Yohannes Haile-Selassie: Ancient & Unexpected Neighbors

I sat down with the paleoanthropologist Yohannes Haile-Selassie in January 2016. He’s considered to be among of the great—possibly the greatest—fossil hunters in early human archaeology, and he was on the eve of a major discovery. Even by 2016 he had quite a few major discoveries under his belt, including a partial skeleton of Australopithecus afarensis Kadanuumuu, the slightly more ancient male counterpart of the same species as the famous Lucy. This year Haile-Selassie published the discovery of a quite complete 3.8 million-year-old skull of Australopithecus anamensis, an individual similar to Lucy in many ways, belonging to the same genus, but differing enough to be considered a separate species. This skull is by far the most exciting find in paleoanthropology thus far in the 21st century, and it lends strength to the bewildering but incredible idea that several early human ancestors inhabited the same region simultaneously—imagine a world of gnomes, elves, and halflings (no full size humans existed in Middle–earth at that time).

Haile-Selassie had not yet made that discovery when I first spoke with him—he would do so just a few months later. He describes the incredibly fossil-rich site where he would eventually make his discovery, and talks a bit about his technique for spotting fossils. The conversation touches on the evolutionary uses of creativity, raising problematic questions about why we are creative: is it only to get ahead and create more viable offspring, or is there something more? The earliest tool manufacture and usage, about 2.6 million years ago, began to change the course of human evolution. This shift has remarkable bearing on our current evolutionary direction as well, as contemporary technology is beginning to effect change in the human organism to a greater degree at a faster rate. Read more to find out how it happened the first time, 2.6 million years ago.

Will Corwin: Give me a description of a day in the Afar desert, Ethiopia, looking for fossils. What strikes you when you see one?

Yohannes Haile-Selassie: Fossil hunting is a combination of two things. Of course you have to be lucky—you have to have good eyes—but also you’ve got to know what you’re looking for.

The Afar is so hot, we try to maximize our work time before it gets too hot. Particularly between 11 am and 2 pm. We usually try to leave camp early in the morning.

WC: Five am?

YHS: No, five is too dark. We usually leave … around seven. The light is very critical in finding fossils. The best times [for] seeing fossils are when the light shines on them at an angle, and you can see them reflecting from a distance. In the morning, we go to any targeted locality. We spread our people all over the place in a controlled survey and we start flagging every fossil that is on the ground.

WC: So you don’t touch it?

YHS: Not yet. We just flag it because not everyone in the crew knows exactly what he or she is finding, so I have to make sure that they don’t pick it up from the ground until I see it. Each and every specimen gets flagged with a yellow flag. Sometimes people flag a nonfossil thinking that it’s a fossil—which is fine—it’s better to flag a nonfossil than leave a good fossil. The reason we do not allow people to pick up fossils is because once you pick up a fossil from the ground, you erase the entire history of that fossil; you lose the depositional history. Sometimes fragments on the surface can lead you to partial skeletons just coming out of the ground. If somebody carries it away somewhere, then you’ll never find that fossil again. Then we collect the fossils, we identify them, we [enter it] into our field catalogue in terms of … its provenance in the stratigraphy; its taxa: what species does it belong to, who discovered it; and we record the GPS coordinates because we have a Geographic Information System database where we pinpoint everything and we can actually see the distribution on the landscape.

WC: How about your last excursion into the Afar, what you were looking for and what did you find?

YHS: What has come up between the last field season and this field season is the naming of this new early human ancestor species, Australopithecus deyiremeda, which is about 3.3 to 3.5 million years old, which makes it co-existing with the famous “Lucy” species, Australopithecus afarensis. The fossils from my site are shedding a lot of new light on how we understand our evolution, and how many related species of our own have lived in the past at the same time and probably at the same place—which is one of the most controversial issues in our field right now. So when we go out into the field this time, we are going to try to collect more data to further validate the species that we named last May. And also try to collect more fossils and try to understand the environment in which these early human ancestors were living ….

WC: And how does this newly named species differ from the others? What were the morphological or physical differences between the other things you’ve found before?

