Photo by Aaron Logan

One of the ways The Human Spark investigates what makes us uniquely human is by looking at our closest living relatives, the other great apes. Scientists are attacking the question of how we became human from a number of new directions – in addition to analyzing the more traditional hard evidence of ancient fossils. This article in New Scientist magazine explains several ways researchers are gathering data from primate groups alive today to gain insights into early hominid evolution. Tune in to The Human Spark’s second episode to learn more. What do you think these kinds of inferences can add to our understanding of where we came from and how we became who we are?

• New Scientist: “Ape behavior reveals secrets of human evolution“

by Vicky Horner, Living Links Center, Emory University

To many people, the words “culture” and “chimpanzee” don’t seem to go together. In fact, apart from starting with the same letter, they seem to have little connection at all. It’s therefore always slightly awkward when I have to explain what I do for a living to someone I don’t know very well. When I tell them that I am a psychologist, but that I work with chimpanzees and study their cultural behavior, I get the distinct impression that some folks think perhaps it is me, and not the chimps, that needs a psychologist!

The looks of surprise and confusion come from the fact that for many people the notion of culture equates with the fine arts, a night at the opera, or a refined palate for expensive wine. The idea of a chimpanzee at the opera sipping on a nice glass of chardonnay is pretty comical, even to me. We can all think of lots of examples of cultural differences between groups of people, but actually defining it in biological terms is a little more difficult. Psychologists, anthropologists and biologists have been arguing about culture for decades, and although we still don’t agree, we are getting a little closer to a definition that keeps most people happy. In order to understand culture, and more importantly to understand the evolution of our own cultural abilities, we need to stop getting caught up in examples of our cultural behavior and focus more on how cultural differences develop in the first place. At the fundamental level, culture is simply a collection of learned behaviors that have been passed on from one generation to the next, such as using chopsticks or knives and forks. For many years culture has been regarded as the hallmark of our species, the ‘human spark’ that separates us from other animals. However, before we can make claims about our own uniqueness, we need to check for similar sparks in other animals, starting with our closest living relatives, the chimpanzees, with whom we share a common ancestor and about 99 percent of our DNA.

One of the Yerkes chimps uses a tool to extract a tasty treat from one of Vicky’s puzzle boxes.

A few years ago, a group of scientists working in Africa got together to compare the behavior of the chimpanzees at their field sites. What they found was rather surprising. At every site, the chimpanzees displayed a totally different pattern of behavior, such as how they use tools and weapons. These differences were not easily explained by differences in habitat or genetics. The scientists therefore thought that perhaps these differences represented chimpanzee cultures, and arose because each group had invented different solutions to similar problems (like dipping for ants with long sticks or short sticks), and that these behaviors were maintained over generations by learning from one another.

However, it is very difficult to study culture and learning in the forest because there are so many variables, so at the Living Links Center we study chimpanzee culture in a more controlled captive environment. We study two social groups of chimpanzees who live in large indoor-outdoor enclosures with climbing structures, grass and toys.  We train one chimpanzee in each group to act as an “inventor” who solves a food puzzle (like how to get the banana out of the box with a stick) in one of two different ways. We then track if and how each new behavior spreads within the groups. These studies are important because they show us that chimpanzees have the brains for culture; they can learn and maintain new behaviors accurately enough to support the reports of culture from the wild. I am not claiming that there is no difference between going out to a Chinese restaurant to practice your chopstick skills and staying home to fish for termites in the back yard, but the fundamental psychological mechanism and the evolutionary driving force behind the two is the same.

Alan tries his hand at a puzzle box, though he’s not quite as motivated as a typical chimp to extract the M&M.

So what does all this mean for the human spark? To me there is no single spark that separates us from chimpanzees; we are intricately connected by our common ancestry. The differences between us arise from thousands of tiny differences in the frequency and contexts in which we do things. For example, we imitate one another constantly; chimpanzees imitate each other sometimes. We take other people’s perspectives on situations frequently; chimpanzees take another’s perspective sometimes. We empathize frequently, they empathize in some contexts. It is all of these little tweaks here and there that make up the human spark.

On a final note, I’d like to emphasize the importance of not falling into the trap of thinking that we are the ultimate and desirable endpoint of evolution. Chimpanzees and humans have both been evolving form our common ancestor for the last 5 million years. They may not be at the opera, but chimpanzee culture is remarkable in comparison to other species. We also have a habit of measuring their abilities against our own human checklist in the quest for the human spark. But what would happen if we measured ourselves on a chimpanzee checklist; would we find a “chimpanzee spark”? How do you measure up to this five-year-old chimpanzee?

Darwinium masillae

Our series attempts to locate when and where we transitioned into truly modern human beings — the elusive spark, if you will, that allowed us, here on our own tiny branch on the tree of life, to behave the way we do with all our various abilities and features. Part of this quest involves closely examining our direct ancient lineage, as well as our near and not-so-near cousins. Of course evolutionary history is filled with groups that split into various descendant lines as well as those that hit dead ends and fizzled out. These ancient family trees are pieced together through the fossil record. Looking at the various branches on these trees is one way scientists try to figure out the relationships between various animal ancestors and us.

Recent publications about a fossil called Ida provide the latest example of a creature that seems to have lived at one of those branching points where one group of animals was evolving into a recognizably different one. People in the media have jumped all over this beautifully preserved 47-million-year-old fossil, with some even calling it a “missing link.” Of course, there’s never a single missing link in the huge web of animal evolution, but it does appear that Ida, or Darwinium masillae, was a mammal who shared characteristics with the prosimians (such as lemurs) and also with anthropoids (such as monkeys and apes). Keep in mind, there’s a long, long time — and lots of evolution! — between when Ida lived and when our own species appeared on earth maybe 200,000 years ago.

What do you think of all the media hoopla about Ida and what she means?

• Research article: “Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology“
• Associated Press: “Early Skeleton Sheds Light on Primate Evolution“
• CNN: “Scientists Piece Together Human Ancestry“
• The Independent (UK): “The Big Question: Is ‘Ida’ really the missing link between humans and animals?“

Watch Hauser explain to Alan Alda his concept of humaniqueness – and how we can draw on a multitude of talents to solve a problem, whereas other species are limited to just a few.

When Amanda Henry went through airport security in Washington on her way to Boston she made the inspector nervous when her bag revealed dental instruments – apparently the security officer hates going to the dentist. The officer may have been even more freaked out if she knew the teeth Amanda was on her way to clean with her dental picks belonged to a 100,000-year-old.

A very famous 100,000-year-old at that – at least in archeological circles. The teeth are still all neatly in place in a skull now at the Peabody Museum of Harvard University [tons of images here], where it has resided in secure climate-controlled storage since it was unearthed in the 1930s from a cave in Mount Carmel, in present-day Israel. We had met the skull the day before, when Dan Lieberman had arranged for it to be brought out of storage and introduced to Alan.

Known as Skhul 5, the skull is the oldest known human with almost modern features, and so plays a pivotal role in our story. He poses the central puzzle we’re trying to get to the bottom of: people looked like us apparently long before they started behaving like us – at least according to the commonly accepted view that the modern human mind – with what we are calling the Human Spark – didn’t evolve until tens of thousands of years after the owner of the Skhul skull and his like lived in the Middle East – most likely alongside, or at least at the same time as, their cousins the Neanderthals.

The Human Spark camera rolls while Amanda demonstrates her dental scraping techniques to Alan. Photo: Maggie Villiger

As we’d just been learning from Alison Brooks, it’s now looking increasingly likely that the Human Spark in fact started to glimmer much earlier in Africa, perhaps even before the ancestors of Skhul 5 made their way north. So archeologists would love to know as much as possible about how Skhul 5 lived. It was Alison who told us about Amanda, a student of hers at George Washington University, who – armed with her dental picks – was going to demonstrate to Alan how she’s figuring out what Skhul 5 ate.

After carefully removing the skull from its padded box, Amanda showed us how she very, very gently scrapes dental plaque from the skull’s molars (much more gently than your oral hygienist cleans yours).  Plaque, she explained, is the perfect material to preserve microfossils from the plants Skhul 5 ate – starch grains and tiny silica bodies called phytoliths that Amanda will be able to identify under the microscope and tell what plants they came from.

