John W. Kappelman

Late Oligocene and earliest Miocene primates and faunas from West Turkana

The sites of Nakwai and Losodok in West Turkana preserve evidence of late Oligocene and earliest Miocene sediments that document both apes and Old World monkeys from a time period that is not well represented in the geologic record. These sites also offer evidence of older African mammal groups and some of the first immigrants from Eurasia.

FULL TRANSCRIPT 

Thank you very much, and I want to thank Lawrence and Fred and Alicia for setting this up. I can't honestly imagine how much work went into this, so thank you for a really well-oiled machine. I want to share with you too, my first interaction with Richard Leakey, that was in 1979. I was an undergraduate finishing a term paper that I was sending in as a manuscript for publication. And my professor, David Pilbeam, said, “You know, I think Richard Leakey would like to read this paper. He's in London right now waiting a kidney transplant, and this would be something to give him that would get his mind off of that”. And I'm like, “Whoa! Send this paper to Richard Leakey!” So, it's like, okay. So I did and I included a little note along with the manuscript and didn't think much of it. And about two weeks later I got back one of those nice handwritten letters that Bernard Wood mentioned the other day that was very personable. 

It was on point. He was able to offer comments about the paper. But the thing that I remember the most from that was just how encouraging that letter was. And when I opened that up, I was like, “Oh my gosh! this is a letter from Richard Leakey!”. I was a kid who grew up on a family farm in Idaho and my job was milking cows. And on the night that there was a National Geographic special, by dawn I made sure I had those cows milked, the animals fed. So I had my butt planted in front of the TV when any of you are my age can hum along with me, that National Geographic theme song. 

So I knew where I was when those shows started. And with that letter, again, the thing was just how encouraging it was with his support for me. And at that point I told myself, I said, “Kapp, you may actually have something that you can contribute to the study of human origins and evolution”. And I still remember that today because when I wake up every morning, I think that that's still a testable hypothesis. Will I actually have something to contribute or not? So what I want to talk about today is the really the last slide first. And that's the work we've been doing at Nakwai and also at Losodok, as has been mentioned by everybody, we have large teams that do this work. And to point out here, Mercedes Gutierrez on the other side down here, Tab Rasmussen and then up here, Ellen Miller, this work is one where it has to be collaborative. 

We work together as a group and it can't work otherwise. And I list here all the people and groups that have supported us as well. Well, it's easy for me to give this because Natasha laid this out for us and what we're looking at going into the older part of this record is a completely different time period. We're moving back tens and tens of millions of years within the Turkana Basin and within Africa as a continent. Most of what you'll hear for the rest of the week is going to be much on the much younger interval. If we showed this slide to anybody who's been watching National Geographic specials for their whole life as I have, where do they live? The answer is going to be obvious. These are from Africa. But what that person on the street is not going to be able to tell you is that those animals actually did come in. They're mostly Eurasian forums that entered into Africa at some point that some of the forums within Africa today do have ancient roots within the continent.

But we also see, as Natasha had mentioned, that we have this major extinction event and within this is this period of time so, this is the movement of these forms down from Eurasia into Africa. And we do see also the dispersal of a small number of those tacks so that were the Afrotheres out of Africa, but it's an uneven mix of these two coming across. And so what we see within this, and this is where it was when I had started again back in 79, was this interval of time that's about 10 million years in duration where we had zero fossil sites for the entire continent of Africa, and we named it the missing year. So think about that with regard to this slide. 

Let's say that here's today and we're going to push the record back 10 million years where we have nothing back to 10 million years ago with the fossil record there and try to reconstruct what happened in the last 10 million years. That's what we're looking at with this Oligocene-Miocene record. So, as again, as Natasha had mentioned that that bottom line that I showed you for those Afrotheres, and what that record is, came out of the Fayum. Here we look at the movie for plate tectonics for Afro-Arabia. We hit the reverse button, we close up the triple junction, Gulf of Aden disappears, Red Sea disappears, the east African Rift disappears, and the continent here of Afro-Arabia is separated off. So, here's where we have the Fayum up at the top. So, the taxa known from the Fayum had been known since the early 1900s. We've had them for about a million, or sorry, about 100 years, about a century or so. But when we look at the ages of that, one of the nice things about Torpenawi that you just heard is that there's a volcanic ash or volcanics dated at the top and the bottom, so we have minimum maximum ages for that.

