However, one of the main features distinguishing between monkeys and apes is the intermembral index. This is simply the relative proportion of the forelimbs and hind limbs. Apes have short legs and long arms (unless you are a Man in a Yellow Hat variety of ape) while monkeys have more even length limbs. This image compares a young Chimpanzee to stand in for the apes, a Barbary Macaque, and Curious George, with the limb lengths marked off with a red line.

This seems to indicate the George is an Ape.

Also, note that the Man in the Yellow Hat originally kidnapped George in a Jungle that appears to be in Central Africa, to which he returns in later episodes.

There is another possibility, that Curious George is an undiscovered type of primate that is technically a Monkey but with certain Ape features. We are not certain of the genetic heritage of the mysterious ape Sungudogo, so perhaps George is one of those.

Note that these comparisons are being made among Old World Primates. If New World Primates are included in the mix, there may end up being more questions than answers.

That is a rather dumb thing to say for a number of reasons; nature is not simple. You don’t change one variable and expect other variables to respond as though we were turning a garden hose up or down. For example, while plant growth might be enhanced with more CO2 in the atmosphere, there is no reason to think this would be linear, or similar across all plants. You have to dance with the one who brung ya. The plants we have are the plants that have been under Darwinian selection optimizing growth and maintenance physiology for gazillions of plant generations. Changing a fundamental variable may have little effect (and in fact, CO2 increase only enhances growth somewhat, and for only some plants) and may even have negative effects.

A new paper out in Ecology looks at the nutritional value of plants in a Ugandan rainforest and finds that the nutritional value of the leaves eaten by some Colobine monkeys there has declined, because fibre has increased at the expense of usable protein. From the abstract:

Global change is affecting plant and animal populations and many of the changes are likely subtle and difficult to detect. Based on greenhouse experiments, changes in temperature and rainfall, along with elevated CO2, are expected to impact the nutritional quality of leaves. Here, we show a decline in the quality of tree leaves 15 and 30 years after two previous studies in an undisturbed area of tropical forest in Kibale National Park, Uganda. After 30 years in a sample of multiple individuals of ten tree species, the mature leaves of all but one species increased in fiber concentrations, with a mean increase of 10%; tagged individuals of one species increased 13% in fiber. After 15 years, in eight tree species the fiber of young leaves increased 15%, and protein decreased 6%. Like many folivores, Kibale colobus monkeys select leaves with a high protein-to-fiber ratio, so for these folivores declining leaf quality could have a major impact. Comparisons among African and Asian forests show a strong correlation between colobine biomass and the protein-to-fiber ratio of the mature leaves from common tree species. Although this model, predicts a 31% decline in monkey abundance for Kibale, we have not yet seen these declines.

Jessica M. Rothman, Colin A. Chapman, Thomas T. Struhsaker, David Raubenheimer, Dennis Twinomugisha, and Peter G. Waterman, 2014. Long term declines in nutritional quality of tropical leaves. Ecology

The total number of nocturnal primates known has increased considerably over the years and I’d wager there are many more to be found. “Technological advances have improved our knowledge about the diversity of several nocturnal mammals,” said Rachel Munds from the University of Missouri Columbia. “Historically many species went unrecognized as they were falsely lumped together as one species. While the number of recognized primate species has doubled in the past 25 years some nocturnal species remain hidden to science.”

Tomorrow, a paper will be released providing the diagnosis of a new species of slow loris. From the abstract:

The slow lorises … once included only two species, but recent taxonomic studies resulted in the description of three additional species; … The Bornean loris in particular is characterized by pelage and body size variation. In this study, we explored facemask variation in the Bornean loris (N. menagensis). Differing facemask patterns, particularly influenced by the amount of white on the face, significantly clustered together by geographic regions, separated by notable geographic boundaries. Our results support the recognition of four species of Bornean lorises: N. menagensis, N. bancanus, N. borneanus, and N. kayan. Genetic studies are required to support these findings and to refine further our understanding of the marked variability within the Bornean loris populations

Previously, one species of Bornean slow loris, with three subspecies, was recognized. The present study elevates the three subspecies to species status and add the fourth as a new discovery. Obviously, this significantly increases our conception of diversity in the nocturnal Bornean rainforest. One of the biggest threats to these animals is the pet trade. “The pet trade is a serious threat for slow lorises in Indonesia, and recognition of these new species raises issues regarding where to release confiscated Bornean slow lorises, as recognition by non-experts can be difficult,” said co-author Professor Nekaris, from Oxford Brookes University.

