“There is no branch of detective science which is so important and so much neglected as the art of tracing footsteps.” Sherlock Holmes, Study of Scarlet.
Despite the fictional nature of Sherlock Holmes this statement rings true today. The study of footwear is neglected in modern forensic practice and does have much to offer. What it needs is an injection of technology and associated modern analytical tools. These tools are emerging from the digital revolution currently transforming vertebrate ichnology. Ichnology is the discipline of earth science which focuses on the study of trace fossils such as footprints. This book draws upon both disciplines (geology [ichnology] and forensic science) to show how the two have much to learn from each other especially with regard to the digital capture and analysis of footprints and footwear evidence.
This innovative book which is the culmination of research/innovation funded by the Natural Environment Research Council (NERC) and HEIF provides the practitioner with field and laboratory methods necessary for the collection, analysis and presentation of three-dimensional tracks (footprints) whether from a crime scene or a geological/archaeological excavation. It shows students, researchers and practitioners how to collect and analyse 3D data and take advantage of the digital revolution transforming ichnology. The book forms a natural methods focused complement to the successful text Fossilised Locomotion published by Springer 2014 and written by Professor Bennett.
The book is an illustration of Fusion in action combining professional practice, research and teaching. The team’s work is supported by the Home Office and National Crime Agency as well as several police forces and forensic units throughout the UK. Some of the contents have been co-created with students at BU and the volume will be used in teaching on a range of forensic science programmes at BU.
Here is a link to a piece written for the Nature Ecology and Evolution community. It gives some of the background to the sloth hunting story release in April 2018. Also since the publication of the Science Advances paper we have had another piece appear in Quaternary Science Reviews about the use of geophysics in detecting tracks.
In July of 2018 I was also involved in the rescue of some sauropod tracks on the Isle of Purbeck. It is a nice story and there is more on this to come in time. You can find out a bit about this ongoing work here.
There has been a lot of interest in our discovery of nearly-6m-year-old footprints on Crete, first reported by the The Conversation – suggesting that human ancestors could have roamed Europe at the same time as they were evolving in East Africa.
Sadly the site was vandalised in the last week, with four or five of the 29 tracks stolen. We are fortunate that many of the best tracks remain – the people who did it clearly didn’t know what they were looking for. Our guess is that they were simply intending to sell them.
The theft occurred despite the site being afforded protection under Greek heritage law and being in the care of local officials. Police, we are told, have made an arrest in connection with the incident, and it is hoped that the missing material will be returned soon. The damage, however, is irreparable.
The Cretan authorities moved swiftly to bury the site temporarily while a more permanent conservation solution, such as moving the entire surface, is sought. We are lucky that the whole area has been 3D-scanned with an optical laser scanner in high resolution as part of the original study. In due course this data will be made available via the Natural History Museum of Crete and the Museum of Evolution at Uppsala University in Sweden. So there will fortunately not be much of an impact on the research.
Yet the event is devastating. To understand the significance to someone who studies ancient tracks like these, consider it equivalent to an attempt to steal part of the Sphinx at Giza or vandals dislodging one of lintel blocks at Stonehenge.
Unfortunately, the theft and vandalism of tracks is nothing new. For example, there was a recent case on the Isle of Skye in Scotland of vandalised dinosaur tracks dating from around 165m year ago that lead to a police probe. The ethics around the collection and sale of fossils and artefacts is complex, and many of the great scientific collections today are based on collection and sales by amateurs in the past. Ultimately, it seems wrong to collect and sell artefacts that there’s only a limited number of.
But how can you conserve what is essentially a slab of soft rock, close to the sea and open to the elements? Oddly, erosion at such sites is to be encouraged because it often helps reveal new surfaces which may contain additional prints.
I did some research on this with colleagues and concluded that the only option is to excavate and digitally record them in 3D. This can be done either with a laser scanner or just with a digital camera in the field. Some 20 pictures of a track from different angles is enough to create a 3D image. These days 3D printers can easily create models for museums and for collectors.
Digital preservation is probably the key for the Cretan tracks as well. This worked well for the 2,100-year-old human footprints of Acahualinca
in Managua (Nicaragua), where the originals are perfectly preserved under a roof built over the site, and in an adjacent museum.
