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Early Hominids: Evolution & Timeline

Instructor: Christopher Sailus

Chris has an M.A. in history and taught university and high school history.

In this lesson we explore early hominids: humanity's earliest ancestors. By examining some of these species we can learn the important aspects that fostered human evolution and just some of the difficulties that face modern paleoanthropologists.

Age-old Questions

There comes a time in most every parent's life when their child approaches them and asks 'Where did I come from?' Depending on the age of the child, the answer to this question might be tricky. For some paleoanthropologists, answering the larger question of 'where did we, as a human race, come from?' can be even trickier.

Much of this difficulty is due to time. The only thing that remains from our early hominid ancestors is a few bones that were fossilized and preserved for millions of years. In addition, paleoanthropologists never discover full skeletons of individuals; they piece together species of our ancestors by finding a skull here, a femur over there, and a jawbone down there. Despite these difficulties, paleoanthropologists today have a better understanding of how humans evolved than ever before.

Human Evolutionary Scale

According to best current estimates, early hominids first branched off from their common ape ancestor on the evolutionary tree between six and eight million years ago. What follows is a list of several important human ancestors that walked the earth; it is by no means comprehensive.

  • Sahelanthropus tchadensis

First appearing in the fossil record around six to seven million years ago, S. tchadensis exhibits many apelike features (especially a small, ape-sized brain) and may actually be modern humans' and apes' common ancestor. Unfortunately, few fossils of the species remain and preclude any definitive ancestral links.

  • Australopithecus species

Several hominid species with the genus name Australopithecus followed afterward, and they are unique from previous hominids in that they are the first species to begin showing strong evidence of bipedality - that is, walking on two legs instead of four.

From the earliest Australopithecus anamensis to the latest Australopithecus robustus, multiple species of Australopithecus inhabit the fossil record from approximately 4.2 to 1.5 million years ago. Other than bipedality, the Australopithecus specimens are unique in their increasing brain size over time: earlier species such as Australopithecus afarensis had brains of just under 400 cc., while Australopithecus robustus likely had a brain size of about 550 cc.

  • Homo habilis

Active around 2.5 to 1.5 million years ago, Homo habilis is different than the Australopithecus species in that he certainly had the ability to fashion and use tools. Often referred to as the 'handy man' due to this, Homo habilis had a larger brain as well - on average around 650 cc.

  • Homo erectus

Homo erectus, at 900-1100 cc., had an even larger brain than his handy ancestor and his tools were far more complex. Active around 1.8 million to 300,000 years ago, Homo erectus was more stout than modern day humans, and likely was far stronger than we are today. Evidence at some digs suggests that erectus may have also harnessed the use of fire, and perhaps been more efficient walkers than modern day humans.

  • Homo neanderthalensis

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