The study used 25 photographs and 27 museum specimens including the type specimens for two of the previously designated subspecies. A large number of features were examined and measured, of which eight showed variation across the sample, thus showing promise to use as in classification. Here is an example of one of the traits, called “Crown”:

Various fancy statistical analysis were done to produce two “functions” (combinations of variables) that separate the samples as indicated in this graph:

These traits clearly sort out the groups, and these groups have geographical distinctions as well.

Group 1 is on the island of Bangka and in the southwestern portion of Borneo south of the Kapuas River and east to the Barito River; this group’s boundaries appear not to extend all the way east to Barito River. Group 2 is found in central Borneo, north of the Kapuas and Mahakam Rivers. It is often found in higher ele- vations, but is not restricted to them. The boundary of Group 3 overlaps in part with Group 1, as it is found north of the Kapuas River, but its range ex- tends as far east as the Barito River. Finally, Group 4 inhabits the southern Philippines and northern and eastern Borneo, primarily in coastal and low- land areas. It does not range south of the Mahakam River.

So there are now four species: N menagensis, N. bancanus, N. borneanus and N. kayan. That last one is the new designation, and is named for a river flowing through the region in which it lives..

The conservation and research project responsible for this work has a web page with cute pictures, interesting videos, and more information on conservation related matters: Prof Anna Nekaris’ Little Fireface Project

Munds, Rachel, Nekaris, K.A., & Ford, Susan (2012). Taxonomy of the Bornean Slow Loris, with new species Nycticebus kayan (Primates, Lorisidae) American Journal of Primatology, 75, 46-56 : 10.1002/ajp.22071

“Are we lost?”

“No. I know exactly where we are.”

(In the bottom of some freakin’ uncharted canyon.)

The Young One was always worried about our survival, never really trusting my vast experience and well honed instincts.

“Were lost.”

“Are not.”

Then suddenly, “POP!”

The local bushmen say that baboons are people, and that when we hear them they sound like they are merely speaking in an unknown dialect of their language. This is a story, of course, and they understand fully that the baboons are not people. And they don’t sound anything like us. The story goes on to say that the baboons became persona (as it were) non gratis when they broke a rule in sharing meat: They reciprocated in a meat exchange by giving some unsuspecting bushmen bits of human flesh to eat. Baboons have never quite been trusted since, so the story goes. And as night came closer during our trek up the steep-sided valley, we could hear the baboons beginning to speak from high above us on the cliff that impeded our return to base camp.

The first few sounds were loud pops that could have been rocks thrown against rocks. My traveling companions thought, in fact, that this is what they were, and became concerned over the possibility of rocks falling down the sides. I reassured them.

“No, those are just the baboons.”

“POP!”

“I’ve been hearing them for a while now. They appear to be following us.”

“Following us? They sound like they are throwing rocks at us!”

“Not throwing rocks. That’s just a contact call, letting each other know where they are! But yeah, they are following us. They know we are down here, and they’re tracking our movements by following along at the top of the cliff. It’s getting to the point in time where they will settle into their overnight spots, and they’re probably worried that we’re after them.”

“Oh. So the troop of wild baboons is not following us. They’re just angerly covering our escape routes.”

“Right. Should be no problem.”

Eventually we came to the point where we would go up the side of the cliff and head across the grassy plain in search of our vehicle, left behind hours ago. This was not the point where climbing had become more possible. Rather, this was the point beyond which if we climbed out of the canyon we would be backtracking to the vehicle. In other words, if we went ahead any father, we’d be adding to rather than reducing our estimated time of return to the truck. It was either climb up now and reach the truck just as night fell, or climb up later where it might be easier and spend time crossing the savanna in the dark. The fact that we were on the shaded (north) side of the canyon was also a consideration: As the sun went down, darkness would fall here first and fast. We’d be climbing in the dark.

Or, I could be wrong. I thought at the time that if the truck really was exactly where I thought it was, and we climbed straight out of the canyon and headed exactly north, then we’d bump into it even with our eyes closed, in about seven kilometers. And I would be very impressed, with myself. Or, it could be somewhere else entirely and we could be totally lost. Perhaps the baboons could be blamed in that eventuality.

“Are we lost?” the young one asked again.

“Why would you say that? Here. We climb out right here.”

“We’re totally lost, I know it.”

So as Trusted Companion looked on eagerly trusting that I was doing the right thing, and half smirking at the untrusting Young One, I carefully picked a route that would bring us to a flattish spot in about 12 meters of scrambling mostly across grass and eroded surface, with few thorny bushes. From there I’d pick out the next leg of our ascent. It was difficult and we were all out of breath when we got there. I spotted another target and headed that way.

