Future Humans

Image Credit / Nickolay Lamm

Image Credit / Nickolay Lamm

Humans evolved. We have been aware of this reality for 150 years, yet the implications are not apparent to most. What we have discovered about evolution is that it is A) not goal oriented and B) not hierarchical (i.e., there is no end state). This means that humans, as we currently exist, will not always exist.

Let me be clear before proceeding. This does not mean extinction is inevitable. But it does mean that our current form cannot persist indefinitely. We will change.

As a result of this knowledge, geneticist Dr. Alan Kwan and graphic designer Nickolay Lamm attempted to understand what we might look like in 20,000-100,000 years. Unfortunately for both individuals involved, their work is not science and should only be considered misleading science fiction.

Most biologists have a fantastic understanding of evolution (obviously). Biologists have revealed how the entire biosphere evolved. The theory of evolution by natural selection can explain in fantastic detail how a colony of the first replicating cells could diversify over time to produce endless forms most beautiful, including highly intelligent species like our own.

Despite the theory of evolution’s beautiful simplicity, clearly many people do not understand how it works at all. Evolution is a theory that can explain the history of organisms. Evolution can explain how things change. However, the theory is very rarely useful in predicting specific changes. From our knowledge of the history of biosphere, we can say some things about how a biosphere evolves, and therefore predict a few things about what we should suspect of the biosphere millions of years in the future. Evolutionary Biologist Richard Dawkins expounded on this quite well recently:

Evolution is very seldom in the business of predicting what is going to happen in a million years time. What I would say is that if you asked me what life is going to look like in say, ten million years or twenty million years, […] what there will be is a whole lot of different species doing pretty much the same thing as the present species are, but they’ll all be different. […] What you can predict is that there will be a similar range of species, doing a similar range of things, and that’s a fascinating thought.

Of course I agree with Dawkins main point, which is that we now understand how a biosphere is likely to change, even if we can’t say anything specifically about any one organism. We understand how a biosphere changes given the existence of certain traits like vision, hearing, echolocation, etc.

However, where I would perhaps disagree with Dawkins is that his analysis does not account for intelligence. Intelligence is here now. The Earth has a nervous system. Presently, that is our species: Homo sapiens. Intelligence is a game changer for evolution and it is a game changer for the biosphere. In the history of life on Earth, no intelligent species has ever created technology that itself evolves. As a result, we have no idea what the biosphere will look like over millions of years, given the presence of high intelligence. Anyone who tells you differently is lying.

This is fundamentally why the research done by Alan Kwan and Nickolay Lamm is wrong. But they are wrong for two other important reasons as well:

1) Conventional evolutionary mechanisms for change do not effect our species. For example, all species are subject to the law of natural selection. In all species that have ever existed most individuals did not survive long enough to reproduce. Differential non-random survival produced change over long spans of time. However humans are lifting themselves from natural selection because most people live long enough to reproduce. The mechanisms for change that will take natural selections place will be self-imposed through genetic engineering. This means that we will still be changing, but that change will literally be intelligent. Ironically, we will be intelligently designing ourselves. Although it is possible for me to posit this will occur, it is literally impossible for me to say what humans 500 or 1,000 years hence choose to change about their genetic makeup.

2) Technological evolution is speeding up, which is going to make biological evolution near irrelevant. All other species are subject to biological evolutionary processes that take tens of thousands of years (at least) to make considerable genomic changes. However, technological evolution (which is driven by culture) changes on yearly timescales. And that process is only getting faster. In the next 100 years we will likely witness more technological evolution than perhaps all of previous human history combined. How humans in only the next 100 years decide to fundamentally alter their form is debatable and realistically speaking, approaches unknowability. Many theories posit that the human form in 100 years will be primarily cyborg or robotic. It seems probable to me. But not 100% knowable.

Are we starting to see why predicting what we will look like in 100,000 years is ridiculous?

In the end, there is an important lesson to learn from the work of Dr. Kwan and Nickolay Lamm. First, it is important to acknowledge that the human form has not always appeared as it currently does. Second, that form will continue to change, and although we can gauge some type of directionality to that change, it is impossible to say what change will occur on the scales of deep time. Finally, we need to acknowledge that the human species is different than any life that has come before in the history of Earth. As I stated above, biologists have a good understanding of how life has evolved over the past 4 billion years. But we have no idea how life evolves given high intelligence. Therefore, we cannot predict what the biosphere will look like on the scales of deep time if we include the variable of intelligence. And we definitely can’t predict specific anatomical, physical, or genetic changes that may occur within our species.

Understanding human evolution is a science. We must make sure that when we discuss human evolution, both in the past and in contemporary times, that we focus on what is knowable. Attempting to understand what is probable in the next 100 years is in the realm of science. It is a maturing predictive science, but it is still science. In contrast, attempting to understand what will happen in the next 100,000 is impossible. It is science fiction.

What do you think about the future of human evolution?  Let Cadell know on Twitter!