Perhaps the most controversial of conservation solutions has been to bury the world’s oldest confirmed hominin footprints – from Laetoli in Tanzania – which were first documented in the late 1970s. These tracks were buried as a way of protecting them from weathering and natural-decay.
There has been extensive debate about what should happen at this site and many scientists are unhappy about the lack of access. Plans for the site over the years have varied from an on-site museum to the removal of the whole slab to another site. The debate continues, but ultimately it is money that precludes a solution that would allow access to the public and scientists alike.
Indeed, the challenge is always money. It is expensive to erect and maintain protective structures, and to gain funds you need publicity to ensure that all the stakeholders involved are aware of the scientific, social and emotional value of a site.
One of the reasons for publicising the Trachilos tracks was not only to get the discovery debated in open scientific circles, but also to raise its public profile – thereby seeking better protection and ultimately its preservation in a local museum. That would bring visitors and fuel local revenue.
The trouble is the very publicity aimed to assist the site’s protection may have led to an enhanced perception of its monetary value. After all, the site had been known locally for years. Publicity though, is a double-edged sword and we have been lucky on this occasion to avoid the full length of its blade.
Western society has a rather specific view of what a good childhood should be like; protecting, sheltering and legislating to ensure compliance with it. However, perceptions of childhood vary greatly with geography, culture and time. What was it like to be a child in prehistoric times, for example – in the absence of toys, tablets and television?
In our new paper, published in Scientific Reports, we outline the discovery of children’s footprints in Ethiopia which show how children spent their time 700,000 years ago.
We first came across the question of what footprints can tell us about past childhood experiences a few years back while studying some astonishingly beautiful children’s footprints in Namibia, just south of Walvis Bay. In archaeological terms the tracks were young, dating only from around 1,500 years ago. They were made by a small group of children walking across a drying mud surface after a flock of sheep or goats. Some of these tracks were made by children as young as three-years-old in the company of slightly older children and perhaps young adolescents.
The detail in these tracks, preserved beneath the shifting sands of the Namibian Sand Sea, is amazing, and the pattern of footfall – with the occasional skip, hop and jump – shows they were being playful. The site also showed that children were trusted with the family flock of animals from an early age and, one assumes, they learnt from that experience how to function as adults were expected to within that culture.
No helicopter parents
But what about the childhood of our earlier ancestors – those that came before anatomically modern humans (Homo sapiens)? Children’s tracks by Homo antecessor (1.2m to 800,000 years ago) were found at Happisburgh in East Anglia, a site dating to a million years ago. Sadly though, these tracks leave no insight into what these children were doing.
But the footprints described in our recent study – from a remarkable site in the Upper Awash Valley of Southern Ethiopia that was excavated by researchers from the Università di Roma “La Sapienza” – reveal a bit more. The children’s tracks were probably made by the extinct species Homo heidelbergensis(600,000 to 200,000 years ago), occurring next to adult prints and an abundance of animal tracks congregated around a small, muddy pool. Stone tools and the butchered remains of a hippo were also found at the site, called Melka Kunture.
This assemblage of tracks is capped by an ash flow from a nearby volcano which has been dated to 700,000 years ago. The ash flow was deposited shortly after the tracks were left, although we don’t know precisely how soon after. The tracks are not as anatomically distinct as those from Namibia but they are smaller and may have been made by children as young as one or two, standing in the mud while their parents and older siblings got on with their activities. This included knapping the stone tools with which they butchered the carcass of the hippo.
The findings create a unique and momentary insight into the world of a child long ago. They clearly were not left at home with a babysitter when the parents were hunting. In the harsh savannah plains of the East African Rift Valley, it was natural to bring your children to such daily tasks, perhaps so they could observe and learn.
This is not surprising, when one considers the wealth of ethnographic evidence from modern, culturally distinct human societies. Babies and children are most often seen as the lowliest members of their social and family groups. They are often expected to contribute to activities that support the mother, and the wider family group, according to their abilities. In many societies, small boys tend to help with herding, while young girls are preferred as babysitters. Interestingly, adult tools – like axes, knives, machetes, even guns – are often freely available to children as a way of learning.
So, if we picture the scene at Melka Kunture, the children observing the butchery were probably allowed to handle stone tools and practice their skills on discarded pieces of carcass while staying out of the way of the fully-occupied adults. This was their school room, and the curriculum was the acquisition of survival skills. There was little time or space to simply be a child, in the sense that we would recognise today.