“Follow me.”

“I need to rest.”

“OK, we’ll go ahead and you can watch how we go and follow behind when you’ve caught your breath.”

And so it continued, with the Young One, who was most out of shape, out of breath and falling father and farther behind. And the pops of the baboons continued, and as we went up in elevation we could hear their other chattering as well.

And then we could see them. You had to crane your neck to see the horizon, the edge of the cliff above us. And there you’d see contact between the brown grass and brush and the darkening blue, cloudless sky. And there would be a dark gray lump there, like a fire plug covered with a blanket, or a lawn gnome hiding under a beach towel, and then suddenly the rounded lump would drop out of sight and there would be another POP and some chatter. The bigger baboons stayed visible for longer, the tiny ones, the juveniles, popped in and out of sight quickly and randomly. And as we climbed still higher we could see their faces, and their monkey-face movements and their monkey-face stares. There is a difference between a monkey looking back at you from a cage in a zoo and a monkey looking back at you from a tree in the wild. And, there is a bigger difference still between either of those scenarios and a monkey looking down at you from 15 meters above when its Baboon Bubba and his 25 friends and relatives and you and Trusted Companion trailed some distance back by the Young One, who is still asking …

“We’re lost, aren’t we. I need to rest.”

“POP! … babble babble …”

One could easily imagine the drama as the humans emerge onto the plains. Finally … almost … reaching the edge of the canyon, where there is an abrupt transition from dangerously steep thornbush covered slope to very flat or slightly undulating grass covered plain, just stepping out of the canyon and onto the flats … and suddenly the troop of wild baboons …. wild angry baboons … swoops in from all sides, jumping on the humans and pushing them back down the cliff, Most Trusted Companion letting out a war cry as she pulls a giant baboon off my back as she herself is taken down by three females biting at her ears and ankles, and Young One and a medium size male monkey spinning like a giant eight-limbed Frisbee falling, screaming, all the way back down to the sandy bottom of the canyon’s now fully benighted floor, terror shining from their four collective eyes, the troop’s big male tearing through the tall grass directly at me with two or three of his cohort right behind him, moving in for the kill. Kill the humans!!!!

But that kind of thing never happens. By the time we were within 10 meters or so of the top of the canyon, the baboons had fallen silent and moved entirely out of our sight. They had no interest in being anywhere near us when we gained the plain. Instead of a primordial battle to the death between primate species, there was nothing, and we stepped, breathless, tired, thirsty, and hungry, out of the canyon. I took a compass reading and pointed to a tree in the far distance.

“That tree. We need to cross just to the right of it and we’ll see the car from there.”

And we did. My reckoning was dead on. We had gained valuable data that day. We had learned about ourselves and each other under conditions of adversity. And the baboons …. well, they had one hell of a story to tell, and I’m sure they are still telling it to each other and to their little monkey children to this day.

“POP!”

To give you an idea of the scope and intensity of this coverage, I’ve lifted the table of contents:

Part One – Ecological Costs and Benefits
1. The Physiology and Energetics of Movement: Effects on Individuals and Groups by Karen Steudel
2. Determinants of Group Size in Primates: The Importance of Travel Costs by Colin A. Chapman and Lauren J. Chapman
3. A Critical Evaluation of the Influence of Predators on Primates: Effects on Group Travel by Sue Boinski, Adrian Treves, and Colin A. Chapman
4. Mixed-Up Species Association and Group Movement by Marina Cords
5. Territorial Defense and the Ecology of Group Movements in Small-Bodied Neotropical Primates by Carlos A. Peres
Part Two – Cognitive Abilities, Possibilities, and Constraints
6. Group Movement and Individual Cognition: Lessons from Social Insects by Fred C. Dyer
7. Spatial Movement Strategies: Theory, Evidence, and Challenges by Charles Janson
8. Primate Brain Evolution: Cognitive Demands of Foraging or of Social Life? by Robert A. Barton
9. Animal Movement as a Group-Level Adaptation by David Sloan Wilson
Part Three – Travel Decisions
10. Evidence for the Use of Spatial, Temporal, and Social Information by Primate Foragers by Paul A. Garber
11. Homing and Detour Behavior in Golden Lion Tamarin Social Groups by Charles R. Menzel and Benjamin B. Beck
12. Comparative Movement Patterns of Two Semiterrestrial Cercopithecine Primates: The Tana River Crested Mangabey and the Sulawesi Crested Black Macaque by Margaret F. Kinnaird and Timothy G. O’Brien
13. Mountain Gorilla Habitat Use Strategies and Group Movements by David P. Watts
14. Quo Vadis? Tactics of Food Search and Group Movement in Primates and Other Animals by Katharine Milton
Part Four – Social Processes
15. Social Manipulation Within and Between Troops Mediates Primate Group Movement by Sue Boinski
16. Grouping and Movement Patterns in Malagasy Primates by Peter M. Kappeler
17. How Monkeys Find Their Way: Leadership, Coordination, and Cognitive Maps of African Baboons by Richard W. Byrne
Part Five – Group Movement from a Wider Taxonomic Perspective
18. Birds of Many Feathers: The Formation and Structure of Mixed-Species Flocks of Forest Birds by Russell Greenberg
19. Keeping in Touch at Sea: Group Movement in Dolphins and Whales by Rachel Smolker
20. Group Travel in Social Carnivores by Kay E. Holekamp, Erin E. Boydston, and Laura Smale
21. Ecological Correlates of Home Range Variation in Primates: Implications for Hominid Evolution by William R. Leonard and Marcia L. Robertson
22. Patterns and Processes of Group Movement in Human Nomadic Populations: A Case Study of the Turkana of Northwestern Kenya by J. Terrence McCabe
Concluding Remarks
New Directions for Group Movement by Sue Boinski and Paul A. Garber

