Science Talk

Killer Chimps and Funny Feet: Report from the AAPA Conference

Scientific American editor Kate Wong talks about the recent conference of the American Association of Physical Anthropologists in Portland, Ore., where subjects included killer chimps, unprecedented fossil sharing among researchers and divergent hominid foot forms

Podcast Transcription

Steve:           Welcome to the Scientific American podcast Science Talk posted on April 27th, 2012.  I am Steve Mirsky.  On this episode:

Wong:           Feet were definitely a hot topic at this meeting.

Steve:           That's Scientific American editor Kate Wong.  She recently attended the annual meeting of the American Association of Physical Anthropologists in Portland, Oregon.  We spoke about feet and other foundational subjects at the Scientific American offices.


Steve:           Fascinating conference.  Tell us about it.

Wong:           There were several really, really interesting stories that came out of that meeting.  The first one was a big study looking at the question of why chimpanzees kill other chimpanzees in the wild. And there was a presentation given by Michael Wilson of the University of Minnesota along with a whole bunch of coauthors—sort of l like a who's who of Chimpanzee researchers.  Basically the study looked at 17 communities of chimpanzees that have been studied by scientists for quite some time, and they looked at 86 killings in those communities and tried to figure out what it is that triggers chimpanzees to kill one another. And what they found was, well basically there have been two theories, for why this happens.  One was that it's just an evolved strategy for reducing competition for resources, and the second idea was that it might be triggered by human disturbance; so things like deforestation or in some cases, situations where people have been feeding the chimpanzees, things like that.  So, when they looked at these 86 killings across these 17 communities in Central Africa, East Africa, West Africa, what they found was that the killings occurred in most groups of chimpanzees, not just a couple of them, where the killings have been kind of higher profile. They also found that the killings were conducted mostly by groups of males and the victims were mostly infants and adult males outside the social group, the killers' social group.  So when they looked at all this data, they determined that human disturbance was not actually a factor in the killings, and in fact, the higher the number of males in the group, the higher the number of kills.  Now it wasn't the sex ratio, the ratio of males to females, in a particular group that was the factor in the number of kills, it was just the number of males in the group.

Steve:           The absolute number.

Wong:     The absolute number.  Chimpanzees are mostly peaceful animals.  They're not spending a lot of time killing each other, but when they do kill, apparently it's the number of males in the group that is a factor. And you know, the reasons for this appear to be that, you know, they're reducing the competition for mates and they are, you know, chimpanzees are territorial, so the males are defending their territories; and you know, more work remains to be done on this, but when I spoke with Michael Wilson about his team's findings, he suggested that it may be a situation in which it's the balance of power between neighboring communities of chimpanzees.  So, if you have one community that has a lot of males that can, kind of, gang up together, and the neighboring community has fewer males, then the community with the larger number of males is in a better position to go on the attack and not suffer consequences for it.

Steve:           It's really interesting. And people are exposed to chimpanzees in media, they usually see baby chimps. They may forget what a full-sized adult male chimp looks like and has the power to do physically.  

Wong:           Yeah, male chimpanzees are really strong, and you probably wouldn't win in a fight against one.

Steve:           Oh, you definitely wouldn't; I mean, there might be some professional athletes who're gigantic, who might stand a chance I guess, but I don't think I would stand a chance.

Wong:           And neither would I, absolutely not.

Steve:           There clearly a different species, they have a whole different social structure, but there's so many things about them that just appear to be so similar to us.  I mean, it would seem just as an observation, a truism that if you want trouble, you know, in a human society, just stock it full of guys.

Wong:           (laughs) You know, I talked a little bit with Michael Wilson about whether there are, sort of, implications for understanding human behavior that come out of this study. And  his response was that, you know, we don't know if the chimpanzee and human capacity for lethal aggression is something we inherited from a common ancestor, but you know, the fact that it appears to be an issue of the balance of power in neighboring societies, communities that's striking; certainly that would ring a bell with many humans.

Steve:           So, there was this interesting thing that went on at the conference with casts of fossils, and talk a little bit about the, sort of, sociology of anthropology and how people don't really share their fossils with each other a lot and how there was this, sort of, virtual fossil sharing.

