How prehistoric water pit stops may have driven human evolution

How prehistoric water pit stops may have driven human evolution

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Lake Nakuru.
Brian Rutere

Matthew Robert Bennett, Bournemouth University and Mark O Cuthbert, Cardiff University

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.

Great rift valley.
Redgeographics, CC BY-SA

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.

The lakes of the African Rift Valley.
SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

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.

Mapping human migration.

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 Conversation

Matthew Robert Bennett, Professor of Environmental and Geographical Sciences, Bournemouth University and Mark O Cuthbert, Research Fellow in Groundwater Science, Cardiff University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Our controversial footprint discovery suggests human-like creatures may have roamed Crete nearly 6 million years ago

Our controversial footprint discovery suggests human-like creatures may have roamed Crete nearly 6m years ago

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Foot for thought.

Matthew Robert Bennett, Bournemouth University and Per Ahlberg, Uppsala University

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.

Cradle of humanity

The “cradle of humanity” has long been thought to lie in Africa, with most researchers suggesting that Ethiopia was where the human lineage originated. The earliest known body fossils that are accepted as hominins (members of the human lineage) by most researchers are Sahelanthropus tchadensis from Chad (about 7m years old), Orrorin tugenensis from Kenya (about 6m years old) and Ardipithecus kadabba from Ethiopia (about 5.8-5.2m years old).

Laetoli footprints.
Tim Evanson/Flickr, CC BY-SA

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.

Oldest known footpints.

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.

Alternative solutions

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.

The footprints.
Author provided

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.The Conversation

Matthew Robert Bennett, Professor of Environmental and Geographical Sciences, Bournemouth University and Per Ahlberg, Professor of Evolutionary Biology, Uppsala University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Engaged: to be or not to be? Or why bother with lecture notes?

There is nothing more dispiriting as a tutor than to look out at a sea of blank or vacant faces.  These days many hide behind expensive laptops, doing who knows what!  Attendance can be variable especially after the first flush of a new term is over.  As staff we are required to post our lectures and now under pressure to record our lectures.  The idea behind this by the way is that a student can return to key sections in the future.  In truth at least from my perspective if you are going to do this why run formal lectures at all?  Units might be better packaged as YouTube videos?  From a tutor’s perspective the equation is often simple, the more you give the less your students need to engage and attend.  May be this is not very fair but it is borne out by my own experience.

Whether it is with rose tinted glasses or not I believe I used to have stronger student engagement when I set out lecturing in the 1990s.  In those days (as in mine the decade before) a student needed to write notes or leave with nothing.  Attendance was much better and I believe so was student performance.  The introduction of a succession of Virtual Learning Environments (VLEs; currently Bightspace at BU) killed this to some extent.  Slides had to be posted.  Despite what others argue I believe strongly that the VLE weakens student engagement.  In the old days you had to write notes, you had to engage while these days you simply have to download the slides.  Or so the theory goes, until you encounter someone like me who’s slides are simply a pile of graphs, diagrams and pictures.  The narrative that goes with them is the bit you get by attending and engaging with the lecture.

I am a realist about such matters knowing that the competition between a cold lecture hall and a warm student bed is tough especially on a cold Monday morning in winter!  So from a student’s perspective let’s explore the question of engagement with lectures.  Why does it matter and what does engagement actually mean?

Well you go to university – rather than college or the like – to learn from those that are creating new knowledge.  To learn from the people active in your discipline area and driving research forward.  That is the theory at least and how it should be, especially if you are paying £9,000 plus for the privilege each year.  Your tutors should have pedigree either in professional practice or as academic researchers and if they don’t you have in my view the right to question this.  The difference between a textbook and real researcher is that you gain from their experience, from their perspective and ultimately from their knowledge and research which unlike a textbook is evolving all the time.  You gain this through lectures and in the case of geography/geology through fieldwork.  A lecture should be different every time, should refer to new literature and emerging debates.  It is by its nature unpredictable, if it is predicable then it has lost its relevance and has become simply an audio/video file and something that is static.  I am not here to teach, but to share my knowledge and to join with you in debating the latest ideas and to develop them together.  So the very best lectures should be unpredictable in a good way that is and that is why you need to attend and accept that they will divert from script and posted material from time to time and so they should.  If you don’t attend then you a missing out one of the key facets of a university education at least in my view, that and learning to think critically and communicate those thoughts.

