Thursday, 2 February 2023

Australia's Prehistoric Giant Eggs

Australia's Prehistoric Giant Eggs 

I didn't know it was a controversy, but it has now been settled!

In the 1980s people started finding large eggs, and fragments of eggs in eroding sand dunes in the centre of Australia. Some were identified as emu eggs but others were identified as being laid by Genyornis, an extinct member of the thunderbirds.(!)

The eggshells were age dated and ranged from 400,000 years old to 50,000 years. Some of the youngest eggs showed signs of having been cooked. Did Genyornis become extinct due to human predation?

Then the controversy started. One group said that the eggs came from Progura an extinct relative of brush turkeys. And until recently no agreement was to be had.

DNA was no help - the molecules were too degraded. So, as described in THIS ARTICLE, proteins were recruited to settle the matter. Proteins last longer than DNA and partial protein sequences were retrieved from some eggshells and these were used to get structures for the molecules using very sophisticated computer software. Proteins provide similar information as DNA.

These structures were then compared with a database of bird genomes. The birds position in the tree of bird genomes could not be determined but it could be proved that it was not related to brush turkeys. So the only candidate standing was Genyornis.

Isotope work on the shells showed that the diet of Genyornis had changed over the lifetime of the species. And by the time it died out summer grasses had disappeared from its diet. The reduction in monsoon rain was the cause of that. That, and the start of human predation, was enough to cause the extinction of the giant birds.

The giant bird Genyornis went extinct in Australia around 50,000 years ago. Gifford Miller

No comments: