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So what does make humans unique?

 Human origins and evolution  Comments Off
Mar 312013
 

I went to hear Dr. Kim Hill's talk on Thursday on the origins of human uniqueness. Hill began by framing our uniqueness in terms of our energy usage and biological dominance&emdash;for example, the fact that we cycle more nitrogen than all other terrestrial lifeforms combined, and we represent 10 times more biomass than any other large species that ever lived. We also exhibit extreme social complexity and specialization; no other species has anything remotely resembling the New York Stock Exchange or the NCAA basketball tournament, for example. Moreover, even before agriculture, we had colonized every landmass, and hunter-gatherers exhibited unusually complex social behavior compared to that of other animals. However, although we exhibit non-unique traits that arose through non-unique processes, we somehow turned into this distinctive species. The question is, how?

Hill described a combination of critical features that enabled all this to happen: cumulative culture, non-kin cooperation, language, and various cognitive capacities. These features emerged from various preadaptations, including bipedality, a change in our dietary niche, and a shift in the human life history (that is, the timing and duration of the events that make up the human lifecycle) and social structures. He focused on a chain of events involving non-kin cooperation and cumulative culture. To illustrate each link in the chain, he used a great deal of data from his own work and that of others with current-day hunter-gatherers in South America and Africa. The story goes roughly like this:

  • Our feeding niche shifted from collecting foods to extraction and hunting. (Extraction Includes the gathering of roots, nuts, and other things that require some labor or ingenuity to get.)
  • As a consequence, there was more variation in the quantity of food available each day. This in turn led to daily food sharing. In two hunter-gatherer tribes that he mentioned, nuclear families never keep more than 50% of any type of resource that they acquire. This buffers the variability for everyone day by day and on longer timescales, and provides protection against starvation due to illness or injury.
  • The result of this is a fourfold difference in adult mortality between humans and chimpanzees. Adult mortality affects the entire life cycle: delaying maturity, delaying senescence, and extending the productive years of adults.
  • Because maturity is delayed, and children depend on their parents for food, parents have multiple dependent offspring at any one time. As anyone who has bought groceries for a large household can imagine, this is difficult for parents. Several strategies arose to address this problem. One of them is that adults without children, for example, siblings of the parents, may help out (AKA opportunistic cooperative breeding, or helpers in the nest). In fact, the food sharing that arose initially as a way of reducing the variation in the food supply, and thus the risk, became intentional overproduction. That is, people seek out excess, for instance, by gathering more food than they need rather than stopping when they have enough for themselves.
  • An additional consequence is that women live past their reproductive capacity. That is, women go through menopause.
  • These cooperative breeding arrangements favored the evolution of prosocial emotions, or investment in the well-being of other people in the same group. In insect colonies, cooperation occurs because the insects are closely related. Hill presented evidence that shows that this is not the case for hunter-gatherer bands: People cooperate and do things for the benefit of others even if they are not related.
  • Juvenile dependence and the resulting investment of fathers in their children and pair bonding gave rise to a pattern described as the exogamy complex which, in a nutshell, eventually created complex social networks that included people who were not genetically related (e.g., in-laws) that allowed cumulative culture to arise.
  • Cumulative culture is what happens when you not only learn how to build or use a spear or grinding stone or web page, you figure out a better way to do the job. Although other animals learn things from each other, like learning how to use sticks to dig out termites, none of them build on what they learn and improve on what they have learned. Hill suggested that the shift to large social networks may have been as important as evolved cognition in explaining why we begin to produce cumulative culture in the late Middle Pleistocene 200,000 years ago.

Obviously this leaves out important things like language and brain size and other cool things about how we got to be the way we are. However, it's still a fascinating story of our roots. What struck me in particular is the difference between this and Hobbes's description of life in the natural state as nasty, brutish, and short. The hunter-gatherer societies that he described have a form of income insurance that protects against illness or injury, for example, and the entire system of hunter-gatherer life that he described was nothing like “every man for himself.”

At the end of his lecture, Hill noted that maybe we shouldn't be thinking so much about whether we will ever contact intelligent species in the rest of the universe; perhaps we should be thinking instead about highly cooperative social species. A single intelligent human could never have gotten to the moon alone.

One of the most interesting questions that came up in the Q&A afterword was the question of whether it's likely that there could be one more than one such species per planet. The answer, rather sadly, is probably not. It looks as though the price of our success might have been the extermination of all competitors, even distant ones. Hill estimates that we exterminated at least five other hominin species that could have also followed our trajectory, and right now we seem to be in the process of exterminating the chimpanzees.

You can read more about Prof. Hill's work in this New York Times article.

 

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Oct 312012
 

This is a week and a half old, but worth looking up if you haven’t seen it: An article on Slate examines what prehistoric art can tell us about the human brain. According to the article, cave paintings and other very early art may represent a kind of visual shorthand and abstraction in which salient features are exaggerated. The dots, squiggles, and other more obviously abstract features may be a representation of what early humans saw in hallucinations or trance visions deep in the caves where they painted, which are essentially visual noise in the brain that becomes amplified when visual input from the outside world is absent. The more haunting question of what exactly these paintings and other art objects meant to their creators and exactly why they created them is harder to answer.

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 Permalink  10/31/2012  Posted by at 9:52 am Human origins and evolution Tagged with:  Comments Off

Updating the past

 Human origins and evolution  Comments Off
Jun 302012
 

I was struck by a headline about how the discovery of ancient pottery in China “could change [the] history of mankind.” The history of humans (and other hominids) is indeed changing as we learn more about it. Here are links to some recent stories.

  • The pottery fragments found in China come from the oldest known ceramic containers. They were dated back to around 19,000–20,000 years ago (10,000 years before the beginnings of agriculture), and are 2,000–3,000 years older than a previous find which used to be the oldest known pottery. Burn marks on some of the pottery suggest that the hunter-gatherers who made and used it were cooking some of their food well before the advent of agriculture and settled communities. Science News has an article on this. The paper was published in Science (only the abstract is available to nonsubscribers).
  • Another study, reported in Science NOW, suggests that the Mesolithic hunter-gatherers that lived in Europe 8,500 to 3,000 years ago, before farming caught on, might have been genetically and culturally more similar than expected. However, the study is based on analysis only two Mesolithic skeletons (~7,000 years old, from Iberia), so there is a lot of room for debate. The paper is available online at Current Biology (nonsubscribers can see only the summary).
  • Last but not least, we’re learning more about the primate Australopithecus sediba, which was identified in 2010 and shows an interesting combination of primitive traits resembling those of other apes and modern human-like traits (e.g., they had long arms but apparently walked upright at least some of the time). The latest news is about what they ate; according to an analysis of teeth from two A. sediba skeletons, their diet was surprisingly similar to that of chimps and even giraffes (more bark and leaves, for example), and different from that of other known human ancestors. Again, it’s a small sample, but an interesting result nonetheless. Scientific American has a blog post on the story. Nature just published the research online (subscription required).
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E. O. Wilson on how we got to be this way

 Being human, General, Human origins and evolution  Comments Off
May 042012
 

Distinguished evolutionary biologist Edward O. Wilson, who coined the term consilience as it was used at the conference I attended last weekend, gave the keynote address. His talk was based on his latest book, The Social Conquest of Earth.

Wilson began his talk with three haunting questions that Gauguin wrote on a painting he made toward the end of his life: Where do we come from? What are we? Where are we going? These questions are central to philosophy, religion, and science. Continue reading »

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Perspective!

 Being human, General, Human origins and evolution  Comments Off
Apr 012012
 

You may remember the Total Perspective Vortex from the Hitchhiker’s Guide books by Douglas Adams. The vortex gave its unfortunate occupant a realistic view of his or her place in the context of the entire cosmos, a humbling vision that drove the victim mad. I have to say that as I learn more and more about our proper place in the grand scheme of things, I become exhilarated rather than distressed. Gaining greater perspective is a thrill.

The emerging interdisciplinary field of big history seeks to weave together all we know of the history of the universe and everything in it and to teach this coherent big picture. Geologist Walter Alvarez was one of the co-discoverers of a significant event in Earth’s history, the extinction of the dinosaurs after an asteroid impact, that had a tremendous effect on the subsequent history of the planet. He began teaching a big history course at Berkeley a few years ago, and he came to IU last week to talk about big history, which he described as a bridge between science and the humanities.

One of the problems, when you teach big history, is that creatures who have a maximum lifespan of about a century (and generally don’t last even that long) have a hard time grasping the time scales involved. Or as Carl Sagan put it:

Part of the resistance to Darwin and Wallace derives from our difficulty in imagining the passage of millennia, much less the aeons. What does seventy million years mean to beings who live only one-millionth as long? We are like butterflies who flutter for a day and think it is forever.