So let us take as read that attendance is essential if at all possible, why else would we bother to schedule classes otherwise?  So the next question and one many students ask is should you listen or write notes?  Well if your lecturer is talking and talking fast as they do then verbatim notes are a waste of time, but capturing key points is not.  I am not talking about listening to them read PowerPoint slides; heaven help you if that is the experience you get.  In fact you have my sympathies and I would encourage you to push back if that is the case.

Some students seek to record lectures as a way around the problem – they talk to fast!  I am guilty of talking to fast and I am personally not opposed to having my lectures recorded, but unless there is a specific reason for doing so my advice is not to.  Why sit through the same talk twice?  Engage the first time.  If you don’t understand something when you review your notes then find a time to ask a question and seek help even if the cohort is large and the tutor is scary!  This is also part of the learning process.

Now our learning styles are all different so we are told frequently, and they may be, but there is a key step here that is true to most elements of life (and to the lecture) and we use every day in conversation – listen, think/reflect and respond through action.  It is the process of active listening and is evidenced by action.  In conversation it is the act of responding to what is said rather than just talking.  It is a skill that often needs to be learnt even by those who talk and gossip continuously. Whatever you’re learning style find a way to listen, distil/reflect and to record those thoughts.

Writing can be a challenge for some but writing/noting for oneself is a key way of engaging.  You just need to work out here what works best for you through some experimentation.  May be pictures, abbreviations, bullet-points or thought maps, there are loads of things to try.

Call me traditional but I would say that it is always a good idea (and an excellent habit to form) to write notes fast and legibly by hand for your own use.  They don’t have to look pretty!  There is certainly no point making them pretty after the event as long as you can read them, to do so is to waste time. The note writing skill is like any other and needs to be practiced and mastering it will serve you well in professional practice and later life.  Lectures allow you to practice this skill.  Writing fast is a useful skill for exams now and in the future for meetings, taking statements, receiving instructions and jotting down ideas and decisions.  Annotating printed PowerPoint slides is a common solution, but is not as good as listening and noting in your own words what is actually being said.  A slide is the lecturer’s summary not yours and yours is the one that counts, the one you will digest, understand and own.

Whatever you do find a way to engage in lectures and value them for what they are; a key part of your university educations and always remember there are good lectures and there bad lectures just as there are good days and bad days.

Academic writing I: Lots of opinions no right answers or dealing with uncertainty

In a previous post I wrote about the concept of ‘rhetoric’ and the interplay between the audience, the writer and the context (Fig. 1).  This helps explain why there is no right or wrong way to set about a piece of academic writing or coursework.  Ultimately the audience is always right and is often fickle.

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Figure 1: The use of rhetoric.

There are lots of reasons for this, different disciplines have their own way of doing things and everyone has their own personal ‘writing experience’.  Essentially they ‘do unto you, what was done (rightly or wrongly) unto them’.  Different bosses like things done in different ways and in truth most of your tutors at University will have different opinions.  These will depend on their academic history, how much they publish and where they publish.  As the phrase says ‘what is breed in the bone will out in the flesh’.

In the case of your boss you may be able to slowly challenge them and educate them into your (hopefully better) way of writing, but in most cases you will need to confirm to your audiences expectations.  Just because all your tutors are from the same faculty don’t assume that they all write in the same way or expect the same output.  Your audience will always have different perspectives, experiences and values.  Your tutors are all different and hurray for individuality!  In most cases therefore you are appealing to the likes and dislikes of your audience and to ‘like-minded’ readers, but it is always good to remember that if you always conform you cannot change minds and opinions.  Ultimately it is about the way you go about this.

The lack of certainty about what is required can be a nightmare for students.   You are not going to solve this however much you wish or demand conformity, so best to embrace it and work within the constraints that you do have.

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Figure 2: Your tutors are individuals each with their own perspective of how things should be done.

