Anna K. Behrensmeyer

Faunas, floras, and footprints – the paleontological context of human evolution in the Turkana Basin

Interest in human evolution in the Turkana Basin has helped to generate a wealth of knowledge about the ancient faunas and floras of this rift basin. Kay Behrensmeyer will present highlights of this extraordinary fossil record and how it provides essential information for understanding human evolution.

FULL TRANSCRIPT 

It's a great honor to be representing all the people that have contributed to paleontology over the many decades. And when I was given the choice of topics, it was like the paleontology of the Turkana Basin and I thought, oh my goodness, how can anyone cover that in days much less 45 minutes? So I, I'm starting with a bit of a caveat and an apology to the many people, some of whom are in the audience whose work I will not really be able to include in this. But you'll be hearing about some of it, at least like the earlier record in other talks. So we have our, of course, focal organism ourselves, and the context of their evolution involves, of course, faunas and all the organisms, floras that were part of their ecosystems in the Turkana Basin.

So one of the important things to notice about this map of the Turkana Basin is that it is a low spot. This is geography, it's tectonics, it's the evolution of the African roof system. The Turkana Basin sits in a low altitude area between Highlands, which then represent a place where the water is collected by the higher grounds and fed down into this lake, which today we see there's been lakes. There've been times when there haven't been lakes in this Basin, but it's always been a special kind of place that not only was going to demand different things from the Faunas and Floras in terms of the climate parameters, but also collecting sediments and preserving a lot of this amazing record that you'll hear something about.

We've heard some of the history, the older history from other speakers yesterday. For me, my primary advisor when I was a grad student was Brian Patterson, who was working in the Turkana Basin looking at the Miocene. And he was invited there by Louis Leaky who didn't think there would be in this part of the Turkana Basin West Turkana much in the way of later deposits at that time at least. But Brian Patterson ended up finding some hominins and stopped work in 1967, which was the year that I became his grad student In the Omo, the work started with the French and then Clark Howell was invited. I found this photograph, which you can see with Camille Arambourg and the French, and the Americans assembled teams and were going strong up there, creating two records, actually the French and the American. And they had a path between their field areas, which was not safe to cross even though the strike of the deposits was continuous across the north south trajectory of those two areas.

Interesting politics in those days. But they did come up with a tremendous amount of information from the Omo record. And then of course we've heard the story of how Richard started in the Omo and flew over East Turkana and then started work there in 1968. And I joined in 1969. I was at Lothagam in 1968 with a graduate student of Brian Patterson's, Vince Maglio, and that's how I met Richard. And he asked me to come on as a geologist with his project, which was for me a quandary because Louis leaky and my advisor had fallen out about the fact that Brian Patterson had found hominins where he wasn't supposed to in the Turkana Basin. Anyway, that's another long story, be it as it may. Patterson was gracious, didn't mind too much that I went to work with the son of the person that he had fallen out with.

I wanted to give a little bit of nostalgia here. Louise encouraged me to provide some background. These are just some images from that first magical year, 1969, you've heard about the 406 skull. The camel safari went off and came back with this skull wrapped in one of the headbands head dresses that they were wearing. And it was a fantastic thing to have. And then later on in that season, Mary and Louis both came up, I think at maybe different times. And if you look carefully, you can see that Richard is helping her get on a camel. She didn't go on a long camel ride, but she wanted to try it. And she's smoking her characteristic. Cigarillo Louis, looking at some of the fossils, the hominin, it's just quite a wonderful thing, which I'll always be grateful to have been part of. And oh, in the right you can see we are trying even with the wind, and you can see that Richard is trying to keep this long string of air photographs that were pasted together with celltape from flying away in the wind. And we had to take our own air photographs. There were no maps, there was nothing to document. So I'm sitting here trying to paste them together and that's how we were first documenting where the fossils were coming from.

The geology, of course, you can't really do geology if you can't do mapping

At that time. And in the 1970s in general, as you've also heard a little bit about, there were wonderful organisms all around us and this is just a collage of some of them that we're sharing the habitat and also providing a wonderful analog, a modern analog for what we were looking at in the past and reminding us about how all these organisms interacted. And I've also put in a picture of Zuma the dog over here because that dog came into our camp and became a friend of Richard's. And every time he heard the airplane coming and he would go up to the airstrip. And this was just one of the local dogs that decided to adopt us. And it's pretty certain that he also was interbreeding with the jackals up there.