We Are Not Aquatic Apes

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Anthropology is a subject that has attracted its fair share of anti-intellectual theorists before. These anti-intellectuals are scientists from other areas of scientific inquiry that attempt to propose their own theories about who we are and where we came from despite having no formal anthropological training. Consequently, these people are usually a massive headache because they have no idea what they are talking about. Dr. Jonathan Marks did a great job elucidating why anthropology may attract this type of anti-intellectualism in a recent podcast I did with him.

Either way, I woke up yesterday to an infuriating article published in the Guardian: Big brains, no fur, sinuses… are these clues to our ancestors’ lives as ‘aquatic apes’? The article gave an international platform to several scientists that support the Aquatic Ape Hypothesis/Theory (AAH/T). This hypothesis proposes that there was a, as yet unidentified, aquatic phase of human evolution causing our ancestors to develop bipedalism, big brains, subcutaneous fat, sinuses, and lack of fur. Supporters of the AAH believe that these features are all indicative of an ancestral past spent living primarily in deep creeks, river banks, and the sea.

But there is one major problem: there is no evidence to support it. No evidence is usually a problem in science. No ancestral hominids have ever been found that lived in an aquatic environment.

The theory was first developed in 1960 by Sir Alister Hardy. Since then its supporters have generally been from biology. The AAH has received little to no serious consideration from the anthropological community. And nor should it. Paleontologist Chris Stringer accurately acknowledged in the Guardian article that:

[T]he whole aquatic ape package includes attributes that appeared at very different times in our evolution. If they were all the result of our lives in watery environments, we would have to have spent millions of years there and there is no evidence for this – not to mention crocodiles and other creatures would made the water a very dangerous place.

These are all very important points. If the AAH is valid we would have spent millions of years in a watery environment and we should suspect all features of the “aquatic ape package” to have evolved together, not at separate times. But this is not what paleoanthropology has taught us about our past. We know that our hominid ancestors lived primarily in woodlands 6 million years ago, and primarily in savanna landscapes 3 million years ago. Furthermore, two of the most important features that the AAH attempts to explain, bipedalism and encephalization, developed millions of years apart from each other.

Paleoanthropologist John Hawks has previously deconstructed why no anthropologists take the AAH seriously. He accurately pointed out that the AAH’s single assumption does not explain why we retained these “aquatic characteristics”:

Certainly it makes sense that hominids would develop new anatomies to adapt to such an alien [aquatic] environment. But once those hominids returned to land, forsaking their aquatic homeland, the same features that were adaptive in the water would now be maladaptive on land. What would prevent those hominids from reverting to the features of their land-based ancestors, as well as nearly every other medium-sized land mammal? More than simple phylogenetic inertia is required to explain this, since the very reasons that the aquatic ape theory rejects the savanna model would apply to the descendants of the aquatic apes when they moved to the savanna. […] It leaves the Aquatic Ape Theory explaining nothing whatsoever about the evolution of the hominids. This is why professional anthropologists reject the theory.

And yet anti-intellectuals still get a credible platform to spout nonsense about our aquatic past. Perhaps I could contain my disappointment if it all remained academic. However, ecologist Dr. Michael Crawford claims that our brain growth was solely because our aquatic ancestors had a diet rich in Docosahexaenoic acid (DHA), which is found in seafood. So he then makes the dangerous (and ridiculous) argument that:

[W]ithout a high DHA diet from seafood we could not have developed our big brains. We got smart from eating fish and living in water. More to the point, we now face a world in which sources of DHA – our fish stocks – are threatened. That has crucial consequences for our species. Without plentiful DHA, we face a future of increased mental illness and intellectual deterioration. We need to face up to that urgently. That is the real lesson of the aquatic ape theory.

Using an unsupported theory of human encephalization to claim that lack of fish in someone’s diet will lead to mental illness and intellectual deterioration is just anti-intellectual pseudoscience. Considering how far evolutionary theory has progressed in the past few decades, it is disappointing to see these scientists employ it so poorly. The Aquatic Ape Hypothesis is nothing more than an unsupported adaptive story. It has not been supported by evidence, and I find it highly unlikely that it ever will be.

In 2009, John Hawks thought the AAH fit the description of pseudoscience. In 2013, it still fits the description. We have never been aquatic apes.

What do you think of the AAH?  Let Cadell know on Twitter!

Also posted via Svbtle:

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Extreme Evolution

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The coelacanth is the oldest living species of lobe-finned fish. In fact, it is so old that it has acquired the nickname “living fossil.” The distinction is probably more an artifact of the history of science than of the coelacanth’s ancientness. In the early 20th century scientists believed that the coelacanth went extinct 70 million years ago (15 million years before the K-T mass extinction!). So when a live specimen was discovered off the coast of South Africa it came as a major shock. Upon first analyzing the fish, South African chemistry professor JLB Smith famously wrote the cable:

MOST IMPORTANT PRESERVE SKELETON AND GILLS = FISH DESCRIBED

Since this discovery scientists have been perplexed by this Lazarus taxon. How has the coelacanth managed to persevere over the past 300 million years without changing at all?