The book is ten years old, but still forms the basis for the relevant literature. Two more or less startling conclusions emerge from the papers in this volume: 1) In primates, there is no apparent association between the mechanisms or abilities of various primate species to coordinate movement or to find food or other resources as a group and the species’ taxonomy. In other words, primate behavior at this level is not determined by phylogeny, and thus, not determined by genes. Or, to be more precise, variation in primate capacities to carry out this complex set of behaviors is not explained by innate programming. This is important when thinking, for instance, of human culture and human variation in behavior, intelligence, or other brain-related features. While modern pseudo-evolutionary pop psychologists are busy telling us that they can predict differences in capacities of humans by ethnicity, national origin, skin color, etc. we find no such predictive power in a major complex behavior across primate species as different as ape vs. monkey or old world primate vs. new world primate. This underscores the degree to which it is essentially a primate thing to not be overly programmed in behavior by some genetic code.

The second finding I’d like to mention is that in many (most?) of the species studied, sociability determines the nature of group movement more than does ecological demand or foraging efficiency. In human forager studies over the last few decades, it was discovered much to the chagrin of many anthropologists that foraging behavior was more often determined by non-optimization effects. Human foragers don’t maximize caloric or protein intake, or optimize hunting or gathering behavior, as much as most researchers thought they would. Well, it turns out that that’s a primate-wide trait. We shouldn’t have expected it. Food is paramount, and much of the overarching behavior of primates does relate to it, but the day to day, or hour to hour optimization that optimal foraging theory predicted simply does not signify.

With never-before-seen video, primatologist Isabel Behncke Izquierdo (a TED Fellow) shows how bonobo ape society learns from constantly playing — solo, with friends, even as a prelude to sex. Indeed, play appears to be the bonobos’ key to problem-solving and avoiding conflict. If it works for our close cousins, why not for us?

I have written before about the “Hauser Effect” and therefore I feel a need to look into the current allegations that scientific research misconduct happened in Hauser’s primate research lab in William James Hall. Could it be that the Hauser Effect is really just misconduct? Alternatively, could it be that what is seen as misconduct is really the Hauser effect? Could it be that there is some complex interconnected process going on here that happened one way in Hauser’s lab but happens generally in science (and human thinking in general)?

Very simply put, the Hauser effect has two levels of manifestation, one particularistic and one general. The particularistic level is this: Researchers working with the usual Old World primates, such as chimpanzees, baboons, and macaques, discover a phenomenon that can only be seen in chimpanzees to the exclusion of the other primates, suggesting that it is a capacity relevant to ape evolution, not found in other primates, and potentially relevant in some general way to human evolution.

Then, Marc Hauser produces a paper in which he shows that his monkeys can do it too. His monkeys, the cotton top tamarins, are New World monkeys of the family Callitrichidae. Mark got his monkeys to pass the Gallup Test. He got his monkeys to count. I heard the other day that he had his monkeys dancing backwards and in high heels. While chewing gum.

(OK, I’m joking about the last one, but the others are true.)

The more general form of the Hauser effect is this: You have a phylogenetic tree, with one branch consistently showing a set of derived traits, derived with respect to the rest of the tree. Like, apes can pass the Gallup test (can you recognize that the thing you see in the mirror is YOU and not just some other primate?). That’s not the Hauser effect. The Hauser effect is when another branch, one not adjacent to (or even near) the derived branch, consistently shows similar derived traits, again and again, almost mockingly of the nice neat pattern seen elsewhere on the evolutionary tree.