And I'd also wanted to make a special tribute to Richard as we know this, a master of bringing people together. But I saw this from the very beginning. He really enjoyed getting all these different groups of people together, some of them more compatible than others. And he invited folks that his team were a little [inaudible] at times, a very young Tim White for one, Donya Hanson, Milford Wolpoff came out. I mean Richard loved to mix people around, put the cat among the pigeons as he sometimes would say, and just see what would happen. And so it was very inclusive. It was a great model for all of us younger folks to see. Even though at the time of course there were lots of controversies and sort of personal feuds going on as well.

So I'm going to start now with my real talk, the outline of the science. And I like to always start with what are the questions, what we know versus what we would like to know. So some things about the fossil record that were a particular focus for my research, the Turkana Basin fossils themselves, just such a quick overview of such a tremendous amount of information and then focus on the mammalian faunal record. That's part of it, but it isn't all of it. Sometimes we forget that and return to the questions and then what next? Look ahead because there is just so much more to be done and understood. So why is the non-hominin fossil record important to all of us? It's good to review this. Sometimes there are fellow travelers through time, there are many more fossils than the hominins. Of course, hominins are less than 5% or maybe less than 1% by some counts, interesting evolutionary stories of their own to be told.

And the evidence for changing environments, they inhabited the same environments, which our ancestors are where they evolved and they record functional in their functional morphology and their isotopes in other ways, their behavior or track ways, what was going on. And they preserved taphonomic information for the hominin behavior, prey choice potentially cut marks, et cetera. And this also kind of hanging in the background of all of our ways of thinking. That is the Savannah hypothesis out of the forest into the open country. It's been looked at and questioned and tested, and some of it's true, some of it's not. But it's always hanging back there as a model that we've grown up with and are continuing to investigate.

Our questions at the beginning of course are just what's out there? What is the fossil record of the Turkana Basin discovery documentation description? And for me at least, how, and where were the different taxa were preserved. And of course, not just for me, but a lot of the geologists and the archeologists and the paleontologists were intrigued with that question as well. And now evolving the questions where we have a body of information, we have databases that have been compiled and we can start asking about the habitats and the change through time not to start but continue the hominin impacts on other taxa. There's now the issue of, well, we are affecting the carnivores. Were we affecting the megafauna much earlier than might have been expected? And was the Turkana Basin a hotspot for arid climate adaptation and evolution when the surrounding areas were lagging behind what was becoming a more global trend toward aridity and extreme seasonality?

So, you can actually put this into a ternary diagram sort of with the influence of the physical characteristics at the top here. And you might think, well, they're affecting human evolution, some of them for sure, more or less directly. But a lot of what's going on goes through the ecology and the faunas and the floras of the Basin in order to actually affect change. And in the Rift Valley or in any evolutionary arena, you have the choice of adapt, move, go somewhere else if you don't like the environment at the time or go extinct. So, there're like three choices and in the Rift Valley there are lots of options for moving around. So then the question becomes, well what would it take to actually drive evolution? And is it something that's going more slowly and gradually or something that's subject to environmental crises? We'll come back to that at the end.

Well, this is a complicated diagram for the morning. I hope everybody's had their stimulants, their coffees, but recently published by my colleague Tyler Faith and a group of us about the different scales of questions on the left and the evidence. And you can overlap those and see how the different scales of evidence really need to be paid attention to in terms of asking a question that your evidence overlaps and matches. And we're going to talk a lot about this arena later. And then the more detailed types of information that are short time periods and small scales, which include track ways and excavation. This is a framework that we're trying to get more people to think in terms of, and I'll come back to it at the end. Alright, so now the Turkana Basin fossils include a lot of different kinds of organisms. So I'm going to give you just a look at that.