This question really gets at the heart of a bigger evolutionary conundrum: does evolution have a uniform speed? Or is the speed of evolutionary change intrinsically variable?

Evolutionary theory pioneer Stephen J. Gould was one of the first to propose that evolutionary change varied tremendously. In order to explain this change he proposed the idea of punctuated equilibrium. This theory proposed that species change is largely contingent on environmental change. Gould recognized that morphological stasis could be correlated with ecological stasis. Therefore, he reasoned that massive ecological changes would prove to be the major drivers of rapid selection over the scale of evolutionary time.

This contradicted dominant theory in the 1970s because all theorists embraced phyletic gradualism: the idea that evolution was steady state with gradual transformations changing lineages. In reality, both punctuated equilibrium and phyletic gradualism are not mutually exclusive. We know now that some species can change quickly (in evolutionary terms) in response to major ecological pressures. However, change can also occur gradually over millions of years in response to more subtle ecological changes.

This brings us back to the “living fossil”: the coelacanth. Has this species really remained unchanged for nearly 300 million years? Is it really a “living fossil”? If so, its history would be a remarkable example of how an organisms environment can stabilize selection.

A recent study published in Nature finally gave us some insight into this decades-old evolutionary mystery. In this study the first genome sequence for the coelacanth was reported. The data revealed what had been obvious to many, the coelacanth’s protein-coding genes are evolving slower than any other known animals. One of the researchers in this study, Kerstin Lindblad-Toh explained that:

We often talk about how species have changed over time, but there are still a few places on Earth where organisms don’t have to change, and this is one of them. Coelacanths are very likely specialized to such a specific, non-changing, extreme environment – it is ideally suited to the deep sea just the way it is.”

However, Lindblad-Toh was also quick to emphasize that the term “living fossil” is unscientific and not an accurate representation of a extant species:

It’s not a living fossil; it’s a living organism, it doesn’t live in a time bubble; it lives in our world, which is why it’s so fascinating to find out that its genes are evolving more slowly than ours.

Here is where we can highlight an interesting (and extreme) example of just how variable evolutionary change can occur. Our species, Homo sapiens sapiens, have evolved very quickly. Let’s put this in comparison by comparing our evolution to our slowly evolving coelacanth cousins. Coelacanth fossils have been found that stretch back to the mid-Paleozoic. This is approximately the time the last supercontinent, Pangaea, first formed. That means the coelacanths emerged 70 million years before the entire Dinosauria clade.

In contrast, our genus, Homo, is approximately 2 million years old. Over this period of time our brain has tripled in size. That is unparalleled evolutionary change. I have written extensively about our genetic origins in the past so I won’t repeat myself here. However, I do want to emphasize that one of the drivers of this change has been ecological disequilibrium. Recent studies by several geoscientists have convincingly demonstrated that the East African savanna was characterized by rapid environmental change during a 200,000 year period approximately 2 million years ago. Clayton Magill, a graduate student involved in one of these studies elucidated how these changes could have stimulated punctuated equilibrium-like effects on human brain growth:

Changes in food availability, food type, or the way you get food can trigger evolutionary mechanisms to deal with those changes. The result can be increased brain size and cognition, changes in locomotion and even social changes – how you interact with others in a group. We show that the environment changed dramatically over a short time, and this variability coincides with an important period in our human evolution when the genus Homo was first established and when there was first evidence of tool use.

Since that period environmental change has played a tremendous role in the creation of our species genotype and phenotype. As modern humans exploded throughout the world, we were forced to adapt quickly to previously alien environments. Most of this adaptation was made possible by our unique ability to drive cultural and technological evolution. However, pertinent contemporary phenotypic differences within our species, like skin colour variation, were also caused by biological adaptation to extreme differences in environmental conditions.

Exploring evolutionary change in the coelacanth and humans represent two major biological evolutionary extremes. Both organisms perfectly encapsulate Stephen J. Gould’s theory of punctuated equilibrium. Ecological pressure can either strongly stabilize selection or drive rapid changes over relatively short periods of time. However, I do want to emphasize that these are the extremes. For many species, phyletic gradualism is king because ecology will change, but it will change slowly.

And don’t forget, today is DNA Day! A time to celebrate the discovery of the molecular backbone of all life on our terraqueous globe! Without the discovery of DNA our knowledge of our own evolutionary past would be relatively impoverished, and this article would not have been possible!

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#DNAday

What do you think about extreme evolution?  Let Cadell know on Twitter!

Also posted via Svbtle:

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Fraud Alert

Science has always had to deal with frauds, and perhaps human evolutionary science more than any other. The biggest of such hoaxes in human evolutionary science was the infamous Piltdown Man case. Piltdown Man consisted of a lower jawbone of an orangutan and the skull of a modern human (pictured above). It was deliberately buried in Sussex, England and was forged by an unknown individual in the early 20th century. For nearly half a century paleoanthropologists debated the validity of the skull and jawbone. And before being revealed as a hoax in 1953, scientists debated whether Piltdown Man represented the common ancestor of all modern humans. This obviously had enormous implications, and was used by many early 20th century scientists to justify racism against non-Europeans.

