A piece in the monkey puzzle: by Nature Video

In the desert sands of Saudi Arabia, a fossil has just been found which fills a crucial gap in the evolutionary history of mammals, including us. Working together with the Saudi team, Laura McClatchy, Eyad Zalmut and Philip Gingrich at Ann Arbor in Michigan couldn't believe their luck. For some years, Philip had been looking in this part of Saudi for fossil whales, presuming the area was in the sea in the Eocene period. What we found, looking for whales, was something completely different. A team from the Saudi Geological Survey were Eyad's guides and collaborators. Eyad had gone off to Saudi Arabia and we said, when you're out there, look in the tertiary deposits, see what you can find. And you could walk over that fossil a hundred times and not see it. You really have to have sharp trained eye, have been in the field for a while. A lot of people would have walked over that and thought, oh, it's just some scrap on the surface and wouldn't have bothered to look. But whatever it was, it was part of a land mammal lying in what they thought was a fossil-rich seabed. It should not have been there. I said, well, this is going to be something exciting. So I took pictures, I took some measurements, and I left the site as it is, undisturbed. I put in an email and with a couple of pictures about the locality and sent it to Ann Arbor. Greg and I received an email from him from the field. We both opened the picture and we were so excited about what we saw that we ran into the hallway, smack into each other and said, did you see that? That's the most extraordinary thing. You can see the email coming from Phil and Bill and Greg and Jeff and everybody involved in this project. It was like, wow, this is a primate. There are two main primate groups, the New World species, such as the squirrel monkey, and the Old World monkeys and apes, such as the gelada baboon. Until now, only one common ancestor of both groups was known, a catarine primate called Aegyptopithecus. Here you can see primates with the more recent things at the top, earlier ones at the bottom, and a gap early in what we call catarine, the beginning of apes, just in here. This is a big area of uncertainty in primate evolution. When that fossil came back, it was immediately apparent that it's really good bone, really nice sediment that comes off of the fossils very easily. So basically what we had found was the face of a very interesting primate. You can see here, there's one orbit, one eye hole, if you will. Here's the other orbit. Here's the forehead going up in this direction. Here's the nose here. Here are some front teeth, incisor teeth here. If you flip it over, I'll put it back down here. You can see a row of teeth here. Here's a large canine and some molar teeth, some grinding teeth back here. And then this other little piece over here actually is the ear region, which preserves some interesting details as well. So here was something wonderful, and you could see that it was very primitive at the same time. And then the next key for us was, how old is this? What was known until now, old-world monkeys, apes, are separate by the early Miocene. But how they connect to Aegyptopithecus and when they became separate from Aegyptopithecus and new-world monkeys has been a big mystery. The new species was named Sardinius hejazensis, a monkey found in this Hejaz region. If we look at the paleogeography of the African continent today, it's separated from Arabia by the Red Sea. But at the time we're working in the Oligocene, the two were part of the same geography, and they were separated by the Red Sea. But at the time we're working in the Oligocene, the two were part of the same geography, the same faunal province. I've been working in fossil beds that are younger than this since about 1994, very interested in understanding about early ape evolution. And it's been frustrating in that our fossil record is basically, for apes, you know, goes back to about 21 million years and there's nothing prior to that. Part of what's interesting about this is it is not a monkey and it is not an ape. Humans, apes, and old-world monkeys all share a common ancestor. This specimen would have been very close to when apes and old-world monkeys would have diverged from one another. Very close in time and we think also in anatomy to the morphology of the common ancestor between old-world monkey and apes. First question I ask people like Ead when they find nice fossils is, where's the rest of it? You can see it has a beautiful face, the forehead is here, but the rest of the orbits, the eye sockets are missing. If we turn it, where's the brain case? So definitely we'll go back and try to find more and better specimens like this. We have a plan to open a quarry in the locality where we found this primate. We think this publication is important because it's an important missing link. I know some people don't like that term, but I do like it because it fills a gap in time, fills a gap in form, and it helps tie things together that we weren't able to tie together convincingly before. This is just the beginning.