There are three explanations that I’ve considered for the Hauser effect: 1) The trait s really there in all or most members of the larger tree in some form that is usually invisible except in certain lineages because of the way we generally interface with the animals. For instance, at one point in time we could see the Gallup effect in orangs and chimps but not in gorillas, in a test setting, but researchers had in fact observed one gorilla using a mirror with clear self recognition, outside of the context of the test. Gorillas, perhaps, are doing something differently in the laboratory setting. Or the putative results of elephants having various cognitive abilities, but whereby those abilities must be tested for using different, non-visual, modalities in order to make comparisons with highly visual apes. 2) Parallelism. Always interesting, in this case not as interesting as other possibilities. In this case, the ability just happened to evolve twice, perhaps because off some similarity in ecological or social context (a very likely explanation for the cotton-top’s behavior). 3) The master experimenter phenomenon. A master designer of experiments, and Marc Hauser is one, could overcome reason 1 and find the effect if it is there. Marc would have gotten Koko the gorilla to check her hair in a mirror during the lab tests rather than only as a casual activity in the hallway on the way back to her enclosure. But a master experimenter may also be able to do something else, which no one else can do. A master may be able to make earthworms sing jingle bells, fleas design new kinds of computer circuits, and giraffes tap dance. Well, I exaggerate. A master experimenter can make dolphins dance, horses count, and New World monkeys act like chimps. And yes, that mention of horses is a reference to clever Hans.

Clever Hans was the horse that could to math. We now think, looking back on Clever Hans, who performed the trick for many audiences over many years, that the horse’s keeper unwittingly gave clues to the horse telling it when to stop enumerating with it’s hoof. Ask the horse “Hans, what is five minus two” and the horse knows to start stomping its hoof. Then, an unconscious cue is given by the horse’s keeper … like a poker player’s tell … when the horse hits the number ‘three’ and this tells Hans to stop. So, it turns out that the horse can’t do math. But it can read subtle cues unknowingly exhibited by a human that no other humans picked up on for years. Stupid horse.

For whatever reason, Marc Hauser’s monkeys did things that were surprising. Considering how little we know about the landscape of behavioral capacities of New World Monkeys (as opposed to the much more studied Old World Monkeys like macaques and baboons) we might be able to conclude that the NWM branch is simply more ape-like than the OWM branch of primates. This is surprising, interesting, and untested … more work would have to be done with more New World Monkeys. But there may be reasons to not be that surprised. New World Monkeys spend more time in multi-species associations than OWM’s do. Callitrichids have an unusual mating and offspring rearing system that may require more personal political savvy than other monkeys, or at least, a different kind. There are all kinds of reasons that Marc’s monkeys impress, technically it is always a case of the Hauser effect (as narrowly defined above) regardless of the reason. The reason being, in my mind, either that the monkeys are different, or that Marc is smarter than the average experimenter, possibly too much smarter.

Fraud or misconduct never crossed my mind. I have read nothing about the specific accusations, and I have no secret inside knowledge. And, in fact, I wanted to get these thoughts down on ‘paper’ and on my blog for others to see before I learned anything more about Marc’s situation.

I’m like the neighbor who is interviewed after the spectacular arrest of the guy down the street for some over the top crime.

“Marc kept to himself, in his lab. He produced his papers, got on with his job. Nobody ever thought he would carry out misconduct. He wasn’t the type. I can’t believe this is happening.”

That’s what I think.

The fossil was found while University of Michigan paleontologist Iyad Zalmout was busy looking for dinosaur fossils in western Saudi Arabia. He found the monkey, from a much later time period, instead. Ooops.

“I didn’t know whether to be disappointed or not, but I thought, well, maybe something interesting will pop up here, so I started looking around. Within minutes, I found teeth sticking out of the ground, and when I realized what they were I was shocked. I had worked with Phil [Gingerich] on terrestrial mammals in the Bighorn Basin, and my first look at the size and shape of these teeth told me I had found a primitive primate.”

Zalmout sent a photo to Philip Gingerich, top monkey fossil expert, who confirmed its primate status and potential importance.