Since then the science investigating our origins has encountered many more frauds, most of them identifiable, but no one quite as deceptive and troubling as Dr. Melba Ketchum. She is a veterinarian and the founder of DNA Diagnostics. However, the only reason she is being discussed within the scientific community is because of her ongoing claim that she has sequenced three nuclear genomes of a Sasquatch.

For those of you who don’t know, the Sasquatch is a mythical animal that 16% of Americans believe to be a giant ape-like creature roaming the Pacific Northwest. Although there is absolutely no evidence that the Sasquatch exists, the myth persists. Ketchum, for a reason unknown to me, is trying to confuse the uninformed and discredit evolutionary anthropology by claiming it exists.

Of course, scientists in evolutionary anthropology have found surprising ancient hominids before. One of the most shocking was the discovery of Homo floresiensis (Brown et al., 2004), a small hominin most likely related to Homo erectus, that lived on an isolated island in contemporary Indonesia until between 13,000-17,000 years ago. The discovery of Homo floresiensis has certainly forced scientists to reconstruct the phylogenetic history of our species and the evolution of the genus Homo in Asia. However, the scientists that discovered Homo floresiensis were transparent with their methods and submitted their results to peer-reviewed journals so that the rest of the scientific community could evaluate their claims. Since their discovery other scientists have been given access to Homo floresiensis remains and other teams of paleoanthropologists have worked at the Liang Bua cave site where the remains were found to conduct further research by testing hypotheses. This process, the scientific process, allows real factual knowledge to be produced and considered by the world as a whole. This process prevents frauds from gaining cultural credibility and allows our species to continually improve our understanding of the universe. Consequently, our knowledge of Homo floresiensis morphology, ecology, behaviour, and phylogeny has accumulated over the past 9 years and our understanding of human evolution is much improved.

In contrast, the methods and data of Dr. Melba Ketchum’s “discovery” have hoax written all of them. She claims that her and her team of geneticists have been sequencing the DNA of the Sasquatch for the past five years, and that her results reveal that Sasquatch is extant (still living), and is a hominin hybrid that arose 15,000 years ago. Furthermore, she claims that the Sasquatch has novel nuclear DNA, but identical mitochondrial DNA to humans. The implications of her research, if true (which they aren’t), would force us to reconstruct the narrative of early human migration and expansion in North America. Her claims would indicate populations of the first human women in North America interbred with a large currently unknown extinct ape species producing a hybrid population of Sasquatch that has been hiding in North America for thousands of years.

Here is the official press release from Ketchum’s abstract in DeNovo Journal of Science (more on this journal later) from February 13, 2013:

“A team of eleven scientists with expertise in genetics, forensics, pathology, biochemistry, and biophysics has sequenced three whole nuclear genomes from a novel, contemporary species of hominin in North America. The study, “Novel North American Hominins, Next Generation Sequencing of Three Whole Genomes and Associated Studies,” which analyzed DNA from a total of 111 high-quality samples submitted from across the continent, appears in the inaugural issue of Denovo: Journal of Science (http://www.denovojournal.com) on February 13.

The team, led by Dr. Melba S. Ketchum, DVM, of DNA Diagnostics in Nacogdoches, TX, sequenced the three whole nuclear genomes using the next-generation Illumina HiSeq 2000 platform at University of Texas, Southwestern from a tissue sample, a saliva sample, and a blood sample. The three genomes all attained Q30 quality scores above 88 on the Illumina platform, significantly higher than the platform average of 85, indicating highly-purified, single-source DNA with no contamination for each sample. The three Sasquatch genomes align well with one-another and show substantial homology to primate sequences.

In addition to the three nuclear genomes, Ketchum’s team also sequenced 20 whole and 10 partial mitochondrial genomes from the Sasquatch samples. In contrast to the nuDNA results, the Sasquatch mtDNA was fully modern Homo sapiens, indicating that the species is a hybrid cross between modern Homo sapiens in the maternal lineage and an unknown hominin male progenitor.”

Well that all seems legitimate doesn’t it? She worked with a lot of scientists, sequenced genomes from biological samples, and published her results in a scientific journal. So why am I calling her a fraud?

Science is concerned with facts and reality, so if her methods and data were sound, any scientific journal would jump at the opportunity to publish such an earth-shattering discovery. Unfortunately for Ketchum, no scientific journals are actually biting. DeNovo Journal of Science is a journal that mysteriously just came into existence. There is currently one edition of DeNovo with one scientific study (Ketchum’s “Sasquatch study”). Apparently Ketchum acquired the rights to this journal, but no one really knows how, and no one knows who peer reviewed the paper. Dr. Sharon Hill has called Ketchum out on her bullshit on Doubtful News and claims: “It looks suspicious. This is not how science works.”

