Why is it difficult for historians to determine the scale of the great dying

The reason why the historians are able to determine the scale of the great dying was due to the fact that all lives vanished from earth.

This was a mass extinction that took place in  the planet earth about 250 million years ago. The scientists are unable to figure out the reason for this due to the fact that most of humanity was lost.

The period was what saw to the loss of many animals such as dinosaurs that were once on the earth.

Read more on the great dying here:

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all life on Earth vanished. Scientists are now starting to figure out what happened. ... What caused the Great Dying has long been a mystery. ... It also would have made it harder for creatures to build new shells. ... reptile Cold-blooded vertebrate animals, whose skin is covered with scales