Major early Oligocene to early middle Miocene Afro-Arabian catarrhine primate sites. Key: 1, Harrat Al Ujayfa, Saudi Arabia; 2, Thaytiniti, Oman; 3, Taqah, Oman; 4, Fayum, Egypt; 5, Gebel Zelten, Libya; 6, Lothidok, Kenya; 7, Meswa Bridge, Kenya; 8, Koru, Kenya; 9, Songhor, Kenya; 10, Buluk, Kenya; 11, Moroto, Uganda; 12, Napak, Uganda; 13, Kalodirr, Kenya; 14, Rusinga, Kenya; 15, Loperot, Kenya; 16, Ryskop, South Africa; 17, Wadi Moghara, Egypt; 18, Ad Dabtiyah, Saudi Arabia; 19, Malembe, Angola. Map and caption from original paper.

The time period in question, the Oligocene, is circled on this time chart from the USGS.

African “higher” primates, the Old World Monkeys and the Apes, are collectively known as the Catarrhini. The Catarrhini split from the New World monkeys at least 40 million years ago, though this date is subject to revision. That would be somewhere in the middle of the Eocene. Later on during the late Eocene and subsequent Oligocene, around 20-something mya to 30-something mya, Catarrhini gave rise to populations that would have been the ancestors of the major living groups as well as some lineages that have gone totally extinct. The split between living Old World Monkeys and the apes would have been somewhere in the middle of this time range.

Saadanius hijazensis in situ. The fossil, found in 2009, preserves most of the face, the front upper portion of the skull, the temporal bone, and the palate, with some of the left and right upper teeth. The specimen was found with the palate and teeth facing upward, imbedded in an iron-rich clastic conglomerate in the middle part of the Shumaysi Formation. Credit: Iyad S. Zalmout, University of Michigan Museum of Paleontology

Frontal view of Saadanius hijazensis (holotype SGS-UM 2009-002). source

Within a relatively short time span, several ape lineages arose, causing much subsequent confusion among palaentologists. The short version of the story is that some four major ape lineages emerged between the middle Oligocene and the end of the Oligocene (around 23 mya), most of which we tentatively refer to today as “Apes of ancient aspect,” with all of those being extinct, and one lucky lineage that is not extinct, the “Apes of modern aspect.” (The latter get to be “modern” because they are more derived than the others.) You would be safe thinking of the latter as the “hominoids” and the others as “Miocene apes” since they mostly lived in the Miocene and the “hominoids” kept it simple by leaving very few fossils behind. Today, when we try to piece these apes together into a coherent pattern, to understand what form of ape gave rise to what other form of ape, we become confused and argue. If only we had a better idea of what the ancestral species of all these apes looked like, in order to test hypotheses about ape evolution in the early days.

Videoscan of the face of Saadanius hijazensis, a new genus and species of primate that lived in the Arabian Peninsula during the late Oligocene epoch, 29-28 million years before present. nsfnsf

Meanwhile, over on the Old World Monkey lineage, there was much less diversification and a relatively straight forward body plan easily represented by macaques or baboons persisted to modern times (though it is a bit more complex than that).

Thick solid vertical lines indicate known temporal ranges of taxa; thick dotted vertical lines show intervals of occurrence or possible extension for temporal ranges of taxa. Diagram and caption from original paper.

Now, here’s the rub: We have some fossils (Propliopithecoidea)from around 30-35 mya that show us what the ancestor to this complex series of developments look like, and we have what are essentially modern Old World Monkeys and Apes, and a fairly large collection of Miocene apes (of ancient aspect) post dating 23 million years ago. For the monkeys specifically, there are bits and pieces but mainly fossils that look pretty much like modern moneys and date to the last 5 mya or so.

In order to understand the evolution of a set of species, it is necessary to know about the nodes … the common ancestors of various sets of species. Ideally, we would have a good understanding of the population that gave rise to the Old World Monkeys and the Apes, so we could sort out differences among subsequent lineages with a knowledge of what specific traits are expected to be present in given animal because its ancestors had it. In other words, is a certain trait seen in one species and not another, sister species, because it was added by the first species, or lost in the second species?

There is a major difficulty in figuring this out with primates: The primates, with respect to untangling fossils, have three overwhelmingly important characteristics. First off, Many of the lineages are extinct and left incomplete fossil records. DNA can’t help us with them an the scrappy fossil are not exactly coming to the plate.

Second, the physical form of Catarrhini (many of the living and extinct apes and monkeys of the old world) is highly selected to adapt to arboreal lifeways. All species have selective forces working on them, but some selective forces are stronger and more overwhelming than others. The key characteristic of birds is flight. There are few features of flying birds that are not shaped directly or (barely) indirectly by the requirements of flight. The key characteristic of a moose is that it eats aquatic vegetation seasonally and lives in the snow the rest of the year. So it has long legs. Big whoop. The shape of, say, the top of the head of the moose is not adapted to this characteristic, but for birds, every part is shaped by the flight adaptation. Large mammalian arboreal species are not as constrained as vertebrates that fly, but they are fairly constrained. (I do simplify … some primates are not as arboreal as others, and the constraint I mention here is more severe in the New World where arboreality is much more intense.) The result of this constraint is that some features are either very conserved (once they emerge) or are converged on over time from multiple directions. This confuses us.