When I first started working in the Fayum in 79, we had some ages for the very top of the section. So, this is the Widen el Faras basalt that you see eroding down in black. Widen el Faras means ears of the mayor in Arabic is a very distinctive site. Elwyn Simons was the one who ran this project for decades. We have some dates on that upper basalt, some that Simons and Fred had run, some that John had run, some that with Carl Swisher I had run. But again, they give us the minimum date. So how old are these fossils actually?

We figured they were probably going to be early Oligocene, probably late Miocene. And so, what we did was go in and run paleomag on the section. So this is looking at reversals of the earth's magnetic field. And what we found was a long period of predominantly reversed magnetism toward the base of the section that is, if you were out in Egypt at that point with your north seeking compass, it would actually point to Antarctica. So with the convention here, if the magnetic polarity is like today, it's shown in black and if it's reversed, it's shown in white. We had two options for that correlation. One was that long reversal coming in with chron C13r. The second is C12r, so a little bit younger, mostly based on the sedimentation rate, what that curve is showing here that we thought that correlation one was a little more likely.

Erik Seiffert, who you've mentioned with some new sites coming in, again early Oligocene from Oman, looked at those data and what, sorry, hit the wrong button there, and what he found, and again with these sites being intercalated with marine sediments have an absolute date with them. He actually thinks that the correlation is probably better with chron 12, so that makes the Fayum a little bit younger. Still testable that we've gone through, me, Tom bound, every other geologist who's worked out there, through that Fayum section, top to bottom looking for ashes, tephra, we haven't found anything. But who knows, maybe someday something will come in so that we have a date within the middle of that. So, here's what we had when I started out in 79, that's when I first met John Fleagle, also Elwyn Simons said, “Hey Kapp, I want you to go down to Kom Oshim and pick up Fleagle”. 

And what that meant was driving across the Sahara Desert, across the escarpment, down to Kom Oshim. I had a Dr. Livingston, I presume, moment with John Fleagle and we've been colleagues and friends ever since. So with the Seiffert work, what that did was move things a little bit younger. So we have a somewhat fewer missing years within this, but it's still a long interval of time where we don't have any sites. And so try to figure that out when that exchange actually occurred. So what I want to do next is run you through some of the other sites that have come up from the late Oligocene with Torpenawi, I don't have that in here, but it's going to be down at around Fayum age. And you can see with the red here for the late Oligocene sites, we've actually plugged in quite a few and I'm going to run through these pretty fast for you. 

So, the first ones with Losodok that you've heard, this is in west Turkana. That we have a very thin layer of sediments within that they are Eragaleit beds. They've been dated the basalt's top and bottom to about 27, 28 or so. Meave Leakey worked that section in 1987, and the fossils, they collected, quite a few fossils there, they only published on a Hominoid from there and they placed it at about 25 million years or so in age. Chilga is a site in northwestern Ethiopia that we discovered 1997-98. John was along on that project as was Erik Seiffert. And what that did with the dating those sediments date between 27 to 28 million years old is that you can see that it moved a lot of the last appearance datums up and down. So, we have Gomphotheres showing up much earlier in time, we have paleomastodons coming up younger in time. So we move these things around and we start to fill in those missing years. The Embrithopoda arsinoitherium that we have from Chilga actually got a call out in Pixar's movie “Up”. So that was kind of a fun thing to have. 

Lokone, this is again in west Turkana, it's a small sediment hill out there that the French have worked. It is not absolutely dated, but based on the faunal correlations, what's more derived, what's a little bit more primitive? I think it's around 27 or so, probably a little bit younger than Chilga, and you can see that it's also filling in records for some of the taxa that we have that we know go through as you see here. And some other ones that are interesting with Parapithecids that are diagnostic and very characteristic of the Fayum showing up for the first time. Coming down into Tanzania with Rukwa, with Nancy Stevens work that we have a fossil ape Hominoid here named after John. And then we have a M3 from an early monkey. That site comes in at around a little over 25 million years or so. So again, we're starting to plug in what we see from this range of time. Now that takes us into the work at Losodok and Nakwai, you can see the sites along the side of the lake here. And when you look at the satellite imagery, all the grayish in here, these are basalts. So we're working into within sediments that are intercalated or underneath these basalt flows that you see. 

