A Mosaic of Human(?) Evolution: Australopithecus sediba's Challenges

The anthropology community has been filled with buzz recently about the discovery of a new species, Australopithecus sediba. Is it really an ancestor to modern-day humans? Does it have a human-like brain or an ape-like brain? What do its humanoid hands but ape-like feet mean for the evolution of walking? We may be arguing about these issues for a while, but the completeness of the skeleton and its distinctive blend of early and more modern humanoid features set it on par with Lucy (Australopithecus afarensis) in importance. In a field where many even critical discoveries revolve around no more than a piece of jaw or a corner of a hip bone, this is a prize opportunity to learn more about how we developed the features that set humans apart from chimps and gorillas. For the longest time, the world has known of Lucy, the star of the paleoanthropological world, as our ancestor from about 3 million years ago. Despite many interesting findings since her fateful discovery, either due to the lack of a fossil record from incomplete skeletons or theoretical arguments about our family tree, we haven’t been able to draw a clear timeline of what led from Lucy to the first Homo habilis, the “handyman” that led to our own (Homo) sapiens. This all changed when a dig in Africa produced four fossil skeletons of stunning completion. They are now known as Australopithecus sediba, dated to a little less than 2 million years ago. The star of the show so far has been MH1, a juvenile male with a skull so complete that scientists have constructed a virtual model of its brain.

How can we even know what kind of brain it had if all we get is bone? Scientists used a CT scan of the male skull to create a model of the interior of the cranium. This endocast is constructed from many X-ray scans, rotated 360-degrees around a central point, so that each scan is like a cross-sectional slice of the skull. By digitally modeling the combination of those slices, scientists can deduce what type of brain and therefore what mental capacity it had. Based on that, we can then try to predict whether it used tools, and even speculate on its social organization and its capacity for planning and self-awareness.

A. sediba’s brain challenges what we thought we understood about the evolution of childbirth, bipedalism, and tool use. Some scientists are even claiming that the four fossils aren’t a separate species at all. Anthropologists are arguing not just about where to place A. sediba in our family tree, but about old and established theories about human evolution that have dominated the field for decades.

A Challenge to Childbirth

We originally thought that it was our big brains that caused our pelvises to evolve the way they did. After all, one major constraint on brain size, and therefore head size, is childbirth. How could our enormous brains fit through our tiny pelvises? We compensated for that with severely delayed development: compared to other mammals, human babies are basically born premature. When sheep are born, they can stand up within minutes. For a human baby, that process can sometimes take twelve months. We grow our brains, and the rest of ourselves, outside the womb, whereas other mammals emerge nearly ready-made. As a result, the easiest explanation would be that our pelvis has also rotated and reshaped to accommodate the wider birth canal.

A. sediba has thrown a wrench into this theory, because it has a small head, but its pelvis is still rotated the way a Homo pelvis would be, and yet its narrowness still echoes of Lucy. If we look closely at A. sediba’s pelvis and skull, we find that while its pelvis is a blend of the rotated hominin pelvis and the narrower australopithecine pelvis, its brain measures only 420 cubic centimeters (cc). To put that into context, a modern human brain averages upwards of 1500 cc. Lucy (A. afarensis) had a brain of around 400 cc. A. sediba has a brain size comparable to that of a chimp, clocking in at less than 500 cc on average. This means that even though A. sediba shares the same brain volume as Lucy and chimpanzees, its pelvis (and the rest of it, as we shall later see) was already beginning to change. So if A. sediba didn’t have a big brain to reshape its pelvis, what did it have instead?

A Challenge to Bipedalism

The answer to that question lies outside of the cranium, and requires us to think about how bipedal A. sediba was compared to Lucy or to a modern human. One feature that sets us “above” our ancestors is our ability to rise up and move about on two legs alone. Humans are completely bipedal; for the most part, we do not suddenly decide to switch to all fours in the middle of a meeting, or swing from the pipes on a train platform because it’s easier than walking to the train. Chimpanzees primarily travel on all fours, and although they can occasionally walk around on their hind legs, knuckle walking is much easier for them than for us. Human and ape skeletal features have evolved to suit their nearly locomotion lifestyles, but we see something different when we look at fossils from the transition between the ape-like australopithecine and the modern human.