However, these observations contrasts to the story that emerged last year based on tracks from the older Homo Homo erectus (1.5m-year-old) at Ileret, located further south in the Rift Valley, just within the northern border of Kenya. Here the tracks have been interpreted as the product of adult hunting groups moving along a lake shore, rather than a domestic scene such as that at Melka Kunture. However, these scenes aren’t mutually exclusive and both show the power of footprints to provide a snapshot into past hominin behaviour.
But it does seem like the overwhelming parenting lesson from the distant past is that children had more responsibilities, less adult supervision and certainly no indulgence from their parents. It is a picture of a childhood very different from our own, at least from the privileged perspective of life in Western society.
A fossil footprint is one of the most evocative insights into the past. It can tell you not only about presence, but also about the biomechanics of the track-maker. We have studied ancient footprints from around the world for more than a decade – and perhaps most notably we were part of the team that discovered the second oldest human footprints at Ileret in northern Kenya in 2009. They date back 1.5m years and were likely made by Homo erectus.
Over the past ten years, we have witnessed unparalleled technological advances. We used to take a large, expensive and delicate optical laser scanner into the field, encased in a shroud specially made by a sail maker. I remember with horror how it exploded on the first day of one particular field trip.
It had been flown at great expense first to the Kenyan capital, Nairobi, and then on a small plane which landed on a dirt strip. But then, on its first day out, it was connected to a generator supposedly that had been repaired in a back street Nairobi shop – and the sparks flew. My colleagues had to infill the excavation and it was another six months before I was back out with a repaired scanner and a new generator.
These days, thankfully, we need nothing more than a digital camera in the field. We take 20 pictures from different angles and I have a 3D model to rival those I once created by physically scanning the footprint. And with far fewer headaches. In fact, in October, Microsoft demonstrated a 3D scanner that works on a smart phone – technology is changing fast.
Great leaps forward
Despite this, 3D models have yet to make an impact in some areas. One of these is in the analysis of footwear evidence at crime scenes. Here, traditional methods of photography and casting still prevail and footwear evidence is no longer routinely collected at many crime scenes. Yet it has real power, especially when brought into 3D – and the 21st century.
Footwear impressions provide an important source of evidence from crime scenes. They can help to determine the sequence of events and – if distinctive due to the wear patterns – can link a suspect to multiple crime scenes. The value is not only as a tool in prosecution, but crucially in intelligence gathering often around petty crime. Unfortunately, it isn’t being routinely used – at least until now.
Working with a talented team of software developers, we have now translated academic know-how and software developed for research into a freeware package that puts 3D tools into the hands of everyone. Over the past year, with funding from a Natural Environment Research Council Innovation Award and with the help of the Home Office and the National Crime Agency, we have developed DigTrace a bespoke software tool for footprint analysis. This tool is now freely available to police forces and forensic services both in the UK and overseas.
DigTrace is the first integrated freeware product that allows crime scene officers to capture 3D images of footwear impressions with nothing more than a digital camera and then to visualise, analyse and compare these traces digitally. It integrates fully with existing databases and approaches and we hope it will change the cost benefit equation of footwear analysis.
From the extraordinary to the everyday
The use of 3D modelling of this kind need not only be used in high capital crimes but can also be used to tackle the petty crime that often plagues society. Take, for example, a series of grass verges on the edges of car parks of ill repute. Using this tool, you can easily scan footprints in these areas. And if you can link the same piece of footwear to several of these disreputable areas, you know you are looking for one individual or group rather than several. The power lies in improving intelligence.
We’ve been developing the software for the better part of a decade. What started as a collection of tools for addressing specific research tasks, built using a variety of technologies, has now been consolidated with the help of NERC into a standalone software suite. There is some neat mathematics that underlies the various 3D transformations required. Keeping things simple, however, has been the key to building trust with end-users who are not computer scientists.
At the heart of the approach is the idea of digital photogrammetry – take a series of images, identify common pixels in each and triangulate the pixels to define their location in 3D space. The result is a 3D pixel cloud that can be scaled, transformed and surfaced. We are actively researching the enabling technology here at Bournemouth University to develop new tools from this basic premise. Creating 3D models from video and even CCTV footage is in our sights. Our aim is to provide tools that make society safer, not just from high profile-crime, but that which affects everyday lives.