The reason Ketchum couldn’t get through an actual peer review process in any scientific journal was because no one knows how or who collected the samples of ‘Sasquatch tissue, blood, and saliva.’ And there is no genetic database of Sasquatch DNA with which to compare and confirm the fact that those samples were from a Sasquatch. Furthermore, there is absolutely no evidence of a large ape from anytime in the natural history of North America.

To make matters even more ridiculous, Ketchum issued a statement to the United States government to recognize Sasquatch as:

“An indigenous people and immediately protect their human and Constitutional rights against those who would see in their physical and cultural differences a ‘license’ to hunt, trap, or kill them.”

She also claims:

“[We] have at our disposal, high-def footage, that will not be released until which time the publication finished, high-def video of the Sasquatch. It’s quite remarkable.”

If such footage actually existed, it is hard to figure out why she wouldn’t release it now, since it would potentially erase credibility issues regarding the collection of the samples she claims to have analyzed. Ketchum’s behaviour throughout this whole process has to make me wonder if she is psychologically stable. And if she is, that brings me to my biggest question: Why? Why is she doing this?

Her methods and data are so clearly fraudulent. Any educated individual would realize that something so methodologically flawed would not trick a 21st century scientific community. She is an actual geneticist, and as a result has nothing to gain from this and everything to lose. This whole debacle will only result in her marginalizing and discrediting herself. Why is she doing this? The only possibilities I can think would be to gain some measure of fame within fringe Sasquatch-believer groups. Perhaps as a result of that fame and notoriety she could make money from people coming to her with random animal samples that they want tested?

I’m not sure. Either way she is bad for science. And in my opinion, some science and most general news sources are treating this case fairly neutrally. I think that is bad for science as well. The science is either fraudulent or it isn’t. In the case of Ketchum, she is either trying to create a Piltdown Man for the 21st century, or she is psychologically imbalanced.

Want more evolution in your life?  Follow Cadell Last on Twitter!

Also posted via Svtble:

References:

Brown, et al. 2004.  A new small-bodied hominin from the Late
Pleistocene of Flores, Indonesia. Nature, 431: 1055-1061.

Great Ape and Human Genetic Diversity

Last week I wrote about what molecular anthropologists know about our genetic origins.  Within that post I discussed human genetic variation, great ape genetic variation, the founder effect, and hominid genetics.  However, I feel as though I didn’t spend enough time explaining one mind-bending aspect of these discoveries: genetic variation between humans and great apes.

All great apes are more genetically diverse than our species: Homo sapiens.  Recent genetic studies by molecular anthropologists have revealed that there are only 38 million unique genetic variants among the 3 billion base pair sequences within our species genome.  Although 38 million unique variants may seem like a lot, it is actually a very small fraction of our genome.  All the great apes are far more dissimilar than humans.  We appear to be a homogenous group!

But this begs the question: why are we so similar?

On further reflection it becomes very perplexing.  After all, there are seven billion humans on Earth!  That’s a lot of Homo sapiens.  And we don’t all look similar; there is incredible phenotypic diversity within our species.  There are people with all different shades of skin colour, hair texture, height, weight, shape, and size.

In contrast, chimpanzees, bonobos, gorillas, and orangutans all have relatively small populations.  In the wild, there are <250,000 chimpanzees, <110,000 gorillas, <60,000 orangutans, and <50,000 bonobos.  Furthermore, there appears to be relatively little phenotypic diversity among these species.  It is difficult to tell different subspecies of great ape apart, even for experts!

So why are all the great apes more genetically diverse than us?  Shouldn’t a species with 7 billion phenotypically diverse individuals be more genetically diverse than species with less than a million individuals that all look relatively similar?  Apparently not; molecular anthropology is teaching us that our differences are genetically superficial.  And there are two main reasons why we are so genetically similar: a) the age of our species and b) our rate of migration.

Our species is actually very young.  Anatomically modern humans have only been on the planet for 150,000-200,000 thousand years.  That may seem like a really, really long time.  But in fact, it is not that long on evolutionary timescales.  All species of great ape have existed for hundreds of thousands of years more than our species.  We are young apes!

But why does being a young species have anything to do with genetic diversity?  Well, the number of unique mutations that could have accumulated within our lineage is largely dependent on how long we have existed.  Most human lineages are 150,000 years or younger, which isn’t very much time for mutations to accumulate between or within populations.

A second factor causing our low genetic diversity is our migration rate.  Humans move quickly, and consequently, so do our genes.  Our migration speed is much faster than any other great ape species, and it has been that way since we emerged in East Africa 150,000 thousand years ago.  We have always been mobile, exploring new landscapes, and continents.  In contemporary times, this rate of migration has only increased.  In contrast, great apes have static home ranges on a continental scale; they don’t move around too much.

But again, why does a quicker migration rate have anything to do with the level genetic diversity?  It all has to do with gene flow.  Gene flow is the transfer of genes and/or alleles from one population to another.  And gene flow always decreases diversity because it homogenizes the gene pool of otherwise genetically distinct populations.

