Human Environmental Footprint Reaches Far Back in Time

You’d literally have to be a cave dweller to be oblivious to the major global environmental changes happening in the world today.

It reads like a litany of crimes against the planet:

  • The many and far reaching impacts of global warming.
  • Disruption of the planet’s chemical cycles, such as carbon, nitrogen, phosphorous and others.
  • Air pollution from combustive sources.
  • Light pollution from our 24-hour cities.
  • Clearing and cultivation of the land and the ensuing loss of biodiversity.
  • Erosion and siltation of waterways.
  • Overfishing of the seas and oceans.
  • Introduction of exotic species and their disruption of ecosystems.
  • Plastic pollution and acidification of the oceans.
  • Synthetic chemical and pharmaceutical pollutions of land and water, such as antibiotics.

We’ve apparently even slightly altered the planet’s rotation because of the billions of tons of water we’ve locked up in dams over the last 40 years, with many more planned for the coming decades.

A new epoch

The changes made by us to the planet are so profound now that geologists are debating whether to recognise this period of human-induced planetary change as a whole new phase in the Earth’s timeline: dubbed the ‘Anthropocene’.

Next year the International Commission on Stratigraphy, a committee of the International Union of Geological Sciences, the group that compiles the Geological Timescale, will decide whether to adopt the Anthropocene as a new epoch in Earth’s history.

This proposed new phase in the more than four-and-a-half billion year history of the Earth would mark for the first time a catastrophic phase of disruption of the planet’s major systems as a the result of the activity of a single species, us; Homo sapiens.

In the past, the Earth and life were rarely disrupted on a global scale, but when they were it was from by extraterrestrial impacts such as asteroids and meteorites or due to the cooling of the planet’s layers early in its history.

These led to the loss of large numbers of species, shaping the course of the history of life and the planet itself.

Without these major extinction events we simply wouldn’t be here as a species.

The beginning of the Anthropocene is generally regarded to be the year 1800, roughly coinciding with the start of the Industrial Revolution in Europe.

But, this seems like a rather arbitrary break point when we cast our eyes into the prehistoric past.

Too many mouths to feed

When did we start altering our environment to suit ourselves?

Well, we know that humans were responsible for changing the environment well before the Industrial Revolution began, many thousands of years before in fact.

One of the keys to understanding our growing impact on the environment is population growth.

Warren Hern of the University of Colorado estimated in the late 1990s the number of times the human population has doubled in its history.

He estimated that at 3 million years ago our population was doubling in size about every 500,000 years.

And by a million years ago the human population was doubling in size roughly every 100,000 years.

A big shift occurred around 25,000 years ago when our population began to double every 5,000 years or so; and the doubling time from then onwards started to shorten even more dramatically.

Between 10,000 years ago, roughly when farming began, and today, the human population has seemingly doubled almost 11 times leading to the presently more than 7 billion human inhabitants of the planet.

So, the human population has doubled as many times in the last 10,000 years as it did for the previous 390,000 years of our evolutionary history.

Demise of the megafauna

Now, this kind of modeling exercise might seem a little abstract, perhaps far removed from the realities of science or troubles of the planet.

Yet, some scientists think these massive increases in human population were the key reason why the much of the world’s megafauna went extinct between around 50,000 and 10,000 years ago.

This major extinction ‘event’ in Earth’s history saw the loss of at least 200 mammal species weighing over 44 kilograms over a 40,000 year period.

This included our close evolutionary cousins the Neanderthals, Deniosvans, and probably other bipeds as well.

As humans began to spread across the planet from our African birthplace around 70,000 years ago – probably because our population grew rapidly – we began to spill into Asia, Australia, Europe and eventually the Americas.

As we did so, our population grew even more; and we burned the landscape and introduced exotic species and diseases to most of the places where we settled.

We may even have taken advantage of the apparently unfearing megafauna, who probably didn’t recognise us as predators, and hunted them to oblivion.

The slow reproduction rate of the megafauna mammals meant they couldn’t adapt to human impacts and their populations probably collapsed; maybe not overnight; but certainly rather quickly on an evolutionary timescale.

Some scientists see parallels with the megafauna collapse and the Anthropocene.

A human population that has doubled in size more than 11 times since the end of the Ice Age; taking with it another 90 megafauna species that had managed to survive the great Ice Age megafauna collapse, but unable to survive the havoc we have wreaked since the invention of farming 10,000 years ago.

Stone pavements in the desert

The evidence for human alteration of the environment goes back much further though, with the crafting of the earliest stone tools, and may be even fire, at least 2.5 million years ago.

Earlier this month, Rob Foley and Marta Lahr from Cambridge University described in the journal PLoS One an archaeological site in remote Libya called Messak Settafet which shows pre-human populations were changing the environment for hundreds of thousands of years in the one place.

These early humans, belonging to species different to us – perhaps Homo erectus or Homo heidelbergensis – left stone tools and the waste of tool-making on the ground, building up over hundreds of thousands of years, perhaps beginning 900,000 years ago.

Remarkably, the ground at Messak Settafet is strewn in places with as many as 75 tools per square metre; it is, they suggest, a “pavement” of tools and manufacturing waste.

I’ve seen other sites in Africa myself where everywhere you turn you’re literally walking over hundreds of the tools left by our ancestors hundreds of thousands of years ago.

You get a sense at these places, in Africa mostly, that humans have been around for a very long time, and sometimes in abundance in the landscape: we’ve left our mark everywhere.

