Archive for September 11th, 2007
The role of the Achilles Tendon on the Origins of Bipedalism & Human Evolution
Another day, another bit of anthropology news making waves on the internet. This one comes from a University of Manchester study presented to the British Association for the Advancement of Science Festival of Science. Bill Sellers, a primatologist spealizing in biomechanics at the said univerity, is claiming he made the discovery that humans first developed Achilles tendons more than 2 million years ago, before Homo erectus. I’ve got problems with this, and I’ll let you know why right after I get thru some basic anatomy.
Press Round-up:
Ancient humans walked but ‘struggled to run’
Slow start to human race
Was Ability To Run Early Man’s Achilles Heel?
How man became the swift and fearless hunter
The Achilles tendon is located in the lower leg, you can spot it on yourself by feeling for a dense tendonous ‘ribbon’ that extends below your calf muscle to your ankle. It functions as an attachment of the calf and soleus muscles to the calcaneus or heel bone and provides a lot of the spring and shock absorption in our gait. There’s a whole folk tale as to how this tendon got its name, which I won’t get into, because you should know about it already.
Bill Sellers is saying that he’s studied the fossil record and that what he found out is the Achilles tendon would have allowed early humans to move nearly twice as fast as before. Do you catch the mild adaptionist tone with this claim? He uses the lack of an Achilles tendon in the chimpanzees and gorillas as a reference point… or in other words, because those apes don’t have an Achilles tendon, that’s why they can’t run bipedally. That’s partly true and partly false. These apes have an Achilles tendon, but it’s very small. But, there’s a lot more to why non-human apes can’t run bipedally.
Our lineage’s ability to move around bipedally, be it running or walking, is not because of one anatomical feature over another. No one part is more significant.
I’m not doubting that the Achilles tendon isn’t important, what I’m saying is that almost the whole hominid body has an important role in allowing us and our like to walk around on two. I’ve said this before, and I don’t think people get it. From our femora to our tibiae, from our vertebrae to our pelvis, each bone and muscle involved in bipedal locomotion is unique when compared to a non-bipedal animal.
Which leads me to this image and my second point of criticism:
My second criticism is that Sellers is not the first to make the claim that the Achilles tendon is where all of ability to run comes from. So it bugs me that either he or the press is giving him all the credit for it. The first that I know of that talked about the importance of the Achilles tendon in bipedalism was my undergraduate physical anthropology professor, Adrienne Zihlman.
Others like, Dennis Bramble and Daniel Lieberman wrote to Nature in 2004, on “Endurance running and the evolution of Homo.” In their article, they outline the Achilles tendon as one of the important units in helping us be able to run. They also mention other parts of our body that help us run, like the gluteus maximus, a.k.a. our round butts, because that muscle is crucial in stabilizing the leg into the pelvis during high running speeds.
I got the above image from Bramble and Lieberman’s paper, which shows a modern human in the upper left, a Homo erectus in the upper right, a chimp in the lower left, and a australopithecine in the lower right. You can see how the muscles differ between the chimp and human, such as the larger gluteus in the humans and the presence of a larger Achilles tendon.
The point to take home, when studying human evolution, is that the entire body needs to be analyzed. Parts of our body did not evolve in a void from the others. The Achilles tendon, the long femur, the wider pelvis… all these parts and other parts are why are bipedal.
Related readings:
Ask yourself, “Are Modern Women Excellent Gatherers?”
Kudos to Larry Morgan of Sandwalk, who pointed out this New Scientist news article last week, “Modern women are excellent gatherers,”
“Men hunted, women gathered. That is how the division of labor between the sexes is supposed to have been in the distant past. According to a new study, an echo of these abilities can still be found today.
Max Krasnow and colleagues at the University of California, Santa Barbara, have discovered that modern women are better than men at remembering the location of food such as fruit and veg in a market.
The researchers led 86 adults to certain stalls in Santa Barbara’s large Saturday farmer’s market, then back to a location in the center of the market from where the stalls could not be seen. They were then asked to point to each stall’s location. This requires dead reckoning – a skill that men may once have used to return from hunting, and one that men today still usually perform better than women in experiments…”
I’m gonna refrain from commenting in depth on this research because everything I’ve been taught in anthropology has told me this sort of science is ridiculous… As if we can infer how prehistoric societies broke down gender roles and division of labor. I really thought anthropology was beyond this.
If you’re interested in reading the source article, it was published in the Proceedings of the Royal Society Biological Sciences, “Spatial adaptations for plant foraging: women excel and calories count.”
Finding damage patterns in sequences of the Neandertal genome
Preemptively following this early online release in PLoS, comes this paper published just now in PNAS, “Patterns of damage in genomic DNA sequences from a Neandertal.” From the abstract, what I can tell is the authors are defending,”Hey, don’t worry we know where and what the damages are. And that’s okay, because we still have reliable sequences!”
Here’s the abstract,
“High-throughput direct sequencing techniques have recently opened the possibility to sequence genomes from Pleistocene organisms. Here we analyze DNA sequences determined from a Neandertal, a mammoth, and a cave bear. We show that purines are overrepresented at positions adjacent to the breaks in the ancient DNA, suggesting that depurination has contributed to its degradation. We furthermore show that substitutions resulting from miscoding cytosine residues are vastly overrepresented in the DNA sequences and drastically clustered in the ends of the molecules, whereas other substitutions are rare. We present a model where the observed substitution patterns are used to estimate the rate of deamination of cytosine residues in single- and double-stranded portions of the DNA, the length of single-stranded ends, and the frequency of nicks. The results suggest that reliable genome sequences can be obtained from Pleistocene organisms.”