As a result, chimpanzees, bonobos, gorillas, and orangutans have existed for a very long time, in more or less the same areas.  They have had ample time to accumulate novel genetic mutations between and within their populations.  And because they very rarely interact and mate with distant groups, their rate of gene flow is low; which increases genetic diversity.

So what does this all mean for us humans?  I think it means that regardless of how different we all look our differences are largely superficial.  Our species is young and increasingly interconnected.  In the future, these facts about our biology should be reason for hope and optimism.  Our genetic heritage unites us, it does not divide us.

“Chimpanzee Fire”

I recently watched a BBC documentary about the Congo.  It was part of a larger documentary series on Africa narrated by David Attenborough that I highly recommend.  Whenever I watch BBC nature documentaries I feel like I learn something new each time.  But while I was watching Congo, one scene in particular caught my attention.  It was a scene on “chimpanzee fire.”  Immediately my curiosity piqued. In the scene, a camera panned across a dark forest floor, and within moments it started coming to life with a green glow.

Was it chimpanzee fire?  Unfortunately, it was not.  It was bioluminescent fungi that the local Congolese call “chimpanzee fire.”  Bioluminescence is the production and emission of light by a living organism.  Several animal, plant, and fungi species have adapted the ability to produce their own light, and it serves many important functions.  I actually had a chance to learn a lot about bioluminescence at an amazing exhibit at the American Museum of Natural History in New York over the winter break.

It is easy to see why the native Congolese would have started to call this bioluminescent fungi chimpanzee fire.  Modern science has only started to understand how bioluminescence functions and evolves.  And it is kind of counterintuitive to think of organisms that have the ability to produce their own light.  In the early modern era or pre-modern era, I think I would have been far more convinced by the chimpanzee fire hypothesis.

But this little anecdote about chimpanzee fire from the Congo reminds us of something more interesting: people in many areas of sub-Saharan Africa likely realized chimpanzees were behaviourally similar to humans for tens of thousands of years.  Positing that chimpanzees had the ability to ignite fire across the forest floor is laden with symbolic meaning about our connection with them.  And it is not hard to see why they would have attributed the glow to chimpanzees.  In fact the name chimpanzee is derived from Tshiluba (a Congoloese language), and translates roughly as ‘mockman.’  This further supports the idea that we didn’t necessarily need modern science to reason that chimpanzees were human-like. Just like the Ancient Greek philosophers didn’t need telescopes to reason that the stars could be just like our Sun, only further away.

But let’s turn our attention back to fire.  Sure the bioluminescent fungi were not chimpanzee fire, but can any populations of chimpanzee control and use fire?  After all, most behavioural differences between chimpanzees and humans are really best thought of as gradient differences.  Do any chimpanzees gather around a little campfire for warmth?  Or light a torch to get through the forest at night?

Recent research at Fongoli in Senegal has revealed some interesting findings.  Populations of chimpanzees at Fongoli behave a lot differently than many other populations studied to date.  They are the only non-human organisms on the planet known to hunt other animals with weapons.  They also periodically live in caves and travel at night.  And unlike most other chimpanzee populations, they seem to have developed a fondness for water.  But do they use and control fire?

Primatologist Jill Pruetz claims that the Fongoli chimps are confronted with fire more than other chimpanzee populations.  They live in a savanna-mosaic environment and as a result wild fires spread more frequently than in the habitats of other chimpanzee populations.  When confronted with these fires they seem to be able to “predict the movement.” (Pruetz & LaDuke, 2009).  Pruetz says that in such situations she chooses to follow the chimpanzees rather than find her own path out of the woodland.

Despite this, no Fongoli chimp, or any other chimp, has ever been observed to control and use fire.  That appears to be an ability acquired after our split with chimpanzees and bonobos.  However, this leads to an interesting question: when did we start using fire?  And what benefits did using fire have?

The question is harder to answer that it seems.  The beginnings of most distinctively human behaviours leave little-to-no trace in the archaeological record.  When it comes to understanding the origin of things like language or tool construction, theory has less testable evidence than would be ideal.  In the case of fire, traces of fire use are easily and quickly destroyed by wind and rain, so acquiring direct evidence of early campsites may be impossible.  That being said, we have uncovered some answers regarding the origin of the control and use of fire.  This evidence is indirect, but reliable.

Paleoanthropologists believe they have pushed the origin of fire control and use to approximately 1.7 million years ago.  The evidence comes from Wonderwerk Cave in South Africa, where stratified deposits have produced burned cryptocrystalline stones, charred-calcined bones, and traces of ash, which indicate repeated burning events (Beaumont, 2011).

These deposits are associated with the remains of Homo ergaster, the African sister species to Homo erectus.  Evolutionary anthropologists have known for a while that Homo erectus controlled and used fire, but the deposits at Wonderwerk push back its origin by hundreds of thousands of years.

Researchers have hypothesized that Homo ergaster regularly constructed campfires as they would have had considerable protection benefits on the southern savannas against a formidable array of carnivores.  From my own research on chimpanzee nesting patterns, I believe that fire may have been a necessary behavioural adaptation to successfully migrate into a terrestrial niche.  If my hypothesis is accurate, we should expect the origin of fire to be pushed back several millions of years.  Alas, we don’t have evidence for that… yet.