Connections in deep time

The more we learn about our deep time past the more we realise that humans and our ancestors have been altering the environment for as long as we’ve existed; as our ancestors did before us for hundreds of thousands, perhaps millions, of years.

The difference today is that there are more than 7 billion of us, and thanks to science, we’re acutely aware of what we’re doing; ignorance is no longer a defence.

Optimistically, with knowledge comes solutions and hope; we can learn from our past and take heart in the fact that change, in behavior, culture and technology, has served us well for millions of years.

Age of Jawbones Mean the Origins of Humans Just Got Older

There’s plenty of excitement this month amid reports that scientists had identified the “dawn of humankind” in the Rift Valley of Ethiopia.

With reports this discovery of a jawbone could “rewrite the history of human evolution” you might well imagine, my hyperbole detector became instantly aroused.

Putting aside the hype that always accompanies discoveries in human origins research, this turned out to be, refreshingly, an important discovery that dramatically shifts debate on the beginnings of the human genus.

In fact, by uncanny coincidence I assume, two scientific studies bearing on this same issue were published in Nature and Science within a day of each other.

(Image Credit: Brian Villmoare).

A handy find

In Nature we learnt from Fred Spoor and his team that the type fossil for the early species Homo habilis (the “handy man”), which in this case is a lower jaw dubbed Olduvai Hominid 7 (OH7), could be repaired and its anatomy made more accurate using a 3D-CT-scanning approach.

The fossils belonging to Homo habilis were mostly found at Olduvai Gorge in Tanzania by Louis and Mary Leakey during the 1950s and 1960s, with some similar looking bones found a couple of decades earlier in caves near Johannesburg by Robert Broom and John Robinson.

Spoor’s study found that OH7 was a lot more primitive than had been thought since it was described – and named the “handy man” by Louis Leakey, Phillip Tobias and John Napier more than 50 years ago.

Spoor and his colleagues compared this roughly 1.8 million year old jawbone to other examples of primitive Homo, living humans and other apes. They did this to gauge just how variable these early pre-humans may have been, and whether they might sample multiple evolutionary lines, or species.

And they clearly identified several early species of Homogoing back to before 2.3 million years ago, with some of them (not OH7 though) being very modern in the structure of their face and jaws, or remarkably human-like.

Pushing Homo back in time

The Science study published by Brian Villmoare and colleagues showed the origin of Homo could now been pushed back by almost half a million years to at least 2.8 million years ago, with the discovery of a new jaw at Ledi-Geraru in the Rift Valley of Ethiopia during fieldwork in January 2013.

This fossil is a real beauty! It’s largely complete, and overall its physical traits are surprisingly rather modern. The jawbone is not very rugged and fine details of the tooth crowns and pattern of wear on the teeth are rather precocious, hinting at features seen in much later Homo species.

If you’re a human evolution buff like I am, then this is the kind of discovery that truly gets the heart racing. It shifts the ground dramatically and excitingly overnight.

Why? Well, first of all, we simply don’t have that many fossils from the crucial temporal window of 2-3 million years old, especially in East Africa.

Second, the human genus is now getting dangerously close to 3 million years old, much, much, older than current scientific models or textbooks state.

Third, we can largely throw the popular models of climate change used to explain the beginnings of Homo out the window: the Ledi-Geraru jaw is too old to be explained by the onset of global cooling or a shift to more open vegetation in Africa. But it may coincide with a regionally arid ecology.

Fourth, despite the record breaking hyperbole that surrounded discoveries such as Australopithecus sediba, this South African species dated around 1.98 million years old is clearly in the wrong place at the wrong time to be the ancestor of Homoas I stated just two years ago.

The Ledi-Geraru fossil also sidelines the other chief contender for Homo ancestry, Australopithecus garhi. This is a 2.5 million year old species also found in the Ethiopian Rift, on the grounds of its younger age and different anatomy.

The Homo-like features of the bones of sediba and garhi do tell us something important though: there was a lot of diversity in these early pre-humans and that some of their features must have evolved in parallel with Homo probably owing to the species facing similar ecological challenges.

Finally, the new study of OH7 and the discovery of the Ledi-Geraru jaw together show there was, as many of us in the business have been arguing for a long time, numerous species of Homo and Australopithecus in Africa in the period 1 to 3 million years ago.

Just 18 months ago I again found myself criticising another glib study involving a new fossil from Dmanisi in Georgia claiming that more than a dozen species of Homo should be sunk into a single evolutionary line leading to living people.

It’s amazing to think that studies like this and the interpretations of the sediba discovery can be shown to be incorrect so quickly. But, then again, there is often a lot more at play than just the science.

Words, Genes, and the Science of Past Human Deeds

New research reveals a clear link between the ancient spread of European languages and people, while other findings challenge the reliability of commonly used DNA for human ancestry studies altogether.

(Image: Wikimedia Commons)

Human languages have also long been known to be a marker of human cultural affiliation and biological ancestry, used by linguists and archaeologists alike as a marker of human population movements in the deep past.

A textbook example of this is the spread thousands of years ago of Indo-European languages, which are today spoken by a diverse range of people spread from South Asia to the Middle East, and throughout much of Europe.

Linguists and archaeologists have developed two major and competing models to try to explain the origins of this large language family:

  1. The Indo-European languages may have begun 5500-6500 years ago with the early pastoralists (animal herders) of the Pontic-Capsian steppe: a vast region running from the northern shores of the Black Sea, east to the Capsian Sea, and covering countries like Moldova, western Ukraine, and part of Russia and Kazakhstan.
  1. Alternatively, they may have their origins with the early farmers of Anatolia some 8000-10,000 years ago, spreading into Europe and other regions with the dispersal of early farming culture and domesticated plants and animals.

