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Origins of Humankind

Fossils Reveal the Story of Our Relatives

In the 8 million years or so since the earliest ancestors of humans diverged from the apes, at least a dozen humanlike species, called hominids, have lived on Earth. And this list is getting longer. As scientists discover new fossils, the hominid family tree grows new branches.

But fossils are often difficult to categorize neatly as one species or another. Like all creatures, no two individual hominids were alike. And over the millions of years most of the species existed, hominids changed; they evolved; some diverged and became new species.

This is the story of our distant relatives, as told by the fossil record.

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The Hominid Family Tree

Hominid Tree

A

Orrorin tugenensis
(6 mya)

B

Ardipithecus ramidus
(4.4 mya)

C

Australopithecus anamensis
(4.2 to 3.9 mya)

D

Australopithecus afarensis
(3.6 to 2.9 mya)

E

Kenyanthropus platyops
(3.5 to 3.3 mya)

F

Australopithecus africanus
(3 to 2 mya)

G

Australopithecus aethiopicus
(2.7 to 2.3 mya)

H

Australopithecus garhi
(2.5 mya)

I

Australopithecus boisei
(2.3 to 1.4 mya)

J

Homo habilis
(2.3 to 1.6 mya)

K

Homo erectus
(1.8 to 0.3 mya)

L

Australopithecus robustus
(1.8 to 1.5 mya)

M

Homo heidelbergensis
(600 to 100 tya)

N

Homo neanderthalensis
(250 to 30 tya)

O

Homo sapiens
(100 tya to present)

mya = millions of years ago        tya = thousands of years ago

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The Hominid Family Tree

At first glance, it seems there are far more questions than answers regarding the relationships among species on the hominid family tree. The graphic above plots 15 different species along a timeline spanning 6 million years, and it depicts, with connecting lines, how some scientists think these species relate to one another. A few relationships are clear. For instance, there is consensus among scientists that the three most recent species of hominids (Homo heidelbergensis, Homo neanderthalensis, and modern humans, Homo sapiens) all evolved from an earlier species called Homo erectus. But other relationships are murkier.

Indeed, our view of the origins of humankind is incomplete, and the search for pieces to the puzzle continues. But to view the question marks on the hominid family tree merely as gaps in our knowledge belies the reality of evolution. Hominid species were changing over periods of hundreds of thousands of years, adapting to new environmental conditions. And so, given that the present fossil record gives us only a glimpse of these evolving species, it's very difficult -- even unnatural -- to identify exactly when a species "became" something else.

In order to begin to understand human evolution, however, scientists have had to take the fossils they have, analyze them, and categorize them based on similarities and differences. In this way, they are able to find trends among the species and a better understanding of how they came to be. In this way they have allowed us a glimpse into our ancient past -- a glimpse that will undoubtedly become clearer in years to come.

-> Learn about the fossilized evidence of our fellow hominids

 
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