Scientists solved a 50,000-year-old mystery in Australia by studying the burnt eggshells remnants of an ancient 500-pound giant bird. Prior to the arrival of humans in Australia approximately 50,000 years ago, the flightless "big bird" Genyornis newtoni lived across the continent but quickly went extinct afterward.

Today, a study found that early humans cooked up the big bird's eggs for dinner which eventually resulted to its diminishing population. The big birds were about 7 feet tall and weighed 500 pounds. Their 3.5-pound eggs were about as large as an average cantaloupe. The analysis of the human-burnt eggshells support the theory that ancient humans played a role in the big bird's extinction.

"We have documented these characteristically burned Genyornis eggshells at more than 200 sites across the continent," said geological sciences professor Gifford Miller from the University of Colorado, Boulder.

The scientists initially set out to date prehistoric shorelines using the eggshells. In the course of their study covering over 20 years, they found that some of the big birds' eggshell fragments were burned and clumped together.

From over 2,000 locations across Australia, they collected unburnt eggshells. Most were found in sand dunes, which are the big birds' popular nesting place. In 200 locations, they collected burnt eggshell fragments.

A process called radiocarbon dating can determine the age of an object within the last 50,000 years but the big birds lived almost on the cutoff time. To remedy, the researchers used another technique called optically stimulated luminescence (OSL) dating.

This process analyzes the last time the eggshells' quartz grains saw sunlight. The team confirmed that the collected eggshells were between 44,000 and 54,000 years old. The age window coincided with the timeline when the earliest humans were colonizing Australia.

Further analysis showed that the eggshells were burnt using a localized source of heat and not from sustained high heat such as wildfires. The findings suggested that the eggshells were burned in man-made fires, which were mostly used to cook prehistoric meals. The eggshells were then discarded in fragments in or around the man-made cooking fires.

Miller added that the study is the first one to provide direct evidence that ancient humans in Australia also hunted on the now-extinct megafauna.

The study was published in the journal Nature Communications on Jan. 29.