DeKALB – Northern Illinois University Professor Daniel Gebo is one of seven specialists throughout the world who are researching a discovery that will change the study of primate evolution.
Earlier this month, the group, which includes his wife, Northwestern University Professor Marian Dagosto, announced that a complete 55-million-year old primate fossil had been discovered by a Chinese farmer in 2003. The fossil, named Archicebus achilles, is the oldest complete primate skeleton ever found. It indicates a common ancestor for two major lineages of primates and shows that primate life may have originated in Asia, and not Africa, as previously thought.
A biological anthropologist/primatologist with interests in anatomy and primate evolution, Gebo teaches courses in primate and human anatomy and evolution, as well as introductory physical anthropology.
Gebo talked about the discovery and his research last week with MidWeek reporter Doug Oleson.
MidWeek: When was this fossil discovered?
Dan Gebo: The fossil was found a decade ago. It was collected by a farmer in China. There are these lake beds ... in China and people go there and they crack open these rocks and they find fossil fish after fossil fish after fossil fish.
MW: What happened in this case?
DG: It was an accident. ...You get thousands of green fish. But occasionally you find something else. And that’s what happened. The specimen was in two slabs. Half the fossil was on one side and bits and pieces were on the other. It’s so tiny, a little over three-and-a-half inches from the tip of its nose to its butt, not counting its tail. It was so tiny and fragile it was hard to prep out of the rock.
MW: What happened then?
DG: We took it to a scanner in Texas, but they weren’t great. ...Eventually, we took it to Grenoble, France. This is where NASA takes things. They have these super-duper X-rays, and they do this in very fine slices for like, 24 hours. Then you take all these images and you can make these beautiful 3-D graphics. Even though some parts of the fossil fell out of the rock when you took it apart, it still made impressions on the rock and you could actually see that anatomy.
So I get pictures of bones that I can spin around on my computer and see both sides, which in the rock you cannot do.
MW: Are most discoveries made by accident?
DG: It goes in a couple of ways. Usually, you go out to a certain rock age where you know there are fossils. You can wander around the eroding beds and pull up fossils or you go to a place like a quarry, which is more what this was like, and you can split rocks and every so often there are fossils in the rocks. ...We usually have a pretty good idea of where to look.
MW: What exactly was discovered?
DG: This is a fossil primate. It’s in our lineage. It’s not related to horses or cats. What makes this fossil special is several things. First, age. It’s 55 million years old. We do have other fossil primates at 55 milion, but usually it’s just a jaw or a tooth. The second point is the most important one: it’s almost a complete skeleton. We are missing the hands and part of the rib cage area, but the rest of it is complete. So it’s pretty impressive. The third thing is it has a new combination of anatomy. We have other fossils that have teeth or the head bones, and some of the arm bones that we already know about. What makes this stand out is that its foot anatomy looks like a monkey, but its body looks more like a primitive primate, related to these things called tarsiers living in southeast Asia today.
Its foot is what makes it really weird. We have these other fossils that look like these tarsiers, but their feet don’t look like Archicebus, which is the name of the fossil.
MW: Just how big a discovery is this?
DG: It’s a big science discovery with huge implications that will rewrite textbooks and things like that. It’s very unique and novel. It’s the discovery that comes in every 50, maybe 100 years. It’s incredibly rare. It goes to the very beginning of primate evolution. It changes our views about early primate evolution.
MW: How do you know it’s 55 million years old?
DG: That doesn’t come from the fossil. That comes from the geology. This lake has been studied by geologists and these fossil fish that come from there, they have figured out that is the date. It’s how you look at the rocks.
That’s a long time, but it’s not as old as the dinosaurs, that are 65 million years ago.
MW: Do you know how old the monkey was when he died?
DG: All the bones are fully fused, so it was a full adult.
MW: When did you and your wife get involved with this?
DG: I’ve been working in China since the mid-1990s. ...I probably got involved in this project about five years ago. The fossil was known for about five years, but not much work was done on it until the American scientists were put on it.
MW: How did you get involved?
DG: I’ve known these individuals, and I am an expert on the body anatomy of living and fossil primates, particularly foot anatomies. Once we had the skeleton, this is actually what I study. Most are in teeth or hips.
MW: I assume this was a team effort.
DG: There are seven authors on this publication from around the world (including China, France and the United States).
MW: Does everyone on the team have a specific area of expertise?
DG: There is some overlap, but yes.
MW: How did you announce it?
DG: This (announcement) came out in a top science journal called “Nature.” It comes out of London. The other top journal is called “Science,” out of D.C. This is what we all hope to get. It’s the top thing. This is my third publication in “Nature.”...Then, as you can imagine, it gets the major media involved.
I’ve gotten published in other journals, but it doesn’t have the same high profile.
MW: What do you do next? Do you write a book about it?
DG: (Nature) is a nice publication, but it’s very small. They only give you so many words. Now we have to write the long publication, which has descriptive elements of all the different bones. It’ll be a long manuscript. The last time I saw it was 100 pages. It’ll probably come out in a museum monograph series, that would be my guess. It’s too long for a regular journal.
It will have more details. We kind of distill the creme of the top, but the real nitty-gritty, it’s going to be more technical.
MW: Any idea when that might come out?
DG: Probably another couple of years, I suspect.
MW: Anything you want to add?
DG: You have to remember how tiny it is. It’s about 25 grams, which is 0.88 ounces, so it’s less than 1 ounce. It could easily fit in the palm of your hand. ...Even though it’s tiny, the smallest living mammals (today) are like two grams.
It is not the smallest living mammal. There is something called a bumblebee bat that is really a bat the size of a bumblebee.
MW: Besides the size and age of the fossil, is there anything else you want to emphasize?
DG: The other point is this is an Asian fossil. Some people would argue that maybe primates come from Africa, but it looks like, from the fossil records, the most primitive primates seem to come from Asia.