Either way, fire may have provided our ancestors with an even greater benefit than protection from predators: cooking.  Fire allowed our ancestors to prepare and cook meals (Wrangham, 2009).  British primatologist Richard Wrangham recently wrote an entire book on the origin of fire and how it changed our species.  He posits that cooking increased food efficiency, which enabled larger brain growth.  His hypothesis is largely supported by current theory and evidence.  It is also interesting to note that modern humans are highly evolved for eating cooked food, and if not prepared properly, raw food can be lethally poisonous to our digestive tract.

Either way, as human-like as chimpanzees can be, they do not control and use fire in the wild (even though they can be taught by humans).  The original discovery that fire can be controlled and used for our benefit may have been the product of one ancient genius, or it may have been stumbled upon several hundreds of times.  It seems that we will never have precise knowledge of how it exactly happened.  However, we do have important knowledge of where it was made, when it was made, and what species discovered it.  Future research should help us better understand how this happened, and consequently, it will help us reconstruct our current story of how we became human.

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References

Beaumont, P.B. 2011.  The Edge: More onFire-Making by about 1.7 Million Years Ago at Wonderwerk Cave in South Africa.  Current Anthropology, 52: 585-595.

Pruetz, J.D. & LaDuke, T.C.  2009.  Brief communication: Reaction to fire by savanna chimpanzees (Pan troglodytes verus) at Fongoli, Senegal: Conceptualization of “fire behavior” and the case for a chimpanzee model.  American Journal of Physical Anthropology, 141: 646-650.

Wrangham, R.  2009.  Catching Fire: How Cooking Made Us Human.  New York: Basic Books.

Are Humans Monogamous?

Humans, like most other animals, are sexual beings. However, unlike other animals, we are an intensely cultural species. This makes understanding our sexual nature incredible difficult. As biological anthropologist Jonathan Marks remarked: “Culture is inseparable from being human [and therefore] cannot be scraped off, like the icing on a cake, to reveal the human nature below.” (Marks, 2009).

As a primatologist, if I study the sexual behaviour of a ring-tailed lemurhamadryas baboon, or white-handed gibbon, it is relatively easy to characterize their socio-sexual system, and test for the selection pressures that may have led to its development. However, the evolutionary history of these species was dominated by biological evolution. In contrast, the human condition was produced via the interaction of biology and culture, a uniquely co-evolutionary process (Wilson, 2012).

As a result, is it possible to understand our sexual nature? Do we have a sexual nature at all? Or is our sexual behaviour simply a product of complex social systems contingent upon cultural evolution? Hopefully our understanding of the evolution of primate behaviour, as well as sexual selection theory, will help us answer these questions.

Primatologists have been researching primate socio-sexual systems and developing sexual selection theory for over four decades. Over this time period we have come to realize that pairbonding in one-male/one-female sexually exclusive units is rare. In fact, only 3% of primates are known to have evolved monogamous social systems. And phylogenetic studies have shown that all monogamous systems are derived states that have convergently evolved 7-10 times (Fuentes, 1998). Behavioural studies have also shown that monogamous behaviour tends to be flexible and conditional on numerous ecological variables. As a result, ancestral non-monogamous sexual states are often used as alternatives to monogamy in different circumstances.

This means that although monogamy is expressed within our order, it is not common, and it is certainly not a stable evolutionary strategy. Furthermore, no primate exhibits exclusive monogamous behaviour over an entire lifetime. Take for example, the gibbon, a lesser ape classically used as an example of primate monogamy. Researchers originally believed that the gibbon was both socially and sexually monogamous. They lived in one-male/one-female adult pairs, and appeared to remain exclusively pairbonded with one individual for decades. However, long-term studies have revealed that 12% of gibbon copulations are “extra-pair” copulations that their pairbonded partner is unaware of (Reichard, 1995). Essentially, gibbons get married and then cheat.

But why even form these systems in the first place? Even though monogamy is rare, and very rarely exclusive over the course of an individual lifespan, it has evolved 7-10 times independently within our order. There must be some important benefits to being exclusive.

Surprisingly, there may be as many as four different selection pressures for the behaviour: male defense of resources, infanticide reduction, direct male care, and male mate guarding. However, none of these pressures is universally necessary, and it is likely that a different combination of these pressures has caused different “types of monogamy” to evolve in different primate species currently defined as monogamous or pairbonded.

This information can all be a little overwhelming and hard to make sense of. Monogamy is rare, never completely explicit, and the evolutionary benefits are highly variable. What can this mess tell us about human sexuality?

It is evident that pairbonds between adult males and females has been a massive component of human socio-sexual systems both throughout history and in contemporary times. Did we evolve to organize ourselves in this way? Were early modern humans in the Middle Paleolithic living in systems we would classify as monogamous? Or did our ancestors organize themselves in different sexual systems? And if monogamy was uncommon in the past, why does it appear to be the system that has been culturally promoted throughout most of written history by various culture groups?

