I think my brain is full

6 10 2007

I just walked in the door from my long day at NYU (I woke up at 5:30 AM to make sure I made the train) and it was definitely worth the trip. The presentations were very interesting, even if I didn’t entirely agree with everything that was said. Unfortunately I have to run off again, but here’s a preview of some of the topics mentioned today that I’ll write some more about when I get a chance;

- Olive & Yellow Baboon Hybridization

- Monkeys that use their tails as tripods

- The role of populations and demographics in evolution

- The elusive Cross River Gorilla

- Alan Walker’s spear-throwing “fantasy”

- Non-adaptive speciation events (?)

I mostly remember the topics that made me go “I don’t think that’s right” more than anything else, but it definitely was a very informative conference and I’m glad I went. Tomorrow I’ll probably be away from the computer again until the afternoon and then I’ll be off to see the Walking With Dinosaurs Live show before it closes, but I’m hoping to have my new blog up and running for the beginning of the week (with lots of juicy new material, plus some older re-polished gems).





Apes aren’t the only primates to use tools

5 10 2007


A chimpanzee cracking open nuts placed on the ground with a large stone. Notice that a young chimpanzee is also present, learning this behavior. This is a sort of Type 1 tool use where a hammer (the rock) is used on another object.

“Tool use” was once considered one of the primary factors that made Homo sapiens distinct from all other animals, but Jane Goodall’s studies of Chimpanzees at Gombe and subsequent research among living apes has shown that the tool use of humans is differentiation of grade and complexity more than anything else. Tool use has now been extended to many other groups of animals, even outside the Class Mammalia, but it still is surprising to see some animals make use of objects in their environment in inventive ways. Indeed, while the idea that humans are distinguished by the possession of tool use is dead in scientific circles, it still is alive in the public mind (I recently had a friend tell me that we were “Man the Tool-User”), and genuinely impressive utilization of tools by other animals is often related to just be a sort of “trick” or purely instinctual mechanism (I’ll save the issue of animal cognition for another day).

Of the animals that use tools, however, among the most impressive are the Capuchin monkeys (Cebus sp.). Capuchins are platyrrhine primates (New World Monkeys) that inhabit the forests of South and Central America from about Honduras to Brazil. They’re generally familiar to everyone, the proverbial “organ grinder’s monkey,” a common household pet (until recently), and a regular in film roles that required a primate (i.e. Marcel from the show Friends). Indeed, Capuchins are easy to train and highly intelligent, but despite their close proximity to people they’ve generally been overlooked as “just monkeys” for a very long time. Recent research, however, has shown that they can tell us much more about the development of intelligence and human evolution than previously thought.

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Capuchin monkeys cracking open nuts. Note the similarities between this footage and the film shown above.

The fact that chimpanzees have the highest brain-to-body size ratio out of all the African apes is well-known, but few people know that Capuchins exhibit brains of similar proportions. Such a fact is readily apparent (or at least easily researched) but Capuchins have generally been ignored because while they are primates they are not as closely related to humans as Chimpanzees, Bonobos, Gorillas, or Orangutans, but fortunately this has changed. While they can be difficult to study in the wild despite their inquisitiveness/ease of acclimation to human presence, Capuchins are primarily arboreal quadrupeds, able to run through the trees as fast or faster than researchers can make it over the forest floor. This may result in some behaviors being missed, and oftentimes studies are carried out in the dry season when foliage is a bit more sparse and allows for a better view of the monkeys. Why are such considerations important? Because the tool-use in Capuchins I’m about to discuss is more often seen in captivity than in the wild, and it’s important to consider what you may not be seeing when dealing with animals in their natural habitat.

