In the study of human evolution, 2015 was an insane year. Paleoanthropologists made discoveries that increased our knowledge about everything from stone tools to Neandertal ancestry. The announcements were surprising, enlightening, and drawn from all corners of the scientific discipline. Some discoveries were those of new fossils, while others drew from ancient DNA, and others still reconstructed fossils we’ve had for decades. In celebration of the huge year, let’s recap my favorite announcements of 2015, which I’ve ranked from 10 to 1!
10. Homo sapiens in China 100,000 years ago?! 47 human teeth found in a cave in China suggest we need to rethink the date at which modern humans arrived to Asia. Originally, it was thought that humans reached Asia around 60,000 years ago, but the Daoxian teeth suggest earlier dispersal of Homo sapiens. Whoa. More on this from Nature.
9. DNA from an Old Denisovan. A molar from the Denisovan cave in the Altai Mountains of Siberia yielded DNA this year that made the already confusing Denisovans even MORE confusing. Known only from a couple teeth and a finger bone, Denisovans were a relatively recent hominin group closely related to Neandertals. Researchers concluded from the new DNA that the tooth dated to about 110,000 years ago, over 50,000 years older than previous Denisovan finds. This means these guys lived in Siberia for some time, not an easy thing to do. Commenting on the find, a molecular anthropologist equated this time period to middle earth, when “a ton of hominins that are closely related to us” were all running around at the same time. More on this from Carl Zimmer.
8. 3.3 Million Year Old Stone Tools?! Lomekwian Technology. Large stone tools were announced this year, found near Lake Turkana in Kenya. These tools are different from anything we have ever seen before, and scientists are arguing that they were intentionally knapped. This would push stone tool making back over 700,000 years, and raises interesting questions about the tool makers. Could Australopiths have made these things, or even Kenyanthropus?! More details on the find from Nutcrackerman.
7. Homo floresiensis Teeth Similar to Homo erectus. Ok so I may only be rating this one as high as number 7 because Homo floresiensis is a subject of my dissertation, but still–this was an interesting study. Researchers did an exhaustive study of H. floresiensis teeth, comparing them to Homo erectus, Homo habilis, and Australopithecines. They argue that this find should confirm that 1. H. floresiensis is indeed a distinct species of hominin (not a diseased modern human or what have you), and 2. They evolved from Homo erectus. More on this here.
6. More Diversity in Africa: Homo Pelvis & Femur from Kenya. A 1.9 million year old pelvis and femur found in Kenya suggests that we have barely scratched the surface of the diversity of hominin species that existed. The team attributes the fossils to early Homo, but argues that they look unlike the bones of other hominins around at the same time, like Homo erectus. Lead scientist Carol Ward argues that this discovery further shows that “many species and types of early humans coexisted for about a million years before our ancestors became the only Homo species left.” More on this find here.
5. Homo habilis Brain Size Revised. This year a team reexamined the badly fragmented bones of the 1.8 million year old Homo habilis individual called Olduvai Hominid 7. OH7 was discovered by the Leakeys in 1964, but reconstructing its brain size and jaw shape was difficult due to its fragmentary nature. Scientists recently used CT scans to virtually reassemble the bones, finding that the brain size of this creature was much larger than originally thought, but the jaw was very primitive. Based on this work, the scientists argue that this fossil is evidence for species diversity at the time (are you sensing a theme yet?) and jaw shape might be more important than brain size in distinguishing species. Lead researcher Fred Spoor said “in the past, there was a big focus on brain size as the distinguishing and driving feature in early Homo. We think about our brains as being very important, and therefore important in all human evolution, but increasingly we found that it’s not important in early human evolution.” Read more about it here.
4. Sima DNA. In the wake of the Homo naledi craziness, the long awaited nuclear DNA from fossils at the incredible site Sima de los Huesos appeared as well. Though still only partially sequenced, the Sima DNA showed close affinity to Neandertals, and had some interesting implications for the modern human/Neandertals’ split! Roberto Sáez has more on this on his site Nutcrackerman.
3. Even MORE Diversity in Africa: Australopithecus deyiremeda. This year, researchers announced the discovery of some jaws and teeth from a site in Ethiopia that is only 23 miles from the famous Lucy site. This wouldn’t be too exciting–except, the scientists argue that the jaw belonged to a difference species than Lucy (who belongs to Australopithecus afarensis) AND they seem to have lived at the same time. A different species of Australopiths living right next door? They named the new species Australopithecus deyiremeda. There’s a great video of discoverer Dr. Yohannes Haile-Selassie talking about the find, and I wrote more about the discovery for EarthArchives.
2. Early Homo Jaw from Ledi-Geraru. A partial jawbone discovery in Ethiopia announced this year fills an intriguing gap in the fossil record: the gap that could shed light on the origins of our own genus, the genus Homo. Dating to 2.8 million years old, researchers argue that the jaw represents an early Homo creature/ This pushes back the origins of our genus over half a million years. The jaw has a number of interesting features and appears to be transitional between Australopithecines and early Homo. I wrote a post on the jaw back in March.
Number Freakin’ One….Insane Diversity in Africa: Homo naledi. You’re not surprised that this is number one, are you? These fossils, found in the Rising Star cave system in South Africa number in at over 1,500 bone fragments and at least 15 individuals (and counting!). This might just be the most significant discovery of the century. These individuals show a weird mixture of human and Austrlaopith features, such as a small brain but evidence for advanced upright walking. Many questions remain about Homo naledi, and what exactly the significance is will continue to be hotly debated. Other questions include–how did the fossils get so deep into the cave? How old are the bones? And so much more. I wrote a little bit about the fossils here, and more can be found in Ed Yong’s great summary, and I’m sure more about naledi will be revealed next year. My major question is, can I do some excavating in that cave? (I could fit!).
Lessons of 2015:
- The human family tree was bushy. It’s important to mention that these announcements are new and will therefore undergo scientific scrutiny and revision over time. Some of these new species may hold up to that scrutiny, others might not. But based on the sheer number of weird looking creatures that were announced this year, one thing looks pretty clear: at multiple points in human evolutionary history, there were lots of diverse hominin species running around at the same time. There wasn’t one lineage, clearly leading from ape to human, as we once believed. Instead, evolution tried out a number of things, and some experiments worked, while others failed. I, for one, think that is pretty darn cool.
- Therefore, defining human is difficult. Many of these finds remind us that defining human, in the broad sense–early Homo, is both important and increasingly complex. Chris Stringer put it well when he commented on the Ledi-Geraru jaw, stating “these new studies leave us with an even more complex picture of early humans than we thought, and they challenge us to consider the very definition of what it is to be human. Are we defined by our small teeth and jaws, our large brain, our long legs, tool-making, or some combination of these traits?”
- 2015 was absolutely awesome. Seriously, what a year. Cheers to all the amazing work that’s being done out there in the field of paleoanthropology, and bring on 2016.
Your turn. What were your favorite discoveries of the year? What did you find surprising and how would you rank these incredible finds? Will we ever beat 2015?! Let me know in the comments!