YHS: One of the major comparisons that we have to do is with Lucy’s species. Based on the specimens that we have that we have assigned to the new species, we’ve done a comparison of the upper jaws, lower jaws, and the teeth. And the differences we saw between the vast number of Australopithecus afarensis specimens [that we already have] and the limited number of specimens that we have for this new species are variable enough to convince us that what we have is something different from what we know as Australopithecus afarensis. Hundreds of specimens have been recovered representing this species, and we have a good understanding of how much variation there is, not only in its teeth, but also in its jaws, in its bones below the neck and so forth.

WC: But you’re responsible for finding Kadanuumuu, which is another variation of Australopithecus afarensis.

YHS: Kadanuumuu is a partial skeleton from my site [that] we described about five years ago … and the full description came out in a 2016 monograph. This is the earliest Australopithecus adult partial skeleton that we have right now, and that individual is large enough that it gives us an idea that Australopithecus afarensis species were not small in terms of their size. Initially, what we knew about Australopithecus afarensis morphology, particularly the body anatomy, was based on Lucy, [who] is unfortunately so tiny—she was a tiny individual ….

WC: She was young, too?

YHS: Yeah, she was, but she’s fully adult—she was not really juvenile or anything. The way we know is because she already had her wisdom tooth, and her teeth have shown some wear, which means they [were] used for some time. All of her bones were fused and they were not going to grow anymore. This individual Kadanuumuu was a male individual, unlike Lucy. That gives an idea of how big and small the male and female of that species could be, and of course anywhere in between has already been sampled from Hadar, where Lucy was found, and other places. What we have from our site is not only fossils of Australopithecus afarensis, but also fossils of other related taxa who lived next door with Australopithecus afarensis.

One of the reasons [it’s controversial to some people] is [that] there is this old theory [wherein] only a single species was believed to have lived at any given time, giving rise to something new, through time. Nobody expected two related taxa of early human ancestors [to be discovered] living side by side. Which means one of them had to go extinct at one point, because both of them, or even more [related species], cannot give rise to another species at the same time. The evidence that we had was that such diversity—meaning the presence of multiple related taxa—did not appear [earlier than] 2.5 million years ago. Now that we have, at 3.3 to 3.5 million years ago, Australopithecus deyiremeda and Australopithecus afarensis, this is a major discovery. Which is why it’s really controversial. Because our sample size is too small, it’s one of the reasons … we’re going back to the field and trying to find more Australopithecus deyiremeda is because this is a real species, it’s not a variant of Australopithecus afarensis, and that’s exactly what we’re going to show the paleontological world.

WC: These specimens that you’ve described, do they overlap with any of the oldest tools that have been discovered? I know they discovered some tools in Kenya that have been dated at 3.3 million years old. Were these tools used by the individuals that you’ve discovered?

YHS: We don’t know yet. The Kenyan tools [whose discovery was] published a few months ago were actually claimed to be 3.3 million years old, which is about the same age as Australopithecus deyiremeda. But interestingly enough, they have another species from [near to] where those fossils were found, known as Kenyanthropus platyops. If these are real tools made by early human ancestors, it would be more likely that [members of] the species [that] was near the stone tools were the ones who made them, instead of Australopithecus deyiremeda from the Afar.

What we have to really understand when we talk about stone tool use is: were they using tools is one thing, and whether they were making tools is another. If you’re talking about using tools—monkeys use tools, chimpanzees use tools, a lot of primates use tools. But do they make them with a mental template is the key thing. What makes us really different, particularly [since] 2.6 million years ago, is that there is good evidence … these early human ancestors were making tools with purpose. Whether Australopithecus deyiremeda in the Afar was making tools or using tools is something we’re going to have to see. So far we don’t have any evidence, but it doesn’t necessarily mean they were not using tools. What we know from other primates should tell us something about these early human ancestors; they must have been smart, smarter than monkeys.

WC: Tell me a bit about the Afar. From looking at articles and specimens, it seems like a magical place that produces this stream of fossils. Is it because that’s where these species were located, or a combination of location and luck and the geological processes that took place over the last three million years?