But I want to reemphasize this Basin that is a low spot between high spots with the river coming in Omo River coming in from the north, there are rivers that have come in from the south and from the west as well and from the east. So, it's a Basin that's been fed when there's a lot of rain around the East African subcontinent, then this has become sometimes an overflowing source of the Nile as well. Other times it's become an alkaline lake that is not palatable for drinking. So it's fluctuated between those and the sites are over here. The main sites that I'm going to talk about, and I know there are many others that are not on this map, but this is about the last 7 million years. And now because of all the wonderful work that's been done partly by the Turkana Basin Institute researchers, we know there are lots of other sites as well. So Lothagam

Started it out for me and for Bryan Patterson with this rather poorly preserved but tantalizing mandible that was discovered in 1967. And the dating of it was not clear, which was why I got to go to look at Lothagam. And this is Vince Maglio and one of our Kenyan assistants carrying just one of the many elephant fossils that he was collecting at that point that mandible never really got published properly. And I moved on to East Turkana. So it took Meave going back in the late 1980s into the 1990s and really doing a thorough job on the paleontology of Lothagam to bring it into our arena of knowledge. And the monograph that she published with John Harris is a classic. For the Shungura formation. This is an air view showing the successive deposits of fluvial sediments and the wonderful volcanic ashes that are the white parts. And Frank Brown was able to, new dating techniques were used to get the dates at the time the first homo over here. And this is a continuous, beautifully exposed sequence. So, they had that advantage over both East and West Turkana. And they also had these amazing bone assemblages that were excavated and sorry, I Went forward. And those represent the river going back and forth within its channel belt. And reworking bones that were coming out of the banks and on the floodplain and in the channel and creating lags of these very rich but very fragmentary and tooth rich deposits. So, their preservation was more like this East Turkana, a different preservational situation with more complete material. And when the project started and then on for years and the East Turkana surface was just litter with fossil bones, it was amazing to go out there in the beginning. Whole elephant mandibles just sitting there and beautiful primate remains. And of course we couldn't really document as well as we needed to. So, some of those specimens still we are trying to track down where they're exactly from. But it was a happy hunting grounds of the best kind in those early years for getting a lot of fossils into the collections. And in 2015, I think I did a calculation sort of back the envelope of how many person hours at that point likely had been devoted to collecting. And now it's probably over a million given what Louise was telling us yesterday and including all the other folks. And I just wanted to be sure to mention the continuing efforts of Louise and TBI and the East Turkana folks, everybody who's building this amazing record ongoing from those beginnings.

So here is the time context of these major deposits in the last 7 million years covers a lot of the temporal record and you can see the thicknesses of these sediments as well now extremely well calibrated with all the radiometric dating that's been done paleomagnetism. And so, it's a phenomenal, well-documented chronological record of the fauna.

Okay, so we all like the mammals, we all like the hominins, but I just had to go through my pictures and find all these other wonderful organisms that haven't had enough attention. The Gastropods were initially studied by Peter Williamson who came up with ideas about punctuated equilibrium based on these that have now been somewhat discounted, but there's a rich mollusk record that has barely been tapped. Phytoliths, crabs, there are crab claws preserved at Lothagam that's in the Lothagam monograph. There are ray tail spines now extinct, but a kind of shark that was in the Turkana Basin. Lots of information from fish spines, ostracods diatoms, there are trace fossils, lots of plant roots. Recently published wood morphology from fossil wood in the Omo-Shungura formation and the stromatolites, which you've heard about too. Here's one that grew around a piece of fossil bone. There's an amazing story yet to be told about the stromatolites of the Turkana Basin.

And the vertebrates, some of the early excavated specimens and surface specimens. And here is a tooth of a rodent, so we don't forget that there is also a micro vertebrate record there. And the footprints, which first turned up on my project in 1978, and they're hippo prints, you can see them in cross section here. We dug a geological trench and thought, well, let's just see what's next to it. What do they look like from the top view? And by the little ruler there, there's a hominid footprint that just turned up amongst the hippo prints. And it was a whole trackway was discovered the same year as the Laetoli print. So they definitely eclipsed it because they were so much older. That's about 1.4 million. But nevertheless, East Turkana has now turned into a source of lots of information about trackways and footprints of different organisms.

So the collecting methods make a big difference in the kind of information that we get. And this is some sketches showing the different methods that surface prospecting, opportunistic or controlled along the outcrops surface scraping, which is done when a hominin or other important fossil is found excavations when you have the ability to do that, always result in more detailed information like these beautiful complete specimens in area 103 in East Turkana. And also, some interesting taphonomy because this was a little channel where a bovid femur got caught against this big euthecodon skull and jaw. So yeah, it's a tradeoff.

