude that it was unlikely that Euparkeria was facultatively bipedal, and was probably quadrupedal, rendering the inference of ancestral bipedal abilities in Archosauria unlikely.

Paper 2: Our next paper was published last month in The Journal of Experimental Biology as part of an invited review to celebrate ‘100 years of discovery’! The paper titled Modern three-dimensional digital methods for studying locomotor biomechanics in tetrapods provides an overview of modern 3D methods to investigate locomotion in tetrapods, ranging from discussions of inverse kinematics to robotics to finite element analysis! Check it out here!

Dr Edgard Camaros I Perez recently won funding to present a booth at the Science if Wonderful! outreach event in Brussels, hosted by the EU Commission, funded by the Marie Skłodowska-Curie actions. Edgard very kindly invited me along to join him and help host the booth. The event was wonderful! 4000 schoolkids from across Europe attended and had the chance to talk to scientists about different types of science and careers, ranging from physics to chemistry to archaeology to biomechanics to plant science, and of course everything in between!

Our booth was titled “Virtual Stories of our Human Evolution”. We brought along some 3D printed skulls and chatted to the students about how these individuals died and how attitudes towards the dead have changed throughout our evolution! We also brought the Arctec Spyder Laser Scanner along to demonstrate how we can create 3D models of fossils in the field and what we can do with those 3D models afterwards! As you can guess, the scanning was popular!!

Amazingly, we were also asked to present in the cinema – which was this wonderful room (see photo below) where students could come along to learn about a particular topic in more detail for 30 minutes. We chatted about fieldwork, data collection, virtual methods of scanning, where to find fossils and what to do with them once found. There was also a short segment that I presented on modelling movement in a fossil – how do we reconstruct muscles, how can we make a model move and also a bit about simulation training/interations to produce a working simulation that reflects reality – this of course involved many blooper reels of human simulations falling over, which the kids loved! It was a challenge to talk about this to an age group of 12-18, but I think Edgard and I nailed it! The cinema ended with us 3D scanning a kid wearing a monkey mask, much to the delight of the kid and all his friends! Many kids were filming this on their mobile phones, so I’m sure this exists on the internet somewhere!

In January I travelled to the NMK in Nairobi, Kenya to scan some fossil specimens. The trip as a whole was a such a wonderful experience – and one that I really hope I can repeat in the future! The opportunity to enter the vaults in the NMK and have a precious, 2.5 million year old hominin fossil placed in your hands was just soooo phenomenal! I, of course, have to thank the Leverhulme Trust for funding this research trip and Professor Marta Mirazon Lahr for making it all happen!

Here I am, very happily standing next to the Turkana Boy skeleton and the wonderful Tom Mukhuyu, who was doing an amazing job on updating the boxes and curation of the fossil. Thanks for all your help on picking out fossils, Tom!

Of course, a trip to Kenya wouldn’t be complete without a sneaky day off to head to the Nairobi National Park to drive on safari to spot some of the Big Five…! An all round amazing trip!

Next steps: putting digital skeletons back together! 🙂

3D volumetric muscle reconstruction of the Australopithecus afarensis pelvis and limb, with estimations of limb leverage

In this project, my main aim is to reconstruct the soft tissues of fossil hominins and then assess their locomotory capabilities… and I’m so pleased to announce that my preprint is finally available on BioRxiv! Before we can reconstruct movement, we first need to have a comprehensive overview of the musculature and its composition/space filling within the body. In this preprint, I recreated the musculature of the famous Australopithecus afarensis specimen AL 288-1’s (nicknamed Lucy) pelvis and lower limbs using the polygonal muscle modelling approach that my colleagues and I developed/published early in 2022 – see that paper here and the associated blog post here.

Don’t forget to check out the video of the muscles below!

For this part of my project, I first obtained scans of the AL 288-1 specimen and created a rigged skeleton – this means that joint centres and rotational axes were defined upon which movement can be animated. Polygonal muscles were then created in the software Maya Autodesk 2022 and a line of action was threaded through each 3D muscle to represent the muscles centroid. This permitted the creation of a musculoskeletal model for use in the biomechanical software OpenSim (for further details on the modelling approach, refer to the preprint or the blog post).

All pelvic, thigh, shank and most foot muscles were modelled (intrinsic muscles of the foot were omitted due to the scarsity of pedal remains in the fossil record). These polygonal muscles can be visualised in the below video:

The muscle origins (the proximal attachment) and insertions (the distal attachment) were identified using comparative dissection data of humans and chimpanzees, assisted by some muscle scarring on the bones and also via the creation of muscle map diagrams:

Sensitivity analyses confirmed the efficacy of the muscle paths and this data was compared to that of a human to assess the recruitment of muscle groups during joint rotations (at this stage, just the moment arms! Check back soon for the next steps…). The moment arm results suggest that muscle groups had comparable leverage to that of a human and, for now, no functional differences can be extracted, although this is not a limitation of the approach, but rather because only moment arms have been included which only tell a part of the story. Next up – we need to be looking at the dynamics of motion to extrapolate any functional differences!