This is the site of that Benson Kyongo had found, so this was found in 1987 when Meave Leakey and Benson went through this area. They collected a lot of fossils both at Losodok and at Nakwai. Meave published on the fossils from Losodok in 1996. And we were working on the material from Chilga and Meave invited Tab to come down to Nairobi to look at what she had found in Losodok, again, most but not published. And during that visit, she said, “Tab, take a look at these other fossils from Nakwai”, and he did. And it was one of these holy by golly moments where this was not Miocene, this was a legacy stuff. And again, just as a comment for Tab that he knew these faunas like nobody's business, we all  cut our teeth on the Fayum at one level or another, but he really cut his teeth there. So that was the beginning of our work in this particular area.

Within Losodok, these are the upper units of the Eragaleit beds. We have about 20 localities in there now or so that we've put in with Tyrone Rooney and Alex Steiner who are at Michigan State. A long section here looking at these basalts from top to bottom. We presented the chemistry on this section at the AGU meetings last December. What we didn't show are some of our dates here. So here is the original dating work from Broschetto, with the base of the Eragaleit beds around 27 or so, of basalt above at 24. So that's where that 25 million number comes in somewhere in there. Our lowest date that we've run comes out at 28.55. So it's basically within the overlap of this 27.9 date. We did not get any basalts through here that actually dated out. 

So last summer we resampled that section and I also put paleomag in through these Eragaleit beds, re-sample what we think are some tephra up here through the top of that. So we just have to stay tuned on what those dates may end up being. We move south about a hundred kilometers to Nakwai, and here we start to see things that those of you are fossil collectors start to get excited about. We see channel sands coming in, we see overbanked deposits some of these are much smaller channels. Down here in these large channels, we actually see beds of the Nile Oyster Etheria. So we know that these are large permanent rivers coming through these areas. This particular hill, we saw this from a distance and it's just like, you know they're going to be fossils there in the top of this hill was covered with fossils. 

Here you can see maybe a person in the background up here back some distance. Here's another one of the sites, Top 73 and one of the things that's characteristic about this area or all of the capping basalt flows and what basalt flows do, and they erode is produce a lot of scree. So ,this area is covered and covered with scree when we're looking for the sediments of these little pockets, these little windows that we see that we then hit on for the fossils, and the bed right above the collector here is a sandstone, so a channel stand. For the dates on that, this is again where we see the basalts capping these areas with both an angular and erosional unconformity there. So we've dated those capping basalts. Again, that's going to give us a minimum age for these areas, and they come out to between 17 to 16 million years ago or so, but again, that's the minimum age it's not the age for the fossils and the sediments that are down below.

This is a view from Google Earth that shows basically a north view coming through, the red line here is the base of those 16 to 17 million year old basalts, remember that's an erosional base. And for Thure and Kay and for Craig who are out there, we look very familiar. This is what we do is we put in measured sections coming across through this. Again, remember that everything that's dark here is a basalt, so it's not working on nice sedimentary exposures. This is pretty heavy lifting with regard to doing the actual section measuring and a description of the sediments. So here are some of the sections, you can think about this as just putting up fence posts with my farm boy analogy, and within that then we string along marker beds when we can find those, add the paleomag to that, and when we're lucky, we can add in some absolute dates.

So this is an ash bed that we've dated that comes in at 22.85. We walk back across with these two paleo mag sections that we can correlate with the tracer beds coming through down through here. That 22.85 puts us into plus or minus CN.1r and what that shows with this overall section is that Nakwai dates from a little over 21 million years ago, back to over 24 million years ago. There is no section that I know in Afro-Arabia that includes this amount of sediment and this amount of geologic time. The other thing we've done, we did this last summer, is to go through and actually fill in some of the intervals where the paleomag sampling is a little low. So, we try to tie in where those reversals actually occur and in this section we've added in additional sampling up here and down below the base. Kevin Uno came through this section after we were there and he said, Kapp, “I've seen all of the holes that you drilled so we've got more samples to run with that”.  

Just to show you briefly some of the fauna that we have, that like you saw from Fayum and also from Torpenawi that is dominated by Hyracoids. This is not any kind of a surprise to anyone. We also have lots of Proboscidea that Bill Sanders at Michigan has been working on this and also at Chilga so he's very excited about all of this material. We have lots of Creodonts, so they evolve in parallel with true carnivores. So these were the primary carnivore type animals at Nakwai and also at Losodok, Ellen Miller has recently described the phiomyids. So again, this is a link that we see coming through. We have, and I'll show you our primates, we have several of these. 

