July 11, 2002
A New Ancestor?

Ok, by now nearly all of you have heard about this (link courtesy Jeff). Since the press monkeys are all working from the same press release, here's some stuff you may not know from your not-quite-a-real-anthropologist:

So, what does this mean?
Well, it depends. Since the guy that wrote the press release obviously works with the guy that found the skull, it sounds pretty earth shaking. But, since it's just one skull and some teeth, in reality we can't be all that sure what it means.

That's not very damned helpful.

Ok. Please keep in mind that I am to a real anthropologist what Alton Brown is to a gourmet chef (we know what we're talking about to a certain extent, but we also know who the "real" cooks are). The skull is interesting because:

  • It's old. Really old for a hominid1. The next oldest one we have, Ardipithecus ramidus2, is probably 5-6 million years old. This one is 7 to perhaps 10 million years old.
  • Chimps and people were thought to have split off from each other between 10-15 million years ago, so this fossil is really close to the time when that happened.
  • It looks funny. If it'd had a really "snouty" face (technically, a large amount of prognothesis), it would be interesting, but not earth-shattering. But it doesn't. It has a relatively "flat" face, which makes it seem a lot more "homo"-like than anything ever found that's close to that age. And it's a lot earlier than the earliest clearly homo fossil ever found (~2.5 million years).
  • It's a relatively complete skull. A lot of hominid fossils are represented by just a few teeth or a jawbone (the toughest parts of any animal's body). A near-complete skull of any age is always a find.
  • It's in an area we didn't know hominids lived. In my own opinion, this is at least as important as the fossil itself. There could be other, better things out there not yet found because we just didn't know to look for them there.

So why aren't you dancing in the streets?

  • It's just one skull. In spite of what the press monkeys are saying, you can't easily overturn an entire chronology based on just a single skull. It may yet, but it's still really early.
  • No postcranial3 remains. Skulls are interesting, but the postcranial stuff can tell you just as much. The things that made Lucy and the Turkana boy so fascinating was the postcranial stuff. Before then we didn't know, for example, that Australopithecenes had long arms and curved fingers4, or that Homo Erectus could get so tall (6+ feet).

So is this the "missing link?"
As we have found more and more hominid fossils, the whole concept of a "missing link" has pretty much gone out the window. It's becoming increasingly apparent that in ancient (Miocene) southern Africa there were a lot of different kinds of bipedal apes wandering around. It changes from time to time, but I think we're up to at least four different species co-existing at one point about three million years ago (from memory: Australopithicenes, Homo, Paranthrapacenes, Aridipithicenes). Our family tree is a lot "bushier" than we originally thought. And this is several million years after the critter that owned the skull we're all talking about became leopard food5. Our family tree may have been even "bushier" at that point, so figuring out just exactly which bipedal ape ended up going to the moon is a lot harder than was once imagined.

So you're saying this poor thing had to worry about leopards and rhinos and who knows what else?
Actually no. Until about 3 million years ago, Africa, and most of Europe as a matter of fact, was covered from end to end in forests. There really wasn't much savannah to speak of. During the time period we're talking about our ancestors were flinging poo at each other through trees instead of across grassland. Them and all the other apes.

You mean chimps and gorillas?
Yes, but a lot of others too. Something not widely understood is that apes and monkeys evolved at roughly the same time, one did not spring from the other6. And at one point there were a lot of apes. Instead of the four pitiful remnants we have today (gorillas, chimps, orangs, and us), there were once more than a dozen different kinds of apes swinging through the trees of Africa and Asia. When the climate changed about three million years ago, ape species (along with everything else that lived in the forests) had three choices: stay put, adapt, or die. The vast majority of them took the third option, a few (at least one) took the second, and three took the first.

Monkeys had a different adaptational strategy that involved having more, dumber offspring that took less time to reach adulthood (and thereby make more monkeys). Smaller brains, more offspring, and quicker growth cycles apparently fit the savannah far better than what apes had (roughly opposite), and so eventually the monkeys took over.

But not all at once. As noted above, at one point there were perhaps as many as four species of bipedal apes motoring around the savannah. The shorter, skinnier ones seem to have taken a crack at scavenging to make a living, while the larger, heavier ones seem to have tried grazing on grasses. The big ones did pretty well for awhile, some had molars as big as the end of your thumb and massive muscular jaws. But eventually, for reasons that are not at all clear, all but one of these savannah apes died out.

There are some indications that the rest of the apes that survived by staying put in the forests (gorillas, chimps, and orangs) were on their way out too, without any help from us at all. We are the spectacularly successful offspring of what is otherwise a dead genus.

So there you go. Human origins in 1000 words or less. A lot of this is from memory, so hopefully I didn't get it too badly wrong. Please feel free to comment with any questions you may have about this stuff, and I'll do my best to answer. For further reading, a great place to start is the talk.origins hominid FAQ. The entire talk.origins site is well worth browsing, especially if you have questions about evolution or want to take your fundie friends down a notch or two.

Posted by scott at July 11, 2002 10:01 PM

eMail this entry!

I bet dem jagoooars said peeples taystid like cheeeekin!

Catz rool!

Posted by: Ted the Cat on July 11, 2002 05:49 PM

I want to know if the missing link lucy is real or not?

Posted by: esmeralda on September 10, 2002 01:30 PM

Yes, Lucy is real, but the whole idea of a missing link is obsolete. I've held a cast of the fossile myself, and known people who have seen the real thing.

Posted by: scott on September 10, 2002 02:27 PM
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