Much of the work on Capuchin intelligence has been carried out in labs by researchers primarily interested in psychology, and as my professor once remarked when considering some of the studies, the background of the researcher can be significant as to what it studied, how it is studied, and how the results are interpreted. Be that as it may, studies in captivity involving Capuchins have shown that they can use tools and that they use tools in a variety of ways depending on the circumstances. Anyone who has used a hammer or other tool to make something recognizes that the way you grip an object has a lot to do with how effective it is going to be; it probably wouldn’t be very effective (or safe) to grip a hammer with the fingertips of both hands and try to use it to bang in a nail. Likewise, when Capuchin monkeys are given a stone and expected to throw the stone into a tub of peanut butter (as in one experiment) they need to choose a grip to accomplish the task, and while there are a number of different variations of grips they usually fall under the category of power grips or precision grips. The names belie what they are used for, and in the throwing experiment I had just mentioned the most popular grip used was called the “jaw chuck,” where an object is held in the palm of the hand with all the fingers holding it in place. The jaw chuck grip was not the most effective in this experiment, however, one monkey having better success during its attempts using a precision grip (the “cup grip,” where an object is held in a cupped hand with the fingers providing support) even though it did not catch on with the other individuals.

In a different experiment, where a tub of peanut butter was covered by an acetate barrier and stones with one sharp edge were placed in the cage, the jaw chuck was even more popular than in the throwing trials, even though similar “power grips” were used as well. Indeed, while the monkeys did use (experiment?) with a number of precision and power grips, the jaw chuck was the most popular overall. Another set of tests, however, showing that monkeys might not use tools at all if they don’t have to. When a tub of peanut butter was covered in 5cm of soil and the monkeys were provided with sticks, the monkeys simply dug with their hands (like baboons do) if the soil was loose. If the soil was hard, however, some of them used sticks, even modifying the sticks by removing leaves and biting off little bits, to reach their prize. This is significant because some people like the !Kung San of the Kalahari use sticks to dig for roots and tubers today and the ability to dig for food underground is considered to be a very important factor in human evolutionary history.

As seen in the video above, however, digging in the dirt isn’t the only thing Capuchins do. They also crack open nuts in a way very reminiscent of Chimpanzees, although not all Chimpanzees exhibit this behavior. Some, like the ones in the Tai Forest do use tools to open nuts (as do other populations), but some populations don’t use tools and some don’t use them in the same way. As I mentioned in my post about Mt. Assirik chimpanzees, the chimpanzees there use the large Baobab tree limbs and trunks as anvils to crack open the fruit of that tree, using a level of tool use lower than that of other populations that put a nut on an anvil and then use a hammer (the Mt. Assirik chimps are just using the tree as an anvil). Again, as described in my earlier post about the Mt. Assirik chimpanzees, tool use can evolve given the proper ecological opportunities and cognitive steps, going from simply using a hammer or anvil on an object to using two tools (hammer and anvil) to open an object to the production of more complex and specialized tools under the proper conditions. In the case of the Capuchins, the monkeys have been known to bang stones together (holding one in each hand), use stones to crack nuts, throw stones against the ground, and hit stones with other stones making a “bipolar” object (it flakes on two sides if held on a stone anvil). Unfortunately I don’t know what becomes of these objects as it seems that Capuchins do not keep or further modify tools they make when they are finished using them, but it could represent the beginnings of tool manufacture, the behaviors requiring the cognitive leap to move ahead.

The cognitive abilities of Capuchins is one of the ways that they differ from Chimpanzees, in fact. While Chimpanzees often recognize themselves if presented a mirror, Capuchins do not (although some have used mirrors to look around objects for hidden food). Capuchins also fail some cognitive tests passed by Chimpanzees, and it seems that while both primates exhibit some similar behaviors the convergence is even more striking because Capuchins are different in terms of their intelligence. Still, the fact that Capuchins can use tools and show convergences with chimpanzees shows us that certain “milestones” that were once considered hallmarks of human evolution can show up multiple times in multiple lineages, recalling the “branching bush” of evolution rather than the orthogenic line.

