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Introduction to Hominins

Human Biology (Year 12) - Hominin Evolution

Ben Whitten

What is a hominin?

Hominins can stand upright with bipedal locomotion. They also tend to have a larger brain and less hair than their ancestors, hominids.

Most of the evidence we have of our early ancestry comes from fossils; these fossils are scarce and often comprise of no more than a few broken fragments of heavily mineralised bone or a few teeth; very occasionally, an almost complete skeleton or skull is discovered, but this is very unusual.

Recognising our evolutionary history is like trying to piece together a jigsaw puzzle with many of the pieces missing; without a clear idea of the picture, we can only infer how the puzzle might fit together.

To date the total amount of fossil material discovered could be loaded into a small truck; the study of DNA has further aided knowledge of our possible ancestry.

The puzzle slowly takes shape; however, the picture is still far from complete and reconstructing our evolutionary history remains one of the most challenging and controversial areas of science.

Why did bipedalism develop; what is the advantage?

Where Hominins first appeared in East Africa, there was a change in the climate, and it became much cooler and drier.

This lead to a change in the vegetation from dense forest to open woodland and savannah; food in a savannah environment is different and more spread out than in a forest.

As a result, Hominin ancestors must have expanded their diet to include a greater variety of foods found on the ground (bulbs, grains, roots). Therefore, they were forced to travel further from their home base to gather food.

There were many advantages to being bipedal.

  • Bipedalism is an energy-efficient means of covering large distances to collect food.

  • It leaves the hands free to carry food, tools, weapons and young

  • Hominins stand taller, so they have greater vision to spot food and/or danger

  • Standing taller also increases the ability to reach food

  • It allows an individual to appear larger, which deters predators

  • Less surface area is facing the sun in hot, dry environments, so they do not heat up as much

  • Body higher from ground minimises heat gain from the ground

Given efficient bipedal locomotion, good eyesight, a smart brain and free hands, early bipeds (Hominins) had a better chance of surviving in a very challenging savannah environment than quadrupeds (non-Hominins).

Who are our Hominin ancestors?

Apes and humans share a common ancestor, an ape-like creature, and from that ancestral ape, the first hominins (modern and extinct humans) evolved. These were the Australopithecines classified in the genus Australopithecus.

It is believed that one or more of the australopithecine species evolved early members of the genus Homo. Species of early Homo gradually evolved into several different species, including Homo habilis, Homo erectus and Homo neanderthalensis, and eventually into modern humans, Homo sapiens.

  • Australopithecus afarensis (4 to 3 mya)

  • Australopithecus africanus (3.3 to 2.5 mya)

  • Paranthropus robustus (2.3 to 1 mya)

  • Homo habilis (2.3 to 1.8 mya)

  • Homo erectus (1.9 mya to 50,000 ya)

  • Homo neanderthalensis (350,000 to 25,000 ya)

  • Homo sapiens (195,000 ya to present)

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