So, this is what we refer to as Kamoyapithecus, Jay Kelly and James Rossie are working on some of this material. Jay's not so sure it's all Kamoyapithecus, maybe it is, maybe it's not but these are specimens that we have from Nakwai that you see here. Here is a upper, sorry, a lower right M3 at the top from Nakwai, the same tooth from Losodok. These are really similar to one or another, so we think there's probably time equivalence between these two areas with regard to the morphology of these teeth. Back in the old days we would've called this Proconsul africanus, but today we're not so sure what that is but it just means, again, there's a different kind of another ape that's in here so quite a bit of diversity, size differences.These are some of the early specimens collected by Meave Leakey from Losodok. We think these are probably male, female with regard to sexual dimorphism for the Hominoids themselves. What's also exciting here is that we start to pick up more of the Fayumian type primates. So we have Propliopithecids that you see here, and this is compared with a tooth from the Fayum and one that we have from Nakwai. 

And here's another Propliopithecid and what it shows is some similarity with some of the later forms from the early Miocene Limnopithecus here. This tooth is a little broken, but maybe this is what we're seeing for some evolutionary diversification from these groups, from Nakwai coming into younger intervals of time. We have this monkey that was a bit of a surprise, it's a non-bilophodont Old World Monkey. One of our reviewers of this paper said, that's not a monkey, that's a pig. And so, we call it “Porkipithecus” among the group, but we're able to document that it is in fact a monkey. And so that bilophodonty probably evolved later on and we're able to document the various steps on the morphology of the dentition of these early monkeys. The one here on the left is from Nancy Stevens down in Rukwa. 

So what's it do for the missing years here that we have trying to fill this in? Well, this is where the Losodok and Nakwai material come in. We've got more time depth that I showed you but just to make this slide legible, I put everything in here about 22-23 million or so. Remember that when Meave Leakey collected the Losodok material, all she published on was the Kamoyapithecus specimen. And so what we found within that is our Arsinoitherium, so that's shown there. And there's also a Deinotheriium here in there that we've added in, so we have that material coming in as well. Other surprises, we have true carnivores at Losodok and at Nakwai, so those come in. And here's your view test here. So where's the fossil? Well, it's always in the middle. And what this is, is a Suid so we have a true pig coming into the record. So ,this is our true Porky specimen rather than our “Porkipithecus” specimen.

So, adding these in, to what we have for the record, it brings our carnivores down. So from Nakwai and Losodok, and then it adds pigs in. This is also the only section at Africa that includes these Eurasian immigrants coming in with these Fayumian forms at the same time. So when we look back at that record about that long interval of time where we had no fossils, when did that exchange occur? If you had talked to most people in 5 or 10 years ago, they would say, oh, probably at the Oligo-Miocene boundary, probably at around 23 million. It's looking now, it may be somewhat younger and rather than being instantaneous from all these forms coming in, it looks like they may come in at different times. We may be seeing different things coming in. 

But again, we have a sample here of n equals two, right, for the number of groups coming in. But when you look at this slide, it's actually starting to fill this in. So, this shows the work of the last 30 years or so where we still have a limited number of sites, but we're getting there. And coming down to the south for one of our other sections, this is unpublished, but we have a debris flow here with big pumice glass in it that we date to a little less than 21 million. These are all sites coming up through that. Again, this basalt coming in at around 17 for the base. So, there's a good chance of being able to fill this record in with even more detail. 

And for the isotopes who are out there, I had to throw this slide in. This is by Lauren Michel, Timothy Myers, Neil Tabor. We're looking at C3 diets here that there's a wider range and a more positive range of the oxygen here. I was surprised at just how negative Torpenawi is for the oxygen. When we look at this with regard to the taxa, we haven't run that much, these are preliminary data for the C3. There's range of variation there, but it's all C3 diets. When we look over at the oxygen, for the Gomphotheres, maybe there's a change through time, but for four samples, I'm not going to bet my lunch today on that. But the oxygen data and the carbon data may give us some other options about what's actually driving that we still don't know what drove the extinction, we lost a lot of animals. Was it competition with those Eurasian forms coming in or did the Afrotheres go extinct before? These are major questions we don't have the answers to because we don't have still enough data to address them. So finally, I just want to say thanks to all of you for listening to this. And also a note of thanks to our colleagues who have passed on from us, and that includes Richard Leakey as well, and that letter of his that I still have. And also thanks to our funding agencies. Thank you very much.

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