Weekly Online Lesson Online Lesson Archive Grade Level: 7-12 Subject: Paleontology

Tracing the Origins of Man

For 20 years, most scientists have agreed that Australopithecus afarensis, represented by the famous Lucy skeleton found in Ethiopia, is the direct ancestor of the many branches of hominids — upright walking human-like primates — including modern man.

But a 3.5 million-year-old skull recently found in Kenya belongs to a completely different and previous unknown creature. Researchers have named it Kenyanthropus platyops, which is Greek for "flat-faced man of Kenya."

The skull has a bewildering mixture of physical features — a flat, human-looking face, small brain and small teeth. This shows that Kenyanthropus had a much different diet than Lucy's species. The two could even have lived side by side.

According to paleontologists, modern humans can't be directly related to both, casting sudden confusion over what scientists know about early humans. It could even add a whole new main trunk to the human family tree.

The findings are published in the March 22, 2001 issue of Nature.

In this week's lesson you will examine age-old fossils and learn about hominid — man's primitive ancestors. Keep in mind that in view of these new findings, some of this information may already be somewhat out-of-date . . . but no more so than your textbooks.

Hominid Evolution

To understand the significance of the flat-faced man of Kenya, you need to understand the what scientists have long believed about the evolutionary tree of man. A good introduction can be found at the Hunterian Museum and Art Gallery at the University of Glasgow, Scotland. Among the online exhibitions you will find a Guided Tour of Hominid Evolution. Each page in the tour displays an image, a timeline, and a written explanation about hominids. Read the text, study the images, and then click the arrow button (>) to move through the tour.

What evidence suggests that hominids were bipedal? What have researchers learned from the teeth of ancient skulls? Which genus is considered the first true humans, and what do we know about their use of tools?

Hominid Species Timeline

For a more detailed timeline of the hominid species, visit Species Timeline at Washington State University. All the hominids you learned about in the guided tour are here, displayed in a chart that shows approximately when they lived. Where would Kenyanthropus platyops fit in this timeline?

Below the timeline chart are links to each genus in the hominid species. Click each link to learn more about them.

Fossil Skulls!

It's time now to get into 3D at the American Museum of Natural History's Fossil Skulls! page (requires Shockwave). This chart of skulls is the best representation you've seen yet of the evolutionary line. At the bottom of the chart is the oldest hominid, Australopithecus afarensis. Keep in mind that this chart may look quite a bit different in coming years to account for Kenyanthropus platyops.

Now for the fun. Click any skull on the chart. When the new page opens you will find a graphic with two skulls (on the right is a modern human), and some text explaining what you are seeing. To move the skulls around, click and drag your mouse up and down or left and right. What does the size tell you? Which hominid skull is most like a modern human?

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