If you go out and do the opportunistic prospecting, you come across wonderful fossils too, but they have less precise information. And so you create different kinds of data sets to address different kinds of questions. But if you do pay attention to the kinds of environments the fossils are coming from, which was something I was very interested in, in this case, here are two kinds of suids and based on what I call the square frequency, which is just the frequency on the ground, the delta, the channel and the floodplain have different relative abundances of these two kinds of suids. And then if you line up also many different kinds of taxa, you can see that the different environments are actually, and this is a lake margin and this is a channel just one set of samples. They represent different kinds of habitats. And that was a question, do the taphonomic processes cancel out this kind of thing or is ecology actually preserved in the depositional settings that these fossils end up in? And indeed ecology is preserved not perfectly, but information is there. And not only that, but at one time period, if a systematic sampling in the three areas of East Turkana, Ileret, Karari, Koobi Fora and Area 103, the greatest differences between the proportions of these major groups of mammals were not between these three areas, but between whether they were in the levee floodplain or in the channel. And just to highlight that a little bit more, this is the hippo, not so different in the top row, but quite different in the between channel and the levee floodplain. And also, as another comparison, the equids are more abundant and primates other things too. So if your big sample is coming all from channel deposits for instance, you will have a signal that's skewed over toward the more open habitat. But if it's from the lake margin, then you'll have potentially one that's more skewed toward the closed habitats. At least that's what we were thinking in the earlier years, still needs more elaboration. But what about the hominins themselves that by then pretty large samples. So just as this example of the 406 skull, because before they cleaned it, I was able to look at it, there's this minimal bone weathering on the skull, no transport abrasion, the dentition was missing,

But it had not been transported very far before it was buried. Here was the actual site, here's this microstratigraphic section, and it was clearly related to this little channel deposit, which then you can imagine as equivalent to something on the modern lake margin. And taking that into the larger sampling of the hominin record as of the early 1970s, I documented a lot of the hominins that were available at the time, the ones that were pretty well both documented geologically, but also taxonomically. And there are differences in where they occur. This needs to be updated of course, but it's very tantalizing that the like margin deposits are having equal numbers of Homo and Paranthropus. I don't think there's any question that they were contemporaneous as well. And in the fluvial environment, Paranthropus was more abundant of course as dead organisms. But other work I've done indicates that this is a fairly good representation of where they actually lived as well.

So, let's go to the faunal record. I'm going to have to go faster, but I want to pay tribute to the people who have contributed so much to caring for these collections. They were pouring out of the Turkana Basin and first into the National Museum in Kenya. And Richard of course was very concerned about that, having a new building, the space that would receive and take care of well, the people as well. Mary Munguu retired in 2016. She was the curator in paleontology, many of you know her. And she was wonderful at being the mother of the collection at NMK and Rene’ Bobe working with Rose when she was just an intern I think, and now she's the head curator there. And so, carrying on this training, and I included Ellen with some students TBI, because I know the collections, there are a major resource, a major concern. And I just want to make a further plea for the future of Turkana Basin and paleontology that the perpetuation of these collections and the information that they represent should be very high priority for finding more resources and training more people.

So just now borrowing the mission statement of the Smithsonian Institution, people working in the Turkana Basin have done an incredible amount of publication on the fossils. So, the monographs that John Harris worked on, the West Turkana and Lothagam, and both Meave and John Harris deserve great credit for the amount of effort they put into these monographs, which will stand as sources of information for and for a very, very long time. And then Henry Wesselman developed a micro vertebra record in the Omo and Rene’,Zeresenay, and I. Various other volumes and the most recent one coming out that Sally Reynolds and Rene’ have edited. So continuing growth of knowledge from these fossils, they aren't going to mean very much if they don't have this kind of attention. Um and that takes a lot of work and a lot of training of people how to identify the taxa.

So, I'm just quickly going through this beautiful array of the march of the carnivores and the herbivores through time, Mauricio Anto’n's drawings, they're wonderful. Each square is supposed to be a meter scale just to give you that. And the Turkana Basin fauna has contributed so much to this story that you're seeing the reconstructions of these animals as well as of course other areas. And the recent compilation in Bob Reynold's Turkana Stratigraphy, you can go to this and see a summary of the large vertebrates arrayed through time and with the climate on the left, so many things are being put together. A few of the surprises that came out from like Lothagam, this giant leopard like Mustelid unknown to science before, the pig record was unknown really until Turkana Basin was developed. And well, I just wanted to point out those pigs were giants relative to the Hominins of the time. So, imagine going out into the woodlands and encountering a pig the size of a small elephant.

