*"Replicating Evolution: How Scientists Fast-Tracked Multicellular Life in the Lab"**

 

 

It took a staggering 2.9 billion years for unicellular organisms to evolve into multicellular life. But what if I told you that scientists at Michigan State University managed to replicate this transformation in just 600 days through a groundbreaking experiment? This is one of the most astonishing scientific breakthroughs ever conducted.  

With this experiment, we may finally uncover the greatest mystery of evolution—one that scientists have been trying to solve since 1988. How did life transition from unicellular organisms, like amoebas, to complex multicellular beings, like humans? The answer, in one word: Oxygen.  

Now, let’s take a closer look at how this was achieved. Back in 1988, evolutionary biologist Richard Lenski of Michigan State University embarked on a study to observe the evolution of multicellular organisms from unicellular ones. For this, he selected *E. coli* bacteria, which replicate rapidly—doubling their population in just four minutes—making them ideal for studying evolution over thousands of generations.  

At the start of the experiment, Lenski cultivated 12 distinct populations of *E. coli* under identical conditions. Over time, these bacteria evolved through 74,500 generations, an equivalent of 1.5 million years of human evolution. Through these observations, Lenski made some groundbreaking discoveries.  

He found that each new generation evolved to grow 70% faster than the previous one, with nearly half of them developing the ability to repair their own DNA. Additionally, after 20,000 generations, the bacteria had shed metabolic functions they no longer needed, streamlining their survival mechanisms. This process mirrored the way early primates evolved into humans, adapting to their environment while discarding unnecessary traits.  

Lenski’s experiment revolutionized our understanding of evolution, showing that we could replicate different stages of life’s history in a controlled laboratory setting. However, there was one limitation—*E. coli* is a bacterium, and bacteria do not form multicellular structures. This meant the experiment couldn't explain how unicellular organisms first transitioned into multicellular life.  

To address this, in 2010, evolutionary biologist William Ratcliffe at the University of Minnesota conducted a similar experiment, but this time using yeast—a unicellular organism that shares 20% of its genes with humans. Yeast was the perfect candidate because, like bacteria, it reproduces quickly, doubling its population every 90 minutes.  

Ratcliffe used *Saccharomyces cerevisiae*, a common species of yeast, and cultivated it in a nutrient-rich medium containing peptone dextrose at an optimal temperature of 30°C. This setup provided glucose for energy and amino acids for protein synthesis.  

After mixing the yeast culture and allowing it to settle, Ratcliffe observed that heavier, multicellular yeast clusters sank to the bottom due to gravity. He selected these clusters and transferred them to a fresh environment, repeating the process for 60 days. What he discovered was astonishing—yeast had evolved into multicellular structures resembling snowflakes, each containing dozens of genetically identical cells.  

While fungi like yeast can form large structures, they typically do so by grouping with different organisms. In contrast, these snowflake-like structures were composed entirely of genetically identical yeast cells, proving that unicellular yeast had evolved into a multicellular organism.  

However, there was a problem—these multicellular yeast structures stopped growing beyond 100 cells. Scientists were puzzled until one researcher suggested simulating the environmental conditions of primitive Earth, where oxygen levels were much lower.  

Ozan Buzdag, a member of the research team, placed the yeast in an oxygen-free environment. The results were astonishing—what was previously limited to 100 cells now grew to a staggering 450,000 cells. Within 600 days, the yeast clusters had grown so large that they were visible to the naked eye.  

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So, what caused this rapid transformation in an oxygen-deprived environment? Upon closer examination, scientists discovered that the yeast cells were forming strong branches, concentrating their thin cell walls at junction points to make them thicker and more resilient. In fact, while normal yeast cell walls are 100 times weaker than gel, these multicellular yeast structures had cell walls as tough as wood.  

In oxygen-poor conditions, yeast undergo anaerobic respiration, breaking down carbohydrates to produce alcohol and carbon dioxide. Under extreme environmental stress, the yeast adapted by forming larger, more robust multicellular structures for protection. This led researchers to conclude that primitive organisms may have evolved into multicellular life to survive the harsh conditions of early Earth.  

Now, we had a definitive answer to how multicellular evolution took place. However, one question remained—was yeast the first organism to make this evolutionary leap 600 million years ago?  

To find out, researchers examined other unicellular structures that might have had the potential to transition into multicellular life. Their search led them to an unexpected place—the human mouth.  

In 1970, Dr. Niels Hoebe was studying cystic fibrosis, a condition where thick mucus blocks the windpipe. When he examined saliva samples from patients under a microscope, he noticed something extraordinary. The bacteria in these samples weren’t just multiplying—they were forming colonies encased in a slimy, protective layer.  

This bacterial colony, known as a biofilm, was highly resistant to external threats. When scientists treated the samples with acetic acid, only the bacteria outside the biofilm died, while those inside remained protected.  

Further research revealed that 70% of bacterial infections in humans are caused by biofilms, which shield bacteria from immune system attacks, making them incredibly resilient. Scientists now believe that biofilms may represent the missing evolutionary link between unicellular and multicellular organisms.  

With this discovery, we had answers to two fundamental questions: how unicellular eukaryotes transitioned into multicellular life, and how bacteria formed protective biofilms, marking the first stage of this transition. But a new question emerged—how did unicellular life originate in the first place?  

To solve this mystery, researchers at the University of Glasgow, led by Leroy Cronin, conducted an experiment to create a primitive cell from inorganic molecules.  

They mixed two water-based solutions—one containing oxygen ions and positively charged carbon compounds, and another containing sodium ions and polyoxometallate (POM) crystals made of heavy metals like tungsten and molybdenum. When these solutions were combined, the carbon compounds and POM crystals spontaneously formed a thin membrane.  

Remarkably, scientists observed that ions flowed through this membrane, much like nutrients flow in living cells or how electrical current flows through a circuit. This process essentially brought the inorganic structure to life, marking the birth of an "inorganic chemical cell," or *I-Cell*.  

According to the endosymbiotic theory, such primitive inorganic cells could have given rise to prokaryotic cells, which later evolved into cell organelles like mitochondria and chloroplasts. Over time, these components merged to form eukaryotic cells—the foundation of all complex life.  

Eukaryotic cells, enclosed within a cell wall, provided a stable environment for biochemical reactions, setting the stage for evolution. This experiment provides strong evidence supporting Darwin’s theory, proving that life can emerge from inorganic matter given the right conditions.  

If these experiments continue, it may one day be possible to evolve *I-Cells* into fully functional organic cells. Through these four groundbreaking studies, scientists now have a rough blueprint of how life originated from inorganic matter and evolved into complex multicellular organisms.  

This is an extraordinary step in understanding the origins of life itself. Evolution, once just a theory, now has experimental proof. Until now, the vast timescales involved made it difficult to demonstrate evolution in real time. But these experiments have successfully replicated key evolutionary transitions in the lab.  

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However, evolution is a double-edged sword. Along with life’s advancement, highly dangerous disease-causing bacteria and viruses continue to evolve. In fact, scientists have recently discovered a deadly fungus that attacks the human brain, raising concerns about its potential global impact.  

If you found this fascinating, stay curious, keep learning, and continue exploring the mysteries of science!