Bipedalism requires changes in the shoulder blade, the pelvis, the legs, and the feet. Even the neck and spine are involved in upright mobility. Although chimpanzees and humans might share a common ancestor and are not related in any direct line of descent, it’s still useful to compare the chimpanzee’s ape features with our own. Our arms are relatively short compared to our legs, but apes and australopithecines have long upper limbs, with large joints to handle the weight they share with the rear limbs. The thickness and strength of the arm, leg, and wrist bones adjust in humans and in chimps based on how much weight they habitually need to support. On a chimpanzee, the shoulder blade is completely rotated so it can swing between branches, and humans still retain some of that flexible shoulder joint. The thickness of the spinal vertebra and the orientation of the pelvis both shift to accommodate the suddenly vertical load that humans endure in order for us to lift our heads above the crowd of ape-like relatives.

When we take all these comparisons and apply them to Australopithecus sediba, it’s as if we had tripped along the way and tossed all these features together. The sides of A. sediba’s pelvis are more vertical like you would expect of Lucy, and the size is more like Lucy’s, but the shape and angle of the pelvis where it sits in the body is more like a human’s. It also has the strong, long arms of a chimpanzee or an australopithecine, and the large joints of someone used to supporting their weight on their arms. Parts of the hip, knee, and ankle look like they would be best for bipedalism, but the foot looks much more like an ape’s knuckle walking foot. Overall, there is a mix of tree-swinging, knuckle-walking australopithecine and a large, bipedal hominin, with each individual distinct feature creating a confusing bigger picture.

There is no change in brain size or head size that could explain the change in pelvis, but there are changes in the rest of the body that are related to a newfound reliance on bipedalism, rather than swinging from branch to branch or knuckle walking over the ground. These differences happen in an otherwise australopithecine body carrying an australopithecine-sized brain. The old theory of childbirth changing our pelvises may just be untrue, and A. sediba might be the perfect exception that disproves the rule. It might just be possible that bipedalism, and not babies with bigger brains, is the cause for the signature changes in our pelvis that mark the evolution from Australopithecus to Homo. Then again, as many scientists have pointed out, why can’t it be both? The jury’s still out and the papers are still being written.

A Challenge to Tool Use

If walking came before bigger brains, does that also mean it came before smarter brains? The precise origins of stone tools are murky, and even if we see evidence of tool use 3 million years ago, that still doesn’t tell us how we came up with the idea of creating knives or axes out of bits of boulders. Whether a stone broke into a chopping blade by accident, or a few australopithecines started pounding rocks together out of sheer boredom at night (a wonderful image from an old professor of mine), the invention of tools had profound changes on human ancestral physiology.

The stunning endocast created for A. sediba, combined with skeletal evidence from its hands, can tell us a great deal about the changes in brain capacity, diet, and maybe even social complexity as it developed towards human society.

We associate the brain’s frontal lobe with planning, thinking, emotions, and other higher functions. Your frontal lobe stops you from saying something rude, helps you decide not to steal, and recognizes that surprise from a practical joke isn’t a signal for your body to go into survival mode. Many scientists think that planning ahead is a very human thing, and specifically, planning several steps ahead with many other humans. Chimpanzees are known to get a bunch of friends together for precise attacks against other chimpanzees. Baby baboons will fake an injury to get more food. Other primates can be just as devious as we are, but no chimpanzee has ever led a concerted and sustained effort to conduct siege warfare or to coordinate a commodities trading market in bananas. The simplified answer is that they do not have the same frontal lobe organization that we do.