There are some important evolutionary clues regarding the composition of our ancestral socio-sexual system. The biggest comes from our pronounced sexually dimorphic traits. Human males are on average taller, heavier, and stronger. Our level of dimorphism is moderate when compared to say, gorillas, which are highly sexually dimorphic. However, our level of dimorphism is characteristic of a species with a moderately polygynous mating system with higher levels of male-male competition for mates, than female-female competition for mates. Past behaviours do not fossilize, but our dimorphism indicates a combination of moderate male harem building and strong female mate choice for large body size.

During the formation of early city-states between 5,000-10,000 years ago, several human populations made a transition from a traditionally hunter-gatherer lifestyle to a settled agricultural existence. Many evolutionary theorists contend that during this transition, the demands of agricultural life distorted human mate choice patterns. Humans were increasingly sedentary and had to prepare and maintain a plot of land for an entire lifetime. This new system required long-term investment from two adult individuals. Also, for the first time in human history, individuals could accumulate substantial wealth and surplus resources. As a result, males could use a lifetimes worth of resources as leverage against other males in competition for access to mates. In order to level the playing field, it is likely that many early city-states promoted monogamy, to avoid male harem building and avoid the collapse of early agricultural networks (Sanderson, 2001).

So does this mean that we are all naturally polygynous? Are cultures that promote monogamy simply the product of the early agricultural city-states attempt to promote equality of mating opportunity between disproportionately wealthy males?

You may have guessed that it isn’t that simple. From a neurological perspective humans really are designed to pairbond. Chemicals like oxytocin and vasopressin are released in our brains when we establish long-term sexual relationships with one individual. Studies have also shown that humans that form long-term pairbonds live longer and are psychologically healthier. Pairbonds also serve important evolutionary functions.

Quinlan & Quinlan (2007) conducted a massive cross-cultural study on human pairbonds in order to understand what specific pressures may have selected for pairbond formation. They discovered that human pairbonds form and are most stable cross-culturally when paternal investment and male-male competition is high. Their results indicated that a pairbond with little paternal investment is nearly worthless to women. As a result, the bond quickly disintegrates. Interestingly, pairbond stability was also unstable when male contribution was disproportionately higher than female contribution. The most stable pairbonds formed with equal contribution rates (Figure below). Pairbonds were also the most prevalent and stable when male-male competition for mates was high. Combined, this indicates that monogamous human socio-sexual systems are most likely when subsistence requires reciprocal cooperation, and when females have more control over mate choice than males.

Disparity in mate choice may be important because males, by nature, are less choosy. Females invest more matter and energy into producing eggs than males invest in sperm. Consequently, potential male fecundity increases with increase in mating partners, whereas female fecundity does not (Trivers, 1972). Ergo, it shouldn’t surprise us that reducing male mate choice is key to establishing stable pairbonds.

This all matters regarding our evolutionary interpretation of monogamy. The Quinlan & Quinlan study provides solid data that there are important adaptive functions of monogamy actually being played out among human societies today, regardless of culture. It shows that there are important ecological and environmental mechanisms that can increase (or decrease) the probability that humans will exhibit monogamous behaviour.

But are we getting closer to our answer? Of course humans can be monogamous, but are they monogamous?

After analyzing the data and theory evolutionary studies has to offer, it seems evident that we are a sexual hybrid. Within certain socio-cultural and environmental settings, humans are biologically capable of engaging in the most intensely monogamous behaviour within the Order Primates, and perhaps the entire animal kingdom. Pairbonding has really strong neurological effects that have been selected for, and offer us some really important long-term benefits.

However, as with other “monogamous” primates, polygyny is almost certainly our ancestral state. And like other “monogamous” primates, in certain circumstances we can use our ancestral state as a viable alternative to monogamy.

In conclusion, it may be a general rule among primates that species with derived monogamous socio-sexual systems are by nature highly flexible sexually and exist as sexual beings conditionally upon important ecological variables.

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References:

Fuentes, A.  1998.  Re-Evaluating Primate Monogamy.  American Anthropologist, 100: 890-907.

Marks, J.  2009.  Nature/Culture.  pp. 260-279.  In: Why I Am NOT A Scientist.  Berkely: University of California Press.

Quinlan, R.J. & Quinlan, M.B.  2007.  Evolutionary Ecology of Human Pair-Bonds: Cross-Cultural Tests of Alternative Hypotheses.  Cross-Cultural Research, 41: 149-169.

Reichard, U.  1995.  Extra-pair copulations in a Monogamous Gibbon (Hylobates lar).  Ethology, 100: 99-112.

Sanderson, S.K.  2001.  Explaining Monogamy and Polygyny in Human Societies: Comment on Kanazawa and Still.  Social Forces, 80: 329-335.

Trivers, R.  1972.  Parental investment and sexual selection.

Wilson, E.O.  2012.  The Social Conquest of Earth.  New York: W.W. Norton.