Third, we are talking about a long period of time with a spotty fossil record. Any kind of confusing convergence or random loss of a feature or other complexities that might occur over time is more likely in a very time-deep fossil record. Think of it this way: Monkeys and apes are evolving (from monkeys and apes) over and over across vast periods of time. In enough time to see the evolution of monkeys or apes from non-monkey or ape ancestors occur several times, the same lineages are traveling the adaptive landscapes altered by both random and adaptive forces that themselves are changing over time.

So, imagine a family tree with prosimians and New World Monkeys represented as lower branching events, and then two focal living groups, the Old World Monkeys and the Apes as two additional tips that we presume to join subsequent to the split with Old World Monkeys, but with no real fossil record at the point of that split. We can’t be sure of much of what is going on there. For instance, if a fossil that looks ape like (but this is only one bone or some teeth) is found from a deposit around 25 million years ago, does a particular feature of that fossil indicate that it post-dates the monkey-ape common ancestor (because it is novel, not seen in the last common ancestor) or does it indicate nothing other than membership in the Catarrhini (becuase the feature is seen in the last common ancestor)? Without a detailed set of information about the last common ancestor, we can’t say, and can thus not be sure of this fossil or what it tells us about the timing and nature of the ape-monkey split or other important questions.

So, Saadanius hijazensis is a missing link right? It represents the last common ancestor of Old World Monkeys and the Apes. Problem solved!

Well, no, unfortunately not, but Saadanius hijazensis is close to the last common ancestor and is thus very helpful. Saadanius hijazensis is considered to be close to the base of the ape-human clade. Not “the missing link” but very very helpful in understanding what the ape and monkey lineages we know of for later periods evolved from.

Saadanius hijazensis has a tubular ectotympanic (the bone that contains the canal runnig to the ear from the outside). This is a features that separates the Old World Monkesy from the earlier-split-off New World Monkeys, shared by the Old World Monkeys and living and Miocene Apes. So Saadanius hijazensis is a Catarrhini. Miocene apes have frontal sinuses, palates that are less uniform in size front to back than monkeys, really large male canine crowns, a few other esoteric tooth-related features, and are typically large. Saadanius hijazensis lacks these features, making it not an ape. Compared to the above mentioned really early primate fossils (from the Eocene), Saadanius hijazensis is similar but different in the ways one would expect if it was an Old World Monkey. And, the fossil seems to date from prior to, but just prior to, the monkey-ape split.

These facts together put Saadanius hijazensis near the common ancestor of Old World Monkeys and Apes, in both time and morphology. The fossil is found in the Arabian Peninsula, which at the time was part of Northeast Africa (the Red Sea did not exist yet) which places the fossil in space within a region (a very large region) thought to be the location of the evolution of these monkeys and apes. And, although this could quite accidently turn into a tautology, Saadanius hijazensis helps to pin down the timing of the split to about 23 to 25 million years ago, simply because it fits nicely with a morphology representing the pre-split form and dates to that period. This does not rule out an earlier split, of course, because Saadanius hijazensis could certainly represent an earlier evolutionary event. With respect to the timing of the monkey-ape split Saadanius hijazensis also provides hope that more fossils of this time period can be found, and although a single species may be hard to place in fossil space-time, a set of species can reveal a pattern that may make for interesting study.

Given this position, Saadanius hijazensis can help resolve conflicts regarding early Miocene apes, since Saadanius hijazensis approximates the ancestor from which they evolved, and help to understand (given further analysis) the behavioral biology of the Old World primates of that period. For instance, did the ancestor of the living apes have a flat face (like a gibbon) or a long snout (like many monkeys including baboons). According to my old friend and schoolmate, Laura MacLatchy, this fossil should cause us to lean towards the baboon-face model.

Here’s a Nature video about the fossil:

Zalmout, I., Sanders, W., MacLatchy, L., Gunnell, G., Al-Mufarreh, Y., Ali, M., Nasser, A., Al-Masari, A., Al-Sobhi, S., Nadhra, A., Matari, A., Wilson, J., & Gingerich, P. (2010). New Oligocene primate from Saudi Arabia and the divergence of apes and Old World monkeys Nature, 466 (7304), 360-364 DOI: 10.1038/nature09094

A University of Michigan press report on the find is here.