Two new studies examining the history of the Indo-European languages have independently confirmed the first of these ideas, the so-called ‘Great Steppe’ model.

The first new study, by Chang and co-workers published in the journal Language, used a new rigorous method to develop an ‘evolutionary’ language tree based on the changes in vocabulary through time, and incorporating ancient and medieval languages.

Its strength seems to be in its statistical rigor and more accurate estimates of the pace of change through time in these languages and the production of a more reliable ancestry tree.

In the second study, a large team led by Wolfgang Haak at the University of Adelaide’s Australian Centre for Ancient DNA, and published on the preprint server bioRciv, extracted and analysed the nuclear DNA of 69 skeletons from Europe dating between 3000 and 8000 years old.

While, again, their worked confirmed the Great Steppe model for the origins of Indo-European languages, it also showed that the genetic history of the people speaking these languages in Europe was far more complicated than anyone had thought before.

Around 8000 years ago, Western Europe seems to have been inhabited by farming people whose ancestry was distinct from the hunter-gatherers of the region. In the steppe region of Eastern Europe/Central Asia, the opposite situation applied, the area being occupied by nomadic foraging people.

By about 6000 years ago, people with hunter-gatherer ancestry had seemingly reoccupied Western Europe, while in the steppe region, the earlier hunter-gatherers had now been replaced by herders.

At about 4500 years ago, a massive migration of people from the great steppe region seems to have occurred into the centre of Europe, with the result being that today many European speakers of Indo-European languages are descended from these Eastern European/Central Asian animal herders.

For decades, archaeologist and linguists have debated whether the spread of Indo-European languages was by farmers replacing hunter-gatherers as they spread across Europe, or whether nomadic foragers simply threw away their spears and picked up a sickle instead.

These new studies shows it may actually have been a complex and drawn-out mixture of both.

History misread from mitochondrial genes?

With the development of genetic sequencing technology in the 1980s, allowing the DNA code to be read directly, scientists began to test and develop models of human evolution based previously on the fossil record.

The marker of choice at this time was mitochondrial DNA, championed by geneticists as providing a simple and reliable indicator of recent evolutionary history.

Mitochondrial DNA is abundant in the human body. It is contained within hundreds or thousands of mitochondria contained within each cell, their numbers varying according to tissue type (i.e. blood cells, liver cells or muscles etc.).

This kind of DNA sits within the mitochondria of our cells, organelles that act as the power stations for each cell, contrasting with nuclear DNA (or our ‘genome’) found only within the nucleus.

Human mitochondrial DNA is small, containing 37 genes, while our nuclear DNA houses close to 25,000 genes.

While nuclear DNA mixes up (recombines) during the production of new cells, some of which become eggs and sperm, mitochondrial DNA doesn’t shuffle about.

Furthermore, we all inherit the mitochondrial DNA contained within other mothers’ ovum, making it a marker of maternal evolution.

Pioneering early studies of the genetic origins of living people by Rebecca Cann and Alan Wilson during the mid-1980s used mitochondrial DNA to show that our species had evolved in Africa tens of thousands of years before we left the continent and settled the rest of the planet.

This was the so-called ‘mitochondrial Eve’ model, and it confirmed one of two major competing theories developed from painstaking studies of fossils –the ‘Out-of-Africa’ theory.

Since this time, mitochondrial DNA has also come to play a major role in forensics and the identification of criminals from human biological samples left at crime scenes or on clothing.

It is also now a major source of information for ‘mail order’ genotypic companies offering popular tests of genetic ancestry for a few hundred dollars, such as the National Geographic’s Genographic Project.

Genetic ancestry or a molecular horoscope?

The widespread use of mitochondrial DNA for these purposes now sits under a cloud following a major study by Leslie Emery and colleagues published in the Journal American Journal of Human Genetics.

They undertook a large-scale global comparison of human mitochondrial DNA with some nuclear genome sequences and got some very sobering results.

Emery and her team studied hundreds of DNA samples from people representing many of the world’s major geographic populations and discovered that in most cases their mitochondrial DNA actually provided very little information about ancestry compared with their nuclear DNA.

At least a third of the mitochondrial DNA makers from various populations across the globe failed to accurately predict people’s geographic continent of origin – say ‘African’ or ‘European’ – or ancestry within a particular continental region – like ‘Northeast Asian’ or ‘Southern African’.

Emery and colleagues concluded that mitochondrial DNA offered an “incomplete” picture of people’s ancestry and called for greater information about the complexities and inaccuracies of DNA results from commercial ancestry-testing to be conveyed to consumers.

This follows on from an article in March of 2013 by the BBC that described some DNA ancestry testing as akin to “genetic astrology”; based on an article warning of the pitfalls of genetic testing posted by the Sense About Science website.

While this new study doesn’t go quite that far, it’s take home message is a powerful one that should resonate with scientists working on human evolution and forensic science, and consumers parting with their cold hard cash for a ‘personal’ DNA history wherein the technology promises much more than it can really deliver.

Baby with the bathwater?

Genetics will continue to surprises us with its major and often unpredictable insights into our collective, deep time, human past.

But sometimes, the surprises even threaten to overturn major branches of genetic research itself. Such is the self-correcting nature of this intellectual juggernaut we call science.