There are problems with the lab studies, however, and more study needs to be undertaken of wild populations to determine how tools are being used (or even made) in natural groups rather than animals in cages. The behavior of the captive animals will only make sense in terms of evolution when compared to that of wild groups, and it would be a mistake to assume that everything Capuchins do in captivity they must also be doing in the wild. Perhaps they are and we haven’t seen it yet, but perhaps it’s a matter of ecology. If a Capuchin lives in an area with lots of soft fruit and food that does not require tools, they’re not likely to turn to tools to solve some of the problems presented by their environment. If the environment is harsher, however, and the monkeys are not naturally well-equipped to crack open nuts or get the most flesh off bone possible (because Capuchins do eat meat when they can get it), tool use is much more likely to emerge if the cognitive connections can be properly made. Some are more proficient than others, and it make take a while for certain behaviors to become established, but the tool use of Capuchins teaches us some important lessons about evolution and how it is never finished shaping life in the most surprising ways.

References;

Visalberghi, E., and McGrew, W.C. “Cebus meets Pan.” International Journal of Primatology, Vol. 18, No. 5, 1997

Westergaard, G.C. “What Capuchin Monkeys Can Tell Us About the Origins of Hominid Material Culture.” National Institute of Child Health and Human Development,1998.

Westergaard, G.S., and Suomi, S.J. “Capuchin Monkey (Cebus apella) Grips for the Use of Stone Tools.” American Journal of Physical Anthropology, 103: 131-135 (1997)

Westergaard, G.C., and Suomi, S.J. “The Production and Use of Digging Tools by Monkeys: A Nonhuman Primate Model of a Hominid Subsistence Activity.” Journal of Anthropological Research, Vol. 51, No. 1 (Spring, 1995)





I’m going, are you?

4 10 2007

I apologize for the short notice, but I only just found out myself; this Saturday (October 6) NYU is going to host an Evolutionary Anthropology conference in honor of the work of Cliff Jolly. Jolly, basing much of his work on baboons, proposed that seed-eating could have played a significant role in hominid evolution, and the conference will primarily deal with the hypotheses and studies of Jolly. The whole program starts at 9 AM and goes until about 5 PM (with a reception afterwards), and I’ll be headed in with one of my professors Jack Harris, although I don’t know how late I’ll stay as I’ll have to take the train back (if any one has any tips on how to get back to Penn station from NYU, I’d be much obliged). If you’re interested, the program and contact information (RSVP is required) is up online, and if any readers of this blog are going to attend please feel free to drop me a message; I’d be delighted to meet any readers/other bloggers who might be there.





The Chimpanzees of Mt. Assirik

25 09 2007

When chimpanzees (Pan troglodytes) appear in documentaries they are often shown inhabiting relatively dense tropical forest, their lives taking place within the green refuge of the forests. As with any other species that is spread over a considerable distance, however, different populations of chimpanzees have different habits, and one of the most remarkable populations are those around Mt. Assirik. Located in the southeastern part of the Parc National du Niokolo-Koba in Senegal, the chimpanzees in this area have to deal with a local ecology that is drier and more open than some of their relatives elsewhere, and their behavioral adaptations to the environment is of great interest to those study human origins.

The Mt. Assirik study area is remarkable in that 55% of the habitat is open grassland, only about 37% being woodland of varying density and only 3% being more dense forest (the remaining area being made up of bamboo forest and isolated trees). Such open spaces allow some of the major Carnivora of Africa to live in close proximity to the chimpanzees; Lions (Panthera leo), Leopards (Panthera pardus), Wild Dogs (Lycaon pictus), and Spotted Hyenas (Crocuta crocuta) are all frequently seen in the area. As if having so many predators at their doorstep were not enough, the Mt. Assirik area seems to have fluctuations of food that aren’t correlated with seasonal changes, and in the dry season water is the most prized of any resource. The apes are not entirely helpless in the face of such pressures, however, and they’ve been behaviorally adapted in some very interesting ways.