Figure 2 tries to crystallise this.  The known constraints are the assignment brief, the style guide to which you are working and your aim is to land the assignment in the ball-park remembering that each ball (i.e. tutor) is different.  They are kept broadly (and I mean broadly) by external examiners and professional benchmarks.  A good illustration of this is the use of the first person.  When I was a student and a young lecture the first person was a big no, for some academics it remains a no, but in the last 30 years this has changed and many journals now encourage the use of the first person.  In my own writing practice I embrace it.  There are people in my own faculty, however, who still think it is a huge sin.  This is an example of the uncertainty around how to land an assignment.  Well in this example the simple answer is to ask the tutor for whom you are writing and/or check out what the style is in the journals specific to their subject area or in which they write.  A bit of simple audience research can really help.  If a tutor tells you to never use the first person, take it with a ‘pinch of salt.’

This level of uncertainty is not just specific to Universities; you will find a similar set of uncertainties in professional practice to (Fig. 3).  And academics work with uncertainty in the form of the opinions of peer reviewers and their audiences all the time (Fig. 4).

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Figure 3: Landing your report in the right space.

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Figure 4: Landing an academic paper (publication) in the right space. 

So the first thing to remember is to know your audience and write for them within the formal and informal constraints that are set.

Now don’t get me wrong I am not in favour of just writing any old rubbish to conform and flatter your audience.  Some messages are easier however:

  • ‘I found the same as them!’
  • ‘We are doing a wonderful job.’
  • ‘This evidence supports your case.’
  • ‘This evidence supports your site model.’

It is much harder to challenge:

  • ‘We have to change the way we are doing things, and now!’
  • ‘The evidence doesn’t support the Boss’s view.’
  • ‘Your prime suspect couldn’t have done it!’

Conforming to your audiences views does not mean ‘rolling over’ but you need to tread carefully and build a strong evidence case when challenging the status quo.  The so called ‘tempered radical’ usually wins the day, if slowly.  The second lesson is to always evidence your claim and build a reasoned argument which considers alternatives and provides context.  You can conform to audience expectations while also punching them in the face!  Gently!

Uncertainty can extend to definitions of different types of written work.  Take the humble essay for example much loved as an assessment.  Personally I think that the use of sub-heading is appropriate to help provide some structure, but others argue that there should be none at all.  The dictionary is of little help:

‘Short piece of writing on a particular subject’

‘A short literary composition on a particular theme or subject, usually in prose and generally analytic, speculative, or interpretative.’

Generally, a piece of writing that gives the author’s own argument — but the definition is vague, overlapping with those of a paper or an article.  Formal essays are characterized by “serious purpose, dignity, logical organization, length,” whereas the informal essay has a more personal element.   Nowhere is the any guidance about the use of subheadings!  Now an essay is not a report.  A report is a more factual and any argument is confined to the discussion or conclusion once the data/evidence has been presented.  Here are some definitions but they are mine, not necessarily everyone’s!

  • Essay – a continuous piece of prose which explores/evaluates one or more concepts and/or develops an argument (a thesis or claim). The word thesis is not to be confused with a PhD or Master Thesis, but refers to a central claim or idea which is then argued.  Generally an essay may have broad headings to act as a guide and has a clear logical development of ideas normally around a single thesis.  It can contain general illustrations but is usually free from data.
  • Report – a factual description of a set of results (field and/or laboratory) followed by analysis and discussion of those results. Usually sub-divided into sub-headings following AIMRaD structure (Fig. 5): aims, introduction, methods, results and discussion. It normally contains data, graphs and analysis
  • Dissertation/thesis – an extended piece of work based on original research and/or a systematic review of secondary sources/literature.
  • Literature review – a structured summary and synthesis of previous work on a subject. Note this may be a component of a report, essay or dissertation.
  • Paper – in academic circles this normally refers to a peer reviewed and published paper/article. In some countries especially the USA it is synonymous with ‘essay/report’.

Again the key to dealing with uncertainty is to find out what your audience expects and wants and to give it to them.

AAFS Study Skills_Session#14_15_16

Figure 5: The classic AIMRad structure.

One of the hardest things to do is to write, especially when you are working with uncertainty, but writing is part of the creative scientific process.  It provides a way of working through your arguments and making your case.  Unfortunately there is only one solution and that is to practice and to never forget your audience.

Plate tectonics and driver-less cars?

If driver-less cars are the future then we had better take account of plate tectonics!  You have no doubt heard the stories “driver follows satnav instructions and ends up in a field!”  Well what about driver-less cars?  Their success is crucially dependent on Global Positioning Systems (GPS).  If you have a smart phone you have a GPS; by linking with one or more satellites a GPS can triangulate its position with varying levels of accuracy.  In a driver-less car you want to be sure that the car’s GPS is both accurate and linked to the road map, half a metre out and you could be facing the oncoming traffic! 