And of course the evolutionary ranges, the stories of first appearances, the last appearances, the radiation of the grazing Bovidae has been greatly augmented by our record. And I don't want to forget the rodents, I was telling myself this before, there's so much more to be done with them. And this paper just came out recently, 2020 from Kanapoi. It's amazing microvertebrate record that Kyalo and Alisa Winkler have developed. And you can see the differences if you look between the Kanapoi and the Omo be at the same approximate time period. And there's a lot of paleo-environmental information to be developed from those sorts of comparisons as well. I wish I had more time and maybe will tell you more about it. Okay, and I have about five minutes to go through a few more highlights from the mammalian record. How good is the fossil record of past biodiversity? Was it more diverse then similar? That was a question I was intrigued about here. We can compare relative abundances based on the fossil sites and modern parks in Kenya. And you can see that there are intriguing differences that carnivores are less abundant, but that could be a function of poor preservation.

But the large animals, the megafauna have decreased and that's probably a real signal. But you can also do these by member and do the counts of individuals. This is just a compilation of the overall biodiversity through a lot of time. So, it is time averaged, and you can see that patterns that have been observed that the East Turkana has more diversity up to 50 plus genera. And these are asymptotic curves that are leveling out to the right. So, 40 to 50 genera over those time periods as it seems to be what was then, I don't know, carrying capacity of the Turkana Basin ecosystem. But when you compare with modern environments and modern communities, and the only one I could get with comparable data with Maasai Mara, with abundances and the counts of individuals, it looks like the biodiversity at the time I Turkana Basin was not that much different from what we see in the early 20th century in modern East Africa. I guess you should consider that hypothesis. But before we say that it was more diverse than we need to do a careful look at comparable modern or at least early 20th century communities in East Africa.

Now what about the aridification pattern? We know from stable isotopes, independent evidence that there's this trend from four to one of the Shungura and being a woodland more environment and then becoming more open and the East and West Turkana going toward more open grasslands. We'll hear more about that I'm sure from the isotope specialists. But early on, Rene’ Bobe and I took this array of assigning the taxa to different environments and looked at what was going on in the Omo and it was clear that there was a decrease in the forest adapted organisms, mammals and increase in woodland and very little in the way of grassland all the way through. And there's this persistent pattern of difference between the East and West Turkana and the axial Shungura formation record where if you were a hominin in the Turkana Basin and you didn't like being out in the open, you could go to the Omo, you could go into habitats that had more or less openness, woodland, they are mobile organisms. They weren't the only ones doing that. So, there were choices around the Basin for habitats that were persistent through time. And this has been mentioned in a paper by Michael Fortelius and others that the ramp side, the East side is the more water persistent environment, the West side more fault controlled. And that's had an influence most likely on what you're seeing with the patterns of the faunas

Work by David Patterson showed that within any time, there are differences in the dental isotopes in the different parts of East Turkana. So even within this scale of habit, tens of kilometers, there were different habitats available to all of the organisms at that time.

And Andrew Dew has looked at core species versus transient species. Core species are the persistent members of a faunal community. They're in red. And the Okote is noted up here as the top, the latest one where we have a lot of information. But notice that there's so many persistent taxa and some of these are the browsers. So the idea that it all opened up and there weren't any trees left is not true. There were lots of habitats with trees and they sustained dinotheres, they sustained whatever C3 vegetation was being eaten for a very long period. So the focus has been on the change, but I think we also should have the focus on what was persistent and stable about these environments and also heterogeneous at different scales. And this is a compilation from this paper I just mentioned going through time of the groups count, and this is by identified species and you can focus on differences like this decline maybe in carnivores with the KBS, they come back. Is this really something to focus on the differences or it strikes me that this is also a record of surprising stability in these faunas over time in spite of whatever was happening with the physical environment.

So I'd leave you that with that as a, I'm out of time, but I hope I can take oh five minutes. Thank you. Okay.

