Over 500 million years ago, single-celled organisms on Earth's surface to form multi-cellular clusters that eventually become plants and animals. Now scientists are replicating a key step in a controlled laboratory using yeast.

Yeast evolved into multi-cellular clusters that work together cooperatively, reproduce and adapt to the environment.

"The division is growing so rapidly and repeatedly," said George Gilchrist, deputy director of the Division of Environmental Biology at the National Science Foundation's (NSF).

"The first step towards multi-cellular complexity appears to reduce the barriers of evolutionary theory than there," said Gilchrist.

They are a precursor to life on Earth that underlies all the creatures on this day.

"Starting two years ago when a casual conversation over a cup of coffee to bridge the gap of multi-cellularity," recalls Will Ratcliff and Michael Travisano, bioengineering from the University of Minnesota (UMN).

"Not many scientists perform experimental evolution, and they try to answer questions about evolution, not create it," said Ratcliff.

To understand why the world is full of plants and animals, including humans, we need to know how one-celled organisms turning into groups as a multi-celled organisms.

"This study is the first experimentally observed transition. Provides an event hundreds of millions of years ago," said Sam Scheiner, program director of the Division of Environmental Biology at NSF.

Brewer's yeast (Saccharomyces cerevisiae) is a species of yeast used to make bread and beer because it is abundant in nature and grow easily. Saccharomyces cerevisiae cultured in a medium rich in nutrients and allows cells to grow for one day in a test tube.

Then, centrifuge for stratification weight. Cell group that landed at the bottom of the tube more quickly because it is heavier. Biologists remove the cluster to be moved into new media and so on in 60 cycles. Now a cluster of hundreds of cells looks like a snowball. Cluster is not just a random group of cells attached to each other, but the corresponding cell in the next division.

"A cluster is not a multi-cellular. But when cells in a cluster work together, sacrifice for the common good, and adapt to these changes in the evolutionary transition to multi-cellularity," Ratcliff said.