I don’t yet have access to the paper because my school’s library hasn’t updated access to issue number 37 of their year’s volume of the Proceedings of the National Academy of Sciences. But once I do get my hands on the paper, expect a much thorough review of it.
What can evolutionary psychology say about the social networking fad?
I, Kambiz Kamrani, have a confession to make: I’m on a lot of social networking sites and am pretty addicted. My history with social networking began all the way back in 2000, with LiveJournal which gave rise to Friendster. Friendster died a slow and quiet death, because Myspace was the new hotness. But Myspace’s days were also numbered. Recently, I deleted my account there.
But, I haven’t pulled out completely. I’m still on over a dozen different social networking sites and I check them regularly. From Facebook to Flickr, Pownce to Twitter, YouTube to Vimeo, Digg to del.icio.us… you’d think that I’ve satiated my fix! I haven’t. I am currently waiting to get invite codes to a whole new set of upcoming social networking sites.
Recently, I’ve asked myself, “Self, why are you on so many sites?” Given that I’m so busy and often never make enough time to do activities I enjoy, like go on a hike or a bike ride, I can’t believe I set aside time almost everyday to check these sites. I know one reason why I’m on so many sites and that’s because they all mostly specialize or occupy a certain niche that I find useful. For example, Flickr, is my place to upload photos while Facebook is a place I find and keep in touch with family and friends.
Where it gets tricky are my profiles on Pownce and Twitter, two microblogging platforms that basically do the same thing. Digg and del.icio.us, are also both sort of a social bookmarking and news syndicator… and even YouTube and Vimeo — two video sharing sites. Why am I on both? Why do I ask to be bombarded with messages of every single little thing my friends are doing… what they are reading and bookmarking seems like I’m just asking for a headache?
This condundrum leads me to the other reason as to why I am on so many social networking sites, and possibly why millions others like me (perhaps, you?) are also on them, has to do with our evolutionary history as social beings. That’s what Michael Rogers, columnist at MSNBC, is proposing in his piece, “How social can we get?” I must disclaim the piece is founded on evolutionary psychology, a.k.a. adaptionist story telling, but that doesn’t make it not an interesting read.
Rogers introduces us to a classic book in anthropology and evolutionary psychology, Robin Dunbar, the British anthropologist’s book called “Gossip, Grooming and the Evolution of Language.”
I’ve read the book and it is pretty ground breaking but at the same time horrifcally crippled in its reductionist claims. Rogers summarizes the book for us,
Dunbar is one of the more influential practitioners of [studying] how the human animal behaved in our earliest ancestral environments, long before civilization, for clues about why we are the creatures we are today…
[He] begins with the premise that back when our Paleolithic ancestors were still more [primitive], understanding one’s place in the group hierarchy was exceedingly important. Compared to other creatures, primates are unusually social animals. And thus knowledge about relationships — who’s mating with whom, who became allies, who just had a fight — was crucial for primates to maintain or advance their place in the pack. It was, Dunbar suggests, the birth of gossip. But before language evolved, how was gossip transmitted?
Dunbar speculated that the early hominids maintained and communicated their relationships via the mutual grooming behavior we still see in lower primates. Baboons and chimpanzees spend 20 percent of their time grooming one another. But grooming, Dunbar argues — besides tidying one’s fur and feeling good — was a way to establish and maintain friendships, determine the hierarchy within the tribe and signal one’s social connections to other tribe members. One might almost say that grooming was the first social networking application.
… He speculates that at some point, our early ancestors’ tribes began to get too big for even the most energetic primate to get around to grooming everyone. And thus language emerged to replace grooming as a means of conveying social relationships…. In exchange of personal information with language was far quicker than a 20-minute grooming session, and a single individual could converse with several others at one time. So rather than the traditional anthropologic explanation that language evolved among males to coordinate hunting, Dunbar proposed that language evolved as a way to maintain and identify social relationships. And we haven’t stopped gossiping since.
What Rogers suggests is that social networking fills my (our ?) social need to keep track of our relationships and status. In otherwords, social networking is,
“an incredibly efficient gossip engine.”
That claim is so painfully honest it is not even funny. To save some grace, it is not even worth outlining the amount of time I’ve spent using it as a ‘gossip engine,’ i.e. to see which of my friends are dating whom, who friended whom… etc. All of us social networkers know that we do it. It is one of the subconscious reasons as to why we sign up, why we visit, and why we pull out of a site when it starts to fade away.
Given that statement, and that we can’t comment directly on the MSNBC article, I wanna open up a discussion related to Rogers’ conclusion,
“So the obvious question about Internet-based social networking is whether we humans are once again increasing the size of our effective groups. Is this an evolutionary shift that… will ultimately change the way we operate as social creatures? Will anthropologists of some distant era look back and say that this was the moment when humans once again created much larger social networks than we were able to maintain in the past? Or perhaps in the end we’ll discover that, once again, about 150 “friends” is as far as our capacities can take us.
Whether or not Dunbar’s decade-old theory about language’s origin in gossip is correct, it’s a fascinating way to think about what’s important in human communication. And it suggests that with social software, we’re for the first time arranging the Internet in a way that makes sense to the deeper inclinations of our brains. While we’re only in the very earliest days, this new twist may well be the beginning of the Internet as it is meant to be.”
What do you think? Is he onto something? For those out there with over 1,000 Myspace friends or are being badgered with information on Facebook’s news feed, do you think you can handle having so many relationships in your life?