What have we learned from the finer scale evidence? Just a few little stories going back to this scale, track ways and outcrop sourced information at a very fine scale. This paper has just come out from Amelia Villase’nor and colleagues. It took a lot of wrangling to get all, it's a multi-proxy approach to looking at a site in the sub Tulubor part of the East Turkana record. So a time period that's not very well sampled there. And these teeth turned up in surveys in 2003. And since then there's been all this work by Amelia and others in the authorship to understand as much as possible about this site. Now these are not beautiful hominin specimens, but they record a hominin or several that were mixed in with other fauna at this time and place. And it's a very small place. This is the actual locality.

50 or some meters of surveying here showed that there were lots of small remains and some large ones. And so Amelia and her colleagues have focused on different proxies. And the hominin is here [proceeds to illustrate], and all the other fossils were weathering out of this paleosol. And just to draw your attention to what the proxies are all saying at this early part of the stratigraphy, it was humid, relatively woody biomarkers, phytoliths, the pedogenic carbonates all just above indicating more C4. So it looks like this was a mixed kind of habitat documented as the source for these fossils. And it was a hotspot for other primates, cercopithecids that were recovered from here. The gray part of the bar there is just representing the comparison more at this site than along the Area 129 outcrops where we were getting all of these. But here's the hominins [proceeds to illustrate]

So, at this scale, if there's a lot more information to be developed, and not only that, but the different proxies are also coming up with different signals, and this could mean a lot of things. I don't have time to go into it right now. Maybe you'll hear more later from people talking about the stable isotope records. But when you go, you burrow into the detail, you find out some very intriguing things about these different records and what they're signaling. The pedogenic carbonate may be the specific to the paleosol, the plant wax biomarkers mix, and the mammalian enamel could be from animals that are ranging much farther and into more open habitats and contributing a C4 signal to this assemblage. And then the footprint records back to this image with a very unexpected finding in 1978 of even hominin and prints with toes. And then at Ileret, more footprint levels developed.

And this is a 20,000 years from the dating and there's a lot going on in this stratigraphy from bottom to top, many different footprint layers. The environment had to be such that the prints were recorded and then buried and recorded and buried and never dried out and never mud cracked. They're just beautifully preserved. And this is from Hatala et al., 2017 the map of trackways, the major trackway in the upper footprint level, but there's so many other tracks as well. And now more have been found by Louise's project and Area 103. And it takes a lot of excavation of course, but the information is as a snapshot of behavior at a very short period of time. And it can be very informative and interesting. So back to our questions, we know a lot about what the original goal was and now we're launching into even more elaborate questions at different scales in the second set there. And I hope all of you are thinking about additional questions for the Paleontological record, what next? We can always get more fossils, but there's some groups that have not received the attention they deserve. And that would be a good place for new training and development of paleontology, more excavations because that gives us so much more information and better specimens too. But you need big crews and lots of time and money.

It's the track waves as I mentioned. And then there are archeological faunas in NMK that have not been integrated with the Paleontological departments information. Those specimens have a lot of valuable information, but because they were collected by the archeologists, they've been somewhat separated from what we have easy access to. So I'm a plea for that. And then just the final thought about the last point, Lake Malawi is known to have gone through an amazing crisis recorded in a drill core and about a 100,00 to 130,000 years. There were mega droughts where it dried up to almost nothing and there was so little vegetation, there wasn't even any charcoal which is recorded in the left hand. So that shows the potential for these lakes to go through extreme crises. And if you imagine that under normal circumstances you've got the regional buffers, you've got the habitat heterogeneity, the organisms, if there's something going on with the environment, they can move or adapt and coexist.

And there isn't so much pressure going toward change and evolution. But if you have these extreme environmental events, then the regional buffers are weaker relative to the mega droughts potentially. And the pressure is on, there's competition, there's focusing on resources in particular places, and that's when you could generate more change with small populations, feedback and extinction or at least extra patient. So this is a model, we can think about it and we can develop other models, but you have to figure out some way for all these mega processes and the climate change to get through these regional buffers to actually drive evolution. Otherwise, things can just move around in the Rift Valley, which has a lot of opportunities. So I've been pondering that for a while and maybe we can talk about it more later. And thank you very much everybody for listening, and let's go forward with it.

 

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