Compared to other australopiths, A. sediba’s brain isn’t remarkable except for its frontal lobes. Like the blend of australopith and hominin features we see in is skeleton, its brain is overall australopithecine, but its frontal lobes have the shadows of future humans to come. Why the change? Its australopithecine cousins also have bipedalism, but their brains don’t harbor these glimmerings of the future man to come. They’re also known for tool use, as early as 3 million years ago, but their brains don’t have this kind of neural reorganization.

We might be lost at this point, if not for A. sediba’s hands and teeth. Its hands don’t completely look like ours, and probably wasn’t as good with precision grip as we were. But remember that A. sediba’s hands were occasionally freed to do other things while it walked around bipedally. Its hands could grasp more than tree branches, at least, and we see that in its human-like thumb to finger proportions. It’s as if an almost-human hand was grafted onto an australopithecine arm.

Another hint comes to us in the form of the juvenile male’s molars. Inside its vertical, human-like face, second molars already developed. Their arrangement is australopithecine, but their size is closer to Homo. The simple supposition is that what A. sediba was eating had changed how large its teeth needed to be. If its diet changed, then the way it gathered or reached those foods had changed too. Bipedalism meant it could see higher in non-wooded areas, and the improved finger dexterity meant it might be in same tool-making tradition we share with the early makers of stone “shovels.”

Whatever its brain, teeth, and hands can tell us about its life, we know that evolutionarily speaking, A. sediba’s brain organization was moving towards Homo before its size had tried for that shift.

A Mosaic of Evolution

The arguments surrounding A. sediba are enormous, complicated, and critical for our understanding of human evolution. Scientists are even arguing that it shouldn’t be classified as Australopithecus, or that it isn’t even a new species at all. That would mean no new species, no changes in existing theory; just an expansion of the range of features we used to assign. Even if it was a new species, Australopithecus sediba might not even be related to us; instead, it could be an example of how another organism has experienced similar environmental pressures to evolve in a similar way. It’s hard to say; there aren’t enough skeletons to let us know for certain. As with any new discovery, there are bound to be hundreds of new theories, new ideas, and new papers written arguing new sides to be taken.

Fossil hominins are an elite and lonely crowd, and their rarity makes every new discovery the next potential Lucy. As exciting and puzzling as A. sediba’s skeleton is, each individual piece of bone pieces together a hodgepodge of theories, ideas, and histories. However it ends up getting classified, the fact remains that paleoanthropologists carefully rescued four isolated skeletons from the darkness of history. In the future, there will hopefully be more like A. sediba, of any species, to transform, challenge, and energize our understanding of our origins and what it means to be Homo sapiens.

References

  • Berger, et al. Australopithecus sediba: a new species of Homo-like Australopith from South Africa. Science 328, 195 (2010).
  • Carlson, et al. The Endocast of MH1, Australopithecus sediba. Science 333, 1402 (2010).
  • Cartwright, J. (2000) Evolution and Human Behavior. Great Britain: Palgrave.
  • Gibbons, A. Skeletons present an exquisite paleo-puzzle. Science 333, 1370 (2011).
  • Kivell, et al. Australopithecus sediba Hand Demonstrates Mosaic Evolution of Locomotor and Manipulative Abilities. Science 333, 1411 (2011).
  • Zipfel, et al. The foot and ankle of Australopithecus sediba. Science 333, 1417 (2011).

Patrilineal & matrilineal tribes illustrate gender gap in spatial abilities depends on females' role in society.

in

Gender gap in spatial abilities depends on females' role in society by John Timmer, on Nurture affects gender differences in spatial abilities, by M Hoffman, U Gneezy, & J.A. List. Two closely related tribes in Northeast India share many qualities but differ in one respect: one is patrilineal and the other is matrilineal. Three American researchers decided to see if they could use these research conditions to answer some questions about the innate biological differences between men and women. There couldn’t be a more perfect situation of isolated, biologically similar but culturally disparate polities. The first thing I thought of when I saw the article was, "They've found the perfect research situation."

