Standing on your own two feet!

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LAST article on evolution this week - if your'e bored with it, hard luck! Following the revelation last week that, civilisation notwithstanding, we are the equal of any ape, I continue with my summary of the ideas of Jeremy Cherfas and John Gribbin in New Scientist on how we (and the other apes) got to where we are.

About 20 million years ago(MYA),, the ancestor of all modern apes evolved. Scientists call it Dryopithecus of 'tree-ape', though it lived on the ground.

Over the next 10 million year, the climate of the earth was warm and there was a lush carpet of forest over much of Europe, Africa, the Middle East and Asia. Dryopithecus and its descendants must have found plenty of opportunity to make a living and evolved into several new species of ape which could exploit such favourable habitats.

One group developed the bodily adaptations which enabled them to live in the trees. These were the brachiators (from the Ancient Greek for "arm') and they evolved in the forests of Asia. Gibbons split from this line some 10 mya and orangutans some 8 mya, but both groups still live in the forests of Asia.

The next split probably took place in Africa about 4½ mya, the results being chimps, gorillas and ourselves for rather our direct ancestors). This means that our brachiating ancestors must have travelled from Asia to Africa between 8 and 4½ mya. Darwin's first public defender, Thomas Huxley.

By this time the earth's climate was getting colder and the forests were dwindling, being replaced by grassland.

Culture

How did the arm-swinging tree-dwellers travel the 8,000 kilometres to Africa with no trees to swing chimps and gorillas use.

Incidentally, the bodily adaptations necessary for brachiation also fit an animal well for walking more or less upright. Once in Africa, the walking brachiators would have found forests to swing about in, but these were still shrinking in the colder climate and there would have been a considerable advantage to a brachiator who could also walk upright on two legs. They would be able to wander about outside of the forests, looking for extra sources of food.

If they had also developed a food-sharing culture then we can imagine the beginnings of the line which we would call human. The earliest fossil example of this uprightwalking line is a female of the species AustralopithScience ecus Africanus (African southern ape) named Lucy by her discoverer. Lucy is 3¾ million years old.

Now, round about 4 mya, the climate began to get better and the forests got larger and lusher and there was lots more fruit to eat. Cherfas and Gribbin now start to get a bit more wild in their speculations. The popular misconception about evolution is that humans are descended from apes. Cherfas and Gribbin say it was the other way round.

Some early humans were attracted by the easy living in the forests and, so to speak, went back to the trees. Even now, chimps

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Socialist Organiser, Thursday 24 September 1981 Page 14