Maps and their datum’s

In the UK the Ordnance Survey has been making maps since 1747.  These maps are based on the British National Grid, a system of rectilinear lines (northings and easting) superimposed on the curved surface of the earth.  This is typical of what are known as country, or local-co-ordinate, systems.

Australia is no exception.  In the summer of 2016 it was reported (BBC, 29 July 2016) that Geoscience Australia was moving Australia so that the gap between its local co-ordinate system and that of global navigation satellite systems (GNSS) were in closer agreement.  When we way ‘moving Australia’ what they mean is moving the official longitude and latitude of the origin (zero point) of their local co-ordinate system.  The Geocentric Datum of Australia, the origin for the country’s local co-ordinate system, was last updated in 1994 since when Australia has moved about 1.5 m north due to plate tectonics.  Driver-less tractors are already a feature of some Australian farms so the problem is very real irrespective of what may or may not happen with respect to driver-less cars.

Plate tectonics is constantly and subtly re-arranging the World’s geography.  For example, the distance between London and New York is growing by about 5 cm each year, in a decade that is 50 cm and in a hundred years 5 m.  Plate tectonics is a big deal and is also an essential paradigm to understanding the Earth’s geological past.

Paradigms and gladiatorial science

A paradigm is a model or conceptual framework of ideas with which to organise and interpret observations and data.  It is bigger than a hypothesis, but less definitive than fact or theory.  Scientists make arguments; they advance explanations, models and ideas by reasoned and evidenced argument.  They articulate their ideas, garner supporting evidence and/or test them against that evidence.  In natural science there are few absolute rights and wrongs; it’s not like a maths problem in which you can look the answer up in the back of the book!

Inductive science involves observing and noting everything around you; in our case observing the natural world.  From that body of data you look for patterns, make logical inferences and deductions developing ideas which as they gather support become irrefutable and take on the status of fact or theory.  It is a philosophy of investigation that was first formalised by Francis Bacon (1561-1626) in 1620: one observes nature, proposes a modest law to generalize an observed pattern, confirms it by many observations, ventures a modestly broader law, and confirms that, too, by many more observations, while discarding disconfirmed laws.  In this way a laws grow ever broader but never exceeds the observations on which it is founded.  As a philosophy of science it is not without its problems.  Take the case of the hypothesis ‘do black swans exist?’  Any number of observations of white swans will not address the question, but find one black swan and the hypothesis is proven.

This alternative method of science is called ‘falsification’ – rather than gather supporting evidence for an idea how can you formulate a test that will disprove it?  In this view of science one is constantly working to disprove the ideas and models you propose.  It is a view of science proposed by Karl Popper (1902-1994) amongst others.

Thomas Kuhn (1922-1996) proposed in his famous book The Structure of Scientific Revolutions, influential in both academic and popular communities, that periods of normal science dominated by paradigms are overturned by periods of revolutionary science establishing new paradigms and renewed stasis.

Little did Alfred Wegener (1880-1930), a leading explorer and meteorologist of his time, know that he was laying the foundation for one of the biggest paradigm shifts in earth science when he proposed his idea of continental drift on the 6 January 1912.  Amassing palaeontological, lithological and structural evidence he proposed that continents had moved over the Earth’s surface in the past.  He famously pointed to the ‘jigsaw’ like fit of Africa and South America, something that Francis Bacon had noted previously.  He coined the term Pangea for a giant supercontinent that had once existed.

Science can be brutal, often gladiatorial; propose an idea that is too radical for the scientific establishment and they will turn and savage you.  That is what happened to Wegener and his ideas of continental drift were neglected until geophysical exploration of the ocean following the Second World War began to throw up new data.  On the basis of this data the paradigm of plate tectonics emerged in the late 1960s and early 1970s revolutionising our understanding of our planet both past and present .  One of the greatest scientific paradigm shifts of the twentieth century.  A number of popular reviews were published to mark the centennial anniversary the best of these is by Romano and Cifelli (2015) published in Science.

Finally I came across this wonderful song on YouTube the other day which celebrates Wegener’s contribution; I have no idea what he would make of it!