1. Single salient characteristic, all other physical points being equal. To have two isolated groups of people who share lifestyle (stresses, labor patterns, etc.), diet, proximity, and genetics, yet primarily differ culturally, is a research designer's dream. Often you have to account for external factors that may cause you to conflate one effect for something else. In trying to answer a nature-vs.-nurture question like this, you want to get all your variables down to as discrete a level as possible. Unlike other studies that are deliberately taking into account multiple lines of evidence, from culture to economic status to physical behavior to diet, here we have a question that requires us to make sure culture is the only variant (alternatively, biology is the only variant, but that's not the case here).

2. Ability to analyze or account for variation within a population. To have multiple villages within these two (culturally) isolated groups, so as to get a decent sample size and intra-polity variation is fantastic. This means the researchers can better understand of how one group functions absent any expectations generated by their knowledge of the other group, because they can look at group of substantial size as a whole.

3. Decent sample size With 1,300 participants in the sample size, that's pretty good for statistical purposes, to contribute to the body of scientific work focusing on gender and reasoning. John Timmer is absolutely right when he says "abilities of the tribes in Northeast India are only ever going to provide a small snapshot of the full range of human diversity," because that's what science often is, the accretion of studies depositing their findings year after year until (ideally) a decent and more holistic understanding is born.

4. Objective, quantifiable test that does not rely on self-reporting. One of the things I always liked about archaeology was that all my research subjects were dead; much of any error came from us, because a 2.7 C/N ratio was a 2.7 C/N ratio, but only the researcher could decide whether a pelvic bone was remodeled enough to make the subject 45 years old rather than 25. One of the things I disliked about psychology (and some diet studies) was the reliance on human subject self-reporting. The ideal way to cut down on self-reporting or result-expectation errors is double or even triple blind design, where the research assistants don't even know what they're testing for. The test here doesn't have to worry about that; the only variable I can even think of is the incentive given that might influence what kinds of people you end up getting for the test, but I'm willing to gloss over that because of the sample size and the fragmentation of variables.

The researchers accounted for other cultural factors as well, such as education and property ownership, but my first reaction to hearing the research conditions was, "Jackpot!"

Feminist Media Criticism, George R.R. Martin’s A Song Of Ice And Fire, And That Sady Doyle Piece

in

Feminist Media Criticism, George R.R. Martin’s A Song Of Ice And Fire, And That Sady Doyle Piece by Alyssa Rosenberg A much more level-headed response to criticism of GRRM’s approach to women that asks us to take a more objective view of storytelling, and refuses to equate the story with the writer or the reader.

My friends and I have remarked how GRRM’s mothers (those without grown children: Cersei Lannister, Catelyn Stark, Tanda Stokeworth, Lysa Arryn, etc.) are characterized as having “mother’s madness”. Their attempts to protect their children seem ill-advised, and at times harm their other offspring (Rickon, Myrcella). We had a hard time naming sane mothers who behaved rationally, other than the Queen of Thorns (Olenna Redwyne). Daenerys, the ultimate Mother, also fears the madness of her house’s blood, and my friends and I have yet to decide what this exception might mean for the series’ future and GRRM’s stance on mothers. All the same, it would do our minds a disservice if we reacted to this question with nothing but all-caps outrage and exceptionalism. I’m not saying Sady Doyle doesn’t make some good points about orientalism, etc., but Alyssa Rosenberg points out some telling flaws in her arguments that, I feel, often characterize the more embarassing portions of New Wave Feminism.

UK archaeologists forced to reinter human remains within 2 years of excavation

in

In 2007, the Ministry of Justice (rather than the Home Office) became responsible for regulations concerning exhuming human remains from ancient graves. The Guardian reports that the Ministry of Justice introduced a law in 2008 which declared that all human remains found in British digs must be reburied within two years. This makes sense if you have contractors and construction teams who are shoving deceased ancestors of living people out of the ground and then leaving them there without proper reburial. This does not make sense when you are an archaeologist digging up someone two thousand years old. Why?