YHS: It is a result of a geological phenomenon, and that phenomenon has been going on for the last 10 million years. It starts with the formation of the rift system, which has been exposing long-buried sediments: exposing windows into the past. Erosion reveals the sediments, and the fossils come to life again. What it tells [us] is that all the way back to six or seven million years ago this place was luscious and green, with a lot of water, and there were a lot of animals. Our earliest ancestors lived [there]. The Afar that you know today was not the Afar that was there seven million years ago, it was a totally different environment. The elevation was different, the weather was different. It’s not [because] this place was destined to be the origin of humanity, but … because of geological phenomena that it exposed all these ancient deposits that retained all these fossils.

WC: Because our ancestors weren’t located solely in this region, were they mobile? You say the tools that were found in Kenya had a species that was right nearby that might have used them ….

YHS: These early human ancestors never left the tropics. They always lived in the tropics. If you go to Kenya, there is a fossil record of early human ancestors that goes back six million years. It’s not only in Ethiopia that we find the earliest human ancestors. The earliest—apparently the earliest—dating back … 6.5 to 7 million years ago (although the age is kind of controversial right now) are specimens from Chad, in central Africa, Sahelanthropus tchadensis. That comes from Central Africa, which is even outside the Central African rift system. You go down south to Tanzania and we have early human ancestors from 3.6 to 3.7 million years ago. Most of these early human ancestor fossils are coming from the East African rift system. [Their] presence in Chad tells you they were not limited into this rift system, but they’re still limited to within the tropics. Historically or geologically, all great apes have been living in this tropical region. If there are more sediments of the right age exposed in these tropical regions, then … chances are you might find fossils of these early human ancestors, but, geologically, none of the other areas in the tropics are exposed to the surface, so you can’t find fossils in them. So that’s one of the problems.

WC: You’ve discovered abrasions on the bones of nonhuman ancestor animals … you’ve discovered/excavated that show they somehow interacted with human ancestors: the bones were crushed to get at marrow, or the flesh was removed. So our ancestors were using some kind of tools to do this; were they actively pursuing and killing these animals, or were they for the most part scavengers? What was their mode of [living] after eating protein like that?

YHS: The current understanding right now—and first of all I’ve got to say that at our site we don’t have any indications yet because our site is older than three million years and we haven’t found any sign of tool use or cut marks on bones or anything like that—but a lot of sites that are younger than 2.6 million years ago have some indications of tool use. In the form of the tools themselves or cut-marks on bones. So how were they procuring those animals and exploiting the meat or the marrow is, I think, your question.

There is no assumption at this point that humans were hunters, when they started making tools and consuming a lot of meat and fat [that they added] into their diet. They were, more likely, scavengers: meaning getting meat and marrow from whatever was leftover from carnivores—if the hyenas didn’t get it first, right? But obviously hunting is something that came later in our evolution, with sophistication of tools and understanding [of] how to attack big animals without getting hurt.

WC: An archaeologist I spoke with, Yonas Beyene, talked about how complicated technology influenced the evolution of the mind and the personality of the Homo and various [other] genus, but “caring and sharing,” the anthropological step, how did that also interact with the process? Bipedality also required more capability in provisioning: how did it affect the interactions between the early hominin creatures, ones that you don’t see in chimpanzees and you don’t see in great apes?

YHS: Our course of evolution changes, as far as we know, about 2.6 million years ago, when we started using tools. At 2.5 [million years ago] is also when we see diversity in early human ancestors; we have something called Paranthropus aethiopicus about the same time that we see the origin of our own genus, homo. The coincidence of the appearance of stone tools, and the appearance of our own genus is one of the reasons a lot of archaeologists think that the genus Homo is responsible for making tools.

When they make tools, and use them, they extract meat and marrow from animal carcasses—that’s a good source of protein. Look at our brain size 2.5 million years ago; all of these early human ancestors who lived before 2.5 million years [ago], their brain capacity was not more than that of a chimpanzee. Now starting at about 2.4 to 2.3 million years ago, the brain started expanding. When you think about what happened at 2.5, with the making of tools, with the using of tools, with adding protein—a lot of protein—to your diet, it’s all about fat and it’s all about protein, and the brain is just that. It started growing nonstop. And what we see from 1.8 million years [ago] onwards, is a jump from, like, 550 cubic centimeters to 650cc, and from 650cc we see a jump to 900cc. It kept on increasing through Homo erectus, through Homo sapiens, and it finally got to where it is today. Cognition also increased, because of the brain expansion. There is a good correlation between the beginning of tool making and meat consumption and brain expansion. That’s why Homo is usually considered … the tool maker, [whereas] the other taxa are not. It’s not just because we want it that way but because there is no evidence to show that these Australopithecines, at least earlier than 2.5 million years ago, were making tools. There is no evidence for that. But that is what changed the course of our evolution.