The Curious Story of the Human Backside

The human posterior is rather peculiar compared with the backsides of our close primate cousins. Its unusual form tells the story of our evolution like no other part of the human body.

(Originally published by Australasian Science:  Image Credit: Sculpture by Alfredo Ceschiatti; Image from Wikimedia Commons and modified by author.)

Few parts of the body elicit such a mixed reaction as the human backside. We have an uneasy relationship with this most fundamental of human structures, as is clear from the many colourful terms we have for it in the English language: words like bottom, bum, rear end, fundamentum, posterior, buttocks and arse.

In many cultures, taboos about it preclude us from exposing this part of our anatomy in public unless it is thinly veiled beneath swimwear or, for the more daring, divided up the middle by a thong.

Only in the privacy of our homes, a gymnasium change room or at a nudest beach can we dare to expose that reviled and most mocked of all human features, the gluteal cleft, also known as the bum crack.

We are attracted to it and yet also repelled by it. The shape of our bum distinguishes us as male or female, and has historically been an object of sexual desire used to manipulate the opposite sex. We compare its shape to fruit – as in a woman’s peaches – and talk about men as having no bum at all.

We even use it as a term to describe someone who is a useless layabout or, worse still, somebody who treats people rather badly. At the same time it provides the opening for our gastrointestinal tract, for the removal of solid and gaseous body waste, and is perilously close to our genitals, barely hiding them from behind.

The more talented among us can even play the national anthem or the latest pop music using its more vocal-like qualities: usually a male pastime, I might note.

Yet, in the story of our evolution it seems the backside is an afterthought, rarely mentioned in the textbooks, given a bum steer if you will, neglected despite its vast store of information about our evolution.

Well I’m here to fight a rearguard action, to cast your eyes below the waistline sunshine, to defend the bum!

Why Do We Even Have a Bum?

Our backside is literally just that, part of the back, posterior or dorsal side of our bodies. At the lower end of our trunk, the bones of the hips or pelvis connect the spine to the lower limbs. They allow movement via our hip joints, and many of the muscles that move the thigh are strung from the pelvis to the femur.

Without them we couldn’t walk, run, climb or jump. The standout anatomical feature for all members of the human evolutionary branch is our upright posture and twofooted walking. It defines us as a group of primates, as hominins, or bipedal apes.

The human pelvis is fundamentally different to other apes because our ancestors evolved to walk upright: it is shorter (top to bottom), wider (side-to-side) and deeper (front to back) than a chimpanzee’s or gorilla’s, species evolved for four-limbed (or quadrupedal) locomotion.

Unsurprisingly, many of our walking and running muscles attach to it in ways that are different to other apes. Thus, the shape of the pelvic bones and the different positioning of these muscles, especially our gluteals, is the beginning point for the difference in the shape of our backsides compared with a chimpanzee’s.

Moreover, chimp bums have built-in cushions of fat called ischial callosities, for them to sit on; these features are lacking in us and our gorilla cousins.

A Difficult Birth

The pelvis also provides a protective enclosure for some of our vital organs as well as the nerves and blood vessels that pass to and from our lower limbs. It provides the attachments for the pelvic sling that suspends our external reproductive organs and the opening for our gastrointestinal tract and urethra emptying our bladders. And it also provides passage for babies when we give birth.

When brain size began to increase in our ancestors from around 2.0 million years ago, a further complication emerged for the pelvis: the need to give birth to larger-headed babies would have led to more complicated and dangerous deliveries.

To allow this to happen more safely, the pelvic outlet needed to become wider. There are a several ways in which natural selection could make this occur: first, through widening the pelvis from side-to-side or front-to-back; or second, by enlarging the average body size, and with it pelvis size, for the adults of this new, larger-brained species.

Both adaptations would have had costs, of course, and would also have affected both sexes because of shared genes. A larger pelvis would result in a less energy-efficient style of walking, but in a larger body, especially one with longer legs, this can be offset with a longer stride and lower metabolic costs. A short-statured, wide-hipped biped can’t cover much ground when it walks, and would use a lot of energy doing so.

So, it’s probably no coincidence that significantly larger brains evolved along with increased stature and relatively longer lower limbs. Human babies are also very immature compared with most other mammals when they are born.

In part this results from the slowing down of brain growth in the womb towards the end of gestation to make birth somewhat easier. Thus the size of the maternal pelvis acts to stall growth. It also leads to a rapid period of “catch up” brain growth after birth.

It Took Guts

Another peculiar aspect of our bodies is our much shorter gastrointestinal tract, much of which is contained in the pelvic cavity and of course ends at the backside. While the human stomach is about the same size as a chimpanzee’s, our small intestine is more than twice as long and our large intestine only about half the length of a chimp’s.

Our gut doesn’t bulge out like an ape and our caecum and colon are small as we don’t need to ferment bulky plant food. The reason for this shift in gut proportions was a change of diet to high quality, energy-rich items like starchy vegetables and meat.

Genetic research suggests that some species of tapeworm that infest millions of people around the world each year may also have evolved at this time, making humans a definitive host that they need if they are to reproduce. It may even have been us who gave tapeworms to other mammals like cattle, pigs and sheep.

Now, among other mammals, only carnivores are also definitive hosts for tapeworms, giving some surprising insights into the meat-eating habits of our early ancestors, and emphasising the importance for meat consumption during our evolution.

Some archaeologists even think that cooking may have begun at this time, allowing early humans to sterilise meat, making it more palatable and allowing them to eat starchy foods, the Stone Age equivalent of potatoes, in order to access otherwise indigestible cellulose for energy.

