Duke University paleontologist weighs in on newly-discovered species of human ancestor

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DURHAM, N.C. — Surely, you remember the feeling: being a kid in a room full of adults whose names and relationships you don’t quite grasp.

Aunt who? Cousin what?

That’s kind of the state of affairs in human evolution, especially now that a new branch of the clan has crawled out of some anthropological backwater and horned its way into the party.

Australopithecus who? And exactly how is this Homo naledi character related to me?

A team of scientists discovered this new species of human relative in fossils retrieved from a cave near Johannesburg, South Africa.

But don’t expect the find to sort out humans’ long and confusing family history, says Steven Churchill, a Duke University paleontologist who was part of the Homo naledi team.

Now, as he puts it, “We have a better ignorance.”

But there are clues. Let’s take a look:

The really old people

Like your cousin’s great-grandpa Tobias, who doesn’t talk much anymore and whose lineage even your family-historian mom has a tough time figuring out, Ardipithecus ramidus is the earliest known member of our family tree.

The scientists who discovered ramidus, nicknamed “Ardi,” say this species represents a common ancestor of both humans and African apes, according to the Smithsonian Institution.

These guys were tromping around Africa about 4 million years ago and are part of the earliest most apelike branch of our family tree, known as Ardipithecus.

Everybody’s favorite great-aunt

Hey, look! It’s slightly nutty Aunt Gladys, who throws those great parties and always has a treat for the kids. Everybody knows her!

And everybody knows Lucy, too. Her fossil bones provided the earliest clear evidence of bipedalism: walking on two legs, like humans.

Lucy, and other Australopithecus afarensis, had faces that resembled those of apes, small brains and curved fingers perfect for climbing trees. But these nearly 5-foot-tall characters also had characteristics that suggest they walked upright.

That skill separates them from their Ardipithecus predecessors, making australopithecines one of the big leaps toward modern humans.

Afarensis was around from 3.85 million years ago to about 2.95 millon years ago. Scientists have identified a similar species, Australopithecus africanus, that probably lived as recently as 2.1 million years ago.

Overall, australopithecines were around from about 3.85 million years ago to 1.2 million years ago, according to the Smithsonian.

The uncles

You know these guys. They’re hanging out in the garage, eating chicken wings and talking chainsaws and riding mowers.

And that links them up with our ancestors for whom tool use was a distinguishing characteristic.

Though there’s some evidence Lucy and her relatives may have been using tools as early as 3.4 million years ago, it’s with the transition to the Homo genus of the family tree that tool use — and tool-making — really takes off.

It’s here where our ancestors start to look truly human.

Some of the more important examples of this group are Homo habilis (“handy man”), Homo erectus and Homo heidelbergensis.

Habilis was once thought to be the first hominid to use tools, but evidence now suggests that tool use may somewhat predate its run.

Homo erectus had bodies much like those of modern humans. There’s evidence that they made hand axes and that they cared for the sick, according to the Smithsonian.

And, man, were they successful. They are believed to be the first species to travel beyond Africa — into Asia — and hung around nine times as long as our species has been alive, Smithsonian says.

Then there’s heidelbergensis, which existed some 700,000 to 200,000 years ago and may be the direct ancestor to our own Homo sapiens.

This species is remarkable for being the first to hunt large animals and build shelters, the Smithsonian says.

The cousins

Just like at the family reunion, the kids tend to stick to themselves.

If you’re wondering whether we, Homo sapiens, had anything to do with those old goats of the hominid world, the answer would be no. There is at least one species, however, that Homo sapiens did interact with, and that’s Homo neanderthalensis. You know them as the Neanderthals.

Until Thursday’s announcement, Neanderthals were believed to be the only hominid species other than humans to bury their dead. They were also masters of tool-making and fire.

And they interacted with early humans, who arrived on the scene about 200,000 years ago.

Why did they disappear? No one’s quite sure. Scientists used to think humans wiped them out, but newer research suggests that ancient climate change might have been to blame.

Or, some scientists say, they may have simply melted away by interbreeding with Homo sapiens.

So where does Homo naledi fit into all of this?

The newly discovered fossils haven’t been dated, so it’s a little hard to say, Churchill says.

But looking purely at the physical characteristics, they seem to be a link between the earlier australopithecines and more modern humans like Homo erectus, he says.

In some ways, they seem human: a foot nearly identical to ours, similar facial features, elongated limbs and hands that suggest the ability to carefully manipulate objects.

But in other ways, they seem firmly australopithecine: curved fingers resembling tree-climbers’, an apelike trunk and a very, very small brain.

But they’re not the only possible link. Or maybe even the last one we’ll find, Churchill said.

“Everybody in my field says ‘we need more fossils; we need more fossils,’ ” he said. “Then we find new fossils, and we know less than we did before.”

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