So my eyes traveled to the point from which the birds may have diverged, and there was a fast flying, powerfully flapping raptor. My first thought was Falco peregrinus, the peregrine falcon, because they are big, fast, and eat birds. But after a brief moment I recognized the fluttering moth-like flight of Accipiter gentilis, the northern goshawk. Having no chance of catching up to the pigeons, the goshawk turned towards a lone tree that I always check on passing for raptors, as this is the territory of a pair of Buteo jamaicensis we have been watching for years. Just as the goshawk flew into the canopy, the canopy emptied out like a country western bar at 3:00 AM when the sheriff deputies arrive to break up a fight. Only instead of drunk cowboys it was blackbirds and sparrows which had been hoping no one would notice them, piling out of that place.

(On the way back, a half hour later, Accipiter gentilis was perched on a branch in that very tree, munching on … something with feathers.)

In the Semliki Valley, when I was looking into the behavior of large carnivores and their eating habits and landscape movements, the same principle applied. Drive up to a herd of antelope (in this case, Kobus kob thomasi, the Ugandan kob) and they all stare at you, except three or four who are the farthest away. They are all staring at something else. Kill the engine and sit tight for 20 minutes. Over time, the kob will increasingly ignore you, and more frequently glance in a certain direction, most of them looking the same way. Now you know where gimpy old Uncle Elmo’s remains lie scattered in the tall grass, two or three well fed lions napping in the nearby shade.

For years we have known that monkeys pay more attention to each other’s reaction than to potential threats, under certain circumstances. Indeed, the efficacy of responding to another individual who is not a predator rather than only to predators is so marked that alarm calls have evolved in many species. Alarm calls presumably put the alarm caller at risk. A predator that elicits the call response may well have not noticed the caller, but now, there is no doubt that something to eat is nearby. Of course a well placed alarm call can also signal that the potential prey is on to the predator’s approach, and will thus put the predator off. But the conventional wisdom is that alarm calling has a cost, so it must therefore have a benefit. That benefit has to be realized via kin selection, whereby relatives benefit even if some die warning others. And, once alarm calling gets going, it can play a role interspecifically, with one species gathering information by observing the behavior, including the alarm calls, of another.

A recent study by Kitchen, Bergman, Cheney, Nicholson and Seyfarth (most of you will recognized Cheney and Seyfarth as big kahunas in the primatology world) demonstrates a good example of this. One question they explored is this: Is the reaction towards the alarm calls of a different species something that is mainly encoded in the genes or something that involves more social learning?

To examine whether familiarity and/or shared vulnerability with the calling species might influence the ability of sympatric species to distinguish heterospecific alarm calls, we tested whether four ungulate species (impala: Aepyceros melampus; tsessebe: Damaliscus lunatus; zebra: Equus burchelli; wildebeest: Connochaetes taurinus) could distinguish baboon (Papio hamadryas ursinus) alarm calls from other loud baboon calls produced during intra-specific aggressive interactions (‘contest’ calls). Overall, subjects’ responses were stronger following playback of alarm calls than contest calls. Of the species tested, impala showed the strongest responses and the greatest difference in composite response scores, suggesting they were best able to differentiate call types. Compared with the other ungulate species, impala are the most frequent associates of baboons. Moreover, like baboons, they are susceptible to both lion and leopard attacks, whereas leopards rarely take the larger ungulates. Although it seems possible that high rates of association and/or shared vulnerability may influence impala’s greater ability to distinguish among baboon call types, our results point to a stronger influence of familiarity.

So, even a basic and widespread mammalian trait is shaped by experience. This should help, a little, to calibrate one’s thinking on such matters when it comes to assertions that different groups of humans have genetically determined differences in ability.

The research in this paper (Comparing responses of four ungulate species to playbacks of baboon alarm calls) does have a confounding problem, which the authors recognize: Impala’s ‘get’ interspecific calls better than, say Zebras. But they may also be more vulnerable to predators (for a number of reasons). Selection on this ability may simply be stronger for them.

So, remember this: Next time you are walking to the store and you see and hear a murder of crows which seem focused on a certain large and well flushed tree, don’t think “Noisy Corvus brachyrhynchos.” Rather, think “Ah … Bubo virginianus…”

Kitchen DM, Bergman TJ, Cheney DL, Nicholson JR, & Seyfarth RM (2010). Comparing responses of four ungulate species to playbacks of baboon alarm calls. Animal cognition PMID: 20607576