Amanda’s care in her scraping wasn’t only because, as she reminded us, the skull is priceless, but also because, “I have to leave some plaque behind in case somebody comes up with a different way for studying it in the future.”

Alan wanted to know if she poked around in his teeth, could she find out what he’s eaten.

Amanda: Well it depends, how good are you at brushing and flossing?

Alan: Oh just great, yes.

Amanda: I’ve actually done some experiments where you eat whatever you normally eat for breakfast, lunch and dinner. At the end of the day , you take one of these dental picks…

Alan: And you could say what the person had eaten?

Amanda: Some of it, sure.

Alan: No kidding.

Amanda: It’s quite easy. It’s not just in the plaque. It’s in any of the pellical, basically the scum that builds up on your teeth. As that hardens into plaque then it’s more permanently kept on your teeth. I don’t know, actually, how far back I’d be able to tell what you ate, whether I could just tell this morning what you had for breakfast, or what you had three weeks ago.

Fortunately for Amanda, and despite the astonishingly good shape of Skhul 5’s teeth, he lived a good long time before the invention of dental floss, so she has high hopes of discovering what he ate 100,000 years ago.

Alan summed up the reaction of all of us: “Astonishing.”

- Graham Chedd

Larry Engel films Alan Alda with Dan Lieberman and a VERY old skull at Harvard’s Peabody Museum. Photo by Maggie Villiger

CAMBRIDGE, MASS.

Can a Yalie survive a film shoot at Harvard?

What’s it like to film at Harvard or MIT, two of the most prestigious universities in the United States, if not the world? First of all, we know that there are a lot of really, really smart people here. Thinkers, researchers. So that’s a challenge in and of itself. But for a Yalie, it’s even harder. Okay, so I was at Yale way back in the late 60s and early 70s (during the Vietnam War protests and the Black Panthers in New Haven — interesting time — Google it!) so by now I should be over any sense of competition with Harvard, but alas I discover that The Game (keep Googling, but please come back) still compels me to be somewhat suspicious as we start production here.

Regardless of my slight unease, Cambridge is a beautiful city and Harvard’s campus a classic. Trees and green lawns — well-manicured of course — quads and ivy-covered buildings. Within these halls sit some really fascinating professors and investigators. Between Harvard and MIT, over the next few days Alan will sit down with eight researchers and their associates, and go for a “spin” in an fMRI machine (the big magnet!) Indeed the topics of conversations are far-ranging — from Stone Age tools to Theory of Mind to biomechanics — all in our continued effort to uncover the human spark.

Where to begin? Well, parking is always a challenge around any college campus and Harvard is no exception. It always takes an inordinate amount of time to unload gear, load into the building that we’re working in, and get the cars parked.

Larry sets up his shot to illustrate how human feet have evolved to withstand the impacts of running. Photo by Maggie Villiger

We start in the Peabody Museum and one of the first researchers we pay a visit to is Professor Dan Lieberman.  He looks at biomechanics — namely how we, and other animals, use our bodies to move through the world. He’s done research on running for many years. He argues that we humans evolved to become the best long-distance runners on earth. While we cannot out-sprint many animals, we can outlast them all — and that creates a real advantage for us.  Instead of attacking prey up close and personal (and thereby putting ourselves in peril), all we have to do is run our prey to exhaustion, then dispatch it. This change in hunting strategy may have been one of the “sparks” that we’re searching for. It may have pushed people toward more cooperative behavior, thus building closer bonds among us.

But what got me excited was that Dan has discovered that we’re really meant to run barefoot, not in soft cushy sneakers.  In fact, he tells Alan that running barefoot is around 15% more efficient than what we normally do. Dan takes to the treadmill to talk with Alan (Dan can run and talk at the same time frighteningly easily) and demonstrate how our bodies have evolved to support bipedal running, from the way our necks are connected to our heads to the way our hips are shaped differently than other primates’. The latter may have led to babies being born less developed (in order to pass from the womb through a narrower passage between the hips) and therefore in need of a longer growing cycle outside the womb.