Girls from the Boys

The broader pelvis of human females also clearly distinguishes them from males. Females are born with a broader, relatively wider and deeper pelvis for reproduction.

Yet another, but more difficult to explain, difference between the sexes is the amount of fat we deposit beneath the skin around our hips, buttocks and thighs, as well as other part of our bodies.

These differences are present at birth and become exaggerated from puberty with the action of sex steroids, and are unique in humans among the primates.

One possible explanation is sexual selection. Perhaps in the early evolution of our species, or in another ancestral one, females with a more curvy figure were better able to compete to attract high quality mates. Or, perhaps the larger, more curvaceous bottom of females from puberty acted as a sign of fertility.

One thing we do know is that humans are the second fattest of all primates, in terms of the amount of our body comprising fat. The fattest primate is a loris species that stores large amounts of fat in its tail for annual hibernation.

Thus the larger female backside may be part of the overall fatter human body, perhaps providing a safe and physiologically efficient place to store fat, especially for times of food scarcity, which occurred frequently among our hunter-gatherer ancestors, or for extra energy during breastfeeding.

Also unlike our chimpanzee cousins, the backside doesn’t advertise when a woman is potentially able to make a baby each month.

When chimp females are ovulating – known as oestrus in apes – their rear ends, especially the skin around the external genitals and perineum, engorge with blood and distend to advertise their fertility and interest in sex.

At the End

The shape, anatomy and evolution of our backside are quintessentially human. Yet, throughout history the bum has been much maligned and misunderstood.

It is an evolutionary oddity that reflects many aspects of our complex evolution, from upright posture and bipedalism to shifts in diet and ecology through to exaggerated differences in body shape between females and males as well as our peculiar social and sex lives.

The multifunctional nature of our rear end has resulted in competing and conflicting demands over the 7.0 million years of our evolutionary history. These have led to it being a structure of compromise in terms of its shape, functions and mechanical efficiency.

The creative evolutionary force of natural selection can, after all, only work with structures that exist – it can’t invent ones like the pelvis from scratch – and even then only by minor tinkering with genes that have largely existed for hundreds of millions of years.

I think it’s time to stop giving this remarkable human feature such a bum steer. We should celebrate the bum for its fundamental place in our lives, for its beauty, its fascinating and complicated anatomy, and for the story it has to tell about who we are as a species and the remarkable history of our evolution.

The Palaeolithic Diet and the Unprovable Links to Our Past

We still hear and read a lot about how a diet based on what our Stone Age ancestors ate may be a cure-all for modern ills. But can we really run the clock backwards and find the optimal way to eat and live? It’s a largely impossible dream based on a set of fallacies about our ancestors.

There are a lot of guides and books on the palaeolithic diet, the origins of which have already been questioned.

It’s all based on an idea that’s been around for decades in anthropology and nutritional science; namely that we might ascribe many of the problems faced by modern society to the shift by our hunter-gatherer ancestors to farming roughly 10,000 years ago.

Many advocates of the palaeolithic diet even claim it’s the only diet compatible with human genetics and contains all the nutrients our bodies apparently evolved to thrive on.

While it has a real appeal, when we dig a little deeper into the science behind it we find the prescription for a palaeolithic diet is little more than a fad and might even be dangerous to our health.

Mismatched to the modern world

The basic argument goes something like this: over millions of years natural selection designed humans to live as hunter-gatherers, so we are genetically “mismatched” for the modern urbanised lifestyle, which is very different to how our pre-agricultural ancestors lived.

The idea that our genome isn’t suited to our modern way of life began with a highly influential article by Eaton and Konner published in the New England Journal of Medicine in 1985.

Advocates of the palaeolithic diet, traceable back to Eaton and Konner’s work, have uncritically assumed that  a gene-culture mismatch has led to an epidemic in “diseases of civilisation”.

Humans are, it’s argued, genetically hunter-gatherers and evolution has been unable to keep pace with the rapid cultural change experienced over the last 10,000 years.

These assumptions are difficult to test or even outright wrong.

What did our Stone Age ancestors eat?

Proponents of the palaeolithic diet mostly claim that science has a good understanding of what our hunter-gatherer ancestors ate.

Let me disavow you of this myth straight away – we don’t – and the further back in time we go the less we know.

What we think we know is based on a mixture of ethnographic studies of recent (historical) foraging groups, reconstructions based on the archaeological and fossil records and more recently, genetic investigations.

We need to be careful because in many cases these historical foragers lived in “marginal” environments that were not of interest to farmers. Some represent people who were farmers but returned to a hunter-gatherer economy while others had a “mixed” economy based on wild-caught foods supplemented by bought (even manufactured) foods.

The archaeological and fossil records are strongly biased towards things that will preserve or fossilise and in places where they will remain buried and undisturbed for thousands of years.

What this all means is that we know little about the plant foods and only a little bit more about some of the animals eaten by our Stone Age ancestors.

Many variations in Stone Age lifestyle

Life was tough in the Stone Age, with high infant and maternal mortality and short lifespans. Seasonal shortages in food would have meant that starvation was common and may have been an annual event.

People were very much at the mercy of the natural environment. During the Ice Age, massive climate changes would have resulted in regular dislocations of people and probably the extinction of whole tribes periodically.

Strict cultural rules would have made very clear the role played by individuals in society, and each group was different according to traditions and their natural environment.

This included gender-specific roles and even rules about what foods you could and couldn’t eat, regardless of their nutritional content or availability.