Given a choice, the Mt. Assirik chimpanzees prefer to spend their time in the denser areas of forest, but shifting food resources sometimes require them to move across large expanses of open grassland in order to find nourishment. Wandering out onto the open plains alone is so dangerous as to nearly be suicidal, and the apes form large mixed groups when they have to move across the plains. During this time they are at their most vulnerable, especially since they would be unlikely to outrun any of the major predators (especially those that hunt in packs), and they are extremely alert when undertaking such a journey. What is perhaps most striking of all, hearkening back to Raymond Dart’s “Savanna Hypothesis,” is the fact that the chimpanzees sometimes stand up to get a better look at their surroundings, potentially spotting predators before they get too close, although such an observation should not be taken as a sweeping vindication of Dart’s ideas of human evolution.

The presence of just one tree or a few trees spaced far apart doesn’t help the chimpanzees much either; mothers with children and individuals spent much less time in the sparser woodland areas than in the forest, mixed groups seemingly having to issues with the woodlands. Why should this be so? Well, leopards can climb trees (and often do so to stash their kills), as well as lions, and so simply climbing a tree does not equal escape. Lone chimpanzees are far more comfortable in a habitat where they can climb a tree and move through the canopy out of reach of their assailants, something that is not possible in woodlands. The predators may also have another effect on the diet of the chimpanzees; the Mt. Assirik chimps do not seem to eat young ungulates or monkeys, although such behaviors have been made famous where it has been observed (i.e. Gombe). This may be due to some competition, but it may also be due to the restricted forested habitat and the fact that chimpanzees would have to enter the habitat of the carnivores in order to capture young ungulates, predators being likely to quickly learn about any kills that had been made.

Indeed, the Mt. Assirik population is remarkable in that it often moves long distances in order to obtain food as it becomes available, relying on numbers and vigilance to protect itself from predators when it’s habitat only offers a few isolated islands of relief. Although humans did not evolve from modern chimpanzees, this population may give researchers some idea of the behavior patterns of our ancestors when faced with similar constraints when forests became sparser and the plains were filled with predators. Such social behavior is not the only thing that makes the Mt. Assirik chimpanzees stand out, however; they also make use of Baobab trees in a very interesting way.

By now many people are familiar with the ability of chimpanzees to use a piece of wood as a hammer to break a nut placed upon an “anvil” of rock or tree root; such footage has been shown in television programs again and again. Such behavior did not come out of nowhere, however, and the way Mt. Assirik chimpanzees open nuts may represent a stage of tool use that precedes the hammer-and-anvil technology. While it had been disputed for some time whether the Mt. Assirik population used hammers and anvils or just anvils, recent studies have shown that they are cracking open the hard nuts of the tree on branches and not using a hammer. While we might think of an “anvil” as something that can only be used in conjunction with a hammer, mechanically this isn’t necessarily so, and the Mt. Assirik chimpanzees bang the hard nuts they collect on the branches of the tree (therefore staying aloft, not coming down to use stones or the roots of the tree), the tree itself being the anvil.

Given the basal usage of anvils by the Mt. Assirik chimps and the use of hammers and anvils elsewhere, it becomes possible to hypothesize about the evolution of stone tool use in our own ancestors. The starting point was likely similar to what is exhibited by the Mt. Assirik chimpanzees, banging hard nuts on trees or rocks in order to open them (thus preventing damage to the teeth, if it even would be possible to open the nuts using their jaws). The next step would be adding a hammer, possibly wooden (as seen in some groups today) or possibly stone. At this stage any combination of wood or stone hammers and anvils could be used, but tool use would probably not progress until a population was using stone hammers and stone anvils to open foods. In such a scenario, the apes would sometimes miss their targets and flake off bits of stone, an accident that would shape the tools. When a certain cognitive leap was made, the apes could then move from accidentally flaking their tools to doing it intentionally to truly be making tools rather than making use of naturally occurring bits of wood and stone. The reality of the situation may be forever lost to us, ancient tool use before the knapping of stone became prevalent being notoriously hard to discern, but such a line of behavioral descent is not unreasonable and seems to allow further development merely by chance combinations of naturally occurring resources.