How to hunt a giant sloth

How to hunt a giant sloth – according to ancient human footprints

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: Alex McClelland, Bournemouth University

Matthew Robert Bennett, Bournemouth University; Katie Thompson, Bournemouth University, and Sally Christine Reynolds, Bournemouth University

Rearing on its hind legs, the giant ground sloth would have been a formidable prey for anyone, let alone humans without modern weapons. Tightly muscled, angry and swinging its fore legs tipped with wolverine-like claws, it would have been able to defend itself effectively. Our ancestors used misdirection to gain the upper hand in close-quarter combat with this deadly creature.

What is perhaps even more remarkable is that we can read this story from the 10,000-year-old footprints that these combatants left behind, as revealed by our new research published in Science Advances. Numerous large animals such as the giant ground sloth – so-called megafauna – became extinct at the end of the Ice Age. We don’t know if hunting was the cause but the new footprint evidence tells us how human hunters tackled such fearsome animals and clearly shows that they did.

White Sands National Monument.
Matthew Bennett, Bournemouth University, Author provided

These footprints were found at White Sands National Monument in New Mexico, US, on part of the monument that used by the military. The White Sands Missile Range, located close to the Trinity nuclear site, is famous as the birth place of the US space programme, of Ronald Reagan’s Star Wars initiative and of countless missile tests. It is now a place where long-range rather than close-quarter combat is fine-tuned.

Tracking the footprints.
Matthew Bennett, Bournemouth University, Author provided

It is a beautiful place, home to a huge salt playa (dry lake) known as Alkali Flat and the world’s largest gypsum dune field, made famous by numerous films including Transformers and the Book of Eli. At the height of the Ice Age it was home to a large lake (palaeo Lake Otero).

As the climate warmed, the lake shrank and its bed was eroded by the wind to create the dunes and leave salt flats that periodically pooled water. The Ice Age megafauna left tracks on these flats, as did the humans that hunted them. The tracks are remarkable in that they are only a few centimetres beneath the surface and yet have been preserved for over 10,000 years.

Footprint comparison.
David Bustos, National Park Service

Here there are tracks of extinct giant ground sloth, of mastodon, mammoth, camel and dire wolf. These tracks are colloquially known as “ghost tracks” as they are only visible at the surface during specific weather conditions, when the salt crusts are not too thick and the ground not too wet. Careful excavation is possible in the right conditions and reveals some amazing features.

Perhaps the coolest of these is a series of human tracks that we found within the sloth prints. In our paper, produced with a large number of colleagues, we suggest that the humans stepped into the sloth prints as they stalked them for the kill. We have also identified large “flailing circles” that record the sloth rising up on its hind legs and swinging its fore legs, presumably in a defensive, sweeping motion to keep the hunters at bay. As it overbalanced, it put its knuckles and claws down to steady itself.

Plaster cast footprints.
David Bustos, National Park Service

These circles are always accompanied by human tracks. Over a wide area, we see that where there are no human tracks, the sloth walk in straight lines. Where human track are present, the sloth trackways show sudden changes in direction suggesting the sloth was trying to evade its hunters.

Piecing together the puzzle, we can see how sloth were kept on the flat playa by a horde of people who left tracks along the its edge. The animals was then distracted by one stalking hunter, while another crept forward and tried to strike the killing blow. It is a story of life and death, written in mud.

Matthew Bennett, dusting for prints.
David Bustos, National Park Service

What would convince our ancestors to engage is such a deadly game? Surely the bigger the prey, the greater the risk? Maybe it was because a big kill could fill many stomachs without waste, or maybe it was pure human bravado.

At this time at the end of the last Ice Age, the Americas were being colonised by humans spreading out over the prairie plains. It was also a time of animal extinctions. Many palaeontologists favour the argument that human over-hunting drove this wave of extinction and for some it has become an emblem of early human impact on the environment. Others argue that climate change was the true cause and our species is innocent.