While DigTrace may help fight crime, it is also there for geologists and archaeologists to help them study dinosaur or ancient human tracks. The use of 3D data is a brave new world from printing in 3D to developing tools that visualise and analyse such data – and it is helping to bring the recent, and most distant, past to life.
Our ancient ancestors seem to have survived some pretty harsh arid spells in East Africa’s Rift Valley over five million years. Quite how they kept going has long been a mystery, given the lack of water to drink. Now, new research shows that they may have been able to survive on a small networks of springs.
The study from our inter-disciplinary research team, published in Nature Communications, illustrates that groundwater springs may have been far more important as a driver of human evolution in Africa than previously thought.
The study focuses on water in the Rift Valley. This area – a continuous geographic trench that runs from Ethiopia to Mozambique – is also known as the “cradle of humanity”.
Here, our ancestors evolved over a period of about five million years. Throughout this time, rainfall was affected by the African monsoon, which strengthened and weakened on a 23,000-year cycle. During intense periods of aridity, monsoon rains would have been light and drinking water in short supply. So how did our ancestors survive such extremes?
Previously, scientists had assumed that the evolution and dispersal of our ancestors in the region was solely dependent on climate shifts changing patterns of vegetation (food) and water (rivers and lakes). However, the details are blurry – especially when it comes to the role of groundwater (springs).
We decided to find out just how important springs were. Our starting point was to identify springs in the region to map how groundwater distribution varies with climate. We are not talking about small, babbling springs here, but large outflows of groundwater. These are buffered against climate change as their distribution is controlled by geology – the underlying rocks can store rainwater and transfer it slowly to the springs.
We figured that our ancestors could have stayed close to such groundwater in dry times – playing a greater part in their survival than previously thought. When the climate got increasingly wet, groundwater levels would have risen and made springs more plentiful – feeding smaller rivers and leading to lakes becoming less saline. At this point, our ancestors would have roamed across the landscape free of concerns about water.
Life and death decisions
To test this idea, we embarked on a computer experiment. If the springs and water bodies are thought of as the rest stops, or service stations, then the linkages between can be modelled by computers. Our model was based on what decisions individuals would have taken to survive – and what collective behaviours could have emerged from thousands of such decisions.
Individuals were give a simple task: to find a new source of water within three days of travel. Three days is the time that a modern human and, by inference, our ancestors could go without drinking water. The harder and rougher the terrain, the shorter the distance one can travel in those vital three days.
We used the present landscape and existing water springs to map potential routes. The detailed location of springs may have changed over time but the principles hold. If our agent failed to find water within three days, he or she would die. In this way we could map out the migration pathways between different water sources as they varied through 23,000-year climate cycles. The map shows that there were indeed small networks of springs available even during the driest of intervals. These would have been vital for the survival or our ancestors.
The model also reveals movement patterns that are somewhat counter-intuitive. One would assume that the easiest route would be along the north to south axis of the rift valley. In this way, hominins could stay at the bottom of the valley rather than crossing the high rift walls. But the model suggests that in intermediate states between wet and dry, groups of people may have preferred to go from east to west across the rift valley. This is because springs on the rift floor and sides link to large rivers on the rift flanks. This is important as it helps explain how our ancestors spread away from the rift valley. Indeed, what we are beginning to see is a network of walking highways that develop as our ancestors moved across Africa.
Human movement allows the flow of gossip, know-how and genes. Even in modern times, the water-cooler is often the fount of all knowledge and the start of many budding friendships. The same may have been true in ancient Africa and the patterns of mobility and their variability through a climate cycle will have had a profound impact on breeding and technology.
This suggests that population growth, genetics, implications for survival and dispersal of human life across Africa can all potentially be predicted and modelled using water as the key – helping us to uncover human history. The next step will be to compare our model of human movement with real archaeological evidence of how humans actually moved when the climate changed.
So next time you complain about not finding your favourite brand of bottled spring water in the shop, spare a thought for our ancestors who may died in their quest to find a rare, secluded spring in the arid African landscape.
This research was carried out in partnership with our colleagues Tom Gleeson, Sally Reynolds, Adrian Newton, Cormac McCormack and Gail Ashley.