Such a discussion is only a brief sketch based upon what I have only recently learned myself, but I hope that it has been at least somewhat informative. Different populations of chimpanzees show different behaviors and live in differing ecologies, and it would be a mistake to assume what the famous Gombe chimpanzees are doing holds true for all the other populations. Another population that I soon intend to write about spends time in caves, probes trees for bush babies, and may even have the beginnings of a fire culture; others do not show the same exact behaviors, but they have their own cultures and reactions to the local ecology. While we should be careful in analyzing the living populations of chimpanzees and their perceived similarities to humans, it would be foolish to think that they can tell us nothing of our own past, and if very well may be that some of traits (behavioral or otherwise) they now exhibit were present in our own lineage, vignettes of evolutionary history being replayed with different actors in our own time.





When your dials are pupilated…

21 09 2007

Drop what you’re doing; Neil has one of the most singularly excellent posts I have ever seen up over at microecos about the eyes of the Aye-Aye, a very rare and bizarre endangered strepsirhine primate that is truly unusual (and, although the “rodent-like” characters of the Aye-Aye are likely derived characters, famous morphologist W.E. le Gros Clark suggested in The Antecedents of Man, truly shows that primates evolved from animals like shrews). [Many thanks to those in the comments that corrected my bad phrasing] There is such a thing as being too bizarre, however, and even though habitat loss is a huge problem for these animals, so is the local mythology; the aye-aye is so weird that local legends deem them to be evil creatures, and they are often killed to prevent them as they are seem as symbols of death and evil. Now that’s enough of my yammering; check out Neil’s essay, post haste!





What?!

20 09 2007

I rarely listen to the radio, but when I do, I always turn on NPR (usually WHYY from Philadelphia). While I much prefer their news coverage and features to that of the “major” news outlets, every once in a while I hear something really crazy come over my computer speakers, as I just did moments ago. As I’m writing, author Diane Ackerman is being interviewed on Radio Times about her book The Zookeeper’s Wife, focusing on the true story of Warsaw Zoo keeper Jan Zabinski during WWII. On the air, Ackerman described how Jan had an uncanny ability of calming animals that were said to be vicious or overly aggressive. In explaining why Jan may have been able to do this, Ackerman suggested that at one time in our evolutionary history it would have been advantageous for mother and child to have a telepathic link, some kind of natural “Fall” degrading that ability in most people. According to Ackerman, Jan may have retained such an ability, intimating that she somehow telepathically soothed the beasts. The discussion on such a topic did not go further, but this is very strange coming from a woman who (even as I speak, oddly enough) prides herself on her understanding of natural history. Telepathy between mother and child has even less support for it than another idea of evolution that is heavily based upon woo, the Aquatic Ape Hypothesis, and it seems like a continuation of the popular mythology that humans were once “in harmony” with nature and have since fallen from grace, losing any number of senses or sensitivities along the way. Indeed, it’d be best to leave telepathic hominids to trashy summer novels, and although The Zookeeper’s Wife sounds like an extraordinary story, Ackerman’s interview definitely turned me off. I know it’s not rational, judging a book I haven’t read by a kooky idea on a different subject, but I would be lying if I said I was going to go out and read it straight away.





Amalgamated Anthro News

19 09 2007

Much to my astonishment, I’ve actually started to receive some news items that people would like me to talk about here on Laelaps, and the past 24 hours or so has been full of anthropology-oriented news.

First up is a talk given by Zeresenay Alemseged, the discoverer of “Selam,” the Australopithecus afarensis child detailed about a year ago in the journal Nature. Brought to us by the Technology, Entertainment, and Design Conference, the talk can be found in either mp4 or zip form (it’s a video) here. The dreaded “March of Progress” rears it’s ugly head, but otherwise it’s an interesting summary if you’re not familiar with the discovery.