For advocates of the palaeolithic lifestyle, life at this time is portrayed as a kind of biological paradise, with people living as evolution had designed them to: as genetically predetermined hunter-gatherers fit for their environment.

But when ethnographic records and archaeological sites are studied we find a great deal of variation in the diet and behaviour, including activity levels, of recent foragers.

Our ancestors – and even more recent hunter-gatherers in Australia – exploited foods as they became available each week and every season. They ate a vast range of foods throughout the year.

They were seasonably mobile to take advantage this: recent foraging groups moved camps on average 16 times a year, but within a wide range of two to 60 times a year.

There seems to have been one universal, though: all people ate animal foods. How much depended on where on the planet you lived: rainforests provided few mammal resources, while the arctic region provided very little else.

Studies show on average about 40% of their diet comprised hunted foods, excluding foods gathered or fished. If we add fishing, it rises to 60%.

Even among arctic people such as the Inuit whose diet was entirely animal foods at certain times, geneticists have failed to find any mutations enhancing people’s capacity to survive on such an extreme diet.

Research from anthropology, nutritional science, genetics and even psychology now also shows that our food preferences are partly determined in utero and are mostly established during childhood from cultural preferences within our environment.

The picture is rapidly emerging that genetics play a pretty minor role in determining the specifics of our diet. Our physical and cultural environment mostly determines what we eat.

Humans show remarkable flexibility and adaptability to a wide range of environments and diets, today and in the past.

Evolution didn’t end at the Stone Age

One of the central themes in any palaeolithic diet is to draw on the arguments that our bodies have not evolved much over the past 10,000 years to adapt to agriculture-based foods sources. This is actually quite wrong.

There is now abundant evidence for widespread genetic change that occurred during the Neolithic or with the beginnings of agriculture.

Large-scale genomic studies have found that more than 70% of protein coding gene variants and around 90% of disease causing variants in living people whose ancestors were agriculturalists arose in the past 5,000 years or so.

Textbook examples include genes associated with lactose tolerance, starch digestion, alcohol metabolism, detoxification of plant food compounds and the metabolism of protein and carbohydrates: all mutations associated with a change in diet.

The regular handling of domesticated animals, and crowded living conditions that eventually exposed people to disease-bearing insects and rodents, led to an assault on our immune system.

It has even been suggested that the light hair, eye and skin colour seen in Europeans may have resulted from a diet poor in vitamin D among early farmers, and the need to produce more of it through increased UV light exposure and absorption.

So again, extensive evidence has emerged that humans have evolved significantly since the Stone Age and continue to do so, despite some uninformed commentators still questioning whether evolution in humans has stalled.

A difficult choice

In the end, the choices we make about what to eat should be based on good science, not some fantasy about a lost Stone Age paradise.

In other words, like other areas of preventative medicine, our diet and lifestyle choices should be based on scientific evidence not the latest, and perhaps even harmful, commercial fad.

If there is one clear message from ethnographic studies of recent hunter-gatherers it’s that variation – in lifestyle and diet – was the norm.

There is no single lifestyle or diet that fits all people today or in the past, let alone the genome of our whole species.

Saga of the Hobbit: A Decade in the Making

It’s 10 years since the discovery of Homo floresiensis (aka the “Hobbit”) was announced. The bones – and debate they’ve generated – can tell us a lot about our evolution and the scientists who reconstruct it.

I remember the day well: the 28th of October 2004 is firmly embedded in my memory, when the discovery of Homo floresiensis was announced. And, I readily confess that my first reaction was disbelief.

It was a discovery that flew in the face of 150 years of understanding of human evolution.

I quickly rang my former PhD supervisor, and then mentor and close colleague, the late Alan Thorne at the Australian National University in Canberra, and he expounded similar disquiet.

We wondered and discussed whether some kind of disease or combination of diseases could have been responsible for it’s remarkable anatomy: a rather prophetic discussion with hindsight.

An incredible find

The first skeleton, published in 2004, was dubbed LB1 (Liang Bua cave find No. 1) and included a partial skull with most of the teeth in place, several lower limb bones, hand and wrist bones, some bones of the shoulders, ribs, and elements of the hips.

Through a combination of dating techniques on cave sediments it was estimated to be only about 17,000 years old.

LB1 was a two-footed (bipedal) ape, reconstructed to have stood just over a metre tall, and weighing close to 30 kilograms.

Even more striking, its estimated brain volume was among the smallest ever found in the hominin, or human evolutionary, group at just 380 cubic centimetres: although, this estimate has now been revised up slightly.

In many other respects its face, teeth and limb bones combined features seen in Australopithecus from several million years ago in Africa, features seen in Homo erectusfrom hundreds of thousands of years ago in Indonesia, some anatomical traits like living humans, and a host of bizarre features new to science.

The next year, more bones were described in another article in Nature, this time their age being extended from a fossil bearing unit dating from 95,000-74,000 years old right up to another one aged around 12,000 years old.

For many sceptics, this new evidence was important, for no longer was the Hobbit a single, aberrant, and incomplete skeleton, it had become a long lived population. Yet, there was, and still is, only one skull.

These new fossils, especially the second lower jaw and its teeth, as well as a large number of spinal (vertebrae) and limb bones were similarly enigmatic in their anatomy and resembled the LB1 remains when they could be compared.

A slow conversion

Now, I readily confess that I was slower than many to accept the Homo floresiensis hypothesis; and all descriptions of a new species are just that, scientific hypotheses that require testing.