It is a giant crime scene in which footprints now play a part. Our data confirms that human hunters were attacking megafauna and were practiced at it. Unfortunately, it doesn’t cast light on the impact of that hunting. Whether humans were the ultimate or immediate cause of the extinction is still not clear. There are many variables including rapid environmental change to be considered. But what is clear from tracks at White Sands is that humans were then, as now, “apex predators” at the top of the food chain.The Conversation

Matthew Robert Bennett, Professor of Environmental and Geographical Sciences, Bournemouth University; Katie Thompson, Research Associate, Bournemouth University, and Sally Christine Reynolds, Senior Lecturer in Hominin Palaeoecology, Bournemouth University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How to build the perfect sandcastle

How to build the perfect sandcastle – according to science

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Now you can do it too.
Matthew Bennett, Author provided

Matthew Robert Bennett, Bournemouth University

Whether we prefer water sports or relaxing with a good book, the humble sandcastle is often a seaside must. But what’s the secret to building a majestic sandcastle that will withstand the tide of time? Luckily, there’s a scientific formula for that.

It all started back in 2004, when a holiday company asked us to investigate the question. As a sedimentologist, someone who studies fragments of rock, I began pondering what kind of beach would work best for castle building. To find out, I compared the sand from the ten most popular beaches in the UK at the time. Though in truth any sandy beach will do, Torquay came out top with its delightful red sand, closely followed by Bridlington, with Bournemouth, Great Yarmouth and Tenby tied in third. At the bottom of the league was Rhyl.

Having selected a beach one has to find the perfect spot. Now this is a question of taste rather than hard rules. Some might prefer a spot close to the car park with easy access when the rain arrives while others might want to stay next to a cafe. Others yet might hanker after the secluded fringes of the beach, perhaps sheltered by natural promontories of rock that keep the biting wind at bay.

Torquay harbour.
averoxus/wikipedia, CC BY-SA

Now a castle should be a symbol of military strength, but to stand proud one needs strong sand. The strength of sand depends on the properties of its individual grains and on the water between them. The more angular the grains, the better they will lock together. The more a grain is transported the more rounded it becomes. Microscopic shell fragments work well in this regard. The finer the grains the more they hold the water. And water matters.

Too much water and your sand will flow, too little and it will crumble. You need to get it just right and your castle will stand proud and last. It’s all down to the surface tension of water – the thing that gives the “meniscus”, or skin, to a glass of water and holds down that glass when placed on a wet bar top. The film of water between individual sand grains is what gives sand its strength, too much and it lubricates one grain over the other, but just right and it binds them strong.

The magic formula

Now the experimentation we did suggested that the perfect sandcastle requires one bucket of water to eight buckets of dry sand. Or if you want the magic formula: Water = 0.125 x Sand. So assuming that you don’t have any science gear with you, then you are looking for a spot close to the high tide line – usually marked by a line of seaweed and flotsam – and the low tide line where sand is still visibly wet and the waves are close. But remember that this will change as the tide comes and goes during the day.

High tide line.

My next tip refers to quality of your tools. In my experience there is a direct correlation between the age of the builder, spade size and the speed at which boredom sets in. Adult helpers find the smallest spade nothing but frustrating, and while young assistants might aspire to use the biggest spade, it is often too big to handle. A selection of tools will keep the workforce in harmony. The bucket also has to be the perfect size and shape. The best buckets are the simple round ones – not the ones with the fancy turrets which when turned out produce a castle in itself. A round bucket will allow you turn out countless towers and architectural features. A single bucket can be turned out several times to create a large mound from which you carve an amazing tower.

As you build, spare a thought to the story, not just of the castle one is building with its tales of derring-do, but also the story of the sand itself. Each grain is a fragment of rock and contains a story of relict mountains, ancient rivers, dinosaur-infested swamps and seas, of past climates and events which tell the amazing story of our planet. The red sand of Torquay once blew in giant sandstorms, as the area was once part of a desert far greater than that of the Sahara. The sand at Bridlington or Great Yarmouth tells a tale of giant ice sheets and drowned lands below the North Sea.

My next tip refers to size. Yes, size matters – at least in the game of sandcastles. The modest castle with perfect towers, battlements and moat is ok, but it is the huge castles which break the beach horizon that inspire awe and wonderment in people that pass by. Think big! Pebbles, shells, driftwood fragments and feathers all enhance a castle. And let’s face it: a castle is about being seen. And although there may be science behind the humble sandcastle, don’t forget to have fun building it.The Conversation

Matthew Robert Bennett, Professor of Environmental and Geographical Sciences, Bournemouth University

This article is republished from The Conversation under a Creative Commons license. Read the original article.