I had a LOT of fun creating these 3D muscle reconstructions and I cannot wait to replicate the approach for other hominins!! I hope you enjoy reading the paper and exploring the muscles* as much as I had fun creating the models.

*all 3D data and scene will be made fully open access upon publication. Hopefully such tools will assist future biomechanical studies of hominins and perhaps even aid evolutionary anatomical teachings.

Our latest paper from the DAWNDINOS project has just been published – see it here! Our paper tackles a conundrum in evolutionary biomechanics – how can we accurately estimate the size (PCSA; Physiological Cross Sectional Area) of a muscle in fossil specimens when soft tissues do not preserve? And why is this important? Well, the PCSA of a muscle is correlated with the maximum force that a muscle can exert and if we underestimate such force then we might be understimating the true capability of an extinct species. And if we over-estimate? Then we have an over-bulked, Hulk-critter. Functionally speaking, we could inaccurately predict that a species was incapable of moving in a certain way. One long standing theory suggests that the size of the muscle’s attachment site is ~correlated to the PCSA of the muscle and that it might be possible to use the attachment site to calculate the PCSA. Whilst there’s a large scope of research out there testing such relationships in skulls, little research has yet tackled this problem in limbs.

In our latest paper, we tested the correlation between muscle attachment area and PCSA in five Nile crocodiles, six tinamous (both from the DAWNDINOS project), a wild turkey, a domestic chicken, an emu and an ostrich (the latter species were from John Hutchinson’s postdoc in 2001!). All specimens were dissected, attachment sites were digitised and we computed a whole bunch of statistics to ascertain the relatioship between the sites and PCSA (note: such approaches will make you develop a love-hate relationship with SPSS in the end!)

So… did we do it? Did we find the relationship? Well.. sort of. The ratios vary A LOT and are very much muscle-dependant. The ratios are not reliable across species (archosaurs), but were instead more similar within a species, hinting that for most muscles it is possible to apply a “one size fits all estimation approach”. We tested our prediction on crocodiles, tinamous, ostrich (a larger-body sized aves) and on the extinct Coelophysis. Our results are a mixed bag, with pros and cons. Importantly, our approach demonstrates that there is a lot we still don’t know about musculature and how to estimate muscle force for extinct species.

There’s definitely a lot more still to be said and done about such approaches and I wait with anticipation for future research which tackles such a problem!

Figure 8 from the paper. Figure shows reconstructed muscle attachment sites of Coelophysis bauri.

Last week, I returned to Le Rozel in Normandy, France – a site which is infamous for the discovery of many Neanderthal footprints (read more about it here). I conducted a few experiments (more about that in due course…), excavated a few exciting things (more about that in due course…), spoke to a few journalists, assisted in Open Days on site for tourists (see here), and had some of my experiments filmed for an upcoming documentary (to be released in France in December 2022) – what a busy and exciting week! Stay tuned for more information…

Reconstructing articular cartilage in the Australopithecus afarensis hip joint and the need for modelling six degrees of freedom

The first paper of my Leverhulme Trust funded project has just been published in Integrative Organismal Biology – Read the paper here!

A detailed post about the paper, methods and results can be found on the Projects Update page of this website, but the abbreviated version…

Example of rotational movement of the hip in the AL 288-1 specimen

To sum up (TLDR): We tested the articulation and possible osteological ROM of the AL 288-1 hip joint by modelling a static single axis translation to investigate increasing joint spacing, which was considered a proxy for measuring maximum cartilage thickness. We expanded upon this by including all six DOFs, thereby reflecting true joint movement. Whilst the resultant ROM maps were quite similar, there was a greater spectrum of viability in the six DOF simulation than the other simulations, in which the femur was capable of osteologically moving into a greater range of poses. With this spectrum of poses, AL 288-1 was capable of a repertoire of movements, such as erect bipedalism across a range of substrates at various speeds and vertical climbing. Overall, six DOFs are a requirement for modelling mobility in fossil hominins, otherwise the resultant functionality of a given joint may be wrong.

We conclude that the likely maximum joint spacing/cartilage thickness of AL 288-1’s hip joint was 2.448 mm which is on par with allometric scaling assumptions (i.e., the smaller bodied AL 288-1 has a more cartilaginous hip joint than the larger bodied human and chimpanzee). Similar estimates were also generated from the single axis translational simulations, despite some implied functional limitations.

The important bit: we cannot ignore translational movement of the hip when estimating the motion-capability of extinct species!

Want to read more? See the paper or the projects update page of this website.