It completely ignores the damage to the human remains themselves in the process of excavation and reinterment. For example, many of Harvard's human skeletons (the ones that haven't been repatriated through NAGPRA) are stored in boxes in climate controlled rooms, forever preserved and protected from the diagenetic processes of soil and sand and clay.

If we were to reinter many of these ancient human remains, we would completely lose:

  1. Preservation. We cannot guarantee the preservation of reinterred ancient human remains. The conditions of the reinterment site may not be protected, and the bones might be destroyed.
  2. Future Research. We are always inventing new research methods and technologies. Reinterring the bones for further decomposition means closing off new avenues of research in the future that would yield valuable evidence.
  3. Education. We would be unable to educate the public by using actual human remains to demonstrate the pathology of a human skeleton. Students would be unable to examine and work with real samples of these remains as a way to gain experience on identifying future excavated remains.

This is different from NAGPRA, which is a very narrowly defined piece of legislation that targets native groups who can reasonably prove a genetic or ancestral link with those to be reinterred or studied respectfully per tribal/Nation traditions and beliefs. What the UK has here is an overbroad rule that needs to be tailored to the needs of archaeology.

"Don't Ask, Don't Tell" Injunction

A California judge finally declared that the US military's policy of "don't ask, don't tell" was invalid. I thought it was inevitable, but with any controversial ruling, appeals are an inevitable result. The response?

A day after a judge in California ordered the Pentagon to cease enforcement of its policy barring gays from openly serving in the military, Gates told reporters that the question of whether to repeal the law should be decided by Congress, and done only after the Pentagon completes its study on the issue.

The reason the California judge's stance is surprising is that for any issues dealing with the military, US courts, including the Supreme Court of the United States, have traditionally deferred to military policy. In the interests of national security, courts tend to defer to whatever the US military thinks is best for defensive purposes, regardless of the issue at hand (property, trespassing, human rights). I emphasized Defense Secretary Gates' statement because that particular section is tantamount to reminding courts what their traditionally accepted position ought to be on these matters. The Family Affairs spokesperson also declared this to be a case of "liberal activist judging," a term which I ordinarily dislike because it is an over-broad stigmatype. Taken from a traditional view, though, it is a departure from the weak deferral stance that US judges have taken in the past towards military policies.

Regardless of historical stance, I applaud this move towards greater equality and recognition of the contribution to national defense that many gay men and women make. Whether or not they're gay and military, recognition for their sacrifices should not be hidden.

quoted from NY Times here.

Where do you find beauty? (Writing Prompt)

This was my answer to a short writing prompt: where do you find beauty? If between the falling angel and the rising ape lies man, then between ecstasy and horror does beauty reside. That undefined realm of possibility bears witness to humanity's distilled grace and disgrace. In each duality that makes up our lives, neither can exist without the other, and yet at some point, both were equally possible.

There is beauty in the longing of an injured bird for flight, because it has the sweet memories of sky and a future full of soaring. There is beauty in realizing truth, because everyone has a chance to lie and sometimes choose not to. There is beauty even in destruction, because out of the ashes emerges hope.

In a world of love and hate, war and peace, and life and death, there are moments of simply being. I wonder at those grey pauses, because for me, the most beautiful thing of all is to feel that crucial moment when everything changes.

Some find beauty in things. I find it in the space between.

Moleskine dump

in

It's been a while! Here are some moleskine sketches from April through now. This moleskine's been through France, South Korea, China, and Bali (Indonesia)! Unlike previous moleskine posts, these drawings are from my own head. I didn't have time or easy access to other pictures and styles that I wanted to practice drawing. (I apologize for any blurriness. I think there's something wrong with my scanner. I'll have to troop to the library to get a BookScan machine for future posts.) I'm showing favoritism and putting the ones I like the most on top. Scroll down for increasing embarrassment.