I never published anything questioning the find, and although a couple journalists and many colleagues did ask my opinion, I declined at that stage to offer one, as advised by Thorne. It was very good advice.

The debate over the finds and their significance got very heated, and sadly, very personal. Long-held animosities began to raise their ugly head in the media, intergenerational squabbles and cultural differences about the role and weight to be given to senior scientists played out publically.

Accusations were made about carelessness in handling the bones. Fingers were pointed and individuals accused of unauthorised and unethical access to the remains.

In 2004, the first of a number of studies criticising the “new species” hypothesis was published by Thorne and Maciej Henneberg of the University of Adelaide, alongside of a response from Peter Brown of the University of New England, and others who had described them.

This article began the assault by a group of scientists suggesting the Liang Bua remains, chiefly LB1, were simply from a diseased modern human, perhaps even an indigenous person from the island of Flores, with short-statured people living there today.

My initial impression had been taken much further, but I was very uneasy. Evidence was quickly garnered by Thorne, Henneberg, Teuku Jacob, Etty Indriati, Charles Oxnard and other scientists from Australia, Indonesia, the United States and other places for pathology as the cause of the features others had come to regard as indicative of a new species.

In fact, over the last decade no less than eight diseases or syndromes have been suggested as possible explanations for the unusual features of LB1, to account for its resemblance to primitive hominins.

Yet, I began to have serious doubts. I had spent the first 10 years of my career working on early hominin fossils in Africa, and had in fact described with the late Phillip Tobias the most complete skull belonging to the earliest species of Homo from South Africa, as well as other early fossils from that country; and had worked on very ancient bones in Kenya as well.

The brain surface anatomy of LB1 was also studied on a virtual model made from CT-scans by Dean Falk and her team, comprehensive examination of the shoulder and wrist bones occurred, and then the foot bones were studied in detail.

All of the evidence was pointing to a very, very primitive brain and skeleton: one like that seen in our ancestors hundreds of thousands, if not millions, of years ago.

By 2007, I became unconvinced that a diseased Homo sapiens could end up resembling primitive hominins in so many ways. And, I told a journalist so, for the first time offering my opinion about the finds: I found the new species hypothesis convincing.

A small brain through arrested brain growth is one thing, short stature another, but the striking resemblance of so many features from across the skeleton would be too much of a coincidence and require far too much ad hoc explaining to ring true, for me anyway.

Clearly others disagreed, and continue to do so, the debate about which disease may have caused such gross disfigurement, nay evolutionary reversion, continues, the latest candidate being Down syndrome published in 2014 by Henneberg and co-workers.

The bigger picture

While it’s true that palaeoanthropology – the science of human evolution – has a history of sometimes rather extraordinary claims, and even downright frauds such as the Piltdown Man, I think the Hobbit debate has by historical standards been rather unusual.

For a start, it has lacked a larger than life colonial figure at the centre of the discovery: historically we have often seen eccentric and exuberant characters like Eugene Dubois, Raymond Dart, Louis Leakey or Robert Broom taking on the world to show how they have more or less single handedly solved a key riddle of human evolution; and in a place far from the centres of European colonial power.

While Homo floresiensis has had its enthusiastic public champions, including the late Michael Morwood, Australian co-leader of the project that discovered it, much of the ego and flamboyancy of earlier eras has been lacking, although the conviction certainly hasn’t been.

Also different this time has been the way a number of leading international scholars rallied around to support the find from its first announcement.

I guess one the key differences has been that the scientific manuscripts describing the Liang Bua finds were anonymously reviewed by senior colleagues prior to their acceptance for publication in Nature.

When Dart described Australopithecus and the Leakeys discovered Zinjanthropus this top-of-the-pops science journal didn’t require such rigorous review prior to articles hitting the printing presses the Hobbit find was subjected to. Instead, discussion and review of the science played out through correspondences sent to Nature.

Ten years on since the announcement of Homo floresiensis we are scarcely any closer to understanding the origins and evolutionary relationships of this very enigmatic species.

While its always a precarious thing to try to second guess where the “silent majority” stands on any issue, I think its fair to say that a majority of specialists accept that the remains represent a new species of a very primitive human relative.

I also think history will show that the Hobbit stands as one of the most surprising, challenging and important discoveries made in the 150 or so year history of palaeoanthropology: up there with Dubois’ Pithecanthropus, Black’s Sinanthropus, Dart’s Australopithecus and the Leakey’s Zinjanthropus.

Image: Modified image from Wikimedia Commons (Ryan Somma). First published in October 2014 and by ABC Science.

The Extraordinary Beginnings of Human Consciousness

Our consciousness sets us apart from all other life. Yet, its evolutionary appearance highlights the accidental nature of our origins.

The beginning of our species is one of the most significant events in the Earth’s — some say the universe’s — history. At its centre is answering big questions like the beginnings of consciousness.

The 20th century luminary of biology, Julian Huxley, believed the evolutionary arrival of humans was so profound an event in Earth’s history that he dubbed the geological period when it occurred the “Psychozoic Era”.

That is, the geological era of the soul or mind.

Contemporary cosmologists like Paul Davies have even argued that the evolution of humans gave the universe self-awareness.

We humans have always thought of ourselves as rather unique in the natural world — even special — a vast intellectual gulf seemingly separating us from all other life.

To reinforce this, we have constructed cosmologies placing humans at the centre of the cosmos: the Sun orbiting the Earth — as seen for example in Ptolemy’s geocentric model of the universe.