I also received notification of a new article in Scientific American (just about the only popular science magazine I don’t presently subscribe to, I think) about “The Trouble With Men.” At first, seeing only the title, I thought I was in for another evolutionary psychology (or “sociobiology”) rant about how inherently evil males of the species Homo sapiens are, but the reality of the article is far more interesting. According to the article, Virpi Lummaa of the University of Sheffield has found that there is something of a higher price to be paid for male offspring in our own species than for daughters, the course of development being more costly on the mother and siblings (both in and out of the womb) than previously suspected. While the data to back up the observations Lummaa has made are still wanting, studies on development in other animals suggest that testosterone has a lot to do with the problems experienced by females, especially if a mother gives birth to opposite-sex twins (the female might even be born sterile as a result of the testosterone influence).

How significant Lummaa’s studies are to modern society is also in question, as she primarily derived her observations from church records from over two centuries ago about premodern mothers among the Sami people of Finland. While such a time period may be slight, the cultural and technological changes have been great, which complicate the application of the data to people living today;

Access to effective birth control, an abundance of food, and low child mortality rates would all obscure the evolutionary influences seen in the preindustrial data. “It’s almost a shock when you realize that 100 to 150 years ago, 40 percent of babies died before they reached adulthood,” even when adulthood was defined as age 15, Lummaa notes.

Still, many, if not most, of the people in the world do not live in an industrialized society, so there is still plenty of opportunity to see if the observed trend still holds. For some reason Scientific American makes no mention (and provides no link) to the study that inspired the article, appearing in the June 26 edition of PNAS and by Lummaa, et al., entitled “Male twins reduce fitness of female co-twins in humans.” From what I can glean from the abstract, the authors argue from an entirely hormonal origin for reduced reproductive success in female twins born with a male brother, even if the brother dies at some point. Societal and cultural values do not seem to make a difference in the group studied, although I am still a bit dubious about the assertion that culture doesn’t compensate and would like to see a similar study undertaken with extant groups of people so more detail can be taken in. Regardless of how accurate the conclusions may or may not be, it is interesting to me personally as I am friends with a family where the mother had two sets of twins, each pair consisting of a boy and a girl.

Still, the idea that males might be favored in one way or another is not so strange an idea, especially since it’s becoming apparent that evolution can work on males in females of the same species in different ways. A study revealed earlier this year about Red Deer seem to show that what makes a successful male deer does not make a successful female deer (and vice versa), and another study involving White Rhinoceros showed that male offspring are favored when it comes to receiving milk from their mothers. The more we learn about species, the more dynamic and interesting things become, and before the study on deer I can’t say that I had considered the idea that an especially successful male deer might produce sub-par female offspring as a result of his prowess (although any sons would gain the benefit of dad’s genes).

Finally, the new issue of Natural History has an article about the skeleton of “Lucy” going on tour in the U.S. by AMNH paleoanthropologist Ian Tattersall. He writes;

Dinosaur bones and many other fossils routinely hit the road, but fossils of extinct hominids tend to be treated as sarcosanct, never allowed to leave their home institutions, let alone their countries of origin. That is regrettable, in part because such fossils are the patrimony of all humankind. Furthermore, paleontology is quintessentially a comparative business: no fossil can be satisfactorily understood in isolation from the wider record.

I’m still not entirely sure how I feel about the bones of Lucy going on tour; I would prefer them to stay safe because they do belong to all mankind (and not just my generation or paying customers at various institutions), but I won’t lie and say I will stay home when her remains come to New York. Also, I have heard from many a paleontologist that they wish America was a bit more strict about its fossils and where they can be taken after being discovered. Many countries, while allowing fossils to be taken to various institutions for study for a number of years, want the remains of organisms from their own country returned for storage, study, or display after a certain amount of time, and as far as I am aware the U.S. has not followed suit.

Many thanks to those who notified me of the new articles and videos; I will continue to write about whatever news is sent my way as often as I can, so if you see something that catches your eye and think should get some attention, send it on in. And, before I forget to mention it again, be sure to check out the new look of The Panda’s Thumb.








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