To address this problem, one of Alvarez’s students, Roland Saekow, wanted to find a way to synthesize all of the timelines on the handouts for the big history course into a single zoomable presentation. He and Alvarez worked on the problem, and eventually their project grew into the ChronoZoom Project. At the website, you can get an overview of all the timelines and then zoom in a particular time period. Dots scattered about the timelines contain relevant images, video, and other embedded material. A couple of tours are also available. The project is in beta, but already it’s enough to light up the mind. It will be interesting to watch it develop and see how the timelines fill up with information.

In his talk, Alvarez focused on two concepts in big history: little big history and contingency. A little big history covers a single place or thing in light of all the timelines we have: cosmic, geological, evolutionary. The basic idea is that you can look at just about anything in terms of “How did this come to be?” and uncover a story in deep time. He offered a fascinating glimpse of this approach with a sketch of what a little big history of Spain (where his family came from) might look like.

One cool thing about this approach is that it shows you the connections between the different fields of academic study: for example, how the geological factors that shaped Spain’s high, dry interior are connected to the presence of so many words of Spanish origin in American cowboy lingo (the interior was not suitable for agriculture but was good for herding livestock, so the Spanish already had experience that was useful when they came to the American west, and that fact lingers in the language). It also gives people a much better sense of the shape of the cosmos and of existence, the time spans involved, and incredible complexity of cause and effect. This hard-won knowledge of who and where and when we are, at least in the broadest outlines, is one of the most valuable birthrights of every human, in my opinion.

An example of this complexity is the idea of contingency, that the facts that seem so solid to us in hindsight actually emerged from a confusing matrix of possibilities. The topic of contingency in history is vast, and I’m sure everyone has personal examples. Here’s one of mine: In his early 20s, my father went to a bank to apply for a job, but the woman he needed to talk to in the personnel department was out having lunch, so he went to another company where a friend of his worked and applied there. He got the job, and that’s how he met my mother. If the person at the bank hadn’t been out to lunch when he came by, I probably wouldn’t be here (or my kids, or the grandchild about to be born).

On a bigger scale, as Alvarez pointed out, that asteroid that hit Earth had about a seven-minute window of opportunity, which is not much out of the 4.5 billion year history of the solar system, especially considering the magnitude of the changes it caused. I think the real point of understanding contingencies, although Alvarez didn’t mention this, is that it clarifies the haphazard nature of existence. There is no plan. The only meaning is the one we supply. Events are a complex web that we understand only incompletely, and the stories we impose upon them are the best we can do with limited facts. They could have been different.

Maybe I shouldn’t have dismissed the Total Perspective Vortex so quickly; there is a certain terror involved sometimes in seeing one’s own small life in the context of the big picture. However, I’ll leave you with these inspiring words from Mountains of the Mind, by Robert Macfarlane:

Contemplating the immensities of deep time, you face, in a way that is both exquisite and horrifying, the total collapse of your present, compacted to nothingness by the pressures of pasts and futures too extensive to envisage. And it is a physical as well as a cerebral horror, for to acknowledge that the hard rock of a mountain is vulnerable to the attrition of time is of necessity to reflect on the appalling transience of the human body.

Yet there is also something curiously exhilarating about the contemplation of deep time. True, you learn yourself to be a blip in the larger projects of the universe. But you are also rewarded with the realization that you do exist—as unlikely as it may seem, you do exist.

In addition to the ChronoZoom page, there are a few books about big history.

This one is by David Christian, who is more or less the founder of the field:
Maps of Time: An Introduction to Big History, With a New Preface (California World History Library).

Here’s one where Christian zooms in on human history: This Fleeting World: A Short History of Humanity.

Here’s a competing popular book of big history (the reviews are mixed, and I haven’t read it): Big History: From the Big Bang to the Present, by Cynthia Stokes Brown.

And finally, a scholarly look at not just the big history of the universe but big history as a field: Big History and the Future of Humanity, by Fred Spier.

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Movie review: Cave of Forgotten Dreams

 Human origins and evolution  2 Responses »
Jan 142012
 

Cave of Forgotten Dreams, documentary film by Werner Herzog, 2010

This documentary is almost certainly as close as you will ever get to exploring the Chauvet Cave in southern France, home to the earliest known cave art, and Werner Herzog provides an excellent vicarious visit. The cave was discovered in 1994 and speedily locked up to protect its prehistoric treasure, a multitude of paintings of wild animals roughly twice as old as any previously known. The cave was evidently visited by humans in two different periods: the Aurignacian, roughly 30,000 to 32,000 years ago, and the Gravettian, roughly 25,000 to 27,000 years ago. Most of the art is from the earlier period; an enigmatic footprint left by a young boy, paired with the tracks of a wolf, are among the fewer remnants of the later period. About 20,000 years ago, a rock slide covered the entrance to the cave, which lay undisturbed until 1994. I groped for an analogy; it is as if some future beings in the year 29,000 by our current calendar found an iPad amongst the debris at the lowest levels of the city of Troy, perhaps.