This view changed of course with Copernicus who showed some 1,300 years later that the Sun was at the centre of universe; well the solar system more accurately, the Earth being just one of several celestial or extraterrestrial bodies orbiting the Sun.

Four hundred years later came the space race. Humans, through the Apollo missions, ventured beyond our Earthly — our evolutionary — home, setting foot on our extraterrestrial neighbour.

We were struck by our seeming aloneness and insignificance in the universe: our pale blue dot of a home set against the vast black expanse of the universe.

This event also marked the serious search for life in outer space, and there’s something rather poignant about our desire to see just whether we ARE actually alone in the universe.

So far we seem to be one of a kind. Yet, it hasn’t always been this way, being alone I mean.

Living with the cousins

Our ancestors shared the planet with other intelligent life not so long ago — the blink of an eye in evolutionary time — with creatures a lot like us.

Our ancestors shared their world with them for most of our evolutionary history stretching back to around eight million years ago, to the beginning of two-footed apes.

Being alone, as we are today, is the unusual state of affairs.

You’ve undoubtedly heard of the Neanderthals, Homo neanderthalensis? They lived up until just 40,000 years ago.

The so-called ‘Hobbit’ — or Homo floresiensis — from the island of Flores. It lived up until around 17,000 years ago.

Or, the Red Deer Cave people, one of my own discoveries with my colleague Ji Xueping, from southwest China. Cousins that lived even more recently, up until about 10,000 years ago.

Arrival of the mind

Our species evolved only about 200,000 years ago: probably the newest arrival on the evolutionary scene.

Yet, if we look at the evidence for the behavior our ancestors — the archaeological record — we can scarcely distinguish the behaviour of sapiens-humans from our cousins.

That is, until somewhere in the geological window of time around 50, 60 or 70 thousand years ago. Roughly three quarters of the way through our species’ evolution.

At this time, we saw a major event which archaeologists have dubbed the ‘Human Revolution’.

At this time we saw the first examples of jewellery being made.

Also at this time, humans took their first steps out of Africa — the humans who went on to the found the world’s living populations across the globe.

People lived for the first time in previously unoccupied areas; like rainforests, intensely arid zones including deserts, high mountain ranges, and they quickly settled the Arctic region.

East Asia was also settled about 50,000 years ago for the first time by humans, as was the island continent of Australia.

All of this occurred about the time our kind left Africa. Not earlier, and sometimes a little later. And despite the fact we had existed as an unremarkable species for around 150,000 years.

We saw the first cave paintings at this time, in Europe, Asia and Australia. Symbolic representations of the internal and external world through vivid paintings of cave and rock shelter walls.

And we saw a much wider range of tools being made, with rapid innovation in tool form and use. Tools called ‘microliths': tiny tools that replaced in many places the bigger, chunkier tools made by our earlier ancestors and relatives.

In short, we saw humans in all of our glory: with our vivid internal world and imagination, and living in virtually every nook and cranny the planet has to offer.

Gift from a departing relative

So, why the ‘Human Revolution’ then and not some other time during the 200,000-year span of our species?

We can piece together the evidence to develop a rather surprising scenario: a truly remarkable narrative of our origins, based on the latest science.

At about 60,000 years ago, when our human ancestors were beginning to make their journey to settle new parts of Africa and the rest the Old World the planet was a very different place to today.

It was a world inhabited by our close relatives: cousins living in parts of Africa, and in Asia and Europe.

Now, something rather extraordinary seems to have occurred about this time, as has been shown by the work of some very clever geneticists.

When our ancestors moved into these new places they did something that seems to be a first in human evolution — they mated with the locals.

Now our genome, it turns out, is like a patchwork quilt. It’s estimated that up to five per cent of the DNA of people living in North Africa and outside of Africa today comprises Neanderthal genes.

And a similar value also for the Denisovans — a mysterious species from Siberia we know from a single tooth and finger bone, but also its genome.

It might strike you as odd that different species interbreed. But, in fact, between species mating is common in nature and is actually an important source of evolutionary innovation right across life.

The Denisovans, for example, probably gave us a raft of genes associated with immune function and genes that allowed people living today in the Himalayas to survive at high altitude.

Accidental origin of us

There’s another really fascinating and potentially profound genetic gift they gave us on their way out: a variant of the microcephalin gene.

This gene plays a key role in brain size in humans and there is ample evidence it has been under strong selection in recent evolution.

Now, genetic studies suggest this gene may actually have been added to our genome through interspecies interbreeding with a close cousin. Maybe even with the Neanderthals.

I don’t wish to suggest this is THE gene for consciousness, for without doubt something as complex as the human mind or consciousness must involve multiple genes or even networks of genes.

But, the microcephalin gene is likely to be a key gene, without which consciousness might not exist.

So, it could be that the psychozoic of Huxley, or the universal consciousness of Davies, resulted from the incorporation of a gene we received from a close evolutionary relative.

Isn’t this the ultimate irony? We get the gene, send them to extinction, and claim universal consciousness while we’re at it!

Science constantly updates and knowledge progresses. And, without doubt, this story will change as well. But, in the end, this doesn’t really matter because it highlights one really important aspect of our evolution.

It is clear that we humans, and our remarkable consciousness, were not planned, nor inevitable, and not built into some design for the universe or the fabric of the cosmos.

Instead we were accidental, our evolution contingent.

The very feature we hold so dearly may in fact result from a chance encounter in a dark alley, even an evolutionary one-night stand.

Image: NASA. First published in October 2014 by ABC Science and based on a TEDx Brisbane Talk.