Above, rice paddies in Bali. Above, an eagle from a painting in the Indianapolis Museum of Art. These two above were practice sketches of Team Fortress 2 characters. I eventually drew a birthday card featuring the Pyro lighting the candles on a Portal cake. Above, a sculpture of two deer in the Indianapolis Museum of Art. I sketched these above at a seaside restaurant overlooking cliffs at Jeju Island, South Korea. Above, some Korean-style houses. An attempt to do a children's rendition of "What I Did On My Summer Vacation" for Bali. Musings about Insadong. "The Imaginarium of Doctor Parnassus" was playing on the flight to South Korea. This is 'supposed' to be Robert Downey, Jr. from the film "Sherlock Holmes." I say "supposed to be." The above boy's head is a riff off of James Jean, I believe.

New website

in

For my birthday, the lovely Eric J. Suh gave me a domain name! I have a website now! I was so excited I went and built it in about four hours. I'm going to move this blog over there when I have the time this weekend, as well as add more content and tweak the code. For now, my website is at JenniferGong.com. (I'm debating whether I should use JenniferZGong.com or JenniferGong.com.)

Aggregate Moleskines

in

Oompah, it's been quite a busy year so far, with a publishing job, museum work, a visit to Paris, and law school. All that left not enough time to scan moleskine pages. I did find some time today, so here is a smattering from between March and now. I am so behind on my scanning that since I last posted, I filled up an entire book and started a new one! A lot of these were efforts at exploring other artists' styles, and where they were copies I shall endeavour to note them as such. I would, however, appreciate any reminders in the event that I have missed one.

Entirely mine: (Above, some people I saw on the T. I loved the man's nose!) (Above, James Hacker, portrayed by Paul Eddington in Yes, Minister) (Above, one of my original characters, Adelice Kalani) (Above, don't know why this scanned so badly, but it's the Seine.)

Entirely others': (Above, from JLA Shogun of Steel) (Above, from Lackadaisy) (Above, from Lackadaisy) (Above left, Doctor Who in Charles Schulz style. Above right, from Nextwave)

Some of mine, some of others': (Above left, from Lackadaisy)

Judges jail youths for profit (NYTimes)

in ,

A recent federal hearing revealed that Judges Ciavarella and Conahan took more than $2.6m in kickbacks for sending teenagers to youth detention centres run by private parties. That's about 5000 juveniles who may have been sentenced wrongly, including

Hillary Transue was sentenced to three months in juvenile detention for a spoof Web page mocking an assistant principal...[Susan Mishanski's] son, Kevin, now 18, was sentenced to 90 days in a detention facility last year in a simple assault case that everyone had told her would result in probation..

This case hits close to home because I was assigned to represent the government in my moot court oral argument in my first year of law school. My task was to defend the constitutionality of juvenile court orders, so that they could be counted as part of the number of prior convictions required in order to reach an enhanced sentencing for a repeat violent crimes and possession offender who was now of age.

Juvenile courts are an interesting constitutional conundrum. The system keeps these proceedings private to the general public to not only protect the privacy of juveniles, but also to lock the records after they have become adults (I'm not sure if this happens in all states). Hidden from public scrutiny, the welfare of these juveniles is purely in the hands of officers of justice. Juveniles have the right to counsel, the right to proof beyond a reasonable doubt (in the eyes of the judge presiding), and other rights which can be waived. In this recent case, all the officrs of justice who might have intervened were too 'intimidated', according to the Marsha Levick of the Juvenile Law Center, to object. 

It extends, I surmise, beyond mere intimidation. There is little incentive not merely on the part of judges, but on the part of these officers (parole officers, public defenders, etc.), to act in such a situation. They are commonly inadequately paid for dealing with heavy workloads and a wide range of bewildered (joke Web sites) to problematic (violent) offenders. It is not merely monetary incentive they are lacking. They are working in a system that lacks the capacity to handle juveniles with the full moral and legal probity that we owe to all minors.

The NYTimes raised the question of requiring counsel (instead of allowing it to be waived) at juvenile proceedings. It may be a step in the right direction, but I fear it would not be enough.

via NYTimes (link)