The human foot is distinctive. Our five toes lack claws, we normally present the sole of our foot flat to the ground, and our first and second toes are longer than the smaller ones. In comparison to our fellow primates, our big toes are in line with the long axis of the foot – they don’t stick out to one side.
In fact, some would argue that one of the defining characteristics of being part of the human clade is the shape of our foot. So imagine our surprise when we discovered fossil footprints with remarkable, human-like characteristics at Trachilos, Crete, that are 5.7m years old. This research, published in the Proceedings of the Geologist Association, is controversial as it suggests that the earliest human ancestors may have wandered around southern Europe as well as East Africa.
The period corresponds to a geological time interval known as the Miocene. The footprints are small tracks made by someone walking upright on two legs – there are 29 of them in total. They range in size from 94mm to 223mm, and have a shape and form very similar to human tracks. Non-human ape footprints look very different; the foot is shaped more like a human hand, with the big toe attached low on the side of the sole and sticking out sideways.
The footprints were dated using a combination of fossilised marine microorganisms called foraminifera and the character of the local sedimentary rocks. Foraminifera evolve very rapidly and marine sedimentary rocks can be dated quite precisely on the basis of the foraminifera they contain. These indicated an age somewhere in the span 8.5m to 3.5m years. However, at the very end of the Miocene, about 5.6m years ago, an extraordinary thing happened: the entire Mediterranean sea dried out for some time. This event left a clear signature in the sediments of the surrounding areas. The sediments that contain the footprints suggest they probably date to the period immediately before this, at about 5.7m years.
The oldest known footprints, however, were found at Laetoli in Tanzania and come from the next geological time interval, the Pliocene. These are some 3.66m years old and even more human-like than those of Trachilos. The second oldest tracks are those at Ileret made by Homo erectus (1.5m years old), and are little different from the tracks that we ourselves might make today.
If – and for many it is a big if – the tracks of Trachilos were indeed made by an early human ancestor, then the biogeographical range of our early ancestors would increase to encompass the eastern Mediterranean. Crete was not an island at this time but attached to the Greek mainland, and the environment of the Mediterranean region was very different from now.
The discovery comes just months after another study reported the discovery of 7m-year-old Greek and Bulgarian fossil teeth from a hominin ape dubbed “El Graeco”. This is the oldest fossil of a human-like ape, which has led some to suggest that humans started to evolve in Europe hundreds of thousands of years before they started to evolve in Africa. But many scientists have remained sceptical about this claim – as are we. The presence of Miocene hominids in Europe and Africa simply shows that both continents are possible “homelands” for the group. In theory, El Graeco could be responsible for the Trachilos foorprints but without any limb or foot bones it is impossible to tell.
But there are other ways to interpret the findings. Some might suggest that the distinctive anatomy of a human-like foot could have evolved more than once. The tracks could have been made by a hitherto unknown Miocene primate that had a foot anatomy and locomotive style not unlike our own.
There are examples throughout the fossil record of what is called “convergent evolution” – two unrelated animals developing similar anatomical features as adaptations to a particular lifestyle. However, there is nothing about the Trachilos footprints themselves that suggests such convergence.
Convergence rarely produces perfect duplicates; rather, you tend to get an odd mix of similarities and differences, like you see when you compare a shark and a dolphin for example. Now, imagine if the Trachilos footprints combined human-like characters with a few other characters that simply didn’t “fit”: for example, that the toes looked human-like but carried big claws. This would be a reason to suspect that the human-like features could be convergent. But the Trachilos footprints don’t show any such discordant characters, they simply look like primitive hominin footprints as far as we can tell.
For those unable to see beyond Africa as the “human cradle”, these tracks present a considerable challenge, and it has not been easy to get the discovery published. Some have even questioned whether the observed features are footprints at all. However, collectively, the researchers behind this study have published over 400 papers on tracks, so we are pretty confidence we know what they are.
Although the results are controversial, suggesting that the rich East African evidence for early hominids may not be telling the whole story, it’s important that we take the findings seriously. The Trachilos tracksite deserves to be protected and the evidence should be debated by scientists.
It is now for the researchers in the field to embark on finding more tracks or, better still, body fossils that will help us to better understand this interesting period of primate diversity, which ultimately led to our own evolution irrespective of where this first happened. The very essence of this type of science is prospection, discovery, evidence-based inference and debate. We are sure that this paper will stimulate debate; let us hope that it also stimulates further discoveries.