We still eat a lot of meat and fat but our brain isn’t expanding anymore—it’s not just going to grow on and on. So, at this point it’s all about how it’s wired, it’s not about how big it is, unlike in the past. That’s what tells you how evolution is changing its course in terms of how we define ourselves. And whatever we think is advantageous for us today may not be good for us in the future. We’re now dominating the world, but we don’t even know when or if we’re going to go extinct. Are we going to exist for another thousand years? Another hundred thousand years? We don’t know, but obviously the way things are going on right now with the environment, the climate, and the rest of the animal community, maybe we won’t survive as long as we were destined.

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THREE YEARS LATER (IN 2019)

WC: Within the context of “caring and sharing” or the early manufacture of tools—which seem to be part of the push-and-pull of evolutionary movement (Progress?)—could you hazard a guess as to the possible use value of the creation of art or the making of seemingly useless spiritual objects? I want to clarify: I’m not saying that making art is part of evolution, but do you see it having a useful result—for example, Jill Cook suggested that exhibiting skills in crafting and offering fine ax heads might have been useful in procuring a mate? Do you think artistic creation has had a use or transformative effect in evolution?

YHS: I’d say that this may have had use after we got to a stage where our brain was enlarged and the various parts partitioned in a way similar to that of ours. While “caring and sharing” is one of the most powerful explanations, albeit difficult to test, for our evolution, it is difficult for me to say that things like skills in crafting had transformative effect in the earlier parts of our evolutionary history.

WC: In the way we discussed that very early stone tool manufacture, back 2.5 million years ago, led to increased ingestion of protein and fat, which may have been a major cause of the evolution of the human brain, do you see the increasing intrusion of technology into the human organism and consciousness as again steering evolution in a particular direction?

YHS: For early hominins as far back as 2.5 million years ago, I think it was more [a case of] of realizing that resource acquisition was increasing with tool-making and tool use, than [it was] thinking about technology per se. Technology is only in our minds, not in the minds of the earliest tool makers in our lineage.

WC: Has this interaction with technology been consistent in changing our species, or do you think there are times when it has a greater or lesser interaction?

YHS: The main driving force of our evolution has largely been the environment, especially in the eastern African rift setting, where the landscape and associated physiognomy changed quite often due to the actions of plate tectonics. Technology probably served as a catalyst.

WC: In the past it seems to have happened incidentally, but do you think we can creatively manipulate our own evolution? Is this perhaps the highest goal of art?

YHS: Art cannot manipulate our evolution; it can only manipulate our brain.

WC: With your discovery of a 3.8 million-year-old and largely complete skull of Australopithecus anamensis, the idea of several species of early human ancestor living together simultaneously in … proximity [to one another] seems increasingly likely. Have we passed the point in our evolution where you think such multiple species co-existing is possible? How could you see it actually happening (in the past), and what do you think caused species like Australopithecus anamensis, Kenyanthropus platyops, or Australopithecus deyiremeda to eventually go extinct in favor of perhaps Australopithecus afarensis (or whichever you think was the successful species of that group)?

YHS: Millions of year ago, early human populations were small in size and limited in space. Today, we are everywhere. That means genetic isolation that would eventually result in speciation is practically impossible.

Australopithecus evolved as a response to a changing environment [that] was becoming drier and [had] less wooded cover. Most of the species that you listed above were probably experimenting in this new environment. Some of them succeeded and some did not. A. afarensis happens to have been one of the successful ones.

The images accompanying this interview are by Abel Tilahun, a cross-disciplinary Ethiopian artist with studio practices in Washington, DC and Addis Ababa. Through sculpture, video, drawing, and painting, Tilahun explores themes such as the universal human experience, science fiction, and spatial landscapes.