But Dan also runs not quite barefoot. In fact, I’m intrigued with his non-sneakers. They have a rubber sole, but it’s very thin. No padding at all. A stretch fabric over the foot and a Velcro strap to hold it secure, really just protection for the skin on your soles. The coolest part is that it looks like a glove for your foot — each toe fits into its own little chamber.

Larry Engel outfitted in his new favorite shooting attire. Check out his feet.

I try one on and instantly like it. I like walking around barefoot anyway at home, and realize that these might come in handy, well “footy,” for filming. Here’s why: When you have the camera on your shoulder you usually want to minimize shakiness and create as smooth movement while walking as you can. One of my techniques is to use short steps and try to think of each joint in my body as a mini-gyroscope that helps separate my body’s movement from the camera’s. I also use sneakers with good soles and cushion. Now I wonder if maybe filming barefoot might not be better, at least for interiors. So in the next scene I take sneakers off and really like the way I can feel the floor and absorb the shocks of walking better!

Much to my wife’s chagrin (she knows I like gadgets), I order a pair.  I start training in them for outdoor and long-term use. Dan warned me that it takes some getting used to because you put different pressure on your joints and especially your calves. He recommends that I start with just two minutes of additional treadmill work a day in them. He also says that using them should help relieve knee pain and swelling, and back aches. Hmm. Well after a few days of taking them on the treadmill, I agree with him — my calves ache. On the other hand, my knees and back don’t.

I now shoot as often as I can with them. Maybe it’ll turn into a trend in the industry; who knows.

- Larry Engel
Director and Director of Photography

Different animals look at the world with different eyes, literally. The colors a species can perceive is dictated by the types and number of visual pigments found in the retina. Humans and most primates are trichromats, meaning we have three pigment varieties that absorb light in our eyes and then transmit that information to the brain. Some birds and reptiles have four pigments, allowing them to perceive ultraviolet wavelengths that we can’t. And other mammals have just two pigments.

This article from Scientific American examines how our color vision system may have evolved. And through their experiments, authors Gerald Jacobs and Jeremy Nathans discovered some intriguing brain adaptability when new sensory inputs are added.

Alison Brooks lets Alan see how perfectly a million-year-old axe fits in his hand. Photo by Larry Engel

We’re in Cambridge, Massachusetts, visiting Harvard and MIT – just across the Charles River from where I’ve lived for almost my whole career as a producer of science programs for public television. So it’s familiar ground. I remember a film shoot on the top of one of the MIT towers (the Green Building, I think) for one of my first NOVA productions, when the scientist held up a ball for a shot that included the golden dome of the State House in Boston as a visual analogy of how far earth is from the sun. That must have been in 1976 or so. The Boston skyline is now very different, with the dome almost lost in a sea of tall modern buildings. That shoot is also memorable because there was a brief glimpse of the top of my head in the rushes, taken while I was with the scientist and the cameraman was lining up his shot from above and behind us. It was the first time I became aware of another emerging shining dome.

One of the people we filmed here is actually a visitor, taking a sabbatical at Harvard’s Peabody Museum from George Washington University, where she is Professor of Archeology and International Affairs. Alison Brooks and a colleague (Sally McBrearty of UConn) set the field of human origins all atwitter almost ten years ago when they published a massive paper in the Journal of Human Evolution challenging the then-prevailing view that the modern human mind suddenly gelled when our ancestors arrived in Europe some 35,000 years ago and began painting the walls of caves in southern France. In other words, that it was in the flickering oil lamps of the artists of Lascaux that the Human Spark ignited.

Sally and Alison had both worked extensively in Africa in the previous decades, and pulling together their own archeological evidence and that of others argued in their JHE paper that instead of a sudden cognitive revolution in Europe, the modern human mind emerged bit by bit much earlier in Africa – that the Human Spark in fact didn’t ignite in one glorious (and European) burst but instead sputtered into existence in the minds of our African ancestors over perhaps a hundred thousand years or even longer.

