Unearthing a pivotal journey

By | Science & Technology
A collection of hominid fossil skulls. Credit@Brentdanleyviaflickr.

Piecing together the story of human evolution gives scientists a glimpse into human ancestry and their evolutionary and physical journey to present modern man. Like a global jigsaw puzzle with an unknown number of pieces, the excavation of fossil remains provides important pieces of evidence for this pivotal journey. A paper published late last month revealed fossil evidence that may change anthropologists’ current understanding of human migration across the planet.

It has long been accepted in the scientific community that Homo sapiens evolved in Africa around 200,000 years ago from one of three species: Homo-heidelbergensis, Homo-rhodesiensis or Homo-antecessor. During their time in Africa, human ancestors learnt to walk upright, use tools and control fire; to name just a few of the key traits associated with today’s modern man. Early Homo sapiens, probably searching for resources, eventually moved away from Africa and populated the rest of the planet.The recent ‘out of Africa’ model describes this migration of Homo-sapiens, as they undertook the momentous route into the Middle East and, subsequently, across the entire globe. This single movement of modern man from Africa was originally thought to have occurred 60,000 years ago and is supported by fossil evidence.

However, as different jigsaw pieces fall into place, scientists may begin to visualise an alternative perspective on the final picture. Evidence for migration, as early as 120,000 years ago, is beginning to mount. The discovery of modern human teeth was described in a paper by Christopher Bae and Wei Wang late in July. The teeth were found at the Luna cave in Guangxi, China, and have been dated between 70,000 and 125,000 years ago from their calcite crystal deposits. Bae and Wang propose that these teeth are strong evidence that modern humans had travelled to Eastern Asia earlier than previously thought.

Careful analysis of new evidence is paramount in the world of anthropology and paleontology, as alternative explanations are proposed. Before the Homo-sapiens, which gave rise to modern humans leaving Africa, there were a number of migration events from other hominid species. Homo-erectus moved from Africa long before Homo-sapiens, around 1.8 million years ago. This is followed by other early hominid species.The Neanderthals and Denisovan men (known for their small stature and Hobbit nickname) were also outside of Africa before modern Homo-sapiens made their appearance. Perhaps Bae and Wang’s teeth belong to another hominid species? Alternatively, these discoveries may belong to a different line of Homo-sapiens. Hominid species may have evolved in parallel to modern Homo-sapiens. Erik Trinkaus from Washington University stated that more knowledge on human teeth is needed before conclusions on earlier migrations may be drawn from these results.

Fossil evidence is vital to the field of anthropology and palaeontology. However, genetic evidence may play an important role in testing the recent ‘out of Africa’ model. Katerina Harvati of the University of Tubingen in Germany, published her findings showing that modern humans left Africa as early as 130,000 years ago. This conclusion was drawn by comparing the genomes of indigenous south-east Asian communities. When more fossil evidence surfaces, perhaps this genetic model may gain more support.

Whilst the fossilised puzzle on early human migration is yet to be completed, evidence is constantly surfacing to help piece together this intriguing story. It is important to recognise alternative perspectives, in order to correctly place these puzzle pieces. Many questions still remain on human origins. However, anthropologists are gradually closing in on the facts, revealing a fascinating picture of how modern humans came to populate the world.

What other explanations might there be for these new human fossil discoveries?

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