Wong:           You know, paleoanthropology has a reputation for being a very secretive science.  So, paleontologists go out into the field, they work under really hard conditions to recover these remains of our ancient ancestors, and they understandably want time after they've unearthed these fossils, to put them together to study them to make their pronouncements, their evaluations of, you know, what these creatures were like. And unfortunately there has been a, sort of, trend in the field to among some researchers to, kind of, keep them to themselves and not allow other researchers access to the material. And it's something that we've been critical in Scientific American, and I was really interested to see this year that the plenary session at this conference, which was organized by John Hawks at the University of Wisconsin, was instead of just a long talk given by an individual, what Hawks did was to send a word out to researchers in the community that he was going to be devoting the session to inviting people to bring in casts of fossils that they had found or had to access to and putting them all out on a whole bunch of tables and inviting the association members to come and just look at them.  So, for a lot of people, particularly students, this was their first opportunity to see replicas of fossils that they've only had the chance to read about.  So, there were things there like there was a copy of the famous Turkana Boy skeleton, for example, from Kenya, it's an early example of Homo erectus, a very complete and famous specimen.  And then there was even this recently analyzed little pinky bone from the site of Denisova in Siberia and this was the specimen that recently geneticists were able to obtain an entire nuclear genome from this little—I mean it's so tiny it looks like, we were laughing about it, like fingernail clippings—and yet through this amazing technology, an entire ancient genome was recovered from it; and that was probably the least seen specimen in the whole group, and people, pretty excited to see it.  It didn't look like much, but it was just incredible to see how much information could be gleaned from such a tiny little scrap.

Steve:           So, you think there will be more resource sharing in the future based on this or this is a one shot?

Wong:           Yeah, it will be really interesting to see; it's maybe a little bit too soon to say. But you know, the fact that, for example, the recently discovered Australopithecus sediba species from South Africa—that's a discovery made by Lee Berger of the University of the Witwatersrand in Johannesburg and his colleagues—that team has made a point of making their project into an open access project, so they have really committed to that and invited researchers from all over the world to come and see the specimens.  And you know, if they're willing to share a discovery that major, then it's going to put the pressure on other researchers to also, you know, to share their materials. And on governments, it's not just researchers, I mean, there are government policies sometimes make it difficult for outside researchers to look at fossils.  So, you know, hopefully it will be setting a great example for other researchers in other parts of the world and everybody can look at all the fossils and do real science.

Steve:           Speaking of fossils, so some possible insights into bipedalism at the conference.

Wong:           Yeah, feet were definitely a hot topic at this meeting.  There were a couple of specimens in particular that people were talking about.  One was this recently discovered foot—a 3.4 million year old foot from the site of Burtele in Ethiopia. And this is a really weird foot, in that, you know, at around the same time we have Lucy's species, Australopithecus afarensis, and that species basically walked upright like us and had a foot, you know, pretty much like ours.  Now this foot is from the same time period but it has this big toe that sticks out to the side—it's very, kind of, ape-like in that regard—you know, it looks like a foot that is adapted to climbing in the trees.  Now this is interesting because researchers thought that, basically, once hominids, the early human ancestors, evolved, the ability to walk upright, it was kind of like there was one way to do that. And with discoveries like the Burtele foot with its divergent big toe and then also Australopithecus sediba from South Africa which I just mentioned, and that's roughly a two-million-year-old species that has a really weird foot too in a totally different way.  You know, one of the most startling aspects of it is it has a heel bone that looks just like an ancient ape's heel bone and then an ankle bone that looks like a modern human's ankle bone. And the way that that's been interpreted—and Jeremy DeSilva of Boston University gave a presentation on this foot at the meeting—he suggested that Australopithecus sediba, when it walked upright was probably hyperpronating, so, when it's walking the foot is rolling inward. And it would have been a pretty awkward way of getting around and yet that's what it appears to have done.  So, there were multiple flavors, if you will, of walking around on two legs and that was just something that in the past we never really thought happened.  So it's just yet another sort of signal that there was more diversity among early hominids than many researchers ever would have expected to see.

Steve:           That's it for this episode.  Get your science news at our Web site,, where you can also read an excerpt from Charles Duhiggs''s new book, The Power of Habit:  Why We Do What We Do in Life and Business. And follow us on Twitter, where you'll get a tweet every time a new article hits the web site.  Our Twitter name is @sciam. S—C—I—A—M. For Scientific American's Science Talk, I'm Steve Mirsky, thanks for clicking on us.

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