So entrenched was the idea of a sudden European origin of modern human behavior that the McBrearty-Brooks paper was met with much skepticism when it was published in 2000. But it has since not only convinced most of their colleagues, but was also one of the inspirations for this project. So it was a great opportunity for us to have Alan and Alison get together at the Peabody, in what Alan was enchanted to discover is the museum’s “Stone Age Laboratory.” Alison had spent several hours prowling through the museum’s huge collection of archeological artifacts and had laid out for us a wonderful collection of items made by humans from over 1.7 million years ago in Africa to some 20,000 years ago in Europe.

Alan was very taken by how nicely the million-plus year old stone axes nestled in his hand, but was most struck by the fact that having invented stone hand axes some 1.7 million years ago, we humans stuck with them for most of our existence. Alison showed Alan several much more elaborate tools in stone and bone found in Europe and dating to between 20,000 and 35,000 years ago as the sort of evidence that it was there and then that the Human Spark ignited. “People looked at these and they said, well, there’s a human revolution here. There’s an incredible development, an incredible flowering of human creativity and human inventiveness. It’s a revolution. Something must explain it.”

Alison told Alan that it was a trip as a graduate student to the Kalahari with her then-new husband, John Yellen, that began to plant the seeds of doubt about the conventional wisdom. In the course of his work with the Bushmen, Yellen had discovered an archeological site where there were hundreds of tiny stone points. Alison showed Alan an example: “If you found these in North America, you would say this is an Indian arrowhead, but these were not in North America and, as we were able to show, they were about 75 to 80 thousand years old.”

The Human Spark camera captures Alison and Alan’s exchange as they examine the ancient points. Photo by Maggie Villiger

Alison argues that these points must in fact have been arrowheads.

Alison: “You could put it on a little tiny spear and go after a little tiny antelope, but would you really want to go up against a giant buffalo with something that size?’

Alan: “Not before it was extinct!”

Alison: “Don’t think so. Let’s say those people didn’t have too many descendants, which is what matters after all in evolution.”

Conventional wisdom had the bow and arrow invented perhaps 20,000 years ago – guess where.

So this was the beginning of Alison Brooks’ career-long quest to demonstrate that there was in fact no single cognitive “explosion” that led to the modern human mind; that instead it was built piece by piece in Africa. And this is the theme of what will be the first program in our Human Spark series. Later we will be going with Alison to an archeological site in Kenya she has been excavating for several years now, and which she believes encompasses the critical time – and perhaps the critical place – where the Human Spark first began glimmering into life.

It will be a long way from my academic backyard. But Alison promises some exciting finds…

Robin Dunbar at the 2008 Nobel Conference

Gustavus Adolphus College in Saint Peter, Minnesota hosted a conference last October focused squarely on the idea of “The Human Spark.” In fact, throughout our travels, the show’s production team met with many of the conference’s speakers! Webcasts of each presentation are available online for the general public.

Robin Dunbar from the University of Oxford discusses the social brain theory and what sets human beings apart from other apes.

Curtis Marean from Arizona State University talks about the implications of his archaeological work along the coast of South Africa for our understanding of human origins – not just anatomically modern humans, but modern behavior too.

Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology presents the implications of his work sequencing the Neanderthal genome.

In many ways, The Human Spark tells a story of evolution as we look at the emergence of different related species over vast quantities of time. British geneticist Steve Jones has lately made the provocative assertion that human evolution is coming to its end. Here’s his explanation for why.

He doesn’t say human beings have achieved perfection –- but he does suggest that our population is becoming much more uniform. Remember that evolution depends on random genetic changes for natural selection to work on. Jones argues that fewer older fathers in the developed world means less genetic variation. And the mutations that do occur don’t give anyone much of a competitive edge because we no longer live under the tough conditions our ancestors did. Populations are much larger and far less isolated than they were in the past, too, which cuts down the possibility that a random change can take hold in a small group.

Check out these sites for more info:

• Daily Mail: “Evolution stops here: Future Man will look the same, says scientist”
• BBC Radio: “Human evolution ‘has stopped’” (audio)
  
• Discover Magazine Blogs: “No More Evolution For You, Says British Scientist”

Jones doesn’t offer much by way of evidence to back up his position.

What do you think? Is evolution coming to an end? What evolutionary pressures do you think still exist? What could a future human look like?