Herzog does these beautiful images justice; he filmed them in 3D under fairly restricted conditions (access to the cave is very limited). The result takes full advantage of the light of moving flashlights, the looming shadows of the film crew and scientists, and the billows and depressions in the stone walls, which the creators themselves exploited to present their visions of their animal cohort. The film also shows some footage of the world outside the cave, including the Ardèche River and a natural stone bridge called the Pont d’Arc. Although one of the messages of the film, underscored by its title, is that the past is in many ways lost to us, this view of the paintings was evocative of the conditions under which they were created. For all our distance in time from these anonymous artists, it was easy to think that you could sense something of their world.

Herzog spends lots of times on the paintings themselves, noting their proto-cinematic aspects (a bison drawn with eight legs, for example, in an attempt to portray movement). There are some satisfyingly long slow pans over the images in all their mysterious beauty: a series of four overlapping horses, a rhinoceros with an exaggerated horn, a pair of rhinos apparently locked in combat, and many more. (The soundtrack gets a little intrusive in spots; silence would have been a fine alternative to what struck me as generic shapeless mystical music.) He also interviews some of the people who study the caves, a passionate and sometimes eccentric bunch. Jean-Michel Geneste, the Chauvet Cave Research Project’s director, describes the rich fauna of the time:

“You have to imagine lions, bears, leopards, wolves, foxes, in very large numbers, and among all these carnivores and predators—humans!”

Archaeologist Wulf Hein, talking about what we can learn of other arts at the time from other sites, appears wearing a rough fur garment of some sort and holding a replica of a tiny bone flute. He gestures at the German valley behind him and speaks as if he were an eyewitness setting the scene for a story:

“In the valley down there, reindeer and mammoth were passing, and it was very cold.”

Another researcher discusses the sounds we can imagine from the paintings, for example, the open mouths of horses suggesting their whinnies. These interviews support another message of the film, that although we can never reconstruct the past fully, we can represent it (and in fact we seem compelled to do so).

One of the most poignant signs of these early humans, to me anyway, was a series of red handprints they left behind. I am always moved by the sight of prehistoric handprints; they are one of the most vivid reminders of the humanity of these long-lost people (“I was here!” they seem to be saying). In this case, one of the people who left handprints had a crooked little finger, so his path through the cave can be traced by the recognizable handprints he left behind. The shadow of the unknown in which so many people once lived makes it particularly astonishing when we can identify a specific individual among those many, many anonymous generations.

In addition to its human traces, the caves contain things left behind by other animals: bones, some of them gnawed, perhaps by cave bears; bones of the bears themselves, including a skull that has since been encased in glittering calcite; scratches the bears made on the walls, some under the paintings and some over them. Most of the stalactites and rippling curtains of stone evidently formed after the rock slide that sealed the cave, so the painters would not have seen them. They emphasize the vast amount of time that has passed since its earlier users left it.

All in all, I highly recommend this film, particularly if you are fascinated by what we can understand of the lives of prehistoric humans or by the way scientists investigate these early ancestors. It is a dazzling visit to a mostly vanished world.

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Big history

 Being human, Human origins and evolution  Comments Off
Apr 192011
 

One point of all the rambling in my last post was essentially that learning the full story about the context in which we find ourselves and how we came to be here, as we have discovered it so far through science, can be mind-opening, inspiring, and profoundly positive. I think this knowledge is the birthright of every child. David Christian is one of the proponents of big history, which is a synthesis of our knowledge of events at diverse timescales and across disciplines (e.g., cosmological, geological, evolutionary, and human history). He recently presented a TED talk that gives an exhilarating glimpse of big history and makes a plug for teaching it to young people.

Christian gave an inspiring talk here at Indiana University a few years ago about the concept of big history. One of the things he talked about was the challenges of developing a curriculum that fits all this information into a single semester, and about his justifiable pride in managing to go from the Big Bang to the present day in the course he was teaching. However, his wife, who is a story-teller, did even better, creating a story that I think he said took about 45 minutes to tell and covered the same turf. I wonder if they worked together to create that presentation.

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